A transcutaneous immunization system delivers antigen to immune cells without perforation of the skin, and induces an immune response in an animal or human. The system uses an adjuvant, preferably an ADP-ribosylating exotoxin, to induce an antigen-specific immune response (e.g., humoral and/or cellular effectors) after transcutaneous application of a formulation containing antigen and adjuvant to intact skin of the animal or human. The efficiency of immunization may be enhanced by adding hydrating agents (e.g., liposomes), penetration enhancers, or occlusive dressings to the transcutaneous delivery system. This system may allow activation of Langerhans cells in the skin, migration of the Langerhans cells to lymph nodes, and antigen presentation.

DETAILED DESCRIPTION OF THE INVENTION

A transcutaneous immunization system delivers agents to specialized cells (e.g., antigen presentation cell, lymphocyte) that produce an immune response (Bos, 1997). These agents as a class are called antigens. Antigen may be composed of chemicals such as, for example, carbohydrate, glycolipid, glycoprotein, lipid, lipoprotein, phospholipid, polypeptide, conjugates thereof, or any other material known to induce an immune response. Antigen may be provided as a whole organism such as, for example, a bacterium or virion; antigen may be obtained from an extract or lysate, either from whole cells or membrane alone; or antigen may be chemically synthesized or produced by recombinant means.

Processes for preparing a pharmaceutical formulation are well-known in the art, whereby the antigen and adjuvant is combined with a pharmaceutically acceptable carrier vehicle. Suitable vehicles and their preparation are described, for example, in Remington's Pharmaceutical Sciences by E. W. Martin. Such formulations will contain an effective amount of the antigen and adjuvant together with a suitable amount of vehicle in order to prepare pharmaceutically acceptable compositions suitable for administration to a human or animal. The formulation may be applied in the form of an cream, emulsion, gel, lotion, ointment, paste, solution, suspension, or other forms known in the art. In particular, formulations that enhance skin hydration, penetration, or both are preferred. There may also be incorporated other pharmaceutically acceptable additives including, for example, diluents, binders, stabilizers, preservatives, and colorings.

Increasing hydration of the stratum corneum will increase the rate of percutaneous absorbtion of a given solute (Roberts and Walker, 1993). As used in the present invention, "penetration enhancer" does not include substances such as, for example: water, physiological buffers, saline solutions, and alcohols which would not perforate the skin.

An object of the present invention is to provide a novel means for immunization through intact skin without the need for perforating the skin. The transcutaneous immunization system provides a method whereby antigens and adjuvant can be delivered to the immune system, especially specialized antigen presentation cells underlying the skin such as, for example, Langerhans cells.

Without being bound to any particular theory but only to provide an explanation for our observations, it is presumed that the transcutaneous immunization delivery system carries antigen to cells of the immune system where an immune response is induced. The antigen may pass through the normal protective outer layers of the skin (i.e., stratum corneum) and induce the immune response directly, or through an antigen presenting cell (e.g., macrophage, tissue macrophage, Langerhans cell, dendritic cell, dermal dendritic cell, B lymphocyte, or Kupffer cell) that presents processed antigen to a T lymphocyte. Optionally, the antigen may pass through the stratum corneum via a hair follicle or a skin organelle (e.g., sweat gland, oil gland).

Transcutaneous immunization with bacterial ADP-ribosylating exotoxins (bAREs) may target the epidermal Langerhans cell, known to be among the most efficient of the antigen presenting cells (APCs) (Udey, 1997). We have found that bAREs activate Langerhans cells when applied epicutaneously to the skin in saline solution. The Langerhans cells direct specific immune responses through phagocytosis of the antigens, and migration to the lymph nodes where they act as APCs to present the antigen to lymphocytes (Udey, 1997), and thereby induce a potent antibody response. Although the skin is generally considered a barrier to invading organisms, the imperfection of this barrier is attested to by the numerous Langerhans cells distributed throughout the epidermis that are designed to orchestrate the immune response against organisms invading via the skin (Udey, 1997).

According to Udey (1997):

• "Langerhans cells" are bone-marrow derived cells that are present in all mammalian stratified squamous epithelia. They comprise all of the accessory cell activity that is present in uninflammed epidermis, an in the current paradigm are essential for the initiation and propagation of immune responses directed against epicutaneously applied antigens. Langerhans cells are members of a family of potent accessory cells ('dendritic cells') that are widely distributed, but infrequently represented, in epithelia and solid organs as well as in lymphoid tissue . . .
• "It is now recognized that Langerhans cells (and presumably other dendritic cells) have a life cycle with at least two distinct stages. Langerhans cells that are located in epidermis constitute a regular network of antigen-trapping 'sentinel' cells. Epidermal Langerhans cells can ingest particulates, including microorganisms, and are efficient processors of complex antigens. However, they express only low levels of MHC class I and II antigens and costimulatory molecules (ICAM-1, B7-1 and B7-2) and are poor stimulators of unprimed T cells. After contact with antigen, some Langerhans cells become activated, exit the epidermis and migrate to T-cell-dependent regions of regional lymph nodes where they local as mature dendritic cells. In the course of exiting the epidermis and migrating to lymph nodes, antigen-bearing epidermal Langerhans cells (now the 'messengers') exhibit dramatic changes in morphology, surface phenotype and function. In contrast to epidermal Langerhans cells, lymphoid dendritic cells are essentially non-phagocytic and process protein antigens inefficiently, but express high levels of MHC class I and class II antigens and various costimulatory molecules and are the most potent stimulators of naive T cells that have been identified."

We envision that the potent antigen presenting capability of the epidermal Langerhans cells can be exploited for transcutaneously delivered vaccines. A transcutaneous immune response using the skin immune system would require delivery of vaccine antigen only to Langerhans cells in the stratum corneum (the outermost layer of the skin consisting of cornified cells and lipids) via passive diffusion and subsequent activation of the Langerhans cells to take up antigen, migrate to B-cell follicles and/or T-cell dependent regions, and present the antigen to B and/or T cells (Stingl et al., 1989). If antigens other that bAREs (for example BSA) were to be phagocytosed by the Langerhans cells, then these antigens could also be taken to the lymph node for presentation to T-cells and subsequently induce an immune response specific for that antigen (e.g., BSA). Thus, a feature of transcutaneous immunization is the activation of the Langerhans cell, presumably by a bacterial ADP-ribosylating exotoxin, ADP-ribosylating exotoxin binding subunits (e.g., cholera toxin B subunit), or other Langerhans cell activating substance.

The mechanism of transcutaneous immunization via Langerhans cells activation, migration and antigen presentation is clearly shown by the upregulation of MHC class II expression in the epidermal Langerhans cells from epidermal sheets transcutaneously immunized with CT or CTB. In addition, the magnitude of the antibody response induced by transcutaneous immunization and isotype switching to predominantly IgG is generally achieved with T-cell help (Janeway and Travers, 1996), and activation of both Th1 and Th2 pathways is suggested by the production of IgG1 and IgG2a (Paul and Seder, 1994; Seder and Paul, 1994). Alternatively, a large antibody response may be induced by a thymus-independent antigen type 1 (TI-1) which directly activates the B cell (Janeway and Travers, 1996).

The spectrum of more commonly known skin immune responses is represented by contact dermatitis and atopy. Contact dermatitis, a pathogenic manifestation of LC activation, is directed by Langerhans cells which phagocytose antigen, migrate to lymph nodes, present antigen, and sensitize T cells for the intense destructive cellular response that occurs at the affected skin site (Dahl, 1996; Leung, 1997). Atopic dermatitis may utilize the Langerhans cell in a similar fashion, but is identified with Th2 cells and is generally associated with high levels of IgE antibody (Dahl, 1996; Leung, 1997).

Transcutaneous immunization with cholera toxin and related bAREs on the other hand is a novel immune response with an absence of superficial and microscopic post-immunization skin findings (i.e., non-inflamed skin) shown by the absence of lymphocyte infiltration 24, 48 and 120 hours after immunization. This indicates that Langerhans cells "comprise all of the accessory cell activity that is present in uninflammed epidermis, and in the current paradigm are essential for the initiation and propagation of immune responses directed against epicutaneously applied antigens" (Udey, 1997). The uniqueness of the transcutaneous immune response here is also indicated by the both high levels of antigen-specific IgG antibody, and the type of antibody produced (e.g., IgM, IgG1, IgG2a, IgG2b, IgG3 and IgA) and the absence of anti-CT IgE antibody.

Thus, we have found that bacterial-derived toxins applied to the surface of the skin can activate Langerhans cells and induce a potent immune response manifested as high levels of antigen-specific circulating IgG antibodies. Such adjuvants may be used in transcutaneous immunization to enhance the IgG antibody response to proteins not otherwise immunogenic by themselves when placed on the skin.

Transcutaneous targeting of Langerhans cells may also be used to deactivate their antigen presenting function, thereby preventing immunization or sensitization. Techniques to deactivate Langerhans cells include, for example, the use of interleukin-10 (Peguet-Navarro et al., 1995), monoclonal antibody to interleukin-1β (Enk et al., 1993), or depletion via superantigens such as through staphylococcal enterotoxin-A (SEA) induced epidermal Langerhans cell depletion (Shankar et al., 1996).

Transcutaneous immunization may be induced via the ganglioside GM1 binding activity of CT, LT or subunits such as CTB (Craig and Cuatrecasas, 1975). Ganglioside GM1 is a ubiquitous cell membrane glycolipid found in all mammalian cells (Plotkin and Mortimer, 1994). When the pentameric CT B subunit binds to the cell surface a hydrophilic pore is formed which allows the A subunit to penetrate across the lipid bilayer (Ribi et al., 1988).

We have shown that transcutaneous immunization by CT or CTB may require ganglioside GM1 binding activity. When mice were transcutaneously immunized with CT, CTA and CTB, only CT and CTB resulted in an immune response. CTA contains the ADP-ribosylating exotoxin activity but only CT and CTB containing the binding activity were able to induce an immune response indicating that the B subunit was necessary and sufficient to immunize through the skin. We conclude that the Langerhans cell may be activated by CTB binding to its cell surface.

Antigen

Antigen of the invention may be expressed by recombinant means, preferably as a fusion with an affinity or epitope tag (Summers and Smith, 1987; Goeddel, 1990; Ausubel et al., 1996); chemical synthesis of an oligopeptide, either free or conjugated to carrier proteins, may be used to obtain antigen of the invention (Bodanszky, 1993; Wisdom, 1994). Oligopeptides are considered a type of polypeptide.

Oligopeptide lengths of 6 residues to 20 residues are preferred. Polypeptides may also by synthesized as branched structures such as those disclosed in U.S. Pat. Nos. 5,229,490 and 5,390,111. Antigenic polypeptides include, for example, synthetic or recombinant B-cell and T-cell epitopes, universal T-cell epitopes, and mixed T-cell epitopes from one organism or disease and B-cell epitopes from another.

Antigen obtained through recombinant means or peptide synthesis, as well as antigen of the invention obtained from natural sources or extracts, may be purified by means of the antigen's physical and chemical characteristics, preferably by fractionation or chromatography (Janson and Ryden, 1989; Deutscher, 1990; Scopes, 1993).

A multivalent antigen formulation may be used to induce an immune response to more then one antigen at the same time. Conjugates may be used to induce an immune response to multiple antigens, to boost the immune response, or both. Additionally, toxins may be boosted by the use of toxoids, or toxoids boosted by the use of toxins. Transcutaneous immunization may be used to boost responses induced initially by other routes of immunization such as by injection, or the oral or intranasal routes.

Antigen includes, for example, toxins, toxoids, subunits thereof, or combinations thereof (e.g., cholera toxin, tetanus toxoid).

Antigen may be solubilized in a buffer. Suitable buffers include, but are not limited to, phosphate buffered saline Ca⁺⁺/Mg⁺⁺ free (PBS), normal saline (150 mM NaCl in water), and Tris buffer. Antigen not soluble in neutral buffer can be solubilized in 10 mM acetic acid and then diluted to the desired volume with a neutral buffer such as PBS. In the case of antigen soluble only at acid pH, acetate-PBS at acid pH may be used as a diluent after solubilization in dilute acetic acid. Glycerol may be a suitable non-aqueous buffer for use in the present invention.

Hydrophobic antigen can be solubilized in a detergent, for example a polypeptide containing a membrane-spanning domain. Furthermore, for formulations containing liposomes, an antigen in a detergent solution (e.g., a cell membrane extract) may be mixed with lipids, and liposomes then may be formed by removal of the detergent by dilution, dialysis, or column chromatography. Certain antigens such as, for example, those from a virus (e.g., hepatitis A) need not be soluble per se, but can be incorporated directly into a liposome in the form of a virosome (Morein and Simons, 1985).

Plotkin and Mortimer (1994) provide antigens which can be used to vaccinate animals or humans to induce an immune response specific for particular pathogens, as well as methods of preparing antigen, determining a suitable dose of antigen, assaying for induction of an immune response, and treating infection by a pathogen (e.g., bacterium, virus, fungus, or parasite).

Bacteria include, for example: anthrax, campylobacter, cholera, diphtheria, enterotoxigenic E. coli, giardia, gonococcus, Helicobacter pylori (Lee and Chen, 1994), Hemophilus influenza B, Hemophilus influenza non-typable, meningococcus, pertussis, pneumococcus, salmonella, shigella, Streptococcus B, tetanus, Vibrio cholerae, and yersinia.

Viruses include, for example: adenovirus, dengue serotypes 1 to 4 (Delenda et al., 1994; Fonseca et al., 1994; Smucny et al., 1995), ebola (Jahrling et al., 1996), enterovirus, hepatitis serotypes A to E (Blum, 1995; Katkov, 1996; Lieberman and Greenberg, 1996; Mast, 1996; Shafara et al., 1995; Smedila et al., 1994; U.S. Pat. Nos. 5,314,808 and 5,436,126), herpes simplex virus 1 or 2, human immunodeficiency virus (Deprez et al., 1996), influenza, measles, Norwalk, papilloma virus, parvovirus B19, polio, rabies, rotavirus, rubella, rubeola, vaccinia, vaccinia constructs containing genes coding for other antigens such as malaria antigens, varicella, and yellow fever.

Parasites include, for example: Entamoeba histolytica (Zhang et al., 1995); Plasmodium (Bathurst et al., 1993; Chang et al., 1989, 1992, 1994; Fries et al., 1992a, 1992b; Herrington et al., 1991; Khusmith et al., 1991; Malik et al., 1991; Migliorini et al., 1993; Pessi et al., 1991; Tam, 1988; Vreden et al., 1991; White et al., 1993; Wiesmueller et al., 1991), Leishmania (Frankenburg et al., 1996), and the Helminthes.

Adjuvant

The formulation also contains an adjuvant, although a single molecule may contain both adjuvant and antigen properties (e.g., cholera toxin) (Elson and Dertzbaugh, 1994). Adjuvants are substances that are used to specifically or non-specifically potentiate an antigen-specific immune response. Usually, the adjuvant and the formulation are mixed prior to presentation of the antigen but, alternatively, they may be separately presented within a short interval of time.

Adjuvants include, for example, an oil emulsion (e.g., complete or incomplete Freund's adjuvant), a chemokine (e.g., defensins 1 or 2, RANTES, MIP1-α, MIP-2, interleukin-8) or a cytokine (e.g., interleukin-1β, -2, -6, -10 or -12; γ-interferon; tumor necrosis factor-α; or granulocyte-monocyte-colony stimulating factor) (reviewed in Nohria and Rubin, 1994), a muramyl dipeptide derivative (e.g., murabutide, threonyl-MDP or muramyl tripeptide), a heat shock protein or a derivative, a derivative of Leishmania major LeIF (Skeiky et al., 1995), cholera toxin or cholera toxin B, a lipopolysaccharide (LPS) derivative (e.g., lipid A or monophosphoryl lipid A), or superantigen (Saloga et al., 1996). Also, see Richards et al. (1995) for adjuvants useful in immunization.

An adjuvant may be chosen to preferentially induce antibody or cellular, effectors, specific antibody isotypes (e.g., IgM, IgD, IgA1, IgA2, secretory IgA, IgE, IgG1, IgG2, IgG3, and/or IgG4), or specific T-cell subsets (e.g., CTL, Th1, Th2 and/or T_DTH) (Glenn et al., 1995).

Cholera toxin is a bacterial exotoxin from the family of ADP-ribsoylating exotoxins (referred to as bAREs). Most bAREs are organized as A:B dimer with a binding B subunit and an A subunit containing the ADP-ribosyltransferase. Such toxins include diphtheria, Pseudomonas exotoxin A, cholera toxin (CT), E. coli heat-labile enterotoxin (LT), pertussis toxin, C. botulinum toxin C2, C. botulinum toxin C3, C. limosum exoenzyme, B. cereus exoenzyme, Pseudomonas exotoxin S, Staphylococcus aureus EDIN, and B. sphaericus toxin.

Cholera toxin is an example of a bARE that is organized with A and B subunits. The B subunit is the binding subunit and consists of a B-subunit pentamer which is non-covalently bound to the A subunit. The B-subunit pentamer is arranged in a symmetrical doughnut-shaped structure that binds to GM₁-ganglioside on the target cell. The A subunit serves to ADP ribosylate the alpha subunit of a subset of the hetero trimeric GTP proteins (G proteins) including the Gs protein which results in the elevated intracellular levels of cyclic AMP. This stimulates release of ions and fluid from intestinal cells in the case of cholera.

Cholera toxin (CT) and its B subunit (CTB) have adjuvant properties when used as either an intramuscular or oral immunogen (Elson and Dertzbaugh, 1994; Trach et al., 1997). Another antigen, heat-labile enterotoxin from E. coli (LT) is 80% homologous at the amino acid level with CT and possesses similar binding properties; it also appears to bind the GM₁-ganglioside receptor in the gut and has similar ADP-ribosylating exotoxin activities. Another bARE, Pseudomonas exotoxin A (ETA), binds to the α₂-macroglobulin receptor-low density lipoprotein receptor-related protein (Kounnas et al., 1992). bAREs are reviewed by Krueger and Barbieri (1995).

The examples below show that cholera toxin (CT), its B subunit (CTB), E. coli heat-labile enterotoxin (LT), and pertussis toxin are potent adjuvants for transcutaneous immunization, inducing high levels of IgG antibodies but not IgE antibodies. Also shown is that CTB without CT can also induce high levels of IgG antibodies. Thus, both bAREs and a derivative thereof can effectively immunize when epicutaneouly applied to the skin in a simple solution.

When an adjuvant such as CT is mixed with BSA, a protein not usually immunogenic when applied to the skin, anti-BSA antibodies are induced. An immune response to diphtheria toxoid was induced using pertussis toxin as adjuvant, but not with diphtheria toxoid alone. Thus, bAREs can act as adjuvants for non-immunogenic proteins in an transcutaneous immunization system.

Protection against the life-threatening infections diphtheria, pertussis, and tetanus (DPT) can be achieved by inducing high levels of circulating anti-toxin antibodies. Pertussis may be an exception in that some investigators feel that antibodies directed to other portions of the invading organism are necessary for protection, although this is controversial (see Schneerson et al., 1996) and most new generation acellular pertussis vaccines have PT as a component of the vaccine (Krueger and Barbieri, 1995). The pathologies in the diseases caused by DPT are directly related to the effects of their toxins and anti-toxin antibodies most certainly play a role in protection (Schneerson et al., 1996).

In general, toxins can be chemically inactivated to form toxoids which are less toxic but remain immunogenic. We envision that the transcutaneous immunization system using toxin-based immunogens and adjuvants can achieve anti-toxin levels adequate for protection against these diseases. The anti-toxin antibodies may be induced through immunization with the toxins, or genetically-detoxified toxoids themselves, or with toxoids and adjuvants such as CT. Genetically toxoided toxins which have altered ADP-ribosylating exotoxin activity, but not binding activity, are envisioned to be especially useful as non-toxic activators of antigen presenting cells used in transcutaneous immunization.

We envision that CT can also act as an adjuvant to induce antigen-specific CTLs through transcutaneous immunization (see Bowen et al., 1994; Porgador et al., 1997 for the use of CT as an adjuvant in oral immunization).

The bARE adjuvant may be chemically conjugated to other antigens including, for example, carbohydrates, polypeptides, glycolipids, and glycoprotein antigens. Chemical conjugation with toxins, their subunits, or toxoids with these antigens would be expected to enhance the immune response to these antigens when applied epicutaneously.

To overcome the problem of the toxicity of the toxins, (e.g., diphtheria toxin is known to be so toxic that one molecule can kill a cell) and to overcome the difficulty of working with such potent toxins as tetanus, several workers have taken a recombinant approach to producing genetically produced toxoids. This is based on inactivating the catalytic activity of the ADP-ribosyl transferase by genetic deletion. These toxins retain the binding capabilities, but lack the toxicity, of the natural toxins. This approach is described by Burnette et al. (1994), Rappuoli et al. (1995), and Rappuoli et al. (1996). Such genetically toxoided exotoxins could be useful for transcutaneous immunization system in that they would not create a safety concern as the toxoids would not be considered toxic. Additionally, several techniques exist to chemically toxoid toxins which can address the same problem (Schneerson et al., 1996). These techniques could be important for certain applications, especially pediatric applications, in which ingested toxins (e.g., diphtheria toxin) might possibly create adverse reactions.

Optionally, an activator of Langerhans cells may be used as an adjuvant. Examples of such activators include: inducers of heat shock protein; contact sensitizers (e.g., trinitrochlorobenzene, dinitrofluorobenzene, nitrogen mustard, pentadecylcatechol); toxins (e.g, Shiga toxin, Staph enterotoxin B); lipopolysaccharides, lipid A, or derivatives thereof; bacterial DNA (Stacey et al., 1996); cytokines (e.g., tumor necrosis factor-α, interleukin-1β, -10, -12); and chemokines (e.g., defensins 1 or 2, RANTES, MIP-1α, MIP-2, interleukin-8).

If an immunizing antigen has sufficient Langerhans cell activating capabilities then a separate adjuvant may not be required, as in the case of CT which is both antigen and adjuvant. It is envisioned that whole cell preparations, live viruses, attenuated viruses, DNA plasmids, and bacterial DNA could be sufficient to immunize transcutaneously. It may be possible to use low concentrations of contact sensitizers or other activators of Langerhans cells to induce an immune response without inducing skin lesions.

Liposomes and Their Preparation

Liposomes are closed vesicles surrounding an internal aqueous space. The internal compartment is separated from the external medium by a lipid bilayer composed of discrete lipid molecules. In the present invention, antigen may be delivered through intact skin to specialized cells of the immune system, whereby an antigen-specific immune response is induced. Transcutaneous immunization may be achieved by using liposomes; however, as shown in the examples, liposomes are not required to elicit an antigen-specific immune response.

Liposomes may be prepared using a variety of techniques and membrane lipids (reviewed in Gregoriadis, 1993). Liposomes may be pre-formed and then mixed with antigen. The antigen may be dissolved or suspended, and then added to (a) the pre-formed liposomes in a lyophilized state, (b) dried lipids as a swelling solution or suspension, or (c) the solution of lipids used to form liposomes. They may also be formed from lipids extracted from the stratum corneum including, for example, ceramide and cholesterol derivatives (Wertz, 1992).

Chloroform is a preferred solvent for lipids, but it may deteriorate upon storage. Therefore, at one- to three-month intervals, chloroform is redistilled prior to its use as the solvent in forming liposomes. After distillation, 0.7% ethanol can be added as a preservative. Ethanol and methanol are other suitable solvents.

The lipid solution used to form liposomes is placed in a round-bottomed flask. Pear-shaped boiling flasks are preferred, particularly those flasks sold by Lurex Scientific (Vineland, N.J., cat. no. JM-5490). The volume of the flask should be more than ten times greater than the volume of the anticipated aqueous suspension of liposomes to allow for proper agitation during liposome formation.

Using a rotary evaporator, solvent is removed at 37° C. under negative pressure for 10 minutes with a filter aspirator attached to a water faucet. The flask is further dried under low vacuum (i.e., less than 50 mm Hg) for 1 hour in a dessicator.

To encapsulate antigen into liposomes, an aqueous solution containing antigen may be added to lyophilized liposome lipids in a volume that results in a concentration of approximately 200 mM with respect to liposome lipid, and shaken or vortexed until all the dried liposome lipids are wet. The liposome-antigen mixture may then be incubated for 18 hours to 72 hours at 4° C. The liposome-antigen formulation may be used immediately or stored for several years. It is preferred to employ such a formulation directly in the transcutaneous immunization system without removing unencapsulated antigen. Techniques such as bath sonication may be employed to decrease the size of liposomes, which may augment transcutaneous immunization.

Liposomes may be formed as described above but without addition of antigen to the aqueous solution. Antigen may then be added to the pre-formed liposomes and, therefore, antigen would be in solution and/or associated with, but not encapsulated by, the liposomes. This process of ma-king a liposome-containing formulation is preferred because of its simplicity. Techniques such as bath sonication may be employed to alter the size and/or lamellarity of the liposomes to enhance immunization.

Although not required to practice the present invention, hydration and/or penetration of the stratum corneum may be enhanced by adding liposomes to the formulation. Liposomes have been used as carriers with adjuvants to enhance the immune response to antigens mixed with, encapsulated in, attached to, or associated with liposomes.

Transcutaneous Delivery of Antigen

Efficient immunization can be achieved with the present invention because transcutaneous delivery of antigen may target the Langerhans cell. These cells are found in abundance in the skin and are efficient antigen presenting cells leading to T-cell memory and potent immune responses (Udey, 1997). Because of the presence of large numbers of Langerhans cells in the skin, the efficiency of transcutaneous delivery may be related to the surface area exposed to antigen and adjuvant. In fact, the reason that transcutaneous immunization is so efficient may be that it targets a larger number of these efficient antigen presenting cells than intramuscular immunization.

We envision the present invention will enhance access to immunization, while inducing a potent immune response. Because transcutaneous immunization does not involve penetration of the skin and the complications and difficulties thereof, the requirements of trained personnel, sterile technique, and sterile equipment are reduced. Furthermore, the barriers to immunization at multiple sites or to multiple immunizations are diminished. Immunization by a single application of the formulation is also envisioned.

Immunization may be achieved using epicutaneous application of a simple solution of antigen and adjuvant impregnated in gauze under an occlusive patch, or by using other patch technologies; creams, immersion, ointments and sprays are other possible methods of application. The immunization could be given by untrained personnel, and is amenable to self-application. Large-scale field immunization could occur given the easy accessibility to immunization. Additionally, a simple immunization procedure would improve access to immunization by pediatric patients and the elderly, and populations in Third World countries.

For previous vaccines, their formulations were injected through the skin with needles. Injection of vaccines using needles carries certain drawbacks including the need for sterile needles and syringes, trained medical personnel to administer the vaccine, discomfort from the injection, and potential complications brought about by puncturing the skin with the needle. Immunization through the skin without the use of needles (i.e., transcutaneous immunization) represents a major advance for vaccine delivery by avoiding the aforementioned drawbacks.

The transcutaneous delivery system of the invention is also not concerned with penetration of intact skin by sound or electrical energy. Such a system that uses an electrical field to induce dielectric breakdown of the stratum corneum is disclosed in U.S. Pat. No. 5,464,386.

Moreover, transcutaneous immunization may be superior to immunization using needles as more immune cells would be targeted by the use of several locations targeting large surface areas of skin. A therapeutically effective amount of antigen sufficient to induce an immune response may be delivered transcutaneously either at a single cutaneous location, or over an area of intact skin covering multiple draining lymph node fields (e.g., cervical, axillary, inguinal, epitrochelear, popliteal, those of the abdomen and thorax). Such locations close to numerous different lymphatic nodes at locations all over the body will provide a more widespread stimulus to the immune system than when a small amount of antigen is injected at a single location by intradermal subcutaneous or intramuscular injection.

Antigen passing through or into the skin may encounter antigen presenting cells which process the antigen in a way that induces an immune response. Multiple immunization sites may recruit a greater number of antigen presenting cells and the larger population of antigen presenting cells that were recruited would result in greater induction of the immune response. It is conceivable that absorption through the skin may deliver antigen to phagocytic cells of the skin such as, for example, dermal dendritic cells, macrophages, and other skin antigen presenting cells; antigen may also be delivered to phagocytic cells of the liver, spleen, and bone marrow that are known to serve as the antigen presenting cells through the blood stream or lymphatic system. The result would be widespread distribution of antigen to antigen presenting cells to a degree that is rarely, if ever achieved, by current immunization practices.

The transcutaneous immunization system may be applied directly to the skin and allowed to air dry; rubbed into the skin or scalp; held in place with a dressing, patch, or absorbent material; otherwise held by a device such as a stocking, slipper, glove, or shirt; or sprayed onto the skin to maximize contact with the skin. The formulation may be applied in an absorbant dressing or gauze. The formulation may be covered with an occlusive dressing such as, for example, AQUAPHOR (an emulsion of petrolatum, mineral oil, mineral wax, wool wax, panthenol, bisabol, and glycerin from Beiersdorf, Inc.), plastic film, COMFEEL (Coloplast) or vaseline; or a non-occlusive dressing such as, for example, DUODERM (3M) or OPSITE (Smith & Napheu). An occlusive dressing completely excludes the passage of water.

The formulation may be applied to single or multiple sites, to single or multiple limbs, or to large surface areas of the skin by complete immersion. The formulation may be applied directly to the skin.

Genetic immunization has been described in U.S. Pat. Nos. 5,589,466 and 5,593,972. The nucleic acid(s) contained in the formulation may encode the antigen, the adjuvant, or both. The nucleic acid may or may not be capable of replication; it may be non-integrating and non-infectious. The nucleic acid may further comprise a regulatory region (e.g., promoter, enhancer, silencer, transcription initiation and termination sites, RNA splice acceptor and donor sites, polyadenylation signal, internal ribosome binding site, translation initiation and termination sites) operably linked to the sequence encoding the antigen or adjuvant. The nucleic acid may be complexed with an agent that promotes transfection such as cationic lipid, calcium phosphate, DEAE-dextran, polybrene-DMSO, or a combination thereof. The nucleic acid may comprise regions derived from viral genomes. Such materials and techniques are described by Kriegler (1990) and Murray (1991).

An immune response may comprise humoral (i.e., antigen-specific antibody) and/or cellular (i.e., antigen-specific lymphocytes such as B cells, CD4+ T cells, CD8+ T cells, CTL, Th1 cells, Th2 cells, and/or T_DTH cells) effector arms. Moreover, the immune response may comprise NK cells that mediate antibody-dependent cell-mediated cytotoxicity (ADCC).

The immune response induced by the formulation of the invention may include the elicitation of antigen-specific antibodies and/or cytotoxic lymphocytes (CTL, reviewed in Alving and Wassef, 1994). Antibody can be detected by immunoassay techniques, and the detection of various isotypes (e.g., IgM, IgD, IgA1, IgA2, secretory IgA, IgE, IgG1, IgG2, IgG3, or IgG4) may be expected. An immune response can also be detected by a neutralizing assay.

Antibodies are protective proteins produced by B lymphocytes. They are highly specific, generally targeting one epitope of an antigen. Often, antibodies play a role in protection against disease by specifically reacting with antigens derived from the pathogens causing the disease. Immunization may induce antibodies specific for the immunizing antigen, such as cholera toxin. These antigen-specific antibodies are induced when antigen is delivered through the skin by liposomes.

CTLs are particular protective immune cells produced to protect against infection by a pathogen. They are also highly specific. Immunization may induce CTLs specific for the antigen, such as a synthetic oligopeptide based on a malaria protein, in association with self-major histocompatibility antigen. CTLs induced by immunization with the transcutaneous delivery system may kill pathogen infected cells. Immunization may also produce a memory response as indicated by boosting responses in antibodies and CTLs, lymphocyte proliferation by culture of lymphocytes stimulated with the antigen, and delayed type hypersensitivity responses to intradermal skin challenge of the antigen alone.

In a viral neutralization assay, serial dilution-s of sera are added to host cells which are then observed for infection after challenge with infectious virus. Alternatively, serial dilutions of sera may be incubated with infectious titers of virus prior to innoculation of an animal, and the innoculated animals are then observed for signs of infection.

The transcutaneous immunization system of the invention may be evaluated using challenge models in either animals or humans, which evaluate the ability of immunization with the antigen to protect the subject from disease. Such protection would demonstrate an antigen-specific immune response. In lieu of challenge, achieving anti-diphtheria antibody titers of 5 IU/ml or greater is generally assumed to indicate optimum protection and serves as a surrogate marker for protection (Plotkin and Mortimer, 1994).

Furthermore, the Plasmodium faciparum challenge model may be used as to induce an antigen-specific immune response in humans. Human volunteers may be immunized using the transcutaneous immunization system containing oligopeptides or proteins (polypeptides) derived from the malaria parasite, and then exposed to malaria experimentally or in the natural setting. The Plasmodium yoelii mouse malaria challenge model may be used to evaluate protection in the mouse against malaria (Wang et al., 1995).

Alving et al. (1986) injected liposomes comprising lipid A as an adjuvant for inducing an immune response to cholera toxin (CT) in rabbits and to a synthetic protein consisting of a malaria oligopeptide containing four tetra-peptides (Asn-Ala-Asn-Pro, SEQ ID NO:1) conjugated to BSA. The authors found that the immune response to cholera toxin or to the synthetic malaria protein was markedly enhanced by encapsulating the antigen within the liposomes containing lipid A, compared to similar liposomes lacking lipid A. Several antigens derived either from the circumsporozoite protein (CSP) or from merozoite surface proteins of Plasmodium falciparum have been encapsulated in liposomes containing lipid A. All of the malaria antigens that have been encapsulated in liposomes containing lipid A have been shown to induce humoral effectors (i.e., antigen-specific antibodies), and some have been shown to induce cell-mediated responses as well. Generation of an immune response and immunoprotection in an animal vaccinated with a malaria antigen may be assayed by immunofluorescence to whole, fixed malaria sporozoites or CTLs killing of target cells transfected with CSP.

Mice may be transcutaneously immunized with cholera toxin, and then challenged intranasally with an LD₇₀ (40 μg) dose of cholera toxin and observed for protection. Mallet et al. (personal communication) have found that C57BL/6 mice develop a fatal hemorrhagic pneumonia in response to intranasal challenge with CT. Alternatively, the mice may be challenged with an intraperitoneal dose of CT (Dragunsky et al., 1992). Cholera toxin-specific IgG or IgA antibody may provide protection against cholera toxin challenge (Pierce, 1978; Pierce and Reynolds, 1974).

Vaccination has also been used as a treatment for cancer and autoimmune disease. For example, vaccination with a tumor antigen (e.g., prostate specific antigen) may induce an immune response in the form of antibodies, CTLs and lymphocyte proliferation which allows the body's immune system to recognize and kill tumor cells. Tumor antigens useful for vaccination have been described for melanoma (U.S. Pat. Nos. 5,102,663, 5,141,742, and 5,262,177), prostate carcinoma (U.S. Pat. No. 5,538,866), and lymphoma (U.S. Pat. Nos. 4,816,249, 5,068,177, and 5,227,159). Vaccination with T-cell receptor oligopeptide may induce an immune response that halts progression of autoimmune disease (U.S. Pat. Nos. 5,612,035 and 5,614,192; Antel et al., 1996; Vandenbark et al., 1996). U.S. Pat. No. 5,552,300 also describes antigens suitable for treating autoimmune disease.
 

Claim 1 of 16 Claims

1. A method of inducing an immune response to at least one antigen comprising

applying a formulation to hydrated skin of an organism,

wherein the formulation comprises

(i) at least one antigen which is derived from a pathogen and

(ii) an adjuvant,

wherein an effective amount of the at least one antigen induces the immune response to the at least one antigen in the organism.
 

____________________________________________
If you want to learn more about this patent, please go directly to the U.S. Patent and Trademark Office Web site to access the full patent.