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Title:  Method for limiting the growth of cancer cells using an attenuated measles virus
United States Patent: 
7,393,527
Issued: 
July 1, 2008

Inventors:
 Russell; Stephen James (Rochester, MN), Fielding; Adele (Rochester, MN), Peng; Kah-Whye (Rochester, MN), Grote; Deanna (Rochester, MN)
Assignee:
  Mayo Foundation for Medical Education and Research (Rochester, MN)
Appl. No.:
 11/532,879
Filed:
 September 18, 2006


 

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Abstract

A method for treating cancer cells is provided comprising directly or systemically administering a therapeutically effective dose of an attenuated measles virus. In one embodiment, the therapeutically effective dose is from about 10.sup.3 pfus to about 10.sup.12 pfus and is delivered by direct injection into a group of cancer cells or via intravenous injection.

Description of the Invention

SUMMARY OF THE INVENTION

The invention provides a means to limit the growth of cancer cells simply and effectively using a form of measles virus typically found in vaccines, e.g., an attenuated measles virus. By directly administering a therapeutically effective dose of attenuated measles virus into a site of cancer cell growth (e.g., intratumorally) or by administering the virus systemically (e.g., intraveneously), the growth of cancer cells is limited.

In one embodiment of the invention, a therapeutically effective dose of attenuated measles virus is administered directly to a group of cancer cells (e.g., a tumor) by injection. In another embodiment of the invention, the therapeutically effective dose is administered directly to a group of cancer cells by implanting a source of attenuated measles virus in proximity to, or within, a group of cancer cells. In this embodiment, the source of attenuated measles virus is a formulation comprising an effective dose of attenuated measles virus and an excipient. Degradation of the excipient by bodily fluids brings the virus into contact with the tumor cells. The therapeutically effective dose can either be provided continuously to the patient or in pulsed doses.

In another embodiment of the invention, the therapeutically effective dose is administered systemically to a patient intravenously, such as by injection or through a medical access device such as a catheter.

In one embodiment according to the invention, the therapeutically effective dose is a dose of about 10.sup.3 to about 10.sup.12 pfu. In another embodiment of the invention, the therapeutically effective dose is greater than about 10.sup.3 pfu. In a further embodiment of the invention, the therapeutically effective dose is about 10.sup.5 pfus, 10.sup.6 pfus, 10.sup.7 pfus, or 10.sup.8 pfus. In one embodiment of the invention, the therapeutically effective amount of attenuated measles virus is an amount effective to cause a reduction in the number of cancer cells in a patient or regression of a tumor is a patient relative to the size of the group of cancer cells or tumor prior to administration of the virus.

In another embodiment of the invention, the therapeutically effective dose of attenuated measles virus is provided in a composition comprising attenuated measles virus, an attenuated mumps virus, and an attenuated rubella virus. In a further embodiment of the invention, the attenuated measles virus is provided in a composition comprising an attenuated rubella virus.

In one embodiment of the invention, the attenuated measles virus is genetically modified to express a marker polypeptide (e.g., .beta.-galactosidase or Green Fluorescent Protein (GFP)) whose expression correlates with the replication of the virus. In another embodiment of the invention, the marker polypeptide is detectable in a bodily fluid obtained from the patient.

In one embodiment of the invention, the method is used to limit the growth of cancer cells which are selected from the group consisting of melanoma, carcinoma, glioma, myeloma cells, and combinations thereof. In another embodiment of the invention, the myeloma cells are lymphoma cells. In still another embodiment of the invention, the lymphoma cells are Non-Hodgkin's Lymphoma cells.

DETAILED DESCRIPTION

Measles virus is a negative strand RNA virus whose genome encodes six protein products, the N (nucleocapsid), P (polymerase cofactor phosphoprotein), M (matrix), F (fusion), H (hemaglutinin) and L (large RNA polymerase) proteins. The H protein is a surface glycoprotein which mediates measles virus attachment to its receptor, CD46 (Dorig, et al., Cell 75: 295-305, 1993). The F protein is responsible for cell-cell fusion after viral attachment has taken place. Measles virus has a natural tropism for lymphoid cells and, in particular, cancerous lymphoid cells.

The tumor selectivity of the virus is due to intracellular restrictions to the life cycle of the virus that is strongly inhibitory to virus propagation in nontransformed cells, but which are overriden by cellular factors present in neoplastic cells (Robbins, et al., Virology 106: 317-326, 1980; Robbins, Intervirology 32: 204-208, 1991). Measles infectivity of lymphoid cells causes a very characteristic cytopathic effect. Multinucleated giant cells develop during measles virus replication in lymph nodes as a result of gross cell-cell fusion (Warthin, Arch. Pathol. 11: 864-874, 1931). In tissue culture, infection with measles virus can cause fusion of a whole monolayer of cells. The F and H antigens are found on the surface of infected cells. Thus, cells which are infected by measles virus and whose membranes express F and H proteins become highly fusogenic and can cause fusion not only of other infected cells but also of neighboring cells which are not infected (Norrby and Oxman, "Measles Virus." In Virology, 1990, B. N. Fields, et al., eds. New York, Raven Press, Ltd., pp 1013-1044). The expression of viral antigens on the surface of a tumor cell can also mediate a tumor specific immune response.

The method according to the invention comprises administering an effective dose of an attenuated measles virus directly at a site of cancer cell growth (e.g., by intratumoral injection), or systemically (e.g., through intravenous injection), to limit and/or reduce the amount of cancer cells in a patient.

Producing Attenuated Vaccine Strains of Measles.

In one embodiment of the invention, an attenuated strain of virus is grown in culture to provide an effective dose which will limit and/or cause regression of a group of cancer cells such as a tumor. Attenuated strains of viruses are obtained by serial passage of the virus in cell culture (e.g., in non-human cells), until a virus is identified which immunogenic but not pathogenic. While wild type virus will cause fatal infection in marmosets, vaccine strains do not. In humans, infection with wild type viral strains is not generally fatal but is associated with classic measles disease. Classic measles disease includes a latent period of 10-14 days, followed by a syndrome of fever, coryza, cough, and conjunctivitis, followed by the appearance of a maculopapular rash and Koplik's spots (small, red, irregularly shaped spots with blue-white centers found inside the mouth). The onset of the rash coincides with the appearance of an immune response and the initiation of virus clearance. In contrast, individuals receiving an attenuated measles virus vaccine do not display classical measles symptoms. Attenuation is associated with decreased viral replication (as measured in vivo by inability to cause measles in monkeys), diminished viremia, and failure to induce cytopathological effects in tissues (e.g., cell-cell fusion, multinucleated cells). However, these biological changes have not been mapped to any single genetic change in the virus genome.

In a preferred embodiment of the invention, an attenuated strain of measles virus which has been clinically tested as a vaccine for measles infection is used to provide an effective dose which will limit and/or cause regression of a group of cancer cells, such as a tumor. The Moraten attenuated form of the virus has been used world-wide as a vaccine and has an excellent safety record (Hilleman, et al., J. Am. Med. Assoc. 206: 587-590, 1968). Accordingly, in one embodiment of the invention, the Moraten strain is used to provide an effective dose. The Moraten vaccine is commercially available from Merck.RTM. and is provided lyophilized in a vial which when reconstituted to 0.5 ml comprises 10.sup.3 pfu/ml. A vaccine against the Moraten Berna strain is available from the Swiss Serum Vaccine Institute Berne.

In a further embodiment of the invention, the Edmonston-B vaccine strain of measles virus is used (MV-Edm) (Enders and Peebles, Proc. Soc. Exp. Biol. Med. 86: 277-286, 1954). MV-Edm grows efficiently in tumor cells but its growth is severely restricted in primary cultures of human peripheral blood mononuclear cells, normal dermal fibroblasts, and vascular smooth muscle cells. A form of the Enders attenuated Edmonston strain is available commercially from Merck (Attenuvax.RTM.). Other attenuated measles virus strains are also encompassed within the scope of the invention, such as Leningrad-16, and Moscow-5 strains (Sinitsyna, et al., Res. Virol. 141(5): 517-31, 1990), Schwarz strain (Fourrier, et al., Pediatrie 24(1): 97-8, 1969), 9301B strain (Takeda, et al. J. VIROL. 72/11: 8690-8696), the AIK-C strain (Takehara, et al., Virus Res 26 (2): 167-75, 1992 November), and those described in Schneider-Shaulies, et al., PNAS 92(2): 3943-7, 1995, the entireties of which are incorporated by reference herein.

In a further embodiment of the invention, the measles virus is provided in a composition comprising a mixture of attenuated oncolytic viruses. In one embodiment, the mumps measles and rubella vaccine (MMR) is used. The MMR vaccine was introduced into the United States in 1972 and into the United Kingdom in 1998. Commercially available preparations of the MMR vaccine is obtainable from Merck, Pasterur Merieux Connaught, or SmithKline Beecham, and also contain the Moraten strain of attenuated measles virus at a minimum titer of 10.sup.3 PFU/ml. In still a further embodiment of the invention, the measles virus is provided in a composition comprising Edmonston Zagreb measles strain (an attenuated strain obtained from the Edmonston-enders stain) and the Wistar RA 27/3 strain of rubella (Swiss Serum Vaccine Institute Berne). It should be apparent to those of skill in the art that any clinically tested measles vaccine is acceptable for use in the invention, and is encompassed within the scope of the invention.

In one embodiment of the invention, an effective dose of an attenuated measles virus is produced by infecting a primary cell or a continuous cell line with a starting innoculum of an stock comprising an attenuated Moraten strain of measles virus (or an innoculum of an MMR stock) or the MV-Edm strain or any of the other strains described above and expanding the virus after serial passage. Cells or cell lines encompassed within the scope of the invention include, but are not limited to, monkey kidney or testes cells or monkey cell lines (e.g., Vero, KB, CV-1, BSC-1, and the like). Viral replication in cells is observed as cell-cell fusion and syncytia formation.

The attenuated measles virus is expanded until a desired dose concentration is obtained in standard cell culture media (e.g., DMEM or RPMT-1640 supplemented with 5-10% fetal bovine serum at 37.degree. C. in 5% CO.sub.2). In one embodiment of the invention, the therapeutically effective dose concentration is about 10.sup.3 to 10.sup.12 pfu. In another embodiment of the invention, the concentration is about 10.sup.5 to 10.sup.8 pfu. Viral titer is assayed by inoculating cells (e.g., Vero cells) in culture dishes (e.g., such as 35 mm dishes). After 2-3 hours of viral adsorption, the inoculum is removed and cells are overlaid with a mixture of cell culture medium and agarose or methylcellulose (e.g., 2 ml DMEM containing 5% FCS and 1% SeaPlaque agarose). After about 3 to about 5 days, cultures are fixed with 1 ml of 10% trifluoroacetic acid for about 1 hour, then UV cross-linked for 30 minutes. After removal of the agarose overlay, cell monolayers are stained with crystal violet and plaques are counted to determine viral titer. Virus is harvested from cell syncytia by scraping cells from the dishes, subjecting them to freeze/thawing (e.g., approximately two rounds), and centrifuging. The cleared supernatants represent "plaque purified" virus.

Viral stocks are produced by infection of cell monolayers (e.g., adsorption for about 1.5 hours at 37.degree. C.), followed by scraping of infected cells into a suitable medium (e.g., Opti-MEM, Gibco-BRL) and freeze/thaw lysis (e.g., 2 rounds). Viral stocks are aliquoted, frozen and stored at 70.degree. C.-80.degree. C. and can be stored at concentrations higher than the therapeutically effective dose. In one embodiment of the invention, the viral stock is stored in a stabilizing solution. Stabilizing solutions are known in the art and include, for example, sugars (e.g., trehalose, dextrose, glucose), amino acids, glycerol, gelatin, monosodium glutamate, Ca.sup.2+ and Mg.sup.2+. Suitable stabilizing solutions are described in U.S. Pat. No. 4,985,244, and U.S. Pat. No. 4,500,512, the entireties of which are incorporated by reference herein.

In another embodiment of the invention, an attenuated measles virus strain is generated from a primary measles strain. In this embodiment, a primary measles virus is isolated by inoculating a cell line with peripheral blood leukocytes or respiratory secretions from a patient. Suitable cells and cell lines include, but are not limited to, primary human cells (e.g., blood, lung, conjunctiva, kidney, intestine, anion, skin, muscle, thymic stroma, foreskin, and uterus), human cell lines (e.g., Wi-38, MRC-5, Hep-2, HeLa, A549), primary monkey cells (e.g., kidneys, and testes), and monkey cell lines (e.g., Vero, KB, CV-1, and BSC-1), and the Epstein-Barr virus-transformed marmoset B lymphocyte cell line (B95-8).

Cells are passaged until propagation of wild-type virus and production of cytopathic effects can be detected in tissue culture, such as cell-cell fusion and syncytia formation. In one embodiment of the invention, viral stocks are prepared using a low multiplicity of infection to avoid the accumulation of defective particles. Plaques become visible after about 3 to five days of culture, and the virus is allowed to continue to replicate until a desired concentration is reached. Viral titers are determined as described above.

Once a primary measles virus is isolated in culture, it serially passaged in a non-human cell line. The Edmonston strain was produced by Enders as a result of successive series of passages through human kidney tissue culture, human andiron tissue culture, embryonated eggs and chick embryo tissue culture. Clones of measles virus obtained in the last culture passage and suspensions of viruses are obtained and purified by centrifugation or filtration to completely remove any culture cells. Attenuated virus suspensions with desired properties are selected (e.g., high infectivity, high immunogenicity, and low pathogenicity).

The infectivity of an attenuated virus suspension is determined by determining a dilution of virus that produces cytopathic effects (cell-cell fusion and syncytia formation observed microscopically) in at least 50% of cultured cells (e.g., 5 out of 10 test tubes comprising 5 ml cultures of Vero cell sheets). In one embodiment of the invention, an attenuated virus suspension is selected which causes cytopathic effects in 50% of infected Vero cells at at least a 10.sup.3-fold dilution (i.e., having a TCID.sub.50 of 3) (see "Review of Medical Microbiology", 13th ed., pp. 344-345, Lange Medical Publications, 1976).

The immunogenicity of an attenuated virus suspension is determined by evaluating seroconversion in monkeys after injection with the virus. Seroconversion is measured by determining the levels of antibody before and after immunization (% of increase in the amount of a specific antibody). In one embodiment of the invention, an attenuated vaccine produces about 70% to 100% seroconversion approximately 2 months after injection.

Low pathogenicity and decreased replication efficiency is determined by evaluating the appearance of classic measles symptoms in monkeys (see, e.g., Kobune, et al., Lab Anim. Sci. 46 (3): 315-20,1996). In one embodiment of the invention, an attenuated measles virus suspension is selected which does not produce classical measles in monkeys (e.g., within a month). Although measles can be viewed as a continuum of symptoms (fever, coryza, cough, and conjunctivitis, followed by the appearance of a rash and Koplik's spots), symptoms that are generally the same as the adverse effects observed with the Attenuvax.RTM. vaccine are not considered "measles," in this embodiment of the experiment. Thus symptoms such as moderate to high fever lasting 1-2 days, a rash lasting 1-2 days, cough and rhinitis, and/or erythma multiforme (skin rash) would not cause a monkey to be identified as having measles. In one embodiment, the classification of a monkey as having measles is dependent on the appearance of Koplik's spots.

In additional embodiments, properties such as thermosensitivity can be selected (see, e.g., U.S. Pat. No. 4,211,843, U.S. Pat. No. 4,071,618 and U.S. Pat. No. 3,133,861, the entirety of which is incorporated by reference herein). Non-human cell lines according to the invention include, but are not limited to chick embryos, quail embryos, duck embryos, and dog and bovine kidney cells.

In still a further embodiment of the invention, recombinant measles viruses comprising genetic modifications are derived from wild type measles virus to generate attenuated viruses, e.g., viruses having high immunogenicity (as measured by 70-100% seroconversion) and no pathogenicity (e.g., not producing classical measles symptoms, as discussed above). In one embodiment of the invention, genetic modifications are introduced through random mutagenesis of a plasmid comprising the sequence of a wild type measles virus. Sequences of wild type isolates are disclosed in U.S. Pat. No. 5,578,448, the entirety of which is enclosed herein by reference.

In another embodiment of the invention, particular cistrons in the measles virus genome are targeted to modify genes whose expression is associated with attenuation (Schneider-Shaulies, et at. PNAS 92(2): 3943-7, 1995; Takeda, et al. J. Virol. 1998 72/11 (8690-8696)). Thus, in one embodiment of the invention, a recombinant measles virus strain is generated comprising a single point mutation or multiple non-contiguous point mutations in any of an H protein, a V protein, a C protein, and combinations thereof. In still a further embodiment of the invention, natural variants of the wild type or attenuated measles viruses are identified (e.g., such as from cultures of virus from infected patients) which have at least one point mutation in their genome.

Methods of Treating Cancer Using Attenuated Measles Vaccine:

Dosage, Administration and Pharmaceutical Formulation

Attenuated measles virus when used to immunize against measles is typically injected in a single 10.sup.3 dose subcutaneously or intramuscularly. The MMR vaccine is typically administered twice at the same dose, and is also administered subcutaneously or intramuscularly.

In one embodiment according to the invention, attenuated measles virus is injected either directly into a group of cancer cells (e.g., a tumor) or is delivered intravenously to cancer cells. Types of cancer cells susceptible to treatment with attenuated measles or MMR include neuronal cells, glial cells, myelomonocytic cells, and the like. Types of cancer treatable by the method according to the invention, include, but are not limited to, myeloma, melanoma, glioma, and breast carcinoma. In one embodiment of the invention, the attenuated measles virus is used to limit or cause regression of lymphomas. In still a further embodiment of the invention, the attenuated measles virus is used to limit or cause the regression of cancer cells in a patient with Non-Hodgkin's Lymphoma. In one embodiment of the invention, direct delivery into one type of cancer cells (e.g., a lymphoma) is used to reduce or limit the growth of a different type of cancer (e.g., a carcinoma).

In one embodiment, the attenuated measles virus is administered to the patient in a biologically compatible solution or a pharmaceutically acceptable delivery vehicle, by administration either directly into a group of cancer cells (e.g., intratumorally) or systemically (e.g., intravenously). Suitable pharmaceutical formulations, in part, depend upon the use or the route of entry, for example transdermal, or by injection. Such forms should not prevent the composition or formulation from reaching a target cell (i.e., a cell to which the virus is desired to be delivered to) or exerting its effect. For example, pharmacological compositions injected into the blood stream should be soluble.

While dosages administered will vary from patient to patient (e.g., depending upon the size of a tumor), a "therapeutically effective dose" will be determined by setting as a lower limit, the concentration of virus proven to be safe as a vaccine (e.g., 10.sup.3 pfu) and escalating to higher doses of up to 10.sup.12 pfu, while monitoring for a reduction in cancer cell growth along with the presence of any deleterious side effects. A therapeutically effective dose will be that dose which provides at least a 10% reduction in the number of cancer cells or in tumor size and can be detected in the circulation by detection of an antigen and correlation of the antigen to the presence of the cancer cell. Escalating dose studies are routine in the art (see, e.g., Nies and Spielberg, "Principles of Therapeutics," In Goodman & Gilman's The Pharmacological Basis of Therapeutics, eds. Hardman, et al., McGraw-Hill, NY, 1996, pp 43-62).

In preferred embodiments of the invention, a composition comprising an attenuated measles virus is delivered in a therapeutically effective dose in the range of from about 10.sup.3 pfu to about 10.sup.12 pfu. In one embodiment of the invention, the dose range is 10.sup.5 to 10.sup.7 pfu. In some embodiments, the therapeutically effective dose is provided in repeated doses. Repeat dosing is appropriate in cases in which observations of clinical symptoms or tumor size or monitoring assays indicate either that a group of cancer cells or tumor has stopped shrinking or that the degree of viral activity is declining while the tumor is still present. Repeat doses (using the same, or further modified virus) can be administered by the same route as initially used or by another route. A therapeutically effective dose can be delivered in several discrete doses (e.g., days or weeks apart) and in one embodiment of the invention, one to about twelve doses are provided. Alternatively, a therapeutically effective dose of attenuated measles virus is delivered by a sustained release formulation.

Devices for providing sustained release formulations are known in the art, and generally include a polymeric excipient (e.g., a swellable or non-swellable gel, or collagen) which is implanted at a site of drug delivery, and from which drug is gradually dispensed over time as a continuous or pulsed dose (see, e.g., U.S. Pat. No. 5,980,508, U.S. Pat. No. 5,001,692, and U.S. Pat. No. 5,137,727, the entireties of which are incorporated by reference herein). In one embodiment of the invention, a therapeutically effective dose of attenuated measles virus is provided within a polymeric excipient and the excipient/virus composition is implanted at a site of cancer cells (e.g., in proximity to, or within a tumor). In this embodiment, the action of body fluids gradually dissolves the excipient and continuously releases the effective dose of measles virus over a period of time. In another embodiment, a sustained release device which comprises a series of alternating active and spacer layers is implanted at a site of cancer cells. In this embodiment, each active layer of the device comprises a dose of attenuated virus embedded in excipient, while each spacer layer comprises only excipient or low concentrations of virus (i.e., lower than the effective dose). As each successive layer of the device dissolves, pulsed doses of attenuated measles virus are delivered. The size/formulation of the spacer layers determines the time interval between doses and is optimized according to the therapeutic regimen being used.

Direct administration can be performed according to any of a number of methods routinely practiced in the art. In one embodiment of the invention, a tumor which is palpable through the skin (e.g., such as a lymphoma) is injected directly with attenuated measles virus through the skin (e.g., using ultrasound guidance). In another embodiment of the invention, direct administration occurs via a catheter line or other medical access device and is used in conjunction with an imaging system (see, e.g., U.S. Pat. No. 6,095,976; U.S. Pat. No. 6,026,316; and U.S. Pat. No. 5,713,858) to localize a group of cancer cells. In this embodiment, an implantable dosing device is placed in proximity to the group of cancer cells using a guidewire inserted into the medical access device. In still another embodiment of the invention, an effective dose is directly administered to a group of cancer cells visible in an exposed surgical field.

In another embodiment of the invention, the attenuated measles virus is delivered systemically. In one embodiment, the attenuated measles virus is delivered intravenously via injection or via an intravenous delivery device designed for administration of multiple doses of a medicament. Such devices include, but are not limited to, winged infusion needles, peripheral intravenous catheters, midline catheters, peripherally inserted central catheters (PICC), and surgically placed catheters or ports (see, e.g., U.S. Pat. No. 6,012,034). Peripheral intravenous catheters and winged infusion needles are inserted into a small peripheral vein in the lower arms and hands. With peripheral intravenous catheters, the entry site must be changed every few days or as required. Peripheral intravenous catheters are often used for short-term therapy and can also be used until a long-term access device can be inserted.

The course of therapy can be monitored by evaluating changes in clinical symptoms (known in the art for each particular type of cancer) or by direct monitoring of the size of a group of cancer cells or tumor. Viral therapy using an attenuated measles viruses is effective if tumor size and/or clinical symptoms are reduced following administration of virus. In one embodiment of the invention, the method effects at least a 10% reduction in the size of a group of cancer cells within a given time period, such as one to four weeks. In further embodiments of the invention, the method effects reductions of 25%, 50% 75% and up to about 100%.

Reduction in size in a group of cancer cells or tumor cells is measured, as discussed above, either directly, using calipers, or by using imaging techniques (e.g., X-ray, magnetic resonance imaging, or computerized tomography) or from the assessment of non-imaging optical data (e.g., spectral data). Reduction in the levels of a cancer specific antigen in a patient can alternatively, or additionally, be monitored. Cancer specific antigens include, but are not limited to carcinoembryonic antigen (CEA), prostate specific antigen (PSA), prostatic acid phosphatase (PAP), CA 125, alpha-fetoprotein (AFP), carbohydrate antigen 15-3, and carbohydrate antigen 19-4. In this embodiment, an effective dose of attenuated measles virus is that which produces a reduction in levels of cancer specific antigens of at least 10%.

In a further embodiment of the invention, cytotoxic lymphocyte (CTL) responses to the tumor are measured to identify an increased tumor specific immune response after treatment. In this embodiment, a patient's T-cells are isolated and frozen both prior to administration of the attenuated measles virus and after treatment, when a group of cancer cells/tumor is biopsied. CTL responses are measured using methods routinely used in the art (e.g., U.S. Pat. No. 6,083,751 and Herin et al., Int. J. Cancer, 39:390-396 (1987)). In still a further embodiment of the invention, a biopsy of a patient's cancer cells/tumor before and after injection is monitored to determine alterations in the histology of the cancer cells/tumor such as cell-cell fusion and lysis. In this embodiment, an effective dose is one which causes at least one cell to have >20 nuclei. Any, or all, of these assays may be used to monitor the effectiveness of an attenuated measles vaccine.

In preferred embodiments of the invention, the vaccines are administered to patients who are not immunocompromised as determined by assessing immunoglobulin levels, absolute lymphocyte count, CD4:CD8 ratio and DTH and who also have a pre-existing measles virus immunity. Throughout the treatment, patients are monitored for the existence of any classical measles symptoms, and dosages are titrated accordingly, to minimize the presence of such symptoms.

Producing Attenuated Measles Virus Expressing Marker Polypeptides

Therapeutic effects of an attenuated measles virus can be correlated with levels of attenuated measles virus replication by measuring levels of viral protein and/or nucleic acids in cancer cells. However, a method which does not require the repeated isolation of tumor cells is preferred. In one embodiment of the invention, an attenuated strain of measles virus is genetically modified to provide a convenient means to measure viral replication. In this embodiment of the invention, a recombinant attenuated virus is modified by the insertion of a marker gene encoding a marker polypeptide within the viral genome.

In one embodiment of the invention, a marker gene encoding a marker polypeptide is inserted into a marker plasmid comprising the sequence of an attenuated measles virus genome but lacking cistrons encoding the membrane glycoproteins or the viral polymerase using standard cloning techniques well known in the art. Recombinant attenuated measles viruses are isolated (i.e., rescued) by co-transfecting a helper cell line with the mutagenized plasmid and a plasmid expressing the measles virus L polymerase. The L protein is expressed transiently, rather than stably, since high levels of L expression can impair the rescue of virus, while transient expression allows titration of the L protein as needed (Radecke, et al., 1995, the entirety of which is incorporated herein by reference). The helper cell line comprises cells (e.g., human embryonic kidney cells) stably expressing the wild type MV N and P measles proteins, i.e., providing the remaining functions of necessary for the virus to infect and replicate. The construction of an exemplary helper cell line (e.g., 293-3-6 cells) is described in Radecke, et al., 1995, supra.

After a suitable period of time following transfection (e.g., two days), cells are expanded into larger culture dishes (e.g., 90 mm dishes) and cultured (e.g., for another two days) before scraping and adsorption to cell monolayers. Infected Vero cells are monitored for syncytia formation, and syncytia are picked and propagated further, until a desired concentration is obtained (e.g., 10.sup.3-10.sup.8 pfu). Viral stocks are produced as described above.

Detection of Marker Polypeptides in a Patient

Detection of the marker polypeptide in a biological fluid sample obtained from a patient is correlated with the expression of viral proteins, and therefore with replication of the virus. The presence of the marker polypeptide in the biological fluid sample can be determined by any qualitative or quantitative method known in the art. Immunologic assays such as ELISA or radioimmunoassay provide specific, sensitive, and quantitative results, and are suitable for automation. Chromatographic methods such as HPLC, optionally combined with mass spectrometry, can also be used. Other analytic methods, include, but are not limited to, the use of specific color reagents, thin layer chromatography, electrophoresis, spectroscopy, nuclear magnetic resonance, and the like.

While it is generally preferred that the marker polypeptide itself be non-functional, i.e., that it not possess any significant biological activity which might interfere with the patient's physiology or therapy, in one embodiment, the marker polypeptide possesses an enzyme activity which can itself be quantified and used as the means of detecting the marker in a biological fluid sample.

Any number of marker polypeptides can be used so long as they are expressed at a level which is directly proportional with the level of viral replication in vivo. In one embodiment of the invention, the marker protein is a non-naturally occurring peptide (e.g., .beta.-galactosidase, Green Fluorescent Protein or GFB). In another embodiment of the invention; a natural marker polypeptide is used. When natural polypeptides are used, the background level of the polypeptide is determined prior to administration of the attenuated measles virus and is simply subtracted from the value determined after infection. Suitable marker polypeptides are disclosed in U.S. Provisional Application Ser. No. 60/155,873, the entirety of which is incorporated herein by reference.

The level of expression of the virus, and hence the amount of viral replication, can be correlated with the concentration of the marker polypeptide in a biological fluid sample. Determination of the relationship between an amount of marker polypeptide in a given biological fluid sample and the actual tissue level of an attenuated measles virus protein is performed by quantifying both the marker polypeptide and a viral protein product itself. In one embodiment of the invention, an infected tissue making the viral protein is extracted and the product is measured over a sufficient time period using HPLC, ELISA, a radioimmunoassay, a Western blot, or another suitable method. This permits a correlation to be made between the level of viral protein being expressed and the level of marker polypeptide detectable in the biological fluid (e.g., blood).

In one embodiment of the invention, the effective dose of attenuated measles virus is monitored by measuring the level of marker polypeptide in a patient's bodily fluid. In one embodiment of the invention, levels of marker protein are titrated against known effective doses which result in a desired therapeutic endpoint (e.g., 10% regression or reduction in the size of cancer cells or tumors or a 10% reduction in the level of a cancer specific antigen). In another embodiment, patients are monitored for levels of marker polypeptide associated with the desired therapeutic endpoint, and additional doses of attenuated measles virus are provided, as needed, to reach a level of marker polypeptide associated with the desired therapeutic endpoint.
 

Claim 1 of 23 Claims

1. A method for reducing the size of a tumor in a mammal having a tumor therein, comprising administering attenuated measles virus to said mammal under conditions wherein the size of a tumor in said mammal is reduced.

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