The present invention provides an immunogen composition and methods for using the same for the development of immunity, and particularly at mucosal sites in a mammal, thereby providing immunity at the site of entry for many major pathogenic organisms and also systemic immunity. The immunogen composition includes an antigen, a biocompatible polymer, and a liquid vehicle, with the biocompatible polymer and liquid vehicle being present in such proportions and interacting in such a way that the immunogen composition exhibits reverse-thermal viscosity behaviour. A delivery vehicle composition including a drug other than an antigen is also provided. Methods are provided for delivering the compositions of the invention to a host.

Description of the Invention

SUMMARY OF THE INVENTION

The present invention provides a delivery vehicle composition for delivery of a drug and methods for administering the delivery vehicle composition to effect a desired biological response in the host. The delivery vehicle composition comprises at least one drug, at least one biocompatible polymer and at least one liquid vehicle, with the polymer and the liquid vehicle being of such a type and being present in such proportions that the delivery vehicle composition exhibits reverse-thermal viscosity behavior, meaning that the viscosity of the composition increases with increasing temperature over at least some temperature range. The delivery vehicle composition also typically includes at least one additive selected from the group consisting of an adjuvant, a penetration enhancer and combinations thereof.

The delivery vehicle composition is such that it will typically be administered to the host in the form of a flowable medium at a temperature below the physiological temperature of the host. The viscosity of the composition then increases as the composition is warmed inside the host, and preferably the composition converts to a substantially immobile gel form so that the composition is retained at the desired location for delivery of the drug.

The delivery vehicle composition is administerable to a host in any convenient way for example by injection or direct application to the desired site. One advantage of the delivery vehicle composition, however, is that it is particularly well suited for mucosal delivery. In one preferred embodiment for mucosal delivery, the delivery vehicle composition is in the form of dispersed droplets in a mist. For many mucosal routes, such as, for example, intranasal, sublingual, oral administration, the mist is introduced into the appropriate cavity of administration. Such a mist is typically generated by a nebulizer.

The delivery vehicle composition is exemplified herein by an immunogen composition of the invention in which the drug is an antigen for stimulating an immune response, and preferably without the use of adjuvants, such as alum, of questionable safety. It should be understood, however, that the principles concerning formulation reverse-thermal viscosity behavior and administration, and concerning other attributes of the immunogen composition, also apply for incorporating and using a different type of drug in the delivery vehicle composition.

In the immunogen composition, the biocompatible polymer helps to protect the antigen from possible degradation and to promote prolonged release of the antigen into the host following administration. A preferred liquid vehicle is water or another aqueous liquid and the biocompatible polymer is typically a reverse-thermal gelation polymer, with polyoxyalkylene block polymers being particularly preferred.

In one embodiment, the biocompatible polymer is dissolved in the liquid vehicle when the temperature of the immunogen composition is at some temperature or temperatures below the physiological temperature of the host (approximately 37.degree. C. for humans) so that the biocompatible polymer/liquid vehicle solution is in the form of a flowable liquid. In this situation, the antigen is also preferably dissolved in the liquid vehicle along with the biocompatible polymer. Alternatively, the antigen may be in the form of a particulate suspended in the biocompatible polymer/liquid vehicle solution. In either case, the composition should be in the form of a flowable medium sufficient for nebulization to produce a spray and/or for injectability.

In another embodiment, the immunogen composition is in the form of a gel (semi-solid gelatinous substance) when the composition is at the physiologic temperature of the host (approximately 37.degree. C. for humans). The gel is formed by the interaction between the polymer and the liquid vehicle. For enhanced performance, the antigen should be uniformly dispersed throughout the gel, which is preferably accomplished by initially preparing the immunogen composition at a temperature at which the polymer is dissolved in the liquid vehicle. The antigen can be dissolved in or uniformly dispersed throughout the solution, and then the temperature of the composition can be raised to convert the immunogen composition to a gel form.

In a preferred embodiment, the immunogen composition exhibits reverse-thermal gelation properties, in that the polymer, as incorporated in the immunogen composition, has a gel-liquid transition temperature such that the biocompatible polymer is in solution in the liquid vehicle of some temperature below the transition temperature and the biocompatible polymer and liquid vehicle form a gel, i.e., become gelatinous, as the temperature is raised above the transition temperature. Such a gel-liquid transition temperature may be referred to as a reverse-thermal liquid-gel transition temperature. The reverse-thermal liquid-gel transition temperature should typically be below, and more preferably just below, the physiological temperature of the host. In this way, the composition is administrable to a host at a temperature at which the composition is in the form of a flowable medium and after administration the immunogen composition then converts to a gel form as it warms inside the host to above the transition temperature. The composition can be placed in a syringe or syringe-like device then administered to the host and it can also be placed in a spray device and administered to the host. The immunogen composition preferably has an affinity to adhere to mucosal surfaces, and conversion to a gel form helps to immobilize the immunogen composition at the mucosal surface to retain the antigen in the vicinity of the mucosal surface, thereby permitting the antigen to be effectively delivered to penetrate the mucosal tissue to induce the desired immune response.

In another embodiment, the biocompatible polymer is bioadhesive, so that when the immunogen composition is contacted with a mucosal surface, at least a portion of the biocompatible polymer readily adheres to the mucosal surface. Preferably, the biocompatible polymer and the antigen are closely associated with each other in the immunogen composition so that when the biocompatible polymer adheres to a mucosal surface, the antigen is held in the vicinity of the surface for effective delivery of the antigen across the mucosal epithelium. This will typically be the case, for example, in a preferred embodiment when the carrier liquid is an aqueous liquid and the biocompatible polymer has surfactant properties.

In yet another embodiment, the immunogen composition comprises, in addition to the biocompatible polymer and the antigen, a penetration enhancer that aids rapid transport of the composition across the mucosal epithelium. Furthermore, in at least some instances, the penetration enhancer has been found to improve the immune response following administration of the immunogen composition. Not to be bound by theory, it is believed that the combination of the penetration enhancer and the polymer provide for significant protection of the antigen from degradation and promote release of the antigen from the composition in an advantageous manner.

In yet another embodiment the immunogen composition includes an adjuvant to nonspecifically enhance the immune response. A particularly advantageous aspect of the present invention is that adjuvant-type enhancements are achievable without the use of alum or other known adjuvant materials of questionable safety. In one preferred embodiment, an additive is included in the immunogen composition that acts as both a penetration enhancer and adjuvant, with chitosan materials being particularly preferred for use as the additive for this purpose.

In one surprisingly advantageous embodiment of the present invention, the immunogen composition is administrable mucosally to stimulate both a strong mucosal immune response and also a strong systemic immune response. In this way, the immunogen composition provides the added immunity protection at the site for entry for many major pathogenic organisms, as a first line of defense against and infection by such organisms. The use of the immunogen composition, therefore, has the potential to replace current injection regimens that are effective at developing only systemic immunity, and are not effective at developing mucosal immunity. Also, the immunogen composition has been found to be particularly advantageous for developing rapid, high levels of immunity when delivered non-mucosally and with fewer administrations than has traditionally been the case with conventional multiple injection regimens. In one embodiment, sufficient immunization is achievable with only a single administration of the immunogen composition.

In another aspect, the invention provides a method for delivering the immunogen composition to a host. In one embodiment, a method for administering an antigen to a host to induce a systemic immune response comprises administering the immunogen composition to a host by injection. In another embodiment, a method for administering an antigen to a host to induce a mucosal immune response comprises administering the immunogen composition to a host, preferably by intranasal administration, such as from a nebulizer, syringe, catheter, bulb or other device. In a preferred embodiment, the composition is administered in the form of a flowable medium in which at least the polymer, and optionally also the antigen, is dissolved in the liquid carrier. In a particularly preferred embodiment, the immunogen composition converts to a gel form, which is substantially not flowable, inside the host following administration. This is accomplished, for example, when the polymer, as formulated in the composition, exhibits reverse-thermal gelation properties with a reverse-thermal liquid-gel transition temperature that is at or below the physiologic temperature of the host. In one embodiment, a host is administered one or more, but preferably only one, mucosal administration after having already received a systemic administration of the same antigen in the same or different composition, with the mucosal administration(s) eliciting a mucosal immune response sufficient to provide the host with mucosal immunity to at least one pathogen without disturbing the integrity of the mucosal membrane. This is particularly advantageous for both boosting systemic immunity and stimulating mucosal immunity for the large population group that has already been systemically immunized by injection, but that would benefit from a systemic immunization boost and/or the added first line defense of mucosal immunity. In another embodiment the host is administered one or more mucosal applications of the immunogen composition to elicit an immune response without having previously received a systemic administration. This is particularly advantageous for replacement of injection regimens for hosts that are being initially immunized, and to also provide the hosts with both systemic and mucosal immunity.

In another aspect, the invention provides a method for manufacturing an immunogen composition in which the antigen is dissolved in or dispersed throughout a solution of the polymer dissolved in the liquid vehicle. In yet another aspect, the present invention provides a method for packaging and storing an antigen in the protective environment of the immunogen composition. Handling and storage may be in a gel or liquid form, as desired.

DETAILED DESCRIPTION

The immunogen composition of the present invention typically includes at least one antigen, at least one biocompatible polymer, and at least one liquid vehicle and exhibits reverse thermal viscosity behavior over at least some temperature range. The immunogen composition may optionally also include other components that may enhance performance of the composition.

In one embodiment, the immunogen composition is in the form of a flowable medium, while in another embodiment the immunogen composition is in the form of a gel. In either case, the antigen should be homogenously dispersed throughout the composition. In a preferred embodiment, the immunogen composition is capable of converting from the gel form to the flowable medium form, and vice versa, by a change in temperature across a reverse-thermal liquid-gel transition temperature, so that the immunogen composition is in the form of a flowable medium below the transition temperature and a gel form above the transition temperature. As used herein, a medium is "flowable" , when it has sufficiently low viscosity to be syringable and/or nebulizable, depending upon the specific application. Such a flowable medium may, for example, be in a liquid form, or may include a liquid in which fine particulate material is suspended, with the medium retaining sufficient fluidity to be syringible and/or nebulizable.

When the immunogen composition is in the flowable medium form, the biocompatible polymer will typically be substantially all dissolved in the liquid vehicle, and the antigen will also preferably be substantially all dissolved in the liquid vehicle along with the biocompatible polymer. Alternatively, some or all of the antigen may be in the form of a fine particulate, such as a fine precipitate, dispersed throughout the biocompatible polymer/liquid vehicle solution. When present, other components are dissolved in the liquid vehicle or are otherwise preferably uniformly dispersed throughout the composition. When the immunogen composition is in a gel form, the antigen, and other components, when present, will preferably be uniformly dispersed throughout the gel.

The immunogen composition of the present invention is useful for delivering an antigen to a host to treat or prevent an infectious disease. For example, one skilled in the art can readily discern that a microbial infection can be prevented by administering an antigen corresponding to that organism to a host animal as a vaccine to elicit a protective immune response. The host is typically a mammal, and more typically a human. Furthermore, the immunogen composition can be used for the treatment of cancers such as those caused by human papilloma virus. Also, the immunogen composition can be used to alter the mammalian reproductive cycle. Antigens useful in the immunogen composition of the present invention include antigens from bacteria, protozoa and viruses that invade their host via a mucosal surface. Other useful antigens include causative agents of childhood illnesses, antigens from rotavirus, hookworm, Neisseria meningitiditis, Streptococcus pneumoniae, Bordatella pertussis, M. tuberculosis, Epstein-Barr virus, Hepatitis C virus, HIV, influenza and tumor-specific antigens, tetanus toxoid, diphtheria toxoid and other non-pathogenic mutants of these toxins, other toxins or non-pathogenic versions of these toxins that cause disease such as anthrax toxic complex, polysaccharides or peptide mimetics of polysaccharides from Neisseria meningitiditis, or Streptococcus pneumoniae. Preferably the antigen is selected from the group consisting of tetanus toxoid, diphtheria toxoid, and other non-pathogenic mutants of these toxins, other toxins or non-pathogenic versions thereof that cause disease such as anthrax toxic complex, antigens from Bordatella pertussis, rotavirus, hookworm, M. tuberculosis, Epstein-Barr virus, Hepatitis C virus, HIV, Neisseria meningitiditis, Streptococcus pneumoniae, polysaccharides or peptide mimetics of polysaccharides from Neisseiria meningitiditis, or Streptococcus pneumoniae, antigens from other blood-borne pathogens, tumor-specific antigens and antigens from viruses or bacteria against which vaccines are currently available. Most preferably the antigen is selected from the group consisting of tetanus toxoid, diphtheria toxoid and other mutants of these toxins, anthrax toxic complex, antigens from Bordatella pertussis, M. tuberculosis, HIV and antigens from viruses or bacteria against which vaccines are currently available. Particularly preferred is for the antigen to include one or more of tetanus toxoid, diphtheria toxoid and antigens from Bordatella pertussis. Although Clostridium tetanii does not generally invade its host via mucosal surfaces there are reported cases of tetanus entering the body through mucosal lesions. The immunogen composition may include two or more antigens. For example, one preferred immuogen composition includes tetanus toxoid (or a non-pathogenic mutant of tetanus toxoid) and diphtheria toxoid (or a non-pathogenic mutant of diphtheria toxoid).

The amount of antigen in the immunogen composition of the present invention varies depending on the nature and potency of the antigen. Typically, however, the amount of antigen present in the immunogen composition of the present invention is from about 0.000001% by weight of the immunogen composition to about 5% by weight of the immunogen composition, more typically from about 0.0001% by weight to about 5% by weight, and more typically from about 0.005% by weight to about 5% by weight. In one particular aspect of the present invention where the antigen is tetanus toxoid, the amount of tetanus toxoid present in the immunogen composition is typically from about 0.0001% by weight to about 0.05% by weight, preferably from about 0.0005% by weight to about 0.01% by weight, and more preferably from about 0.0005% by weight to about 0.003% by weight.

The immunogen composition of the present invention provides a delivery system that typically elicits stimulation of an immune response, which will typically include a systemic immune response when the immunogen composition is administered for systemic delivery of the antigen. Furthermore, the immunogen composition of the present invention provides a delivery system that elicits stimulation of a strong immune response, which will typically include both a strong systemic immune response and a strong mucosal immune response when the immunogen composition is administered for mucosal delivery of the antigen. Furthermore, the immunogen composition when administered for mucosal delivery can act as a boost to an existing immune response. Without being bound by any theory, it is believed that the immunogen composition of the present invention reduces or eliminates degradation of the antigen and allows for a relatively slow sustained administration of antigens to the host. The antigen is at least partially protected by the biocompatible polymer, thereby reducing susceptibility of the antigen to degradation and promoting increased effectiveness of the antigen. Also, it is believed that the immunogen composition of the present invention promotes improved bioadhesion onto and permeation into and across the mucous membrane, or mucosa, thus allowing the immunogen composition to exert its actions more efficaciously at the target site. This is particularly the case according to the invention when the immunogen composition includes an adjuvant and/or penetration enhancer that further enhances performance. Moreover, stabilizing agents may be incorporated into the immunogen composition to further reduce the susceptibility of the antigen to degradation, tending to further enhance the effectiveness of the immunogen composition to stimulate mucosal immunity and to also enhance stability of the antigen during storage and transportation of the composition.

The biocompatible polymer in the immunogen composition of the present invention typically is a reverse-thermal gelation polymer. The biocompatible polymer is selected and the immunogen composition is formulated with relative proportions of the liquid vehicle and the biocompatible polymer so that the immunogen composition exhibits reverse-thermal viscosity behavior across at least some temperature range, preferably a temperature range below 40.degree. C., more preferably a temperature range below 37.degree. C. and even more preferably a temperature range within a range of from 10.degree. C. to 37.degree. C. Typically, the immunogen composition exhibits reverse-thermal viscosity behavior over some temperature range within a range of 1.degree. C. to 20.degree. C. Due to the reverse thermal viscosity behavior of the immunogen composition, the immunogen composition can be administered to the host at a cooler temperature where the composition has a lower viscosity, with the viscosity of the composition then increasing in the host following administration, whereby the mobility of the composition is severely reduced within the host following administration. When the immunogen composition has a reverse thermal gelation property, then the immunogen composition will exist in the form of a flowable medium at least at a first temperature and in the form of a gel at least at a second temperature that is higher than the first temperature. Preferably both the first and second temperatures are below 40.degree. C., and more preferably the second temperature is no higher than 37.degree. C. A preferred situation is when the first temperature is in a range of 1.degree. C. to 20.degree. C. and the second temperature is in a range of 25 .degree. C. to 37.degree. C.

In a particularly preferred embodiment, the immunogen composition is formulated with relative proportions of liquid vehicle and biocompatible polymer so that the immunogen composition has a reverse-thermal gelation property, preferably with a reverse-thermal liquid-gel transition temperature so that when the immunogen composition is administered to a host, the biocompatible polymer and also the immunogen composition becomes a gel or gelatinous in vivo, thus reducing or eliminating degradation of the antigen and/or achieving the ability for slow release, i.e., sustained administration, of the antigen for a time period of many hours, days, weeks or even months, depending upon the specific application.

Any biocompatible polymer may be used that, as formulated in the immunogen composition, is capable of interacting with the liquid vehicle to impart the desired reverse-thermal viscosity behavior to the immunogen composition. Non-limiting examples of some reverse-thermal gelation polymers useful for preparing the immunogen composition include certain polyethers (preferably polyoxyalkylene block copolymers with more preferred polyoxyalkylene block copolymers including polyoxyethylene-polyoxypropylene block copolymers referred to herein as POE-POP block copolymers, such as Pluronic.TM. F68, Pluronic.TM. F127, Pluronic.TM. L121, and Pluronic.TM. L101, and Tetronic.TM. T1501); certain cellulosic polymers, such as ethylhydroxyethyl cellulose; and certain poly (ether-ester) block copolymers (such as those disclosed in U.S. Pat. No. 5,702,717). Pluronic.TM. and Tetronic.TM. are trademarks of BASF Corporation. Furthermore, more than one of these and/or other biocompatible polymers may be included in the immunogen composition to provide the desired characteristics and other polymers and/or other additives may also be included in the immunogen composition to the extent the inclusion is not inconsistent with performance requirements of the immunogen composition. Furthermore, these polymers may be mixed with other polymers or other additives, such as sugars, to vary the transition temperature, typically in aqueous solutions, at which reverse-thermal gelation occurs.

Polyoxyalkylene block copolymers are particularly preferred to use as the biocompatible reverse-thermal gelation polymer. A polyoxyalkylene block copolymer is a polymer including at least one block (i.e. polymer segment) of a first polyoxyalkylene and at least one block of a second polyoxyalkylene, although other blocks may be present as well. POE-POP block copolymers are one class of preferred polyoxyalkylene block copolymers for use as the biocompatible reverse-thermal gelation polymer in the immunogen composition. POE-POP block copolymers include at least one block of a polyoxyethylene and at least one block of a polyoxypropylene, although other blocks may be present as well. The polyoxyethylene block may be represented by the formula (C.sub.2H.sub.4O).sub.b when b is an integer. The polyoxypropylene block may be represented by the formula (C.sub.3H.sub.6O).sub.a when a is an integer. The polyoxypropylene block could be for example (CH.sub.2CH.sub.2CH.sub.2O).sub.a, or could be -- see Original Patent.

Several POE-POP block copolymers are known to exhibit reverse-thermal gelation properties, and these polymers are particularly preferred for imparting reverse-thermal gelation properties to the immunogen composition of the present invention. Examples of POE-POP block copolymers include Pluronic.TM. F68, Pluronic.TM. F127, Pluronic.TM. L121, Pluronic.TM. L101, and Tetronic.TM. T1501. Tetronic.TM. T1501 is one example of a POE-POP block copolymer having at least one polymer segment in addition to the polyoxyethylene and polyoxypropylene segments. Tetronic.TM. T1501 is reported by BASF Corporation to be a block copolymer including polymer segments, or blocks, of ethylene oxide, propylene oxide and ethylene diamine.

As will be appreciated, any number of biocompatible polymers may now or hereafter exist that are capable of imparting the desired reverse-thermal viscosity behavior and/or reverse-thermal gelation properties for the immunogen composition of the present invention, and such polymers are specifically intended to be within the scope of the present invention when incorporated into the immunogen composition.

Some preferred POE-POP block copolymers have the formula: HO(C.sub.2H.sub.4O).sub.b(C.sub.3H.sub.6O).sub.a(C.sub.2H.sub.4O).sub.bH I which, in the preferred embodiment, has the property of being liquid at ambient or lower temperatures and existing as a semi-solid gel at mammalian body temperatures wherein a and b are integers in the range of 15 to 80 and 50 to 150, respectively. A particularly preferred POE-POP block copolymer for use with the present invention has the following formula: HO(CH.sub.2CH.sub.2O).sub.b(CH.sub.2(CH.sub.3)CHO).sub.a(CH.sub.- 2CH.sub.2O).sub.bH II wherein a and b are integers such that the hydrophobe base represented by (CH.sub.2(CH.sub.3)CHO).sub.a has a molecular weight of about 4,000, as determined by hydroxyl number; the polyoxyethylene chain constituting about 70 percent of the total number of monomeric units in the molecule and where the copolymer has an average molecular weight of about 12,600. Pluronic.TM. F-127, also known as Poloxamer 407, is such a material. In addition, a structurally similar Pluronic.TM. F-68 may also be used.

The procedures used to prepare aqueous solutions which form gels of polyoxyalkylene block copolymer are well known and are disclosed in U.S. Pat. No. 5,861,174, which is incorporated herein by reference in its entirety. The relative proportions of the liquid vehicle and the biocompatible polymer, as formulated in the immunogen composition, should be selected so that the resulting immunogen composition has reverse-thermal gelation properties with a reverse-thermal liquid-gel transition temperature of less than about 37.degree. C., preferably between about 10.degree. C. and 37 .degree. C., and more preferably between about 20.degree. C. to about 37.degree. C. The amount of biocompatible polymer in the immunogen composition of the present invention is typically from about 1% by weight to about 50% by weight of the immunogen composition, preferably from about 8% by weight to about 33% by weight, and more preferably from about 13% by weight to about 25% by weight.

In one preferred embodiment of the present invention, the immunogen composition includes an additive that is an adjuvant and/or a penetration enhancer. In some instances a single compound may act both as a penetration enhancer and an adjuvant when incorporated into the immunogen composition. This is the case, for example, with chitosan and other chitosan materials, which are especially preferred additives for use in the immunogen composition. Chitosan is a polysaccharide derived from deacetylation of chitosan. As used herein, "chitosan materials" include chitosan, derivatives of chitosan and other derivatives originating from chitin that provide adjuvant and/or penetration enhancer properties similar to chitosan. The use of chitosan material as a combined penetration enhancer/adjuvant is especially preferred when the immunogen composition is administered mucosally.

Non-limiting examples of penetration enhancers include various molecular weight chitosan materials, such as chitosan and N,O-carboxymethyl chitosan; poly-L-arginines; fatty acids, such as lauric acid; bile salts such as deoxycholate, glycolate, cholate, taurocholate, taurodeoxycholate, and glycodeoxycholate; salts of fusidic acid such as taurodihydrofusidate; polyoxyethylenesorbitan such as Tween.TM. 20 and Tween.TM. 80; sodium lauryl sulfate; polyoxyethylene-9-lauryl ether (Laureth.TM.-9); EDTA; citric acid; salicylates; caprylic/capric glycerides; sodium caprylate; sodium caprate; sodium laurate; sodium glycyrrhetinate; dipotassium glycyrrhizinate; glycyrrhetinic acid hydrogen succinate, disodium salt (Carbenoxolone.TM.); acylcarnitines such as palmitoylcarnitine; cyclodextrin; and phospholipids, such as lysophosphatidylcholine. Preferably, the penetration enhancer is selected from the group consisting of chitosan materials, and fatty acids, polyethylene sorbitol and caprylic/capric glycerides. More preferably, the penetration enhancer is selected from the group consisting of chitosan materials, fatty acids and caprylic/capric glycerides. Particularly preferred as the penetration enhancers are the chitosan materials. As used herein, a "penetration enhancer" is any substance or material that, when added to a formulation including an active agent, such as the antigen in the immunogen composition, enables or enhances permeation of the active agent across biological membranes thereby increasing absorption and systemic bioavailability of the active agent. In the case of a formulation with an active agent delivered by a mucosal route, the penetration enhancer enables or enhances permeation of the active agent across the mucosal epithelium where the active agent is to be delivered.

Non-limiting examples of adjuvants for use in the immunogen composition include those materials that exhibit adjuvantic properties in mucosal tissues including chitosan materials, bacterially derived products such as monophosphoryl lipid A, CpG motifs, detoxified mutants of CT and ET, and outer membrane proteins of Neisseria meningitidis serogroup b. Other non-limiting examples of adjuvants for use in the immunogen composition include those materials that exhibit adjuvantic properties in non-mucosal tissues including dimethyl dioctadecyl ammonium bromide (DDA), CpG motifs, cytokines such as IL-12 and IL-6, as well as chitosan materials.

When present, the amount of penetration enhancer and/or adjuvant in the immunogen composition of the present invention generally varies depending on the particular additive(s) used. However, a typical amount of penetration enhancer present in the immunogen composition of the present invention is from about 0.001% by weight to about 10% by weight of the immunogen composition, preferably from about 0.01% by weight to about 5% by weight, and more preferably from about 0.01% by weight to about 1.0% by weight. In one particular aspect of the present invention when a chitosan materials is used as a penetration enhancer and/or an adjuvant, the amount of the chitosan or chitosan material present in the immunogen composition is typically from about 0.01% by weight to about 10% by weight of the immunogen composition, preferably from about 0.1% by weight to about 1% by weight, and more preferably from about 0.1% by weight to about 0.5% by weight. In one preferred composition, the immunogen composition comprises from 60 weight percent to 85 weight percent of the liquid vehicle, from 0.0001 weight percent to 5 weight percent of the antigen and from 0.01 weight percent to 1.0 weight percent of at least one of the adjuvant an/or penetration enhancer additive.

The immunogen composition of the present invention can also include other additives besides adjuvant and/or penetration enhancer. For example, the immunogen composition can include polymer or protein stabilizers such as trehalose, sucrose, glycine, mannitol, albumin, and glycerol.

Any suitable liquid vehicle can be used that is capable of interacting with the biocompatible polymer to impact the desired reverse thermal viscosity behavior. Preferably the biocompatible polymer, and also preferably the antigen, is soluble in the liquid vehicle at least at a temperature at which the immunogen composition is in the form of a flowable medium suitable for administration. The adjuvant and/or penetration enhancer are also preferably soluble in the liquid vehicle in the flowable medium form suitable for administration. The immunogen composition is typically prepared in water, a saline solution or other aqueous liquid as the liquid vehicle, although any solvent, including mixtures of multiple solvent liquids, can be used, depending upon the specific circumstances of the application. Under ordinary conditions of storage and use, the immunogen composition may also contain a preservative to prevent the growth of microorganisms, Preferably, the immunogen composition is sterile, and is fluid, i.e., in the form of a flowable liquid or suspension, when administered to accommodate easy syringability and/or nebulization. The immunogen composition should preferably be stable under the conditions of manufacture and storage and should also preferably be preserved against the contaminating action of microorganisms such as bacteria and fungi. The liquid vehicle can be a solvent or dispersion medium containing, for example, water, ethanol, polyol (e.g., glycerol, propylene glycol, and liquid polyethylene glycol, and the like), and suitable mixtures thereof. The prevention of the action of microorganisms can be brought about by various antibacterial and antifungal agents, for example, parabens, chlorobutanol, phenol, sorbic acid, thimerosal, and the like. In many cases, it will be preferable to include isotonic agents, e.g., sugars, phosphate buffers, sodium chloride, or mixtures thereof.

In another embodiment, antigen-stabilizing solutes, typically protein-stabilizing solutes, are incorporated into the immunogen composition. The use of protein-stabilizing solutes, such as sucrose, not only aids in protecting and stabilizing the antigen (especially when the antigen is a protein), but also permits manipulation of the reverse-thermal gelation properties of the composition. For example, addition of certain protein-stabilizing solvents permits the composition to exhibit desired reverse-thermal gelation behavior at lower polymer concentration and/or at an altered reverse-thermal gelation temperature than when the protein-stabilizing is not used, especially when using the preferred polyalkoxyalkylene block copolymers. Thus, the working range of polymer concentration can be widened and the transition temperature modified. It is known that in some cases a gel will not form when the concentration of polyoxyethylene-polyoxypropylene block copolymer in water or dilute buffer is outside a particular range, e.g., equal to or less than 15% percent by weight for some polymers. However, by introducing protein-stabilizing solutes to the immunogen composition of the present invention, the transition temperature may be manipulated, while also lowering the concentration of polyoxyethylene-polyoxypropylene block copolymer that is necessary to form a gel. In this regard, preferred protein-stability solvents are sugars, such as, for example, sucrose.

The immunogen composition of the present invention is particularly effective for stimulating or upregulating a antibody response to a level greater than that seen with conventional formulations and administration schedules. More preferably the immunogen composition of the present invention, upon administration, stimulates a systemic immune response that protects the host from at least one pathogen. Most preferably the immunogen composition of the present invention, upon administration, stimulates a systemic and mucosal immune response that protects the host from at least one pathogen. As will be appreciated a immune response involves generation of one or more antibody classes, such as IgM, IgG and/or IgA, and typically for mucosal responses at least IgA.

In one aspect, the invention provides a method for delivery of an antigen to a host to stimulate an immune response in the host. The method involves administering the immunogen composition of the present invention to the host, which is usually accomplished by introducing the immunogen composition into the host in a manner to stimulate a desired immune response. The immunogen composition can be introduced into the host by any suitable technique. For example, in one embodiment, the immunogen composition is introduced into the host by injection, such as, for example, subcutenously, intramuscularly, or intraperitoneally. The injection may be accomplished using any suitable injection device, such as, for example, a syringe.

In another embodiment, the immunogen composition is introduced into the host for delivery of the antigen via a mucosal route. In this embodiment, the immunogen composition is introduced into the host in a manner so that at least a portion, and preferably most or all, of the administered immunogen composition contacts a mucosal surface within the host. At least a portion, and more preferably at least a significant portion, of the immunogen composition adheres to the mucosal surface, thereby retaining the antigen, and also any adjuvant and/or penetration enhancer in the vicinity of the mucosal surface to promote uptake of the antigen across the mucosal surface.

Whether administered by injection or mucosally, the immunogen composition should be in the form of a flowable medium immediately prior to introduction of the immunogen composition into the host. This will typically require that the immunogen composition be at a temperature that is lower than the physiologic temperature of the host. In the case of a human host, having a physiologic temperature of 37.degree. C., the temperature of the immunogen composition immediately prior to administration will frequently be 25.degree. C. or less and more often 20.degree. C. or less. In most instances, the temperature of the immunogen composition immediately prior to introduction into the host will be in a range of from about 1.degree.C. to about 20.degree.C.

After introduction into the host, the immunogen composition is warmed to the physiologic temperature of the host and, due to the reverse-thermal viscosity behavior of the immunogen composition, the viscosity of the immunogen composition increases inside the host as the temperature of the immunogen composition increases. When the immunogen composition has a reverse-thermal liquid-gel transition temperature between the temperature of administration and the physiologic temperature of the host, then the immunogen composition will convert from the form of a flowable medium to a gel form inside the host following administration. Thus the reverse-thermal gelation property of the immunogen composition is advantageous to permit easy administration of the immunogen composition to the host as a flowable medium and the viscosity then advantageously increases after administration at least partially to immobilize the immunogen composition at the location where delivery of the antigen is desired. This is particularly advantageous when the antigen is to be delivered via a mucosal route, because the high viscosity/gel nature of the immunogen composition following administration causes the immunogen composition to readily adhere to mucosal surfaces, so that the immunogen composition, including the antigen and any additives are retained in the vicinity of the mucosal surface to facilitate delivery of the antigen across the mucosal surface.

When the antigen is delivered via a mucosal route, the immunogen composition may be directed to contact any desired mucosal surface to permit delivery of at least a portion of the antigen across the mucosal epithelium at that location to elicit an immune response. The mucosal surface may, for example, be a sublingual, buccal, oral, intranasal, gastrointestinal, pulmonary, vaginal, rectal, aural, or ocular mucosal surface. For many of these mucosal delivery applications, such as for oral, intranasal, pulmonary and sublingual, it is preferred that the immunogen composition is introduced into the host in the form of a mist containing a dispersion of fine droplets of the immunogen composition. Typically, the mist will be produced by a nebulizer actuatable to produce the mist. For example, one preferred mucosal delivery route is intranasal and the mist could be generated by a nasal nebulizer. When generated by the nasal nebulizer, the spray is directed into the nasal cavity to introduce the immunogen composition into the host to contact a mucosal surface within the nasal cavity.

Whether the immunogen composition is delivered by injection or mucosally, the biocompatible polymer, and preferably also the antigen and any adjuvant and/or penetration enhancer are dissolved in the liquid vehicle. As the composition gels within the host, at least a portion of the polymer, and potentially also some or all of the antigen and other additives come out of solution.

In another aspect of the invention, a method is provided for packaging and storing the immunogen composition. According to this aspect of the invention, the immunogen composition is placed in a container when the composition is in the form of a flowable medium. The temperature of the composition is then raised so that the immunogen composition converts to a gel form within the container for storage. Following storage in the gel form, the immunogen composition in the container can be converted back to a flowable medium for administration to the host at the appropriate time by lowering the temperature of the composition in the container. In this way, the immunogen composition is easy to handle during manufacturing and packaging operations, but can be stored in the highly stable form of a gel. Furthermore, the composition can be converted back to a flowable medium for ease of administration.

It is not, however, required that the immunogen composition be stored at a temperature below the transition temperature. The immunogen composition may be stored in a gel form above the transition temperature and then cooled to below the transition temperature prior to administration. This ability to store the antigen in a gel form of the immunogen composition prior to use is a distinct advantage with the present invention. Alternatively, the immunogen composition could be stored in the form of a flowable medium at a temperature below the reverse-thermal liquid-gel transition temperature, but such a fluid form is often not as convenient for handling and storage as a gel form. In either case, the immunogen composition is advantageous for storing the antigen in a highly protective environment prior to use.

In another aspect, a method for making the immunogen composition is provided, comprising dissolving the biocompatible polymer in a liquid vehicle and suspending or codissolving the antigen in the liquid vehicle. Preferably, both the antigen and the biocompatible polymers are dissolved in the liquid vehicle.

The present invention has been described primarily with reference to the immunogen composition. The principles discussed with respect to formulation, manufacture, storage, and administration of the immunogen composition apply equally to the delivery of other drugs. In that regard, the aspects of the present invention as described above can be applied to formulate, prepare, restore, and administer a delivery vehicle composition for delivering any drug in a therapeutically effective amount for treatment of at least one condition in the host. The delivery vehicle includes at least the drug, the biocompatible polymer and the liquid vehicle, with the proportions of the liquid vehicle and the biocompatible polymer being such that the delivery vehicle composition exhibits reverse-thermal viscosity behavior, and preferably, a reverse-thermal gelation property, as discussed above specifically with respect to the immunogen composition. In a preferred embodiment, the delivery vehicle composition includes as an additive at least one of an adjuvant and a penetration enhancer for the drug to be delivered.
 

Claim 1 of 41 Claims

1. A composition for delivery of an antigen for stimulation of an immune response when administered to a host, the composition comprising: an antigen, a polyoxyalkylene block copolymer and an aqueous liquid; the polyoxyalkylene block copolymer being biocompatible, not having toxic or injurious effects on biological function in the host when the composition is administered; wherein, the composition is formulated with relative proportions of the liquid and the copolymer so that the copolymer interacts with the liquid to impart reverse thermal viscosity behavior to the composition, so that the viscosity of the composition increases when the temperature of the composition increases over some temperature range within 1.degree. C. to 37.degree. C.; and wherein, the composition further comprises an additive enhancing the immune response when the composition is administered to the host, the additive being an adjuvant other than alum; and; wherein, the liquid comprises from 60 weight percent to 85 weight percent of the composition, the antigen comprises from 0.0001 weight percent to 5 weight percent of the composition, the copolymer comprises from 5 weight percent to 33 weight percent of the composition and the additive comprises from 0.01 weight percent to 10.0 weight percent of the composition.

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