Sublingual immunization with nonreplicating antigens induces antibody-forming cells and cytotoxic T cells in the female genital tract mucosa and protects against genital papillomavirus infection

Intranasal Immunization of Pneumococcal pep27 Mutant Attenuates Allergic and Inflammatory Diseases by Upregulating Skin and Mucosal Tregs

Conventional immunization methods such as intramuscular injections lack effective mucosal protection against pathogens that enter through the mucosal surfaces. Moreover, conventional therapy often leads to adverse events and compromised immunity, followed by complicated outcomes, leading to the need to switch to other options. Thus, a need to develop safe and effective treatment with long-term beneficial outcomes to reduce the risk of relapse is mandatory. Mucosal vaccines administered across mucosal surfaces, such as the respiratory or intestinal mucosa, to prompt robust localized and systemic immune responses to prevent the public from acquiring pathogenic diseases. Mucosal immunity contains a unique immune cell milieu that selectively identify pathogens and limits the transmission and progression of mucosal diseases, such as allergic dermatitis and inflammatory bowel disease (IBD). It also offers protection from localized infection at the site of entry, enables the clearance of pathogens on mucosal surfaces, and leads to the induction of long-term immunity with the ability to shape regulatory responses. Regulatory T (Treg) cells have been a promising strategy to suppress mucosal diseases. To find advances in mucosal treatment, we investigated the therapeutic effects of intranasal pep27 mutant immunization. Nasal immunization protects mucosal surfaces, but nasal antigen presentation appears to entail the need for an adjuvant to stimulate immunogenicity. Here, a novel method is developed to induce Tregs via intranasal immunization without an adjuvant to potentially overcome allergic diseases and gut and lung inflammation using lung-gut axis communication in animal models. The implementation of the pep27 mutant for these therapies should be preceded by studies on Treg resilience through clinical translational studies on dietary changes.

Understanding Mucosal Physiology and Rationale of Formulation Design for Improved Mucosal Immunity

The oral and nasal cavities serve as critical gateways for infectious pathogens, with microorganisms primarily gaining entry through these routes. Our first line of defense against these invaders is the mucosal membrane, a protective barrier that shields the body's internal systems from infection while also contributing to vital functions like air and nutrient intake. One of the key features of this mucosal barrier is its ability to protect the physiological system from pathogens. Additionally, mucosal tolerance plays a crucial role in maintaining homeostasis by regulating the pH and water balance within the body. Recognizing the importance of the mucosal barrier, researchers have developed various mucosal formulations to enhance the immune response. Mucosal vaccines, for example, deliver antigens directly to mucosal tissues, triggering local immune stimulation and ultimately inducing systemic immunity. Studies have shown that lipid-based formulations such as liposomes and virosomes can effectively elicit both local and systemic immune responses. Furthermore, mucoadhesive polymeric particles, with their prolonged delivery to target sites, have demonstrated an enhanced immune response. This Review delves into the critical role of material selection and delivery approaches in optimizing mucosal immunity.

Vaccine Strategies to Elicit Mucosal Immunity

Vaccines are essential tools to prevent infection and control transmission of infectious diseases that threaten public health. Most infectious agents enter their hosts across mucosal surfaces, which make up key first lines of host defense against pathogens. Mucosal immune responses play critical roles in host immune defense to provide durable and better recall responses. Substantial attention has been focused on developing effective mucosal vaccines to elicit robust localized and systemic immune responses by administration via mucosal routes. Mucosal vaccines that elicit effective immune responses yield protection superior to parenterally delivered vaccines. Beyond their valuable immunogenicity, mucosal vaccines can be less expensive and easier to administer without a need for injection materials and more highly trained personnel. However, developing effective mucosal vaccines faces many challenges, and much effort has been directed at their development. In this article, we review the history of mucosal vaccine development and present an overview of mucosal compartment biology and the roles that mucosal immunity plays in defending against infection, knowledge that has helped inform mucosal vaccine development. We explore new progress in mucosal vaccine design and optimization and novel approaches created to improve the efficacy and safety of mucosal vaccines.

Application of phosphorylcholine derivative as mucosal adjuvant enhancing mucosal immune responses in the upper respiratory tract

OBJECTIVE

A phosphorylcholine (PC)-derivative with high binding ability (PCDB) was intranasally administered to mice with ovalbumin (OVA), and immune responses were investigated to determine whether PCDB has antigenicity and adjuvanticity.

METHODS

BALB/c mice were intranasally immunized with PCDB coupled with OVA, unbound PCDB plus OVA, cholera toxin (CT) plus OVA, OVA alone, and PCDB alone. Then, the production of OVA- and PC-specific antibodies in external secretions and serum, and the secretion of cytokines such as IL-4 and IFN-γ from splenic mononuclear cells by stimulation with PCDB and OVA were examined. Furthermore, the secretion of IL-12p40 from CD11c+ cells following stimulation with PCDB was observed to clarify the adjuvant effect of PCDB through TLR4.

RESULTS

Intranasal immunization with PCDB plus OVA increased OVA- and PC-specific IgA in external secretions and OVA- and PC-specific antibodies in the serum. The analysis of IgG subclasses specific to OVA and PC showed a higher production of IgG1 than IgG2, and the secretion of both IL-4 and IFN-γ was enhanced. However, IL-12p40 secretion from CD11c+ cells was increased and OVA-specific IgE production was not promoted by PCDB stimulation.

CONCLUSION

Intranasal administration of the protein antigen with PCDB enhanced immune responses specific to the mixed antigen and PC. Although PCDB acted to bias the immune response toward the Th2-type, antigen-specific IgE production did not increase. These findings suggest that PCDB has the potential to be a mucosal vaccine with both adjuvanticity and antigenicity without causing side effects due to type I allergy.

A sublingual nanofiber vaccine to prevent urinary tract infections

Urinary tract infections (UTIs) are a major public health problem affecting millions of individuals each year. Recurrent UTIs are managed by long-term antibiotic use, making the alarming rise of antibiotic resistance a substantial threat to future UTI treatment. Extended antibiotic regimens may also have adverse effects on the microbiome. Here, we report the use of a supramolecular vaccine to provide long-term protection against uropathogenic Escherichia coli, which cause 80% of uncomplicated UTIs. We designed mucus-penetrating peptide-polymer nanofibers to enable sublingual (under the tongue) vaccine delivery and elicit antibody responses systemically and in the urogenital tract. In a mouse model of UTI, we demonstrate equivalent efficacy to high-dose oral antibiotics but with significantly less perturbation of the gut microbiome. We also formulate our vaccine as a rapid-dissolving sublingual tablet that raises response in mice and rabbits. Our approach represents a promising alternative to antibiotics for the treatment and prevention of UTIs.

Framing and understanding the whole aspect of oral sex from social and health perspectives: a narrative review

Historically, oral sex is part of human sexual behaviour even though some consider it taboo, and its expression is deemed inappropriate. Human rights also stand out as technology becomes more sophisticated, leading to its practice disclosure in the 21st century. The large-scale oral sex discussion in media encourages people to express it, and there is feedback on whether it is right or not. It all depends on each person’s values. We found this sexual behaviour occurs everywhere regardless of religion, culture and race. Pop culture influences this behaviour considerably. It can be seen in music, movies and television programmes that allude to oral sex. Numerous motivations underlying this behaviour include sexual pleasure for the sake of psychological well-being. It is undeniable that this behaviour is still controversial. There is a risk of it causing disease, but it reportedly provides many benefits. Oral sex is not a new behaviour crossing boundaries, according to our theory. It is an old behaviour that has been highlighted because of the factors that support it. This behaviour, still considered taboo, has its disadvantages, such as sexually transmitted disease and oral cancer, but also has benefits, such as preventing preeclampsia.

Mucosal vaccine delivery: A focus on the breakthrough of specific barriers

Mucosal vaccines can effectively induce an immune response at the mucosal site and form the first line of defense against microbial invasion. The induced mucosal immunity includes the proliferation of effector T cells and the production of IgG and IgA antibodies, thereby effectively blocking microbial infection and transmission. However, after a long period of development, the transformation of mucosal vaccines into clinical use is still relatively slow. To date, fewer than ten mucosal vaccines have been approved. Only seven mucosal vaccines against coronavirus disease 2019 (COVID-19) are under investigation in clinical trials. A representative vaccine is the adenovirus type-5 vectored COVID-19 vaccine (Ad5-nCoV) developed by Chen and coworkers, which is currently in phase III clinical trials. The reason for the limited progress of mucosal vaccines may be the complicated mucosal barriers. Therefore, this review summarizes the characteristics of mucosal barriers and highlights strategies to overcome these barriers for effective mucosal vaccine delivery.

Sublingual Immunization with Chimeric C1q/CD40 Ligand/HIV Virus-like Particles Induces Strong Mucosal Immune Responses against HIV

Development of a vaccine that can elicit robust HIV specific antibody responses in the mucosal compartments is desired for effective prevention of HIV via sexual transmission. However, the current mucosal vaccines have either poor immunogenicity when administered orally or invite safety concerns when administered intranasally. Sublingual immunization has received more attention in recent years based on its efficiency in inducing systemic and mucosal immune responses in both mucosal and extra-mucosal tissues. To facilitate the transport of the immunogen across the sub-mucosal epithelial barrier, we found that CD91, the receptor of C1q, is prevalently expressed in the sublingual mucosal lining, and thus, a modified chimeric C1q surface conjugated CD40L/HIV VLP was generated. The ability of this chimeric C1q/CD40L/HIV VLP to bind, cross the epithelial layer, access and activate the sub-mucosal layer dendritic cells (DCs), and ultimately induce enhanced mucosal and systemic immune responses against HIV is evaluated in this study. We found that C1q/CD40L/HIV VLPs have enhanced binding, increased transport across the epithelial layer, and upregulate DC activation markers as compared to CD40L/HIV VLPs alone. Mice immunized with C1q/CD40L/HIV VLPs by sublingual administration showed higher levels of IgA salivary antibodies against both HIV Gag and Env than mice immunized with CD40L/HIV VLPs. Moreover, sublingual immunization with C1q/CD40L/HIV VLPs induced more Env- and Gag-specific IFN-γ producing T cells than the CD40L/HIV VLPs group. Interestingly, C1q/CD40L/HIV VLP immunization can also induce more mucosal homing T cells than that in CD40L/HIV VLP group. Our data suggest that incorporation of C1q to CD40L/HIV VLPs is a promising novel strategy and that the sublingual immunization can be a favorite immunization route for HIV mucosal vaccines.

The mucosal immune system of the upper respiratory tract and recent progress in mucosal vaccines

The mucosal immune system prevents microorganism invasion through mucosal surfaces and consists of inductive and effector sites. Nasopharynx-associated lymphoid tissue (NALT) functions as an inductive site, inducing mucosal immune responses in the upper respiratory tract. It follows that intranasal vaccines may prevent upper respiratory infections. To induce and enhance the immune response by administering inactivated antigens intranasally, mucosal adjuvants have been developed, including mutant cholera toxin and cationic cholesteryl pullulan nanogel, which do not accumulate in the central nervous system. Moreover, multivalent pneumococcal polysaccharide conjugate vaccines are used to prevent invasive pneumococcal infections and otitis media, although they only provide moderate protection against acute otitis media because non-vaccine serotypes of Streptococcus pneumoniae and Haemophilus influenzae also cause this infection. To address this problem, pneumococcal surface protein A of S. pneumoniae and P6 of H. influenzae are used as broad-spectrum vaccine antigens. Alternatively, phosphorylcholine (PC) is present in the cell walls of both gram-positive and gram-negative bacteria and induces immune responses through antigenic activity. The significant effects of PC as a mucosal vaccine have been demonstrated through intranasal and sublingual immunization in mice. Furthermore, intranasal administration of PC reverses increases in IgE levels and prevents allergic rhinitis. After immunization with pneumococcal polysaccharide conjugate vaccine, intranasal immunization with PC boosts immune responses to vaccine strains and to PC itself. Thus, PC may be useful as a mucosal vaccine to prevent upper respiratory infections and allergic rhinitis, and it could be used as a booster to the currently used pneumococcal vaccine as it protects against non-vaccine strains.

Ovalbumin and cholera toxin delivery to buccal mucus for immunization using microneedles and comparison of immunological response to transmucosal delivery

The oral mucosa is an effective site for vaccination. However, for oral mucosal vaccines, delivery of the right dose of vaccine is not possible due to the water-rich environment. In this study, the buccal mucosa, which is easy to access using a microneedle array in the oral cavity, was selected as the administration site. The immune responses to the use of microneedles to conventional transmucosal delivery were compared. In addition, the adjuvant effect of the addition of cholera toxin (CT) to the drug formulation was observed. Two kinds of patches were prepared: (1) Ovalbumin (OVA) was dip coated only on the tips of microneedles (C-OVA-MN) and (2) OVA was coated on the surface of a flat disk patch substrate without microneedles (C-OVA-D). The drug delivery properties of C-OVA-MN and C-OVA-D were investigated using fluorescent-labeled OVA (OVA/FITC). Each patch was administered to mice twice, 2 weeks apart, and then antibody titers were measured. A microneedle patch can deliver vaccine into the epithelium of the buccal mucosa in a short period of time compared to transmucosal delivery. A microneedle system of C-OVA-MN showed a high serum IgG titer. In addition, CT triggered CD8⁺ and CD4⁺ T cell-mediated immune responses. Through this study, we present the possibility of a new method of vaccination to the buccal mucosa using microneedles and CT adjuvant. Illustration of delivery of vaccine to the oral mucosal epithelium using a microneedle patch: Ovalbumin (OVA)-coated microneedle (C-OVA-MN) consists of tip, step, and coating formulation. Microneedle patch coated with OVA formulation is targeting buccal mucosa, which is easy to access in the oral cavity. OVA is delivered to the buccal epithelium precisely using a microneedle patch, and OVA is delivered by transmucosal route using a disk patch.

Different types of adjuvants in prophylactic and therapeutic human papillomavirus vaccines in laboratory animals: a systematic review

Human papillomavirus (HPV) causes cervical carcinoma, which and is the third most common cancer, accounting for 275,000 deaths annually worldwide. Adjuvants have a key role in promotion of vaccine efficacy; therefore, using prophylactic and therapeutic vaccines combined with adjuvant could be of great benefit in prevention and treatment of cervical cancer. There are different types of adjuvants, including MF59^TM adjuvants, RNA-based, JY (interleukin2/chitosan), cholera toxin (CT), heat-labile enterotoxin (LT), Freund's adjuvant, alum, SA-4-1BBL, λ-carrageenan (λ-CGN), heat shock proteins (HSPs), juzen-taiho-to (JTT) and hochu-ekki-to (HET), ISCOM and ISCOMATRIX™, very small size proteoliposomes (VSSPs), granulocyte macrophage colony-stimulating factor (GM-CSF), and Toll-like receptors (TLRs). Adjuvants have various functions, especially in therapeutic vaccines, and they lead to an increase in cytotoxic T lymphocytes (CTLs), so they are important in the design of vaccines. Here, we review the currently used adjuvants and their combinations with HPV protein vaccines in order to introduce an appropriate adjuvant for HPV vaccines.

Adjuvants and delivery systems based on polymeric nanoparticles for mucosal vaccines

Most pathogens enter the body through mucosal surfaces. Therefore, vaccination through the mucosal route can greatly enhance the mucosal immune response. Vaccination via the mucosal surface is the most effective way to trigger a protective mucosal immune response, but the vast majority of vaccines used are administered by injection. Strategies to enhance the mucosal immunity have been developed by using vaccine adjuvants, delivery systems, bacterial or viral vectors, and DNA vaccines. Appropriate vaccine adjuvants and drug delivery systems can improve the immunogenicity of antigens, induce a stronger immune response, and reduce the vaccine dose and production cost. In recent years, many studies have focused on finding safe and effective vaccine adjuvants and drug delivery systems to formulate the mucosal vaccines for solving the above problems. Great progress has also been made in vaccine adjuvants and drug delivery systems based on biodegradable polymer nanoparticles. In this paper, the research progress of the mucosal vaccine and its related adjuvants and drug delivery systems in recent years was reviewed, and the application of polymers as adjuvants and drug delivery system in vaccine was prospected. This review provides a fundamental knowledge for the application of biodegradable polymer nanoparticles as adjuvants and carriers in mucosal vaccines and shows great application prospects.

Oral immunization with bacteriophage MS2-L2 VLPs protects against oral and genital infection with multiple HPV types associated with head & neck cancers and cervical cancer

Human papillomaviruses (HPVs) are the most common sexually transmitted infections. HPVs are transmitted through anogenital sex or oral sex. Anogenital transmission/infection is associated with anogenital cancers and genital warts while oral transmission/infection is associated with head and neck cancers (HNCs) including recurrent respiratory papillomatosis. Current HPV vaccines protect against HPV types associated with ∼90% of cervical cancers and are expected to protect against a percentage of HNCs. However, only a few studies have assessed the efficacy of current vaccines against oral HPV infections. We had previously developed a mixed MS2-L2 candidate HPV vaccine based on bacteriophage MS2 virus-like particles (VLPs). The mixed MS2-L2 VLPs consisted of a mixture of two MS2-L2 VLPs displaying: i) a concatemer of L2 peptide (epitope 20-31) from HPV31 & L2 peptide (epitope 17-31) from HPV16 and ii) a consensus L2 peptide representing epitope 69-86. The mixed MS2-L2 VLPs neutralized/protected mice against six HPV types associated with ∼87% of cervical cancer. Here, we show that the mixed MS2-L2 VLPs can protect mice against additional HPV types; at the genital region, the VLPs protect against HPV53, 56, 11 and at the oral region, the VLPs protect against HPV16, 35, 39, 52, and 58. Thus, mixed MS2-L2 VLPs protect against eleven oncogenic HPV types associated with ∼95% of cervical cancer. The VLPs also have the potential to protect, orally, against the same oncogenic HPVs, associated with ∼99% of HNCs, including HPV11, which is associated with up to 32% of recurrent respiratory papillomatosis. Moreover, mixed MS2-L2 VLPs are thermostable at room temperature for up to 60 days after spray-freeze drying and they are protective against oral HPV infection.

A Self-Assembling Whole-Cell Vaccine Antigen Presentation Platform

Diarrhea is the most common infection in children under the age of 5 years worldwide. In spite of this, only a few vaccines to treat infectious diarrhea exist, and many of the available vaccines are sparingly and sporadically administered. Major obstacles to the development and widespread implementation of vaccination include the ease and cost of production, distribution, and delivery. Here we present a novel, customizable, and self-assembling vaccine platform that exploits the Vibrio cholerae bacterial biofilm matrix for antigen presentation. We use this technology to create a proof-of-concept, live-attenuated whole-cell vaccine that is boosted by spontaneous association of a secreted protein antigen with the cell surface. Sublingual administration of this live-attenuated vaccine to mice confers protection against V. cholerae challenge and elicits the production of antigen-specific IgA in stool. The platform presented here enables the development of antigen-boosted vaccines that are simple to produce and deliver, addressing many of the obstacles to vaccination against diarrheal diseases. This may also serve as a paradigm for the development of broadly protective biofilm-based vaccines against other mucosal infections.IMPORTANCE Diarrheal disease is the most common infection afflicting children worldwide. In resource-poor settings, these infections are correlated with cognitive delay, stunted growth, and premature death. With the development of efficacious, affordable, and easily administered vaccines, such infections could be prevented. While a major focus of research on biofilms has been their elimination, here we harness the bacterial biofilm to create a customizable platform for cost-effective, whole-cell mucosal vaccines that self-incorporate secreted protein antigens. We use this platform to develop a sublingually administered live-attenuated prototype vaccine based on Vibrio cholerae This serves not only as a proof of concept for a multivalent vaccine against common bacterial enteric pathogens but also as a paradigm for vaccines utilizing other bacterial biofilms to target mucosal infections.

Sublingual administration of 2-hydroxyethyl methacrylate enhances antibody responses to co-administered ovalbumin and Streptococcus mutans

OBJECTIVE

The oral mucosa of patients undergoing dental procedures is often exposed to residual monomers leaking from incompletely cured acrylic resins. We investigated whether 2-hydroxyethyl methacrylate (HEMA) monomers applied to the sublingual mucosa in mice modulate the antibody responses towards co-administered ovalbumin (OVA) or live oral bacteria.

MATERIAL AND METHODS

OVA, live mouse oral commensal Lactobacillus murinus or live human oral commensal Streptococcus mutans were administered sublingually with or without HEMA to BALB/c mice on four weekly occasions. One week after the last administration, the experiment was terminated and serum antibody levels were analyzed using ELISA.

RESULTS

Significantly increased IgG and IgE anti-OVA antibody activity was found in the sera from mice immunized with OVA together with HEMA, as compared to mice immunized with OVA alone. Likewise, S. mutans together with HEMA induced an IgG anti-S. mutans antibody response that was significantly higher than the antibody response detected after application of S. mutans alone. No IgG anti-L. murinus antibody response was detected in mice immunized with L. murinus together with HEMA, as compared to the background activity.

CONCLUSIONS

We report that HEMA monomers have adjuvant properties when sublingually administered in combination with OVA or S. mutans.

Circulating pathogen-specific plasmablasts in female patients with upper genital tract infection

Mucosal antibodies constitute the first line of adaptive immune defence against invaders in the female genital tract (FGT), yet the sequence of events leading to their production is surprisingly poorly characterized. We explored the induction of pathogen-specific antibody-secreting cells (ASC) as a response to an acute infection in the upper FGT. We recruited 12 patients undergoing surgery due to an upper FGT infection (7/12 blood culture positive, 5/12 negative) and six healthy controls. Pathogens were sampled during surgery and PBMC collected in the acute phase of the disease (days 7-10). We searched by ELISPOT circulating pathogen-specific ASC and explored their frequency, immunoglobulin isotype distribution, and expressions of homing receptors (α₄β_7, L-selectin, and CLA). All patients had circulating ASC specific to the infective bacteria; the geometric mean was 434 (95%CI 155-1234) ASC (IgA + IgG + IgM)/10⁶ PBMC. IgA ASC predominated in 7/12, IgG ASC in 3/12, and IgM ASC in 2/12 cases. Of all the pathogen-specific ASC, 60% expressed α₄β₇, 67% L-selectin, and 9% CLA. This study is the first to show induction of pathogen-specific ASC in the peripheral blood in bacterial infection in the human FGT. Our findings reveal that such FGT-originating pathogen-specific ASC are predominated by IgA ASC and exhibit a homing receptor profile resembling that of ASC in acute urinary tract infection. The data thus suggest a characteristic profile shared by the urogenital tract.

Inducing Mucosal IgA: A Challenge for Vaccine Adjuvants and Delivery Systems

Mucosal IgA or secretory IgA (SIgA) are structurally equipped to resist chemical degradation in the harsh environment of mucosal surfaces and enzymes of host or microbial origin. Production of SIgA is finely regulated, and distinct T-independent and T-dependent mechanisms orchestrate Ig α class switching and SIgA responses against commensal and pathogenic microbes. Most infectious pathogens enter the host via mucosal surfaces. To provide a first line of protection at these entry ports, vaccines are being developed to induce pathogen-specific SIgA in addition to systemic immunity achieved by injected vaccines. Mucosal or epicutaneous delivery of vaccines helps target the inductive sites for SIgA responses. The efficacy of such vaccines relies on the identification and/or engineering of vaccine adjuvants capable of supporting the development of SIgA alongside systemic immunity and delivery systems that improve vaccine delivery to the targeted anatomic sites and immune cells.

Improvement of cytomegalovirus pp65 DNA vaccine efficacy by co-administration of siRNAs targeting BAK and BAX

The efficacy of DNA vaccines may be improved by small interfering (si)RNA adjuvants targeting pro-apoptotic genes. The aim of the present study was to investigate the capacity of siRNAs targeting B-cell lymphoma 2 homologous antagonist killer (BAK) and B-cell lymphoma 2-associated X protein (BAX) to improve the efficacy of a cytomegalovirus (CMV) vaccine. BALB/c mice were divided into four groups (n=18 in each): unimmunized and immunized with pcDNA 3.1-pp65 expressing CMV 65 kDa matrix phosphoprotein and BAK + BAX siRNAs, pcDNA 3.1-pp65 and control siRNA, or control pcDNA 3.1 and BAK + BAX siRNAs. Immunizations were performed twice with an interval of 3 weeks. CMV-specific mouse splenocyte interferon (IFN)-γ secretion was assessed by ELISPOT; furthermore, an in vivo cytotoxic T lymphocyte assay was performed 2 weeks after the last immunization. After lethal CMV challenge of the mice, body weight, virus titers in the spleens and salivary glands as well as survival were recorded. The amount of splenocytes secreting IFN-γ in response to CMV pp65 peptides and specific lysis of peptide-pulsed target cells were significantly higher in mice administered pcDNA3.1-pp65 and BAK + BAX siRNAs than those in mice administered pcDNA3.1-pp65 and control siRNA (P<0.05 for each). After the virus challenge, the virus titers in the spleens and salivary glands of mice given pcDNA3.1-pp65 and BAK + BAX siRNAs were significantly lower than those in mice immunized with pcDNA3.1-pp65 and control siRNA (P<0.05 for each). Furthermore, mice immunized with pcDNA 3.1-pp65 and control siRNA or BAK + BAX siRNAs survived for longer, and at 21 days after lethal CMV challenge, 66 and 100% of these mice survived, respectively. These mice also experienced less weight loss compared with mice immunized with pcDNA3.1-pp65 and control siRNA (P<0.05). In conclusion, intradermal administration of siRNAs targeting BAK and BAX improved the efficacy of CMV pp65 DNA vaccine.

Intranasal and sublingual delivery of inactivated polio vaccine

Polio is on the brink of eradication. Improved inactivated polio vaccines (IPV) are needed towards complete eradication and for the use in the period thereafter. Vaccination via mucosal surfaces has important potential advantages over intramuscular injection using conventional needle and syringe, the currently used delivery method for IPV. One of them is the ability to induce both serum and mucosal immune responses: the latter may provide protection at the port of virus entry. The current study evaluated the possibilities of polio vaccination via mucosal surfaces using IPV based on attenuated Sabin strains. Mice received three immunizations with trivalent sIPV via intramuscular injection, or via the intranasal or sublingual route. The need of an adjuvant for the mucosal routes was investigated as well, by testing sIPV in combination with the mucosal adjuvant cholera toxin. Both intranasal and sublingual sIPV immunization induced systemic polio-specific serum IgG in mice that were functional as measured by poliovirus neutralization. Intranasal administration of sIPV plus adjuvant induced significant higher systemic poliovirus type 3 neutralizing antibody titers than sIPV delivered via the intramuscular route. Moreover, mucosal sIPV delivery elicited polio-specific IgA titers at different mucosal sites (IgA in saliva, fecal extracts and intestinal tissue) and IgA-producing B-cells in the spleen, where conventional intramuscular vaccination was unable to do so. However, it is likely that a mucosal adjuvant is required for sublingual vaccination. Further research on polio vaccination via sublingual mucosal route should include the search for safe and effective adjuvants, and the development of novel oral dosage forms that improve antigen uptake by oral mucosa, thereby increasing vaccine immunogenicity. This study indicates that both the intranasal and sublingual routes might be valuable approaches for use in routine vaccination or outbreak control in the period after complete OPV cessation and post-polio eradication.

Sublingual targeting of STING with 3'3'-cGAMP promotes systemic and mucosal immunity against anthrax toxins

Anthrax is caused by Bacillus anthracis, a zoonotic bacterial pathogen affecting humans and livestock worldwide. The current human anthrax vaccine, anthrax vaccine adsorbed (AVA), is an injected vaccine with a cumbersome administration schedule and fails to promote mucosal immunity. Bacterial enterotoxins, which stimulate production of the cyclic nucleotide cAMP are effective experimental mucosal vaccine adjuvants, but their inherent toxicity has precluded their use in humans. We investigated whether cyclic dinucleotides that target Stimulator of Interferon Gamma Genes (STING) in mammalian cells could represent an alternative to bacterial enterotoxins as adjuvant for sublingual immunization and promotion of mucosal immunity and secretory IgA responses in addition to systemic immunity. We found that sublingual immunization of mice with Bacillus anthracis protective antigen (PA) and the STING ligand 3'3'-cGAMP promotes PA-specific serum IgG Ab responses of the same magnitude as those induced after immunization with PA and the experimental adjuvant cholera toxin (CT). Interestingly, this STING ligand also promoted serum anti-PA IgA and IgA-producing cells in the bone marrow. Furthermore, the saliva of mice immunized with the STING ligand exhibited similar levels of PA-specific IgA Abs as groups immunized with CT as adjuvant. The adjuvant activity of 3'3'-cGAMP was associated with mixed Th1, Th2, and Th17 responses. This STING ligand also induced rapid IFN-β and IL-10 responses in sublingual tissues and cervical lymph nodes, and TGF-β responses in the cervical lymph nodes, which could contribute to promoting IgA responses after sublingual immunization.

Sublingual Priming with a HIV gp41-Based Subunit Vaccine Elicits Mucosal Antibodies and Persistent B Memory Responses in Non-Human Primates

Persistent B cell responses in mucosal tissues are crucial to control infection against sexually transmitted pathogens like human immunodeficiency virus 1 (HIV-1). The genital tract is a major site of infection by HIV. Sublingual (SL) immunization in mice was previously shown to generate HIV-specific B cell immunity that disseminates to the genital tract. We report here the immunogenicity in female cynomolgus macaques of a SL vaccine based on a modified gp41 polypeptide coupled to the cholera toxin B subunit designed to expose hidden epitopes and to improve mucosal retention. Combined SL/intramuscular (IM) immunization with such mucoadhesive gp41-based vaccine elicited mucosal HIV-specific IgG and IgA antibodies more efficiently than IM immunization alone. This strategy increased the number and duration of gp41-specific IgA secreting cells. Importantly, combined immunization improved the generation of functional antibodies 3 months after vaccination as detected in HIV-neutralizing assays. Therefore, SL immunization represents a promising vaccine strategy to block HIV-1 transmission.

Optimized Formulation of a Thermostable Spray-Dried Virus-Like Particle Vaccine against Human Papillomavirus

Existing vaccines against human papillomavirus (HPV) require continuous cold-chain storage. Previously, we developed a bacteriophage virus-like particle (VLP)-based vaccine for HPV infection, which elicits broadly neutralizing antibodies against diverse HPV types. Here, we formulated these VLPs into a thermostable dry powder using a multicomponent excipient system and by optimizing the spray-drying parameters using a half-factorial design approach. Dry-powder VLPs were stable after spray drying and after long-term storage at elevated temperatures. Immunization of mice with a single dose of reconstituted dry-powder VLPs that were stored at 37 °C for more than a year elicited high anti-L2 IgG antibody titers. Spray-dried thermostable, broadly protective L2 bacteriophage VLPs vaccine could be accessible to remote regions of the world (where ∼84% of cervical cancer patients reside) by eliminating the cold-chain requirement during transportation and storage.

NKp46+ Innate Lymphoid Cells Dampen Vaginal CD8 T Cell Responses following Local Immunization with a Cholera Toxin-Based Vaccine

Innate and adaptive immune cells work in concert to generate efficient protection at mucosal surface. Vaginal mucosa is an epithelial tissue that contains innate and adaptive immune effector cells. Our previous studies demonstrated that vaginal administration of Cholera toxin -based vaccines generate antigen-specific CD8 T cells through the stimulation of local dendritic cells (DC). Innate lymphoid cells (ILC) are a group of lymphocytes localized in epithelial tissues that have important immune functions against pathogens and in tissue homeostasis. Their contribution to vaccine-induced mucosal T cell responses is an important issue for the design of protective vaccines. We report here that the vaginal mucosa contains a heterogeneous population of NKp46⁺ ILC that includes conventional NK cells and ILC1-like cells. We show that vaginal NKp46⁺ ILC dampen vaccine-induced CD8 T cell responses generated after local immunization. Indeed, in vivo depletion of NKp46⁺ ILC with anti-NK1.1 antibody or NKG2D blockade increases the magnitude of vaginal OVA-specific CD8 T cells. Furthermore, such treatments also increase the number of DC in the vagina. NKG2D ligands being expressed by vaginal DC but not by CD8 T cells, these results support that NKp46⁺ ILC limit mucosal CD8 T cell responses indirectly through the NKG2D-dependent elimination of vaginal DC. Our data reveal an unappreciated role of NKp46⁺ ILC in the regulation of mucosal CD8 T cell responses.

Transportation of sublingual antigens across sublingual ductal epithelial cells to the ductal antigen-presenting cells in mice

BACKGROUND

Sublingual immunotherapy (SLIT) has proven to be safe and efficient for the treatment of type I allergies. However, the mechanisms underlying allergen transportation within the sublingual compartment, the localization of antigens, and the identities of the cells responsible for this immunization remain incompletely understood.

OBJECTIVE

In this study, we focused on the sublingual ductal system and analysed the localization and transportation of antigens after their sublingual application.

METHODS

In mice given adjuvant-free antigens sublingually, tissues were removed at 0, 0.5, 1, or 2 h after the application and subjected to immunohistochemistry. Cells isolated from the sublingual duct and mucosa were analysed by flow cytometry.

RESULTS

Substantial immunoreactivity to ovalbumin (OVA) was evident in sublingual ductal epithelial cells at 30 min and 1 h after sublingual administration of OVA, but it had disappeared at 2 h. The ductal epithelial cells incorporated not only OVA, but also particulate antigens such as latex or silica beads and microbes. MHC class II (MHCII)(+) antigen-presenting cells (APCs) were located around the sublingual ductal system, and MHCII(+) cells were co-localized with, and around, antigen-incorporated sublingual duct cells. CD11b(+) CD11c(-) cells were present among CD45(+) MHCII(+) cells at greater frequency in the sublingual duct than in the sublingual mucosa, and they were the main contributors to the incorporation of OVA in vitro.

CONCLUSIONS AND CLINICAL RELEVANCE

This study reveals that sublingual antigens can be transported across sublingual ductal epithelial cells to the ductal APCs. If the system is the same in humans as in mice, the ductal APCs may prove to be important target cells for SLIT.

Next generation prophylactic human papillomavirus vaccines

The two licensed bivalent and quadrivalent human papillomavirus (HPV) L1 (the major papillomavirus virion protein) virus-like particle (VLP) vaccines are regarded as safe, effective, and well established prophylactic vaccines. However, they have some inherent limitations, including a fairly high production and delivery cost, virus-type restricted protection, and no reported therapeutic activity, which might be addressed with the development of alternative dosing schedules and vaccine products. A change from a three-dose to a two-dose protocol for the licensed HPV vaccines, especially in younger adolescents (aged 9-13 years), is underway in several countries and is likely to become the future norm. Preliminary evidence suggests that recipients of HPV vaccines might derive prophylactic benefits from one dose of the bivalent vaccine. Substantial interest exists in both the academic and industrial sectors in the development of second-generation L1 VLP vaccines in terms of cost reduction-eg, by production in Escherichia coli or alternative types of yeast. However, Merck's nonavalent vaccine, produced via the Saccharomyces cerevisiae production system that is also used for their quadrivalent vaccine, is the first second-generation HPV VLP vaccine to be available on the market. By contrast, other pharmaceutical companies are developing microbial vectors that deliver L1 genes. These two approaches would add an HPV component to existing live attenuated vaccines for measles and typhoid fever. Prophylactic vaccines that are based on induction of broadly cross-neutralising antibodies to L2, the minor HPV capsid protein, are also being developed both as simple monomeric fusion proteins and as virus-like display vaccines. The strong interest in developing the next generation of vaccines, particularly by manufacturers in middle-to-high income countries, increases the likelihood that vaccine production will become decentralised with the hope that effective HPV vaccines will be made increasingly available in low-resource settings where they are most needed.

A Lipopolysaccharide from Pantoea Agglomerans Is a Promising Adjuvant for Sublingual Vaccines to Induce Systemic and Mucosal Immune Responses in Mice via TLR4 Pathway

A lipopolysaccharide from Pantoea agglomerans (LPSpa) has been applied to various fields for human use as a Toll-like receptor 4 ligand and its safety has been confirmed. Here, we showed for the first time the application of LPSpa as an effective mucosal adjuvant for activating vaccine-induced antigen specific immune responses. Mice sublingually immunized with influenza vaccine (HA split vaccine) with LPSpa induced both HA-specific IgG (systemic) and IgA (mucosal) antibody responses, which led to a significant increase in survival rate against lethal influenza virus challenge compared with subcutaneous vaccination. After sublingual administration of ovalbumin with LPSpa, ovalbumin-specific mucosal IgA responses were induced at both mucosal surfaces close to the immunized site and at remote mucosal surfaces. Sublingual administration of LPSpa evoked local antigen-uptake by dendritic cells in cervical lymph nodes. LPSpa induced cytokine production and the maturation and proliferation of innate immune cells via Toll-like receptor 4 in dendritic cells. Collectively, these results suggest that LPSpa can be used as an effective mucosal adjuvant to stimulate and activate local innate immune cells to improve and enhance mucosal vaccine potency against various pathogens.

Sublingual immunization of trivalent human papillomavirus DNA vaccine in baculovirus nanovector for protection against vaginal challenge

Here, we report the immunogenicity of a sublingually delivered, trivalent human papillomavirus (HPV) DNA vaccine encapsidated in a human endogenous retrovirus (HERV) envelope-coated, nonreplicable, baculovirus nanovector. The HERV envelope-coated, nonreplicable, baculovirus-based DNA vaccine, encoding HPV16L1, -18L1 and -58L1 (AcHERV-triHPV), was constructed and sublingually administered to mice without adjuvant. Following sublingual (SL) administration, AcHERV-triHPV was absorbed and distributed throughout the body. At 15 minutes and 1 day post-dose, the distribution of AcHERV-triHPV to the lung was higher than that to other tissues. At 30 days post-dose, the levels of AcHERV-triHPV had diminished throughout the body. Six weeks after the first of three doses, 1×10(8) copies of SL AcHERV-triHPV induced HPV type-specific serum IgG and neutralizing antibodies to a degree comparable to that of IM immunization with 1×10(9) copies. AcHERV-triHPV induced HPV type-specific vaginal IgA titers in a dose-dependent manner. SL immunization with 1×10(10) copies of AcHERV-triHPV induced Th1 and Th2 cellular responses comparable to IM immunization with 1×10(9) copies. Molecular imaging revealed that SL AcHERV-triHPV in mice provided complete protection against vaginal challenge with HPV16, HPV18, and HPV58 pseudoviruses. These results support the potential of SL immunization using multivalent DNA vaccine in baculovirus nanovector for induction of mucosal, systemic, and cellular immune responses.

Induction of intestinal immunity by mucosal vaccines as a means of controlling HIV infection

CD4(+) T cells in the mucosa of the gastrointestinal (GI) tract are preferentially targeted and depleted by HIV. As such, the induction of an effective anti-HIV immune response in the mucosa of the GI tract-through vaccination-could protect this vulnerable population of cells. Mucosal vaccination provides a promising means of inducing robust humoral and cellular responses in the GI tract. Here we review data from the literature about the effectiveness of various mucosal vaccination routes--oral (intraintestinal/tonsilar/sublingual), intranasal, and intrarectal--with regard to the induction of immune responses mediated by cytotoxic T cells and antibodies in the GI mucosa, as well as protective efficacy in challenge models. We present data from the literature indicating that mucosal routes have the potential to effectively elicit GI mucosal immunity and protect against challenge. Given their capacity for the induction of anti-HIV immune responses in the GI mucosa, we propose that mucosal routes, including the nonconventional sublingual, tonsilar, and intrarectal routes, be considered for the delivery of the next generation HIV vaccines. However, further studies are necessary to determine the ideal vectors and vaccination regimens for these routes of immunization and to validate their efficacy in controlling HIV infection.

Optimization of mucosal responses after intramuscular immunization with integrase defective lentiviral vector

Many infectious agents infiltrate the host at the mucosal surfaces and then spread systemically. This implies that an ideal vaccine should induce protective immune responses both at systemic and mucosal sites to counteract invasive mucosal pathogens. We evaluated the in vivo systemic and mucosal antigen-specific immune response induced in mice by intramuscular administration of an integrase defective lentiviral vector (IDLV) carrying the ovalbumin (OVA) transgene as a model antigen (IDLV-OVA), either alone or in combination with sublingual adjuvanted OVA protein. Mice immunized intramuscularly with OVA and adjuvant were compared with IDLV-OVA immunization. Mice sublingually immunized only with OVA and adjuvant were used as a positive control of mucosal responses. A single intramuscular dose of IDLV-OVA induced functional antigen-specific CD8+ T cell responses in spleen, draining and distal lymph nodes and, importantly, in the lamina propria of the large intestine. These results were similar to those obtained in a prime-boost regimen including one IDLV immunization and two mucosal boosts with adjuvanted OVA or vice versa. Remarkably, only in groups vaccinated with IDLV-OVA, either alone or in prime-boost regimens, the mucosal CD8+ T cell response persisted up to several months from immunization. Importantly, following IDLV-OVA immunization, the mucosal boost with protein greatly increased the plasma IgG response and induced mucosal antigen-specific IgA in saliva and vaginal washes. Overall, intramuscular administration of IDLV followed by protein boosts using the sublingual route induced strong, persistent and complementary systemic and mucosal immune responses, and represents an appealing prime-boost strategy for immunization including IDLV as a delivery system.

Buccal and sublingual vaccine delivery

Because of their large surface area and immunological competence, mucosal tissues are attractive administration and target sites for vaccination. An important characteristic of mucosal vaccination is its ability to elicit local immune responses, which act against infection at the site of pathogen entry. However, mucosal surfaces are endowed with potent and sophisticated tolerance mechanisms to prevent the immune system from overreacting to the many environmental antigens. Hence, mucosal vaccination may suppress the immune system instead of induce a protective immune response. Therefore, mucosal adjuvants and/or special antigen delivery systems as well as appropriate dosage forms are required in order to develop potent mucosal vaccines.

Whereas oral, nasal and pulmonary vaccine delivery strategies have been described extensively, the sublingual and buccal routes have received considerably less attention. In this review, the characteristics of and approaches for sublingual and buccal vaccine delivery are described and compared with other mucosal vaccine delivery sites. We discuss recent progress and highlight promising developments in the search for vaccine formulations, including adjuvants and suitable dosage forms, which are likely critical for designing a successful sublingual or buccal vaccine. Finally, we outline the challenges, hurdles to overcome and formulation issues relevant for sublingual or buccal vaccine delivery.

Oral transmucosal drug delivery for pediatric use

The formulation of medicines for children remains a challenge. An ideal pediatric formulation must allow accurate dose administration and be in a dosage form that can be handled by the target age group. It is also important to consider the choices and the amount of excipients used in the formulation for this vulnerable age group. Although oral formulations are generally acceptable to most pediatric patients, they are not suitable for drugs with poor oral bioavailability or when a rapid clinical effect is required. In recent years, oral transmucosal delivery has emerged as an attractive route of administration for pediatric patients. With this route of administration, a drug is absorbed through the oral mucosa, therefore bypassing hepatic first pass metabolism and thus avoiding drug degradation or metabolism in the gastrointestinal tract. The high blood flow and relatively high permeability of the oral mucosa allow a quick onset of action to be achieved. It is a simple and non-invasive route of drug administration. However, there are several barriers that need to be overcome in the development of oral transmucosal products. This article aims to provide a comprehensive review of the current development of oral transmucosal delivery specifically for the pediatric population in order to achieve systemic drug delivery. The anatomical and physiological properties of the oral mucosa of infants and young children are carefully examined. The different dosage forms and formulation strategies that are suitable for young patients are discussed.

Antigen-bearing dendritic cells from the sublingual mucosa recirculate to distant systemic lymphoid organs to prime mucosal CD8 T cells

Effector T cells are described to be primed in the lymph nodes draining the site of immunization and to recirculate to effector sites. Sublingual immunization generates effector T cells able to disseminate to the genital tract. Herein, we report an alternative mechanism that involves the recirculation of antigen-bearing dendritic cells (DCs) in remote lymphoid organs to prime T cells. Sublingual immunization with a muco-adhesive model antigen unable to diffuse through lymphatic or blood vessels induced genital CD8 T cells. The sublingual draining lymph nodes were not mandatory to generate these lymphocytes, and antigen-bearing DCs from distant lymph nodes and spleen were able to prime specific CD8 T cells in a time- and dose-dependent manner. This study demonstrates, for the first time, that antigen-bearing DCs originating from the site of immunization recirculate to distant lymphoid organs and provides insights into the mechanism of distant CD8 T-cell generation by sublingual immunization.

Mucosal imprinting of vaccine-induced CD8⁺ T cells is crucial to inhibit the growth of mucosal tumors

Although many human cancers are located in mucosal sites, most cancer vaccines are tested against subcutaneous tumors in preclinical models. We therefore wondered whether mucosa-specific homing instructions to the immune system might influence mucosal tumor outgrowth. We showed that the growth of orthotopic head and neck or lung cancers was inhibited when a cancer vaccine was delivered by the intranasal mucosal route but not the intramuscular route. This antitumor effect was dependent on CD8⁺ T cells. Indeed, only intranasal vaccination elicited mucosal-specific CD8⁺ T cells expressing the mucosal integrin CD49a. Blockade of CD49a decreased intratumoral CD8⁺ T cell infiltration and the efficacy of cancer vaccine on mucosal tumor. We then showed that after intranasal vaccination, dendritic cells from lung parenchyma, but not those from spleen, induced the expression of CD49a on cocultured specific CD8⁺ T cells. Tumor-infiltrating lymphocytes from human mucosal lung cancer also expressed CD49a, which supports the relevance and possible extrapolation of these results in humans. We thus identified a link between the route of vaccination and the induction of a mucosal homing program on induced CD8⁺ T cells that controlled their trafficking. Immunization route directly affected the efficacy of the cancer vaccine to control mucosal tumors.

Sublingual delivery of vaccines for the induction of mucosal immunity

The mucosal surfaces are constantly exposed to incoming pathogens which can cause infections that result in severe morbidity and/or mortality. Studies have reported that mucosal immunity is important for providing protection against these pathogens and that mucosal vaccination is effective in preventing local infections. For many years, the sublingual mucosa has been targeted to deliver immunotherapy to treat allergic hypersensitivities. However, the potential of vaccine delivery via sublingual mucosal has received little attention until recently. Recent studies exploring such potential have documented the safety and effectiveness of sublingual immunization, demonstrating the ability of sublingual immunization to induce both systemic and mucosal immune responses against a variety of antigens, including soluble proteins, inter particulate antigens, and live-attenuated viruses. This review will summarize the recent findings that address the promising potential of sublingual immunization in proving protection against various mucosal pathogens.

Stimulating an immune response? Oral sex is associated with less endometritis

Secondary analysis of the PID Evaluation and Clinical Health (PEACH) data suggests that among women presenting with signs and symptoms of pelvic inflammatory disease (PID), those who reported oral sex were less likely to have endometritis (adjusted odds ratio [OR] 0.5 [0.3-0.8]) than those who did not report oral sex. Adaptive immunity requires antigenic priming of the lymphatic system. As lymphatic tissue is abundant in the oropharynx, oral sex could lead to effective immune stimulation and prevent PID. To determine whether oral sex could be a protective factor for PID the relationship between self-reported oral sex and endometritis was analysed among 619 women with clinically suspected PID who participated in the PEACH study. Nearly one quarter of participants reported oral sex in the past four weeks. These women also reported a higher number of sexual partners, a new partner within the past four weeks and a higher frequency of sexual intercourse (all P < 0.03). They were more likely to smoke (P < 0.0001), drink alcohol (P < 0.004) and use recreational drugs (P < 0.02). Participants reporting oral sex were significantly less likely to be black or to have a positive test for Neisseria gonorrhoeae (7.8% versus 21.6%, P = 0.001). Women who disclosed oral sex were significantly less likely to have endometritis after adjusting for race, number of partners, recent new partner, smoking, alcohol use and drug use (adjusted OR 0.5 [0.3-0.8]). This is the first paper showing a negative association between oral sex and endometritis. This may be mediated by a protective immune response in the genital tract following priming in the oropharynx. This hypothesis needs to be tested in further studies.

Evaluation of TLR agonists as potential mucosal adjuvants for HIV gp140 and tetanus toxoid in mice

In the present study we investigate the impact of a range of TLR ligands and chitosan as potential adjuvants for different routes of mucosal immunisation (sublingual (SL), intranasal (IN), intravaginal (IVag) and a parenteral route (subcutaneous (SC)) in the murine model. We assess their ability to enhance antibody responses to HIV-1 CN54gp140 (gp140) and Tetanus toxoid (TT) in systemic and vaginal compartments. A number of trends were observed by route of administration. For non-adjuvanted antigen, SC>SL>IN immunisation with respect to systemic IgG responses, where endpoint titres were greater for TT than for gp140. In general, co-administration with adjuvants increased specific IgG responses where IN = SC>SL, while in the vaginal compartment IN>SL>SC for specific IgA. In contrast, for systemic and mucosal IgA responses to antigen alone SL>IN = SC. A number of adjuvants increased specific systemic IgA responses where in general IN>SL>SC immunisation, while for mucosal responses IN = SL>SC. In contrast, direct intravaginal immunisation failed to induce any detectable systemic or mucosal responses to gp140 even in the presence of adjuvant. However, significant systemic IgG responses to TT were induced by intravaginal immunisation with or without adjuvant, and detectable mucosal responses IgG and IgA were observed when TT was administered with FSL-1 or Poly I∶C. Interestingly some TLRs displayed differential activity dependent upon the route of administration. MPLA (TLR4) suppressed systemic responses to SL immunisation while enhancing responses to IN or SC immunisation. CpG B enhanced SL and IN responses, while having little or no impact on SC immunisation. These data demonstrate important route, antigen and adjuvant effects that need to be considered in the design of mucosal vaccine strategies.

Intravaginal immunization with HPV vectors induces tissue-resident CD8+ T cell responses

The induction of persistent intraepithelial CD8+ T cell responses may be key to the development of vaccines against mucosally transmitted pathogens, particularly for sexually transmitted diseases. Here we investigated CD8+ T cell responses in the female mouse cervicovaginal mucosa after intravaginal immunization with human papillomavirus vectors (HPV pseudoviruses) that transiently expressed a model antigen, respiratory syncytial virus (RSV) M/M2, in cervicovaginal keratinocytes. An HPV intravaginal prime/boost with different HPV serotypes induced 10-fold more cervicovaginal antigen-specific CD8+ T cells than priming alone. Antigen-specific T cell numbers decreased only 2-fold after 6 months. Most genital antigen-specific CD8+ T cells were intra- or subepithelial, expressed αE-integrin CD103, produced IFN-γ and TNF-α, and displayed in vivo cytotoxicity. Using a sphingosine-1-phosphate analog (FTY720), we found that the primed CD8+ T cells proliferated in the cervicovaginal mucosa upon HPV intravaginal boost. Intravaginal HPV prime/boost reduced cervicovaginal viral titers 1,000-fold after intravaginal challenge with vaccinia virus expressing the CD8 epitope M2. In contrast, intramuscular prime/boost with an adenovirus type 5 vector induced a higher level of systemic CD8+ T cells but failed to induce intraepithelial CD103+CD8+ T cells or protect against recombinant vaccinia vaginal challenge. Thus, HPV vectors are attractive gene-delivery platforms for inducing durable intraepithelial cervicovaginal CD8+ T cell responses by promoting local proliferation and retention of primed antigen-specific CD8+ T cells.

Mucosal immunization with live attenuated Francisella novicida U112ΔiglB protects against pulmonary F. tularensis SCHU S4 in the Fischer 344 rat model

The need for an efficacious vaccine against Francisella tularensis is a consequence of its low infectious dose and high mortality rate if left untreated. This study sought to characterize a live attenuated subspecies novicida-based vaccine strain (U112ΔiglB) in an established second rodent model of pulmonary tularemia, namely the Fischer 344 rat using two distinct routes of vaccination (intratracheal [i.t.] and oral). Attenuation was verified by comparing replication of U112ΔiglB with wild type parental strain U112 in F344 primary alveolar macrophages. U112ΔiglB exhibited an LD₅₀>10⁷ CFU compared to the wild type (LD₅₀ = 5×10⁶ CFU i.t.). Immunization with 10⁷ CFU U112ΔiglB by i.t. and oral routes induced antigen-specific IFN-γ and potent humoral responses both systemically (IgG2a>IgG1 in serum) and at the site of mucosal vaccination (respiratory/intestinal compartment). Importantly, vaccination with U112ΔiglB by either i.t. or oral routes provided equivalent levels of protection (50% survival) in F344 rats against a subsequent pulmonary challenge with ∼25 LD₅₀ (1.25×10⁴ CFU) of the highly human virulent strain SCHU S4. Collectively, these results provide further evidence on the utility of a mucosal vaccination platform with a defined subsp. novicida U112ΔiglB vaccine strain in conferring protective immunity against pulmonary tularemia.

Sublingual immunization with recombinant adenovirus encoding SARS-CoV spike protein induces systemic and mucosal immunity without redirection of the virus to the brain

Background

Sublingual (s.l.) administration of soluble protein antigens, inactivated viruses, or virus-like particles has been shown to induce broad immune responses in mucosal and extra-mucosal tissues. Recombinant replication-defective adenovirus vectors (rADVs) infect mucosa surface and therefore can serve as a mucosal antigen delivery vehicle. In this study we examined whether s.l. immunization with rADV encoding spike protein (S) (rADV-S) of severe acute respiratory syndrome-associated coronavirus (SARS-CoV) induces protective immunity against SARS-CoV and could serve as a safe mucosal route for delivery of rADV.

Results

Here, we show that s.l. administration of rADV-S induced serum SARS-CoV neutralizing and airway IgA antibodies in mice. These antibody responses are comparable to those induced by intranasal (i.n.) administration. In addition, s.l. immunization induced antigen-specific CD8⁺ T cell responses in the lungs that are superior to those induced by intramuscular immunization. Importantly, unlike i.n. administration, s.l. immunization with rADV did not redirect the rADV vector to the olfactory bulb.

Conclusion

Our study indicates that s.l. immunization with rADV-S is safe and effective in induction of a broad spectrum of immune responses and presumably protection against infection with SARS-CoV.

B cell and T cell immunity in the female genital tract: potential of distinct mucosal routes of vaccination and role of tissue-associated dendritic cells and natural killer cells

The female genital mucosa constitutes the major port of entry of sexually transmitted infections. Most genital microbial pathogens represent an enormous challenge for developing vaccines that can induce genital immunity that will prevent their transmission. It is now established that long-lasting protective immunity at mucosal surfaces has to involve local B-cell and T-cell effectors as well as local memory cells. Mucosal immunization constitutes an attractive way to generate systemic and genital B-cell and T-cell immune responses that can control early infection by sexually transmitted pathogens. Nevertheless, no mucosal vaccines against sexually transmitted infections are approved for human use. The mucosa-associated immune system is highly compartmentalized and the selection of any particular route or combinations of routes of immunization is critical when defining vaccine strategies against genital infections. Furthermore, mucosal surfaces are complex immunocompetent tissues that comprise antigen-presenting cells and also innate immune effectors and non-immune cells that can act as 'natural adjuvants' or negative immune modulators. The functions of these cells have to be taken into account when designing tissue-specific antigen-delivery systems and adjuvants. Here, we will discuss data that compare different mucosal routes of immunization to generate B-cell and T-cell responses in the genital tract, with a special emphasis on the newly described sublingual route of immunization. We will also summarize data on the understanding of the effector and induction mechanisms of genital immunity that may influence the development of vaccine strategies against genital infections.

Humoral, mucosal, and cell-mediated immunity against vaccine and nonvaccine genotypes after administration of quadrivalent human papillomavirus vaccine to HIV-infected children

OBJECTIVES

To characterize the immunogenicity of a quadrivalent human papillomavirus vaccine (QHPV) in human immunodeficiency virus (HIV)-infected children, we studied their immune responses to 3 or 4 doses.

METHODS

HIV-infected children aged 7-12 years with a CD4 cell percentage of ≥15% of lymphocytes, received 3 doses of QHPV with or without a fourth dose after 72 weeks. Type-specific and cross-reactive antibodies and cell-mediated immunity were measured.

RESULTS

Type-specific antibodies to HPV6, 11, and 16 were detected in 100% and ≥94% of children at 4 and 72 weeks, respectively, after the third QHPV dose. Corresponding numbers for HPV18 were 97% and 76%, respectively. A fourth QHPV dose increased seropositivity to ≥96% for all vaccine genotypes. Four weeks after the third QHPV dose, 67% of vaccinees seroconverted to HPV31, an HPV16-related genotype not in the vaccine; 69% and 39% of vaccinees developed mucosal HPV16 and 18 immunoglobulin G antibodies, respectively; and 60% and 52% of vaccinees developed cytotoxic T lymphocytes (CTLs) for HPV16 and 31, respectively.

CONCLUSIONS

Three QHPV doses generated robust and persistent antibodies to HPV6, 11, and 16 but comparatively weaker responses to HPV18. A fourth dose increased antibodies against all vaccine genotypes in an anamnestic fashion. CTLs and mucosal antibodies against vaccine genotypes, as well as cross-reactive antibodies and CTL against nonvaccine genotypes, were detected.

Sublingual immunization with a live attenuated influenza a virus lacking the nonstructural protein 1 induces broad protective immunity in mice

The nonstructural protein 1 (NS1) of influenza A virus (IAV) enables the virus to disarm the host cell type 1 IFN defense system. Mutation or deletion of the NS1 gene leads to attenuation of the virus and enhances host antiviral response making such live-attenuated influenza viruses attractive vaccine candidates. Sublingual (SL) immunization with live influenza virus has been found to be safe and effective for inducing protective immune responses in mucosal and systemic compartments. Here we demonstrate that SL immunization with NS1 deleted IAV (DeltaNS1 H1N1 or DeltaNS1 H5N1) induced protection against challenge with homologous as well as heterosubtypic influenza viruses. Protection was comparable with that induced by intranasal (IN) immunization and was associated with high levels of virus-specific antibodies (Abs). SL immunization with DeltaNS1 virus induced broad Ab responses in mucosal and systemic compartments and stimulated immune cells in mucosa-associated and systemic lymphoid organs. Thus, SL immunization with DeltaNS1 offers a novel potential vaccination strategy for the control of influenza outbreaks including pandemics.

Bacillus subtilis: a temperature resistant and needle free delivery system of immunogens

Most pathogens enter the body through mucosal surfaces. Mucosal immunization, a non-invasive needle-free route, often stimulates a mucosal immune response that is both effective against mucosal and systemic pathogens. The development of mucosally administered heat-stable vaccines with long shelf life would therefore significantly enhance immunization programs in developing countries by avoiding the need for a cold chain or systemic injections. Currently, recombinant vaccine carriers are being used for antigen delivery. Engineering Bacillus subtilis for use as a non-invasive and heat stable antigen delivery system has proven successful. Bacterial spores protected by multiple layers of protein are known to be robust and resistant to desiccation. Stable constructs have been created by integration into the bacterial chromosome of immunogens. The spore coat has been used as a vehicle for heterologous antigen presentation and protective immunization. Sublingual (SL) and intranasal (IN) routes have recently received attention as delivery routes for therapeutic drugs and vaccines and recent attempts by several investigators, including our group, to develop vaccines that can be delivered intranasally and sublingually have met with a lot of success. As discussed in this review, the use of Bacillus subtilis to express antigens that can be administered either intranasally or sublingually is providing new insights in the area of mucosal vaccines. In our work, we evaluated the efficacy of SL and IN immunizations with B. subtilis engineered to express tetanus toxin fragment C (TTFC) in mice and piglets. These bacteria engineered to express heterologous antigen either on the spore surface or within the vegetative cell have been used for oral, IN and SL delivery of antigens. A Bacillus subtilis spore coat protein, CotC was used as a fusion partner to express the tetanus fragment C. B. subtilis spores known to be highly stable and safe are also easy to purify making this spore-based display system a potentially powerful approach for surface expression of antigens. These advances will help to accelerate the development and testing of new mucosal vaccines against many human and animal diseases.