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Title:  Methods for activating natural killer (NK) cells and means for carrying out said methods

United States Patent:  6,849,452

Issued:  February 1, 2005

Inventors:  Zitvogel; Laurence (Paris, FR); Fernandez; Nadine (Paris, FR)

Assignee:  Institut Gustave Roussy (Villejuif Cedex, FR)

Appl. No.:  260512

Filed:  March 2, 1999

Abstract

The present invention relates to a process for activating natural killer cells comprising bringing NK cells into contact with dendritic cells in vitro, ex vivo or in vivo. The invention also relates to cell compositions comprising activated NK cells, NK cell-dendritic cell co-cultures or dendritic cells, and to their use to stimulate the cytolytic activity of NK cells or natural immunity in vivo. The invention also relates to a NK cell stimulation factor present in the dendritic cell membrane, and to triggering media and factor(s) for dendritic cells and to their use, either alone or in combination, to stimulate NK activity, in particular in vivo. The invention can be used to control NK cell activity in vitro, ex vivo or in vivo, in particular under pathological conditions.

Description of the Invention

The present invention relates to the fields of biology and immunology. More particularly, it relates to novel methods for preparing activated natural killer cells and to means for carrying out these novel methods, in particular to novel populations of dendritic cells and products derived therefrom. It also relates to the use of the activated cells obtained using the methods of the invention in the fields of immunology, immunotherapy or, more generally, medical biotechnology.

Natural killer cells (NK cells) are a population of lymphocytes which represent a very early line of defence against viruses and tumour cells. NK cells can be characterized by the presence of CD56 and CD16 markers and by the absence of the CD3 marker. NK cells are involved in non specific anti-tumoral immunity of antigens, to prevent the establishment of primitive or metastatic tumours in the immunocompetent or immunosuppressed host. In particular, the role of NK cells in anti-tumoral immunosurveillance (primitive tumour or metastases) has been suggested in mice with tumours and treated with IL-2 and/or IL-12/IL-15, with or without LAK cells (lymphokine-activated killer cells), adherent NK cells (A-NK) or non-adherent NK cells (NA-NK) obtained ex vivo by stimulating NK cells with high doses of IL-2. In particular, NK cells appear to play a key role against tumour cells or negative class I MHC cell variants.

Because of their non-specific cytotoxic properties for antigen and their efficacy, NK cells constitute a particularly important population of effector cells in the development of immunoadoptive approaches for the treatment of cancer or infectious diseases. In this respect, anti-tumoral adoptive immunotherapy approaches have been described in the prior art. Thus in certain indications such as for patients with intensified malign lymphomas, the results of administering A-NK with small doses of IL-2 have been promising in an adjuvant situation. NK cells have also been used for experimental treatment of different types of tumours and certain clinical studies have been initiated (Kuppen et al., Int. J. Cancer, 56 (1994) 574; Lister et al., Clin. Cancer Res. 1 (1995) 607; Rosenberg et al., N. Engl. J. Med., 316 (1987) 889).

Further, such cells can also be used in vitro for non specific lysis of cells which do not express class I MHC molecules, and more generally any cell which is sensitive to NK cells.

However, adoptive therapy using NK cells (to treat murine or human tumours or other disorders such as infectious diseases) or any other in vitro or in vivo use of such cells involves ex vivo expansion and activation of the NK cells. In this respect, current techniques for activating NK cells are all based on using cytokines, generally in high doses which are not tolerated well by the host. The available data appears to indicate that NK cells do not survive ex vivo and cannot be activated without a nutritive support or without cytokines.

Thus current methods for activating NK cells in vitro involve culturing such cells in the presence of different cytokines (such as IL-1, IL-2, IL-12, IL-15, IFN.alpha., IFN.gamma., IL-6, IL-4, IL-18 in certain circumstances), used alone or in combination, which activation can be considerably increased by adhesion factors or co-stimulation factors such as ICAM, LFA or CD70. Similarly, in vivo, the efficacy of NK cells in anti-tumoral immunity is not dissociable from co-administration of cytokines such as IL-2/IL-15 or IL-12, IL-18, and IL-10. IFN8 also act as activators in association with IL-2. The activation methodologies described in the prior art thus all depend on using cytokines. Such methods have certain disadvantages, however, linked to the cost of preparing the cytokines, to the toxic nature of many cytokines, which cannot be used in in vivo applications, or to the non-specific nature of many cytokines, the in vivo use of which risks being accompanied by undesirable effects. Further, since the natural killing function is often altered in patients with tumours, the possibility of collecting such cells to activate them ex vivo can be considerably reduced.

There is thus a real need for novel methods for activating NK cells. The present application provides a solution to this problem by providing novel original approaches to activating NK cells. In particular, the present application demonstrates for the first time the possibility of activating resting NK cells with another cell population. The present application also describes, for the first time, a method of activating NK cells which is not dependent on the presence of cytokines, and which can thus overcome the disadvantages described in the prior art. The present invention thus describes novel methods for preparing activated natural killer cells and means for carrying out these novel methods.

In a first aspect, the invention thus provides a method of activating NK cells comprising bringing NK cells into contact with dendritic cells. As indicated below, contact can be made in vitro, ex vivo or in vivo. It can comprise either co-culture of NK cells and dendritic cells in vitro, or incubation of NK cells in vitro or in vivo with a preparation derived from dendritic cells, in particular membranous vesicles (exosomes), or a NK cell stimulation factor originating from dendritic cells, or in vivo passive transfer of dendritic cells, or in vivo administration of one or more dendritic cell growth factors.

In a further aspect, the invention concerns the use of dendritic cells or of a preparation derived from dendritic cells to activate natural killer cells in vitro, ex vivo or in vivo.

In a further aspect, the invention concerns the use of dendritic cells or of a preparation derived from dendritic cells to prepare a composition intended to activate natural killer cells in vivo.

In a still further aspect, the invention concerns a co-culture of dendritic cells and NK cells.

In addition, the invention concerns a composition comprising an NK cell stimulation factor originating from dendritic cells.

In a yet still further aspect, the invention concerns a method for triggering dendritic cells to improve (or cause) their capacity to stimulate NK cells, also a dendritic cell triggering factor and any composition comprising it. The invention also concerns a novel population of dendritic cells, termed "triggered dendritic cells", and any composition containing them, and uses thereof.

In other aspects, the invention provides a sub-population of NK cells activated by the method of the invention and using these cells or NK/CD cell co-cultures to stimulate cytotoxic activity in vivo or in vitro against target cells sensitive to NK cells. In a further aspect, the invention also relates to methods for greatly increasing the cytolytic and IFN.gamma. secreting activity of resting NK cells.

The invention also concerns novel therapeutic approaches, in particular for treating infectious, tumoral, autoimmune or congenital disorders or for disorders connected to transplantation, for example. In particular, the methods of the invention involve passive transfer (i) of NK cells activated by dendritic cells ex vivo, or (ii) of dendritic cells (in particular triggered dendritic cells) or a preparation derived from dendritic cells, to directly activate the NK cells in situ, or (iii) of two cell populations co-incubated ex vivo, or the method involves (iv) administration of the dendritic cell triggering factor to trigger dendritic cells in vivo such that they become capable of efficiently activating NK cells, the factor being administered alone or in association with chemokines or cytokines or dendritic cell growth factors, for example, or administration of a NK cell stimulation factor or a dendritic cell growth factor, used alone or in combination.

As indicated above, a first aspect of the invention thus concerns a method for activating NK cells using dendritic cells. This method comprises bringing NK cells into the presence of dendritic cells or a preparation derived from dendritic cells. The present invention is based on a demonstration by the Applicant of the capacity of dendritic cells to activate resting NK cells.

The results presented in the present application demonstrate that resting NK cells, co-cultivated in the presence of dendritic cells, survive and are very strongly activated for their lytic capacity and for the production of IFN.gamma.. Further, the activated cells obtained lyse NK-sensitive targets but do not lyse LAK-sensitive targets, which differentiates this activation phenomenon from the conventional LAK phenomenon, which is IL-2 dependent. The present application also demonstrates that allogenic and autologous dendritic cells are capable of activating NK cells in vitro, and that the mechanisms of activating NK cells in the presence of dendritic cells or a preparation derived from dendritic cells does not involve IL-12, nor IL-2, nor IL-15 nor IFN.alpha.. Further, the results presented also demonstrate the involvement of an interaction between NK cells and the membranes of dendritic cells in the activation method, demonstrating the existence of a membrane factor for dendritic cells intervening in this activation. The results obtained also show that membranous vesicles produced by the dendritic cells are also capable of activating NK cells, which indicates that the NK cell stimulation factor expressed by dendritic cells is present in said vesicles.

The pertinence of this activation of NK cells by dendritic cells has also been demonstrated in vivo, in a negative class I MHC tumour model. In mice with this tumour, a single expansion of dendritic cells can eliminate the tumour in NK-dependent manner. Further, passive adoptive transfer of dendritic cells to an immunosuppressed animal deficient in T and B cells, with a tumour, also significantly slows tumour growth.

These results thus demonstrate that dendritic cells or preparations derived from dendritic cells have the capacity to induce activation of NK cells in vitro, ex vivo or in vivo, that this activation can stimulate in vitro lysis of NK sensitive cells and in vivo natural immunity of a host organism, and can thus lead to in vivo elimination of tumours, infected cells, or can be involved in other pathological processes (autoimmune diseases, graft rejection, graft versus host disease, etc. . . . ).

The results obtained in the present invention are all the more surprising since, until now, few or no studies have suggested that NK cells could be activatable in vitro by another cell type except for transfectants coding for IL-2 and/or IL-12, IL-15 and CD70. In contrast, certain studies appeared to suggest an inhibitory role for macrophages on IL-2 dependent activation of NK cells via the intermediary of PGE2.

To our knowledge, the present invention constitutes the first evidence for NK cell activation which is not dependent on cytokines and uses another cell population or a preparation or a factor derived therefrom.

More particularly, the term "activation" of NK cells within the context of the invention designates an increase in the production of IFN.gamma. and/or the cytotoxic activity of NK cells. These two parameters can easily be measured using techniques which are known to the skilled person and illustrated in the examples. Generally, the activation of the invention is not accompanied by a large increase in NK cell proliferation, all populations together, but could induce proliferation of a sub-population thereof. In contrast, this activation is accompanied by a significant increase in the survival of NK cells in vitro. More particularly, NK cell the activation within the context of the invention is independent of the use of conventional cytokines. The term "activated" NK cells as used within the context of the invention designates NK cells with at least one of the properties mentioned above.

The NK cell activation method of the invention can be carried out in vitro, ex vivo or directly in vivo.

NK Activation in the Presence of Dendritic Cells

In a first particular implementation, the method of the invention comprises activation of NK cells in vitro or ex vivo by co-culture of NK cells with mature or immature, autologous or allogenic, preferably triggered, dendritic cells.

In this first implementation of the method of the invention, NK cells are co-cultures with dendritic cells. In this implementation, the dendritic cells used can either be autologous (i.e., originating from the same individual as the NK cells), or allogenic (i.e., originating from another individual from the same species). The results shown in the examples demonstrate that NK cell activation is not significantly affected by the allogenic nature of the dendritic cells. This has the particularly advantageous effect of enabling "universal" banks of dendritic cells to be used to activate the NK cells. As described below, such banks can be constituted, for example, by modifying dendritic cells to render them immortal. In this respect, different lines of dendritic cells can be used to carry out the present invention, preferably established from immature human dendritic cells.

Prior to their use, it is possible to pre-treat the dendritic cells to improve their properties or to render them compatible with pharmaceutical use. Thus the dendritic cells can be irradiated prior to their use to activate NK cells. Such irradiation can completely eliminate any risk of cancer associated with certain populations of dendritic cells such as immortalised dendritic cells. Pre-treatment by irradiation can be particularly desirable when the dendritic cells or co-cultures are used in vivo. A further pre-treatment for dendritic cells can consist of incubation in the presence of dendritic cell stimulation factors (for example cytokines, chemokines, heat shock protein), to improve their NK cell stimulation activity or to trigger the production of dexosomes.

Preparation and Use of Triggered Dendritic Cells

A particularly advantageous treatment for dendritic cells comprises treating the cells in the presence of a triggering medium. The present invention describes the production and characterisation of a novel population of dendritic cells with greatly improved NK cell stimulation capacities. These "triggered" dendritic cells, the preparation thereof and the uses thereof constitute a further aspect of the present invention.

The term "triggering" as used in the context of the present invention means bringing dendritic cells into the presence of a signal, which is different from modulating their differentiation stage, which induces a large capacity for stimulating NK cells in the dendritic cells. The "triggering medium" can thus comprise any substance, generally a biological substance, which can provide dendritic cells with a signal inducing a high capacity to stimulate NK cells. In the present application, treated dendritic cells are also designated "triggered" dendritic cells (for "tDC").

In a particular aspect, the invention thus concerns a method for treating dendritic cells comprising bringing the dendritic cells into contact with a triggering medium to improve (or cause) their capacity to stimulate NK cells.

In a still further aspect, the invention provides a medium for triggering dendritic cells, i.e., a medium for improving (or causing) the capacity of dendritic cells to stimulate NK cells.

A suitable triggering medium for the present invention comprises, for example, cells which can provide dendritic cells with the appropriate signal, a preparation derived from such cells, a factor derived from such cells, or any substance, preferably biological, which can trigger dendritic cells.

Advantageously, the triggering medium further comprises growth factors and/or cytokines, in particular GM-CSF and/or interleukin-4 and, if necessary, constituents of a mammalian cell culture medium (serum, vitamins, amino acids, etc. . . . ).

Particularly included among the cells which can be used to trigger dendritic cells is the extracellular matrix, in particular stromal, endothelial or fibroblastic cells. These cells, more particularly when they are in the division phase, can trigger dendritic cells. The same is true for certain tumour cells such as mastocytoma cells. One particular implementation of the invention comprises using fibroblasts for triggering. The Applicant has demonstrated that fibroblasts enable dendritic cells to stimulate NK cells with much higher efficiency. In this respect, immortalised fibroblasts, transformed lines, or primary cultures, which may or may not be activated, can be used, prepared in advance or extemporaneously, etc. Preferably, cells used for DC-triggering cell co-culture are in division or capable of dividing. Examples of suitable fibroblast lines are NIH3T3, L-929, MRC5 and TIB80.

In order to carry out this method, the fibroblasts (or other cells) used can be autologous, allogenic or xenogenic as regards the dendritic cells. Surprisingly, the results shown in the examples demonstrate that human dendritic cells can be triggered by fibroblasts of a different species, in particular by murine fibroblasts. In this implementation (in vitro co-culture), triggering (treatment) can be carried out using a DC/cell ratio of about 0.1 to 100, preferably 0.5 to 10, in particular 1 to 5. It should be understood that this ratio can be adjusted by the skilled person. Further in this implementation, irradiated cells are preferably used (for example between 2000 and 8000 rads).

Instead of intact cells, the triggering medium can also be a preparation or a factor derived therefrom. Thus it is possible to use a supernatant, a lysate, an acellular preparation, or an isolated and/or purified factor, etc. The results shown in the examples demonstrate in particular that a fibroblast culture supernatant can trigger dendritic cells, i.e., can render them capable of activating resting NK cells very effectively (more rapidly). In this implementation, for example, about 1 to 20 ml of a cell supernatant (for example from fibroblasts) can be used per 106 dendritic cells, in a final volume of about 30 ml. It is thus possible to use a supernatant diluted by 1.5 to 30 times, preferably 2 to 5 times. These conditions can, of course, be adapted by the skilled person depending on the cell populations used. Further, the activity described above for the culture supernatant demonstrates the existence of a soluble factor which is responsible for or sufficient to carry out the triggering, secreted by the cells, in particular fibroblasts. A further triggering medium thus comprises, for example, a supernatant concentrate/filtrate, more particular a soluble factor as mentioned above, in an isolated and/or purified and/or recombinant form. Thus the triggering medium can be the soluble factor described above or a recombinant cell expressing this factor. It is also possible to use any other substance, in particular, a biological substance, to trigger dendritic cells to activate NK cells.

Generally, triggering is carried out by incubating dendritic cells in the presence of a triggering medium for a period of 15 to 72 hours, usually about 20 to 48 hours. The "triggered" state of the dendritic cells does not modify their immunological phenotype. Thus immature dendritic cells remain immature after triggering (expression of HLA-DR, CD40, CD80, CD86, CD83, CD1a). The "triggered" stage can be demonstrated in a number of ways, generally by testing the capacity of the cells to activate NK cells in vitro, as described in the examples, or by measuring the soluble triggering factor in the culture supernatant.

Further in the context of activating NK cells, dendritic cells can be triggered prior to incubation in the presence of NK cells, or concomitantly therewith.

As indicated above, the present invention also concerns a population of dendritic cells termed triggered dendritic cells. In this respect, in a further aspect the invention also provides a composition comprising triggered dendritic cells, in particular human dendritic cells, which are mature or immature, i.e., dendritic cells with an increased capacity to stimulate NK cells, in particular by a factor of at least two with respect to non triggered dendritic cells.

More particularly, the triggered dendritic cells of the invention can be defined as activating resting NK cells and in that they can be obtained by treating mature or immature dendritic cells in the presence of a triggering factor or medium as defined above, preferably comprising a culture of extracellular matrix cells or a supernatant of such cells.

DC-NK Co-cultures

In order to carry out the NK cell activation method of the invention, the dendritic cells used can be mature dendritic cells (in particular in a murine system) or, preferably, immature dendritic cells (in human and murine systems). As will be shown in the examples, dendritic cells can activate NK cells at any stage in their maturity, in particular after triggering as described above.

To increase the efficacy of activation, certain parameters should advantageously be satisfied such as the ratio of NK cells to dendritic cells and/or the co-incubation time. Thus the experiments carried out by the Applicant have demonstrated that the best performances of the in vitro or ex vivo activation method were obtained when the initial NK cell to dendritic cell ratio was in the range 0.01 to 10, preferably in the range 0.05 to 5. It should be understood that the skilled person is free to adapt this ratio depending on the cell population used, taking into account the stifling effect of NK cells which can be observed when the quantity of dendritic cells is too high, and the low level of activation which can be observed when the number of dendritic cells is too low. Particularly preferred conditions are those in which the initial ratio of NK cells to dendritic cells is in the range 0.1 to 1, more preferably in the range about 0.1 to 0.5.

The co-culture time can also be adapted by the skilled person as a function of the cell populations used and in particular of the maturation stage and triggering of the dendritic cells. In general, optimal NK cell activation is observed after co-culture for a period in the range about 18 to 48 hours. Preferably, when the dendritic cells are triggered as described above, resting NK cells are activated after a co-culture period of less than 20 hours. The co-culture periods indicated above can in particular produce the best combination between the proportion of activated NK cells and the proportion of viable cells. It should be noted in this respect that, during the dendritic cell activation period, no significant global NK cell proliferation is observed (a factor of about 2) not excluding isolated and particular proliferation of an NK sub-population. Further, particularly unexpectedly, it appears that dendritic cells also exert a positive effect on the survival of cultured NK cells. Because of this, the method of the invention can produce activated NK cells without the need to use cytokines, and with improved yields. Similarly, NK cells increase the survival of mature DC.

NK cell activation and triggering dendritic cells in vitro can be carried out in any suitable cell culture apparatus, preferably under sterile conditions. In particular, they may be plates, culture dishes, flasks, pouches, etc. Co-culture is carried out in any medium suitable for culturing dendritic cells and NK cells. More generally, it may be a commercially available culture medium for culturing mammalian cells, such as RPMI medium, DMEM medium, IMDM medium or GBEA media (AIMV, X-VIVO), etc.

In a first particular variant of the method of the invention, NK cells are activated in vitro or ex vivo by co-culture of mature dendritic cells with NK cells.

In a typical experiment, dendritic cells derived from bone marrow by treatment with GM-CSF+IL-4, matured in LPS, or cells of an established dendritic cell line in the mature state, are re-suspended in their culture medium in a concentration of 1 million/ml. They are then cultured on plates or any other appropriate apparatus. Fresh resting NK cells (autologous or allogenic), obtained after the adhesion step, are re-suspended in a suitable medium (supplemented RPMI medium, for example) in a concentration of 1 million/ml. They are then added to the plate containing the dendritic cells such that the initial NK:DC ratio is about 0.1 to 0.3. The co-culture is recovered after about 18-36 hours. The activated character of the NK cells is monitored by measuring the IFN.gamma. production in the supernatant and measuring the cytotoxicity against target cells. The NK cells are also counted (for example using trypan blue) and analysed (for example by flux cytometry) for expression of characteristic markers (such as NK1.1Dx5 or asialo-GM1 in the mouse) and to evaluate the cell mortality.

In a further particular variation of the method of the invention, in vitro or ex vivo activation of NK cells is carried out by co-culture of immature dendritic cells with NK cells.

In a typical experiment, the cells are treated in identical manner to those described above, but they are not incubated in a maturation medium, so as to keep the dendritic cells at an immature stage. In this implementation, co-culture is advantageously maintained for at least 36-72 hours to provide optimal NK activation. The activated NK cells can then be analysed and monitored as described above.

In a preferred implementation of the method of the invention, NK cells are activated in vitro or ex vivo by co-culture of triggered dendritic cells with NK cells. In this implementation, a co-culture of less than 20 hours is sufficient to enable optimal NK cell activation. The activated NK cells can then be analysed and monitored as described above. More preferably, they are immature dendritic cells pre-incubated in the presence of a triggering medium. More preferably still, they are immature dendritic cells pre-incubated in the presence of fibroblasts or a fibroblast supernatant or a proteic factor produced by fibroblasts.

When the NK cells have been activated in this manner, either the NK cells can be separated from the dendritic cells, or the NK cell: dendritic cell co-culture can be harvested directly. In this respect, the invention also provides a composition comprising NK cells and dendritic cells, in particular a NK cell: dendritic cell co-culture. As indicated above, they are advantageously activated NK cells. Further, they may be mature or immature dendritic cells, preferably triggered. Finally, in these compositions of the invention, the cell populations are preferably autologous, i.e., from the same organism. These compositions are advantageously constituted by isolated cell populations, i.e., each of the two cell populations is composed of at least 10%, preferably at least 30%, in particular at least 50%, of the corresponding cell type (NK or dendritic). Further, preferred compositions of the invention generally comprise at least 10%, preferably 20% to 60%, more preferably 30% to 60% of NK cells, and at least 40%, preferably 40% to 80%, of dendritic cells. The invention also concerns any composition comprising activated NK cells as described in the present application. The compositions of the invention can be packaged in any suitable apparatus such as pouches, flasks, ampules, syringes, vials, etc., and can be (cold) stored or used extemporaneously, as described below. Advantageously, these compositions comprise 104 to 109 NK cells, preferably about 106 to 108 (in particular for administration to humans) or 105 to 106 (in particular for administration to mice).

NK Cell Activation in the Presence of a Preparation Derived from DC

In a further implementation, the method of the invention comprises in vitro, ex vivo or in vivo activation of NK cells by bringing NK cells into the presence of a preparation derived from dendritic cells. The preparation derived from dendritic cells can be any preparation or membranous fraction of dendritic cells, a cell lysate of dendritic cells, membranous vesicles of dendritic cells, or the stimulation factor derived from dendritic cells, in an isolated, enriched or purified form.

As illustrated in the present application, the NK cells can be activated not only in the presence of intact dendritic cells, but also in the presence of membrane preparations thereof, in particular of membranous vesicles (for example dexosomes), or in the presence of a proteic stimulation factor.

In a first variation, the method of the invention comprises in vitro, ex vivo or in vivo activation of NK cells by bringing NK cells into the presence of membranous vesicles produced by dendritic cells. In this respect, dendritic cells have been shown to produce membranous vesicles, with a diameter which is generally in the range 50 to 100 nm, termed dexosomes (French patent applications FR 97 09007, FR 98 01437). The present invention shows that these vesicles are also endowed with a NK cell stimulation activity. In particular, the present application demonstrates that the dexosomes produced from human or murine dendritic cells can activate murine NK cells. Further, the results obtained show that this activation is observed even with dexosomes produced by non triggered dendritic cells.

To implement this variation, dexosomes produced from immature dendritic cells are preferably used, preferably autologous or allogenic. For in vitro or ex vivo applications, the dexosomes are preferably used in a concentration range of 10 to 100 .mu.g of exosomal proteins per million NK cells. The quantity of exosomal proteins can readily be determined by the skilled person, for example using the Bradford test (Annal. Biochem. 72 (1976) 248). More preferably, dexosomes are used in a concentration of 15 .mu.g/106 NK cells or more, more preferably still 20 .mu.g/106 NK cells or more. It should be noted that these concentrations can be adapted by the skilled person, and can be transposed to in vivo use. In particular, for in vivo use, exosome doses of over 50 or 100 .mu.g/injection can be used.

The dexosomes can be prepared using techniques described in French patent applications FR 97 09007 and FR 98 01437, for example, which are illustrated in the examples. In brief, dendritic cells are cultivated, preferably to the immature stage, preferably in a medium which encourages dexosome production. The dexosomes are then isolated by methods such as centrifugation (in particular differential centrifugation at 70 000 g), or any other technique which is known to the skilled person. The dexosomes are then isolated, divided into aliquots and preserved or used extemporaneously to stimulate NK cells.

In a further variation, the method of the invention comprises in vitro, ex vivo or in vivo NK cell activation by bringing the NK cells into the presence of a stimulation factor originating from dendritic cells, in particular from triggered dendritic cells.

The results shown in the present application illustrate the specific nature of the activation of NK cells by dendritic cells, and thus indicate the involvement of one or more factors produced or expressed by dendritic cells in carrying out this effect. In this respect, the present application also shows, in a "transwell" experiment, that intercellular contact between NK cells and dendritic cells or a membranous preparation derived therefrom appears to be necessary for activation. These results clearly indicate the existence of a NK cell stimulation factor expressed (on the surface) by dendritic cells and dexosomes, responsible for or at least necessary for NK cell activation. This (membranous) (co-) stimulation factor, or any acellular preparation containing it, or any derivative or recombinant forms of this factor and the corresponding nucleic acids, can thus also be used in vitro or in vivo to activate NK cells, in particular for anti-tumoral or anti-viral immunisation applications. This factor can also be blocked using a competitor, specific or anti-sense antibodies, for certain situations such as graft versus host disease.

In a further aspect, the present invention provides a composition comprising a NK cell stimulation factor derived from DC, in particular a membrane factor involved in the activation of NK cells by dendritic cells. The term "involved" means that this factor is necessary or at least participates in the activation of NK cells by dendritic cells. This composition is, for example, composed of an acellular extract of dendritic cells comprising said factor, or membranous vesicles or any isolated or purified form of this factor. The term "derived" indicates that this factor, which is essentially proteic in nature, can in particular be purified by different isolation methods which are well known to the skilled person, such as cell lysis, followed by different centrifugation steps (differential centrifugation, ultracentrifugation, etc), and/or chromatography, electrophoresis, the production of neutralising antibodies and their use for isolation by immuno-affinity, etc. Each of these techniques, used alone or in combination(s), can be used to isolate the stimulation factor involved in activation, following the different purification steps with a NK cell activation test as described in the present application. A further approach for identifying this factor resides in the use of a dendritic cell DNA bank, and in the search for clones endowed with activity or capable of complementing dendritic cell mutants which are deficient in this activity. From this point of view, differential DNA banks (by subtraction between a triggered dendritic cell and a non triggered dendritic cell) can be established.

More generally, the present invention describes a method for preparing factors which can stimulate NK cells, involving inter-membrane contact between NK cells and a test composition. More particularly, the invention concerns a method for identifying and/or preparing an NK cell stimulation factor, comprising bringing a biological substance comprising a membranous fraction into contact with a preparation of NK cells, demonstrating NK cell activation, and isolating the activating factor present in the biological substance. More preferably, the biological substance comprising a membranous fraction is a dendritic cell, a sub-cellular dendritic cell preparation (in particular a membranous vesicle), or a cell transformed by a nucleic acid coding a polypeptide product. Thus it may be mammalian cells (for example COS cells) transformed by a DNA bank of human origin, in particular a dendritic cell DNA bank. Clones inducing stimulation of NK cell activity are selected, and the insert they contain is isolated, purified and characterised. This method thus enables any nucleic acid coding a NK cell stimulation factor to be cloned. The nucleic acid obtained can be modified, introduced into an expression vector and used in a method for producing a proteic stimulation factor.

The invention also concerns a method for identifying and/or preparing a NK cell stimulation factor, comprising bringing a biological substance comprising a membranous fraction into contact with a NK cell population, demonstrating NK cell activation, and isolating an activation factor present in the biological substance.

A particular composition of the present invention thus comprises a NK cell stimulation factor derived from DC, which is essentially proteic in nature, which can be obtained from the membranes of mature dendritic cells or membraneous vesicles produced by immature dendritic cells.

A more particular composition comprises a factor with an essentially proteic nature which can be obtained from exosomes produced by immature human dendritic cells, and which can stimulate secretion of gamma interferon by resting NK cells.

Further, the term "derived" also indicates that the compositions of the invention can comprise any variant or recombinant form of the stimulation factor identified above, in particular expressed from a cultured recombinant cell, such as a yeast or a mammalian cell.

In this respect, the compositions of the invention can also contain any nucleic acid coding for the stimulating membrane factor for dendritic cells (in particular triggered) as described above. This nucleic acid can be obtained using any technique which is known to the skilled person, in particular from a DNA bank of triggered dendritic cells. Finally, the compositions of the invention can also contain any other NK cell co-stimulation factor, in particular any lymphokine or cytokine which can activate NK cells in combination with the stimulation factor described above.

In a particular implementation, the invention thus comprises a process for in vitro, ex vivo or in vivo activation of NK cells by bringing NK cells into contact with a stimulation factor derived from dendritic cells.

The invention thus also concerns the use of a stimulation factor as described above to prepare a composition for increasing the cytolytic activity of NK cells or the in vivo production of IFN.gamma. and/or TNF.alpha..

The invention also concerns the use of a stimulation factor as described above to prepare a composition intended to increase the natural immunity of an organism.

The invention further concerns a stimulation factor as described above to increase the cytolytic activity of NK cells for the in vitro or ex vivo production of IFN.gamma. and/or TNF.alpha..

The invention still further concerns a process for negative control of in vitro or in vivo NK cell activation comprising bringing NK cells into the presence of a compound which can interfere with (i.e., at least partially inhibit) the interaction between NK cells and dendritic cells. Such a compound can, for example, comprise a soluble form (soluble receptor) or any other stimulation factor fragment (the extracellular domain, in particular the binding site), an analogue, an antagonist, a competitor, an antibody or an antibody fragment, an anti-sense, etc. Such a compound can be identified and/or characterised in a screening test using a stimulation factor as described above, or in any functional direct or indirect NK cell activation test.

In this respect, the invention also concerns a method of identifying and/or characterising a compound capable of inhibiting NK cell activation, comprising incubating a test compound or a composition comprising one or more test compounds with resting NK cells and dendritic cells, preferably triggered dendritic cells, or dexosomes, or a NK cell stimulation factor as described above, measuring the NK cell activation, and selecting compounds/compositions which are capable of inhibiting (i.e., reducing) NK cell activation, compared with a control experiment carried out in the absence of test compound/composition. The invention thus also concerns the use of compounds which inhibit this activation of NK cells by dendritic cells, as a drug or pharmaceutical composition for external (ex vivo) or internal (in vivo) use.

In this respect, the invention still further concerns any compound which can interfere with the interaction between dendritic cells and NK cells and thus at least partially inhibit contact between a dendritic cell (or a dexosome) and a NK cell. As described above, this compound can be a neutralising antibody, a competitive ligand, an analogue, a stimulation factor fragment or derivative, any chemical molecule etc. The invention also concerns the use of such a compound for in vivo or in vitro control of NK activation, in particular in applications such as graft rejection prevention, and GVHD. Further, the invention also concerns the use of "tolerogen" phenotype dendritic cells such as GC-DC, described by Grouard et al., (Nature 384, 364-367, 1996) or a product derived from tolerogenic dendritic cells to inhibit NK cell activation.

NK Activation by Increasing DC in vivo

In a further implementation of the invention, the method of the invention comprises in vivo activation of NK cells by increasing the level of dendritic cells in vivo. This in vivo increase can exert an in situ activation of NK cells and can thus reinforce the natural immunity of an organism, in particular against tumour or infected cells.

Dendritic cells can be increased in vivo by in vivo administration of dendritic cells, optionally triggered (passive transfer) or also by in vivo administration of one or more growth factors and/or triggering factors for dendritic cells, possibly in association. Administration can be carried out by injection, for example, preferably by subcutaneous or systemic injection. Injection is preferably a local or regional injection, in particular into the site or close to the site to be treated, in particular close to a tumour. The results shown in the examples demonstrate in particular that administration by subcutaneous or intravenous injection of immature or mature, allogenic or autologous dendritic cells in vivo, to the tumour site, can retard the growth of negative class I MHC tumours. Injections are generally carried out on the basis of cell doses of 104 to 109 dendritic cells, preferably in the range 105 to 107 inclusive. Further, the skilled person can adapt the injection protocol to the situation (preventative, curative, isolated tumours, metastases, extended or local infection, etc.). Thus it is possible to carry out passive transfer of dendritic cells by repeated administration, for example 1 or 2 administrations per week, over several months.

In vivo increase of dendritic cells can also be carried out by in vivo injection of dendritic cell growth factor. Such factors are, for example, the compound Flt3L (hereinafter termed "FL"), described by Lyman S. D. et al., (Blood 83, 2795-2801, 1994, "Cloning of the human homologue of the murine Flt3L: A growth factor for early hematopoietic progenitor cells) and Maraskovsky E. et al., (J. Exp. Med. 184, 1953-1962, 1996) or GM-CSF, for example. The examples show that in vivo stimulation of natural immunity (and thus the activity of NK cells) is obtained after daily injection of Flt3L. The results shown also demonstrate that this injection produced an increase in the absolute number of in situ NK cells, and induced anti-tumoral effects, which were dependent on lymphoid dendritic cells and the B7/CD28 interaction and an IFN.gamma. in vivo. As indicated below, the FL compound can also advantageously be associated with the dendritic cell triggering factor.

This implementation thus constitutes a further particularly effective approach to increasing the cytolytic activity of NK cells in vivo. This approach can advantageously be associated with in vivo co-administration of a NK cell growth factor.

The invention thus also concerns the use of dendritic cells for the preparation of a composition intended to activate NK cells in vivo. The invention also concerns the use of dendritic cells to prepare a composition intended to activate the cytolytic activity of NK cells in vivo and the production of IFN.gamma. and/or TNF.alpha. by activated NK cells. As indicated above, the dendritic cells used are mature or immature, autologous or allogenic cells, in particular triggered cells. Further, they may also be dendritic cells sensitised to one or more antigens.

The invention also concerns a dendritic cell growth factor for the preparation of a composition intended to activate NK cells in vivo and for the preparation of a composition intended to activate the cytolytic activity of NK cells in vivo. The growth factor is preferably FL. The growth factor can advantageously be associated with the dendritic cell triggering factor in vivo.

The invention also concerns the use of a proteic factor, or more generally a biological factor, for triggering dendritic cells to directly activate NK cells in vivo, optionally in association with a dendritic cell growth factor and/or one or more chemokines or cytokines.

In a particular implementation of the method of the invention, the number of dendritic cells is increased in vivo either by in vivo administration, under the conditions described above, of dendritic cells triggered in vivo as described above (passive transfer) or also by in vivo administration of one or more dendritic cell growth factors and one or more dendritic cell triggering factors. This implementation can improve the efficacy of NK cell activation in vivo, provided that the cells or compounds administered can produce high levels of triggered dendritic cells in vivo.

In this respect, the invention also concerns a composition comprising at least one dendritic cell triggering factor and a dendritic cell growth factor, as described above, for their simultaneous, separate or time delayed use. More particularly, such a composition comprises FL and a preparation derived from fibroblasts comprising a soluble triggering factor. More particularly still, it comprises a recombinant soluble factor. The invention also concerns the use of such a composition for preparing a composition intended to activate NK cells in vivo and for preparing a composition intended to activate the cytolytic activity of NK cells in vivo. For use, these compounds can be packaged in any suitable medium (saline solutions, buffers, etc.), preferably isotonic, and in any apparatus known to the skilled person (ampule, flask, tube, syringe, pouch, etc.).

Preparation of Resting NK Cells

NK cells can be obtained for the present invention using different techniques which are known to the skilled person. More particularly, these cells can be obtained by different isolation and enrichment methods using peripheral blood mononuclear cells (lymphoprep, leucapheresis, etc.). Thus these cells can be prepared by Percoll density gradients (Timonen et al., J. Immunol. Methods 51 (1982) 269), by negative depletion methods (Zarling et al., J. Immunol. 127 (1981) 2575) or by FACS sorting methods (Lanier et al., J. Immunol. 131 (1983) 1789). These cells can also be isolated by column immunoadsorption using an avidine-biotin system (Handgretinger et al., J. Clin. Lab. Anal. 8 (1994) 443) or by immunoselection using microbeads grafted with antibodies (Geiselhart et al., Nat. Immun. 15 (1996-97) 227). It is also possible to use combinations of these different techniques, optionally combined with plastic adherence methods.

These different techniques can produce cell populations which are highly enriched in resting NK cells, preferably comprising more than 70% of resting NK cells. More preferably, the NK cell populations used to carry out the invention generally comprise more than 30% of NK cells, advantageously more than 50%. The purity of the cell populations can be improved if necessary using specific antibodies such as anti-CD56 antibodies and/or anti-CD16 antibodies and/or anti-CD3 antibodies (depletion).

The NK cells can be preserved in a culture medium in a frozen form for subsequent use. Advantageously, the NK cells are prepared extemporaneously, i.e., they are used for activation after production.

Preparation of Dendritic Cells

The dendritic cells used in the present invention can be prepared using different techniques. These cells can be immature or mature, autologous or allogenic, naive or sensitised to one or more particular antigens, preferably triggered. Further, the dendritic cells used can be cell cultures enriched in dendritic cells, or cell cultures comprising essentially dendritic cells. Advantageously, they are human dendritic cells.

The preparation of dendritic cells has been well documented in the literature. Thus it is known that these cells can be prepared from hematopoietic stem cells or from monocyte precursors, or they can be directly isolated in a differentiated form (review by Hart, Blood 90 (1997) 3245).

The production of dendritic cells from stem cells is illustrated, for example, by Inaba et al., (J. Exp. Med. 176 (1992) 1693) for the mouse, and by Caux et al., (Nature 360 (1992) 258) or Bernhard et al. (Cancer Res. 55 (1995) 1099) for man. These studies show that dendritic cells can be produced by culturing bone marrow in the presence of Granocyte-Macrophage Colony Stimulation Factor (GM-CSF) or, more precisely, from hematopoietic stem cells (CD34+) by culture in the presence of a combination of cytokines (GM-CSF+TNF.alpha.+IL-3 and IL-4 or CD40L).

The production of dendritic cells from monocyte precursors is illustrated, for example, by Romani et al. (J. Exp. Med. 180 (1994) 83), Sallusto et al. (J. Exp. Med. 179 (1994) 1109), Inaba et al. (J. Exp. Med. 175 (1992) 1157) or Jansen et al. (J. Exp. Med. 170 (1989) 577). These methodologies are essentially based on removing mononuclear cells from blood and culturing them in the presence of different combinations of cytokines. A particular method consists of treating monocyte blood precursors in the presence of combinations of cytokines such as interleukin-4+GM-CSF or interleukin-13+GM-CSF, for example. This technique is also illustrated by Mayordomo et al., 1995 (rat). Further, it is also possible to treat monocyte precursors with pharmacological cell differentiation agents, such as calcium channel activators or CD40L directly.

A further approach for producing dendritic cells consists of isolating dendritic cells which have already differentiated from biological samples. This approach has been described, for example, by Hsu et al. (Nature Medicine 2 (1996) 52). The methodology described by this team essentially consists of harvesting samples of peripheral blood and treating them with different gradients and centrifugations to extract dendritic cells.

The preferred methodology used in the present invention is based on the production of dendritic cells from monocyte precursors or bone marrow. These methodologies are illustrated in the examples. More particularly, the present invention preferably uses dendritic cells obtained by treating monocyte precursors (contained in blood or marrow) in the presence of a GM-CSF+IL-4 or GM-CSF+IL-13 combination.

As indicated above, to implement the present invention, it is possible to use a population of dendritic cells comprising immature and/or mature dendritic cells. Advantageously, a population of dendritic cells principally composed (i.e., at least 60%, preferably 70%) of immature dendritic cells, preferably triggered, is used. The immature state of dendritic cells corresponds to an early stage in their development, in which they have a high endocytic activity and express low levels of class I and II MHC molecules and lymphocytary co-simulation molecules on their surface.

Further, within the context of the present invention it is also possible to use dendritic cell lines. They may be immortalised dendritic cells produced, for example, by introducing an oncogene into dendritic cells. A murine example of such a line may be the following lines described in the prior art: D1 line (Winzler et al., J. Exp. Med. 185, 317-328, 1997), XS line (A. Takashima et al., J. Immunol 1995; Vol 154: 5128-5135), tsDC line (Volkmann et al., Eur. J. Immunol. 26: 2565-72, 1996). The importance of using dendritic cell lines is based on the constitution of "universal" cell banks used commercially to activate populations of allogenic NK cells from different subjects. In this implementation, the line is preferably maintained in 30% triggering medium or with an optimum concentration of triggering factor.

When dendritic cells are prepared, they can be maintained in culture, further purified, stored or used directly to implement the present invention (in vitro, ex vivo or in vivo activation of NK cells, production of acellular extracts, dexosomes, producing a membrane stimulation factor, etc). Further, prior to their use to activate NK cells, the prepared dendritic cells can be sensitised to an antigen or a group of antigens. The presence of antigenic moieties on the dendritic cell surface can improve (by cross-priming) or inhibit (in a KIR mode) their immunogenic activity (acquired immunity) in particular in in vivo use.

In this respect, different techniques can be used to sensitise dendritic cells to antigens. In particular, these techniques are:

Bringing dendritic cells into contact with antigenic peptides ("peptide pulsing"). This approach consists of incubating dendritic cells, for a variable period (generally 30 minutes to about 5 hours) with one or more antigenic peptides, i.e., with a peptide from an antigen, such as could result from treating said antigen with a cell presenting the antigen. This type of approach has been described, for example, for antigenic peptides of the HIV virus, influenza virus or HPV or for peptides derived from Muc-1, Mart, Her2/Neu antigens, for example (Macatonia et al., J. Exp. Med. 169 (1989) 1255; Takahashi et al., Int. Immunol. 5 (1993) 849; Porgador and Gilboa, J. Exp. Med. 182 (1995) 255; Ossevoort et al., J. Immunother. 18 (1995) 85; Mayordomo et al., cited above; Mehta-Damani et al., J. Immunol. (1994) 996). It is also possible to incubate dendritic cells with an acidic peptide eluate of a tumoral cell using the methodology described by Zitvogel et al. (1996, cited above).

Bringing dendritic cells into contact with one or more antigens ("antigen pulsing"). This approach consists of incubating dendritic cells not with one or more antigenic peptides, but with the intact antigens. The importance of this technique is based on the fact that the antigen will be transformed into antigenic peptides by natural mechanisms in the dendritic cells, such that the resulting antigenic peptides presented by the dendritic cell should provide better immunogenicity. This approach has been illustrated, for example, by Inaba et al. (J. Exp. Med. 172 (1990) 631) or Hsu et al., (Nature Medicine 2 (1996) 52).

Bringing dendritic cells into contact with one or more antigenic proteic complexes. This approach is similar to the preceding approach but can improve the efficiency of transformation and/or of presentation of the antigen. In particular, the antigen can be used in a soluble form or complexed with targeting elements, in particular to target membranous receptors such as mannose receptors or immunoglobulin receptors (RFc) (immune complexes). It is also possible to render the antigen particulate so as to improve its penetration or its phagocytosis by the cells.

Bringing dendritic cells into contact with cells (hybridoma-like fusion) or membranes, lysates or sonicates of cells expressing antigens or antigenic peptides. This technique is based on direct transfer of antigens or antigenic peptides by fusion of cells or cell membranes. This approach has been illustrated, for example, by fusion between dendritic cells and membranes of tumour cells (Zou et al., Cancer Immunol. Immunother. 15 (1992) 1, and Gilboa, cited above).

Bringing dendritic cells into contact with membranous vesicles containing antigens of antigenic peptides (in particular exosomes of tumour cells such as those described above). This approach for sensitising dendritic cells using exosomes, such as is shown in the present invention, is particularly advantageous in that it does not require a knowledge of particular antigens and where the loaded antigenic peptides are in a native conformation. The technology has been illustrated in the examples.

Bringing dendritic cells into contact with liposomes containing antigens or antigenic peptides (Nair et al., J. Exp. Med. 175 (1992) 609).

Bringing dendritic cells into contact with RNAs coding for antigens or antigenic peptides, (see Boczkowsky et al., 1996, cited above).

Bringing dendritic cells into contact with DNAs coding for antigens or antigenic peptides or nucleic acid sequences coupled to proteic antigens (optionally incorporated into plasmid, viral or chemical type vectors). Thus one method of sensitising dendritic cells consists, for example, of infecting dendritic cells with a virus against which protection is desired. This has been described, for example, for the influenza virus (Bhardwaj et al., J. Clin. Invest. 94 (1994) 797; Macatonia et al., cited above). A further approach consists of delivering, using a virus or other nucleic acid transfer vectors, a DNA coding for the antigens or antigenic peptides of interest. Such an approach has been illustrated, for example, by Arthur et al., (Cancer Gene Therapy, 1995) or by Alijagie et al. (Eur. J. Immunol. 25 (1995) 3100). Certain viruses such as adenovirus, AAV or retroviruses appear to be able to be used to this end, to deliver a nucleic acid into a dendritic cell.

Applications

The invention also concerns the use of the methods, cells and compositions described above, in particular in the fields of immunology, immunotherapy or medical biotechnology. As indicated above, these uses are multifold, both in vitro and in vivo, to control the activity of NK cells. Such applications are in particular the treatment of different disorders such as cancers of infectious diseases, in particular viral diseases, or other pathogens, autoimmune diseases, disorders linked to transplantation (graft rejection, GVHD), congenital disorders (deficits in the interferon receptor or interleukin-12 receptor, for example), etc. The methods, cells and compositions of the invention are in particular used to retard the growth, or even to suppress tumours (in particular tumours with low expression of class I MHC molecules) or other pathological cells. For this type of application, as indicated above, cell compositions (activated NK cells, NK/DC co-cultures or dendritic cells) can be administered loco-regionally, preferably by subcutaneous or systemic injection. The cell doses are indicated above and in the experimental section below. The invention can also be used in vitro to treat cell preparations, in particular to destroy cells sensitive to NK cells. The invention can also be used in combination or as an adjuvant for immunisations based on the development of a specific cytotoxic T lymphocyte antigen activity. The invention further concerns the use of dendritic cells or a membranous factor of dendritic cells to increase survival of NK lymphocyte populations in vitro, ex vivo or in vivo, and to increase, if necessary, the proliferation of NK lymphocyte sub-populations. The invention also concerns the use of NK cells or a membranous factor of NK cells to increase the survival rate of mature dendritic cells in vitro, ex vivo or in vivo.

Claim 1 of 15 Claims

What is claimed is:

1. A method for producing activated natural killer (NK) cells in vitro or ex vivo, the method comprising bringing an enriched population of resting NK cells into contact with mature or triggered dendritic cells in vitro or ex vivo, under conditions allowing activation of said resting NK cells by said mature or triggered dendritic cells, thereby producing activated NK cells


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