A novel adjuvant for mucosal immunity to HIV-1 gp120 in nonhuman primates

Mucosal vaccines: wisdom from now and then

The oral and nasal cavities are covered by the mucosal epithelium that starts at the beginning of the aero-digestive tract. These mucosal surfaces are continuously exposed to environmental antigens including pathogens and allergens and are thus equipped with a mucosal immune system that mediates initial recognition of pathogenicity and initiates pathogen-specific immune responses. At the dawn of our scientific effort to explore the mucosal immune system, dental science was one of the major driving forces as it provided insights into the importance of mucosal immunity and its application for the control of oral infectious diseases. The development of mucosal vaccines for the prevention of dental caries was thus part of a novel approach that contributed to building the scientific foundations of the mucosal immune system. Since then, mucosal immunology and vaccines have gone on a scientific journey to become one of the major entities within the discipline of immunology. Here, we introduce our past and current efforts and future directions for the development of mucosal vaccines, specifically a rice-based oral vaccine (MucoRice) and a nanogel-based nasal vaccine, with the aim of preventing and controlling gastrointestinal and respiratory infectious diseases using the interdisciplinary fusion of mucosal immunology with agricultural science and biomaterial engineering, respectively.

Oral Mucosal Immunity and HIV/SIV Infection

Human Immunodeficiency Virus (HIV) transmission through genital and rectal mucosa has led to intensive study of mucosal immune responses to HIV and to the development of a vaccine administered locally. However, HIV transmission through the oral mucosa is a rare event. The oral mucosa represents a physical barrier and contains immunological elements to prevent the invasion of pathogenic organisms. This particular defense differs between micro-compartments represented by the salivary glands, oral mucosa, and palatine tonsils. Secretory immunity of the salivary glands, unique features of cellular structure in the oral mucosa and palatine tonsils, the high rate of oral blood flow, and innate factors in saliva may all contribute to the resistance to HIV/Simian Immunodeficiency Virus (SIV) oral mucosal infection. In the early stage of HIV infection, humoral and cellular immunity and innate immune functions in oral mucosa are maintained. However, these particular immune responses may all be impaired as a result of chronic HIV infection. A better understanding of oral mucosal immune mechanisms should lead to improved prevention of viral and bacterial infections, particularly in immunocompromised persons with Acquired Immune Deficiency Syndrome (AIDS), and to the development of a novel strategy for a mucosal AIDS vaccine, as well as vaccines to combat other oral diseases, such as dental caries and periodontal diseases.

Intranasal Immunization with DOTAP Cationic Liposomes Combined with DC-Cholesterol Induces Potent Antigen-Specific Mucosal and Systemic Immune Responses in Mice

Despite the progress made by modern medicine, infectious diseases remain one of the most important threats to human health. Vaccination against pathogens is one of the primary methods used to prevent and treat infectious diseases that cause illness and death. Vaccines administered by the mucosal route are potentially a promising strategy to combat infectious diseases since mucosal surfaces are a major route of entry for most pathogens. However, this route of vaccination is not widely used in the clinic due to the lack of a safe and effective mucosal adjuvant. Therefore, the development of safe and effective mucosal adjuvants is key to preventing infectious diseases by enabling the use of mucosal vaccines in the clinic. In this study, we show that intranasal administration of a cationic liposome composed of 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) and 3β-[N-(N',N'-dimethylaminoethane)-carbamoyl] (DC-chol) (DOTAP/DC-chol liposome) has a potent mucosal adjuvant effect in mice. Intranasal vaccination with ovalbumin (OVA) in combination with DOTAP/DC-chol liposomes induced the production of OVA-specific IgA in nasal tissues and increased serum IgG1 levels, suggesting that the cationic DOTAP/DC-chol liposome leads to the induction of a Th2 immune response. Additionally, nasal-associated lymphoid tissue and splenocytes from mice treated with OVA plus DOTAP/DC-chol liposome showed high levels of IL-4 expression. DOTAP/DC-chol liposomes also enhanced OVA uptake by CD11c+ dendritic cells in nasal-associated lymphoid tissue. These data demonstrate that DOTAP/DC-chol liposomes elicit immune responses via an antigen-specific Th2 reaction. These results suggest that cationic liposomes merit further development as a mucosal adjuvant for vaccination against infectious diseases.

Nasal Administration of Cholera Toxin as a Mucosal Adjuvant Damages the Olfactory System in Mice

Cholera toxin (CT) induces severe diarrhea in humans but acts as an adjuvant to enhance immune responses to vaccines when administered orally. Nasally administered CT also acts as an adjuvant, but CT and CT derivatives, including the B subunit of CT (CTB), are taken up from the olfactory epithelium and transported to the olfactory bulbs and therefore may be toxic to the central nervous system. To assess the toxicity, we investigated whether nasally administered CT or CT derivatives impair the olfactory system. In mice, nasal administration of CT, but not CTB or a non-toxic CT derivative, reduced the expression of olfactory marker protein (OMP) in the olfactory epithelium and olfactory bulbs and impaired odor responses, as determined with behavioral tests and optical imaging. Thus, nasally administered CT, like orally administered CT, is toxic and damages the olfactory system in mice. However, CTB and a non-toxic CT derivative, do not damage the olfactory system. The optical imaging we used here will be useful for assessing the safety of nasal vaccines and adjuvants during their development for human use and CT can be used as a positive control in this test.

Modulation of HIV-1 immunity by adjuvants

Purpose of review

To summarize the role of adjuvants in eliciting desirable antibody responses against HIV-1 with particular emphasis on both historical context and recent developments.

Recent findings

Increased understanding of the role of pattern recognition receptors such as Toll-like receptors in recruiting and directing the immune system has increased the variety of adjuvant formulations being tested in animal models and humans. Across all vaccine platforms, adjuvant formulations have been shown to enhance desirable immune responses such as higher antibody titers and increased functional activity. Although no vaccine formulation has yet succeeded in eliciting broad neutralizing antibodies against HIV-1, the ability of adjuvants to direct the immune response to immunogens suggests they will be critically important in any successful HIV-1 vaccine.

Summary

The parallel development of adjuvants along with better HIV-1 immunogens will be needed for a successful AIDS vaccine. Additional comparative testing will be required to determine the optimal adjuvant and immunogen regimen that can elicit antibody responses capable of blocking HIV-1 transmission.

Vaccination with Toxoplasma lysate antigen and CpG oligodeoxynucleotides: comparison of immune responses in intranasal versus intramuscular administrations

Toxoplasma gondii (T. gondii) is one of the most successful intracellular protozoan parasites on earth and highly prevalent in most warm-blooded vertebrates. There are no drugs that target the chronic cyst stage of this infection; therefore, development of an effective vaccine would be an important advance in disease control. Oligodeoxynucleotides (ODN) which contain immunostimulatory CG motifs (CpG ODN) can promote T-helper 1 (Th1) responses, an adjuvant activity that is desirable for vaccination against intracellular pathogen. In this study, we compare the immune responses of Toxoplasma susceptible C57BL/6 mice following intranasal and intramuscular vaccination with Toxoplasma lysate antigen (TLA) with or without CpG ODN as adjuvant. Immunized and control non-immunized mice were challenged with 85 cyst of the moderately virulent Beverley strain of T. gondii. Intranasal vaccination gave significantly a higher protection compared to other groups as indicated by prolonged survival and significantly reduced brain cyst burden (P < 0.01). Intranasal vaccination stimulated cellular immunity towards Th1 response characterized by significant INF-γ production (P < 0.01). Furthermore, fecal IgA antibody levels as an indicator of mucosal immune responses were significantly higher (P < 0.05) in intranasal vaccinated group before the challenge compared to all other groups. Intranasal vaccination was not able to upgrade the Th1 humoral arm. In contrast, intramuscular vaccination enhanced humoral immunity towards a type Th1 pattern characterized by a significant increase of specific IgG and Ig2a. Our results suggest that intranasal administration of CpG/TLA would provide a stable, pronounced, and effective vaccine against toxoplasmosis through stimulation of Th1 cellular immunity and mucosal IgA.

Novel vaccine development strategies for inducing mucosal immunity

To develop protective immune responses against mucosal pathogens, the delivery route and adjuvants for vaccination are important. The host, however, strives to maintain mucosal homeostasis by responding to mucosal antigens with tolerance, instead of immune activation. Thus, induction of mucosal immunity through vaccination is a rather difficult task, and potent mucosal adjuvants, vectors or other special delivery systems are often used, especially in the elderly. By taking advantage of the common mucosal immune system, the targeting of mucosal dendritic cells and microfold epithelial cells may facilitate the induction of effective mucosal immunity. Thus, novel routes of immunization and antigen delivery systems also show great potential for the development of effective and safe mucosal vaccines against various pathogens. The purpose of this review is to introduce several recent approaches to induce mucosal immunity to vaccines, with an emphasis on mucosal tissue targeting, new immunization routes and delivery systems. Defining the mechanisms of mucosal vaccines is as important as their efficacy and safety, and in this article, examples of recent approaches, which will likely accelerate progress in mucosal vaccine development, are discussed.

Thymic stromal lymphopoietin (TSLP) acts as a potent mucosal adjuvant for HIV-1 gp140 vaccination in mice

The development of a successful vaccine against HIV is likely to require the induction of strong and long-lasting humoral immune responses at the mucosal portal of virus entry. Hence, the design of a vaccine strategy able to induce mucosal antibodies and in particular specific IgA, may be crucial to providing immune protection. Nasal immunisation is known to induce specific IgG and IgA responses in the cervicovaginal mucosa; however, there is an urgent need for the development of safe, effective and accessible mucosal adjuvants for nasal application in humans. To reduce the potential for adverse events associated with some nasal adjuvants, we have assessed whether the B-cell-activating cytokines APRIL, BAFF and TSLP enhance humoral immune responses to HIV-1 gp140. Following intranasal immunisation, TSLP but not APRIL or BAFF induced strong humoral responses both in serum and mucosa. The adjuvant effect of TSLP on humoral responses was similar to that of cholera toxin (CT). The use of TSLP as an adjuvant skewed both the cellular and humoral immune responses towards Th2 cells. This is the first time that TSLP has been demonstrated to have a positive effect as a mucosal adjuvant, and specifically to promote mucosal and systemic responses to HIV gp140.

Use of nonhuman primate models to develop mucosal AIDS vaccines

The HIV vaccines tested in the halted Step efficacy trial and the modestly successful phase 3 RV144 trial were designed to elicit strong systemic immune responses; therefore, strategies to direct immune responses into mucosal sites should be tested in an effort to improve AIDS vaccine efficacy. However, as increased CD4(+) T-cell activation and recruitment to mucosal sites have the potential to enhance HIV transmission, mucosal immune responses to HIV vaccines should primarily consist of effector CD8(+) T cells and plasma cells. Controlling the level of mucosal T-cell activation may be a critical factor in developing an effective mucosal AIDS vaccine. Immunization routes and adjuvants that can boost antiviral immunity in mucosal surfaces offer a reasonable opportunity to improve AIDS vaccine efficacy. Nonhuman primate models offer the best system for preclinical evaluation of these approaches.

Dendritic cell-targeting DNA-based mucosal adjuvants for the development of mucosal vaccines

In order to establish effective mucosal immunity against various mucosal pathogens, vaccines must be delivered via the mucosal route and contain effective adjuvant(s). Since mucosal adjuvants can simply mix with the antigen, it is relatively easy to adapt them for different types of vaccine development. Even in simple admixture vaccines, the adjuvant itself must be prepared without any complications. Thus, CpG oligodeoxynucleotides or plasmids encoding certain cDNA(s) would be potent mucosal adjuvant candidates when compared with other substances that can be used as mucosal adjuvants. The strategy of a DNA-based mucosal adjuvant facilitates the targeting of mucosal dendritic cells, and thus is an effective and safe approach. It would also provide great flexibility for the development of effective vaccines for various mucosal pathogens.

Development of mucosal adjuvants for intranasal vaccine for H5N1 influenza viruses

An increasing number of infections of highly pathogenic avian influenza virus (H5N1) in humans has been reported in South-East Asia and other areas of the world. High mortality (>60%) of this viral infection and its pathosis of systemic infection are features of this new human disease. Moreover, there is great concern that this avian H5N1 virus could cause a pandemic of new influenza in humans, once it acquires the ability for human to human transmission. To prevent such highly contagious infectious diseases as influenza, it is essential to prepare effective vaccines. Especially in the case of new influenza virus, we cannot predict the strain which will cause the pandemic. In such a situation, a vaccine that induces cross-protective immunity against variant viruses is extremely important. However currently used parenteral seasonal influenza vaccine is strain-specific, and is less effective against variant viruses. In order to overcome the weakness of current vaccines we need to learn from the immune responses induced by natural infection with influenza viruses. In the case of mucosally acquired acute respiratory infection such as influenza, mucosal immunity induced by natural infection plays important role in protection against the infection, as mucosal secretory IgA antibody plays an important role in cross-protection. In this review we describe the advantages and development of mucosal vaccine against highly pathogenic H5N1 influenza viruses.

A combination of Flt3 ligand cDNA and CpG ODN as nasal adjuvant elicits NALT dendritic cells for prolonged mucosal immunity

We explore cellular and molecular mechanisms of nasal adjuvant of a combination of a plasmid encoding the Flt3 ligand cDNA (pFL) and CpG oligodeoxynucleotides (CpG ODN). The double DNA adjuvant given with OVA maintained prolonged OVA-specific secretory IgA (S-IgA) Ab responses in external secretions for more than 25 weeks after the final immunization. Further, both Th1- and Th2-type cytokine responses were induced by this combined adjuvant regimen. The frequencies of plasmacytoid DCs (pDCs) and CD8(+) DCs were significantly increased in nasopharyngeal-associated lymphoreticular tissue (NALT) of mice given the combined adjuvant. Importantly, when we examined adjuvanticity of pFL plus CpG ODN in 2-year-old mice, significant levels of mucosal IgA Ab responses were also induced. These results demonstrate that nasal delivery of a combined DNA adjuvant offers an attractive possibility for the development of an effective mucosal vaccine for the elderly.

Oral immunization of rhesus macaques with adenoviral HIV vaccines using enteric-coated capsules

Targeted delivery of vaccine candidates to the gastrointestinal (GI) tract holds potential for mucosal immunization, particularly against mucosal pathogens like the human immunodeficiency virus (HIV). Among the different strategies for achieving targeted release in the GI tract, namely the small intestine, pH sensitive enteric coating polymers have been shown to protect solid oral dosage forms from the harsh digestive environment of the stomach and dissolve relatively rapidly in the small intestine by taking advantage of the luminal pH gradient. We developed an enteric polymethacrylate formulation for coating hydroxy-propyl-methyl-cellulose (HPMC) capsules containing lyophilized Adenoviral type 5 (Ad5) vectors expressing HIV-1 gag and a string of six highly-conserved HIV-1 envelope peptides representing broadly cross-reactive CD4(+) and CD8(+) T cell epitopes. Oral immunization of rhesus macaques with these capsules primed antigen-specific mucosal and systemic immune responses and subsequent intranasal delivery of the envelope peptide cocktail using a mutant cholera toxin adjuvant boosted cellular immune responses including, antigen-specific intracellular IFN-gamma-producing CD4(+) and CD8(+) effector memory T cells in the intestine. These results suggest that the combination of oral adenoviral vector priming followed by intranasal protein/peptide boosting may be an effective mucosal HIV vaccination strategy for targeting viral antigens to the GI tract and priming systemic and mucosal immunity.

Progress towards an AIDS mucosal vaccine: An overview

The mucosal immune system acts as a first line of defense against infection caused by luminal pathogens. Because HIV is transmitted primarily via mucosal-associated tissues, particularly with sexual transmission, understanding antiviral immunity present at these sites is important. HIV infection results in depletion of gut-associated lymphoid tissue (GALT) and in this sense can be considered to be a disease of the mucosal immune system. A stumbling block for efforts to develop a vaccine against this disease has been the escape of vaccine-induced neutralizing antibodies and cytotoxic T lymphocytes (CTLs) at mucosal compartments and the resulting viral spread. To avoid these problems, the ideal mucosal vaccine would induce HIV-specific secretory IgA (S-IgA) and mucosal CD8(+) CTL as a first line of defense at a very early stage of HIV infection, before the virus can seed into the secondary lymphoid organs in mucosal and systemic tissues. In this review, we provide an overview of mucosal vaccine concepts and vaccination strategies that have been proposed for the development of an HIV mucosal vaccine, including live recombinant vaccines, peptide-based vaccines, virus-like particles (VLP), subunit vaccines and DNA vaccines.

Development of a mucosal vaccine for influenza viruses: preparation for a potential influenza pandemic

Highly pathogenic avian H5N1 influenza A virus has caused influenza outbreaks in poultry and migratory birds in Southeast Asia, Africa and Europe, and there is concern that it could cause a new pandemic. This fear of an emerging pandemic of a new influenza strain underscores the urgency of preparing effective vaccines to meet the pandemic. One way to mitigate current concerns is to develop an influenza vaccine that is fully functional against drift influenza viruses. In our current situation, in which we cannot predict which strain will cause a pandemic, cross-protective immunity using potential and novel mucosal vaccines plays a particularly important role in preventing the spread of highly pathogenic influenza virus.

Mucosal vaccine development for botulinum intoxication

Botulism has classically been considered to be a food- and water-borne disease. However, it was recently classified by the US National Institute of Allergy and Infectious Diseases (National Institute of Health) and the US Centers for Disease Control and Prevention as a Category A agent. Thus, the botulinum exotoxin, a neurotoxin, could be easily disseminated by bioterrorists through the air-borne route with a high morbidity and mortality rate. In this regard, a high priority should be given to the development of a safe and effective mucosal vaccine to protect against botulinum neurotoxins (BoNTs) since it is well known that the mucosal immune system is the first line of defense against major pathogens. Further, mucosal immunization has been shown to induce both mucosal and systemic immunity to pathogens. By contrast, the current injection-type vaccine only provides protective immunity in the systemic compartment. Clearly, the development of a safe and effective mucosal vaccine against this toxin should be a high priority. In this regard, it has been shown that both nasal and oral immunization approaches have been taken in order to protect from BoNT intoxication. In this article, we will discuss the importance of the development of a mucosal vaccine against botulinum and introduce current aspects of BoNT mucosal vaccines, which show that they effectively prevent mucosal BoNT intoxication.

A second generation of double mutant cholera toxin adjuvants: enhanced immunity without intracellular trafficking

Nasal application of native cholera toxin (nCT) as a mucosal adjuvant has potential toxicity for the CNS through binding to GM1 gangliosides in the olfactory nerves. Although mutants of cholera toxin (mCTs) have been developed that show mucosal adjuvant activity without toxicity, it still remains unclear whether these mCTs will induce CNS damage. To help overcome these concerns, in this study we created new double mutant CTs (dmCTs) that have two amino acid substitutions in the ADP-ribosyltransferase active center (E112K) and COOH-terminal KDEL (E112K/KDEV or E112K/KDGL). Confocal microscopic analysis showed that intracellular localization of dmCTs differed from that of mCTs and nCTs in intestinal epithelial T84 cells. Furthermore, both dmCTs exhibited very low toxicity in the Y1 cell assay and mouse ileal loop tests. When mucosal adjuvanticity was examined, both dmCTs induced enhanced OVA-specific immune responses in both mucosal and systemic lymphoid tissues. Interestingly, although both dmCT E112K/KDEV and dmCT E112K/KDGL showed high Th2-type and significant Th1-type cytokine responses by OVA-specific CD4+ T cells, dmCT E112K/KDEV exhibited significantly lower Th1-type cytokine responses than did nCT and dmCT E112K/KDGL. These results show that newly developed dmCTs retain strong biological adjuvant activity without CNS toxicity.

Capric acid and hydroxypropylmethylcellulose increase the immunogenicity of nasally administered peptide vaccines

Immunization by the nasal route is an established method for the induction of mucosal and systemic humoral and cell-mediated antigen-specific responses. However, the effectiveness of nasal immunization is often hampered by the need for increased doses of antigen. Bioadhesives and absorption enhancers were investigated for their ability to enhance immune responses in mice after nasal immunization with model HIV-1 peptide and protein immunogens. Two additives, hydroxypropylmethylcellulose (HPMC) and capric acid, consistently enhanced antigen-specific serum IgG endpoint titers under conditions in which antigen dose was limiting. Nasal immunization of mice with 20 microg of an HIV-1 peptide immunogen plus cholera toxin (CT) as adjuvant induced serum antipeptide IgG titers of 1:9.5log2 after four immunizations while the addition of CA or HPMC to the vaccine formulation increased serum antipeptide IgG titers to 1:15.4log2 and 1:17.6log2, respectively. When 5 microg recombinant HIV-1 gp41 was used as the immunogen, the addition of CA or HPMC to the vaccine formulation increased serum anti-gp41 IgG titers to 1:11.6log2 and 1:8.8log2, respectively, compared to 1:5.2log2 after three nasal immunizations with 5 microg gp41 + CT alone. Thus, HPMC and capric acid may be useful additives that increase the immunogenicity of nasally administered vaccines and permit less antigen to be used with each immunization.

Brucella spp. lumazine synthase: a novel adjuvant and antigen delivery system to effectively induce oral immunity

Brucella lumazine synthase (BLS) has been previously used with success as a delivery system for systemic immunization against murine cysticercosis. We herein determined the usefulness of BLS as a new antigen-delivery system and mucosal-adjuvant using KETc1, one of the peptides of the anti-cysticercosis vaccine. A protection of up to 98% was induced when KETc1 was used as a chimera fused to BLS. Used as adjuvant of KETc1, BLS also induced a high level of protection (79%), which did not significantly differ from that induced by the cholera toxin (74%). KETc1 and BLS administered separately also reduced the parasite load. KETc1 administered orally as a chimera, and to a lesser extent with BLS as adjuvant, elicited IgG and IgA specific antibodies, which were detectable both in fecal extracts and in sera, and increased B and CD4 activated cells. BLS-KETc1 also increased the levels of transcription of TNF-alpha, IL-2 and IFNgamma in Peyer's patches, and in spleen, only increased TNF-alpha was observed. Overall, these results showed that BLS can be used as both an antigen-carrier and as an adjuvant in the design of new oral subunit vaccines.

AIDS vaccine: Intranasal immunization using inactivated HIV-1-capturing core-corona type polymeric nanospheres

Polymeric nanospheres have been widely used in biomedical applications, such as drug, gene and vaccine delivery systems. Nanospheres with entrapped antigens have recently been shown to possess significant potential as vaccine delivery systems and adjuvants. We previously reported that concanavalin A-immobilized polystyrene nanospheres (Con A-NS) could efficiently capture HIV-1 particles and intranasal immunization with inactivated HIV-1-capturing nanospheres (HIV-NS) induced vaginal anti-HIV-1 IgA antibody responses in mice. In addition, vaginal washes from intranasally immunized mice were capable of neutralizing HIV-1. Moreover, simian/human immunodeficiency virus KU-2-capturing nanospheres (SHIV-NS) immunized macaques exhibited partial protection when vaginally and systemically challenged with pathogenic viruses. HIV-NS is suggested to be particularly suitable to enhance antigen delivery to dendritic cells (DCs). In this study, we investigated the mucosal antibody response in mice after the intravaginal or intranasal immunization in detail with using different sized (360, 660, 940 and 1230 nm) HIV-NS. The amount of immobilized Con A to NS was dependent on the surface area of the particle. Moreover, Con A-NS with different sizes could equally capture inactivated HIV-1. Intravaginal or intranasal immunization by HIV-NS with diameters ranging 360 to 1230 nm significantly induced vaginal antibody responses. However, significant differences on vaginal anti-HIV-1 gp120 IgA and IgG antibodies were not found after intravaginal or intranasal immunization with different sized HIV-NS. These results suggest that HIV-NS provides an efficient vaccine delivery system for the induction of a mucosal immune response and the development of a mucosal vaccine.

Comparison of intranasal and transcutaneous immunization for induction of protective immunity against Chlamydia muridarum respiratory tract infection

Chlamydia pneumoniae causes a range of respiratory infections including bronchitis, pharyngitis and pneumonia. Infection has also been implicated in exacerbation/initiation of asthma and chronic obstructive pulmonary disease (COPD) and may play a role in atherosclerosis and Alzheimer's disease. We have used a mouse model of Chlamydia respiratory infection to determine the effectiveness of intranasal (IN) and transcutaneous immunization (TCI) to prevent Chlamydia lung infection. Female BALB/c mice were immunized with chlamydial major outer membrane protein (MOMP) mixed with cholera toxin and CpG oligodeoxynucleotide adjuvants by either the IN or TCI routes. Serum and bronchoalveolar lavage (BAL) were collected for antibody analysis. Mononuclear cells from lung-draining lymph nodes were stimulated in vitro with MOMP and cytokine mRNA production determined by real time PCR. Animals were challenged with live Chlamydia and weighed daily following challenge. At day 10 (the peak of infection) animals were sacrificed and the numbers of recoverable Chlamydia in lungs determined by real time PCR. MOMP-specific antibody-secreting cells in lung tissues were also determined at day 10 post-infection. Both IN and TCI protected animals against weight loss compared to non-immunized controls with both immunized groups gaining weight by day 10-post challenge while controls had lost 6% of body weight. Both immunization protocols induced MOMP-specific IgG in serum and BAL while only IN immunization induced MOMP-specific IgA in BAL. Both immunization routes resulted in high numbers of MOMP-specific antibody-secreting cells in lung tissues (IN>TCI). Following in vitro re-stimulation of lung-draining lymph node cells with MOMP; IFNgamma mRNA increased 20-fold in cells from IN immunized animals (compared to non-immunized controls) while IFNgamma levels increased 6- to 7-fold in TCI animals. Ten days post challenge non-immunized animals had >7,000 IFU in their lungs, IN immunized animals <50 IFU and TCI immunized animals <1,500 IFU. Thus, both intranasal and transcutaneous immunization protected mice against respiratory challenge with Chlamydia. The best protection was obtained following IN immunization and correlated with IFNgamma production by mononuclear cells in lung-draining LN and MOMP-specific IgA in BAL.

A novel neurotoxoid vaccine prevents mucosal botulism

The threat posed by botulism, classically a food- and waterborne disease with a high morbidity and mortality, has increased exponentially in an age of bioterrorism. Because botulinum neurotoxin (BoNT) could be easily disseminated by terrorists using an aerosol or could be used to contaminate the food or water supply, the Centers for Disease Control and Prevention and the National Institute of Allergy and Infectious Diseases has classified it as a category A agent. Although clearly the development of a safe and effective mucosal vaccine against this toxin should be a high priority, essentially no studies to date have assessed mucosal immune responses to this disease. To bridge this gap in our knowledge, we immunized mice weekly for 4 wk with nasal doses of BoNT type A toxoid and a mutant of cholera toxin termed E112K. We found elevated levels of BoNT-specific IgG Abs in plasma and of secretory IgA Abs in external secretions (nasal washes, saliva, and fecal extracts). When mice given nasal BoNT vaccine were challenged with 4 x 10(3) LD50 of BoNT type A (BoNT/A) via the i.p. route, complete protection was seen, while naive mice given the same dosage died within 2 h. To further confirm the efficacy of this nasal BoNT vaccine, an oral LD50 was determined. When mice were given an oral challenge of 5 microg (2 x oral LD50) of progenitor BoNT/A, all immunized mice survived beyond 5 days, while nonimmunized mice did not. The fecal extract samples from nasally vaccinated mice were found to contain neutralizing secretory IgA Abs. Taken together, these results show that nasal BoNT/A vaccine effectively prevents mucosal BoNT intoxication.