Comparison of mucosal and systemic humoral immune responses after transcutaneous and oral immunization strategies

Gut Microbiota and Development of Vibrio cholerae-Specific Long-Term Memory B Cells in Adults after Whole-Cell Killed Oral Cholera Vaccine

Cholera is a diarrheal disease caused by Vibrio cholerae that continues to be a major public health concern in populations without access to safe water. IgG- and IgA-secreting memory B cells (MBC) targeting the V. cholerae O-specific polysaccharide (OSP) correlate with protection from infection in persons exposed to V. cholerae and may be a major determinant of long-term protection against cholera. Shanchol, a widely used oral cholera vaccine (OCV), stimulates OSP MBC responses in only some people after vaccination, and the gut microbiota is a possible determinant of variable immune responses observed after OCV. Using 16S rRNA sequencing of feces from the time of vaccination, we compared the gut microbiota among adults with and without MBC responses to OCV. Gut microbial diversity measures were not associated with MBC isotype or OSP-specific responses, but individuals with a higher abundance of Clostridiales and lower abundance of Enterobacterales were more likely to develop an MBC response. We applied protein-normalized fecal supernatants of high and low MBC responders to THP-1-derived human macrophages to investigate the effect of microbial factors at the time of vaccination. Feces from individuals with higher MBC responses induced significantly different IL-1β and IL-6 levels than individuals with lower responses, indicating that the gut microbiota at the time of vaccination may "prime" the mucosal immune response to vaccine antigens. Our results suggest the gut microbiota could impact immune responses to OCVs, and further study of microbial metabolites as potential vaccine adjuvants is warranted.

Selenium Nanoparticles Induce Potent Protective Immune Responses against Vibrio cholerae WC Vaccine in a Mouse Model

The aim of this study was to evaluate the efficacy of selenium nanoparticle (an immune booster) and naloxone (an opioid receptor antagonist) as a new adjuvant in increasing immune responses against killed whole-cell Vibrio cholerae in a mouse cholera model. The Se NPs were synthesized and characterized by UV-visible, DLS, and zeta potential analysis. The SEM image confirmed the uniformity of spherical morphology of nanoparticle shape with 34 nm in size. The concentration of the Se NPs was calculated as 0.654 μg/ml in the ICP method. The cytotoxic activity of Se NPs on Caco-2 cells was assessed by the MTT assay and revealed 82.05% viability of cells after 24 h exposure with 100 μg/ml of Se NPs. Female BALB/C mice were orally immunized three times on days 0, 14, and 28, and challenge experiments were performed on immunized neonates with toxigenic V. cholerae. Administration of Se NP diet led to significant increase in V. cholerae-specific IgG and IgA responses in serum and saliva and caused protective immunity and 83.3% survival in challenge experiment against 1 LD50 V. cholerae in a group receiving diet of Se NPs compared with other groups including Dukoral vaccine. The IL-4 and IL-5 were significantly increased in response to WC+daily diet of Se NPs with or without naloxone. Naloxone proved no effect on IL-4 and IL-5 increase and is proposed as null in the cytokine and antibody production process. These results reveal that daily diet of Se NPs could efficiently induce immune cell effectors in both humoral and mucosal levels.

Mucosal vaccine delivery: Current state and a pediatric perspective

Most childhood infections occur via the mucosal surfaces, however, parenterally delivered vaccines are unable to induce protective immunity at these surfaces. In contrast, delivery of vaccines via the mucosal routes can allow antigens to interact with the mucosa-associated lymphoid tissue (MALT) to induce both mucosal and systemic immunity. The induced mucosal immunity can neutralize the pathogen on the mucosal surface before it can cause infection. In addition to reinforcing the defense at mucosal surfaces, mucosal vaccination is also expected to be needle-free, which can eliminate pain and the fear of vaccination. Thus, mucosal vaccination is highly appealing, especially for the pediatric population. However, vaccine delivery across mucosal surfaces is challenging because of the different barriers that naturally exist at the various mucosal surfaces to keep the pathogens out. There have been significant developments in delivery systems for mucosal vaccination. In this review we provide an introduction to the MALT, highlight barriers to vaccine delivery at different mucosal surfaces, discuss different approaches that have been investigated for vaccine delivery across mucosal surfaces, and conclude with an assessment of perspectives for mucosal vaccination in the context of the pediatric population.

Induction of mucosal immunity through systemic immunization: Phantom or reality?

Generation of protective immunity at mucosal surfaces can greatly assist the host defense against pathogens which either cause disease at the mucosal epithelial barriers or enter the host through these surfaces. Although mucosal routes of immunization, such as intranasal and oral, are being intensely explored and appear promising for eliciting protective mucosal immunity in mammals, their application in clinical practice has been limited due to technical and safety related challenges. Most of the currently approved human vaccines are administered via systemic (such as intramuscular and subcutaneous) routes. Whereas these routes are acknowledged as being capable to elicit antigen-specific systemic humoral and cell-mediated immune responses, they are generally perceived as incapable of generating IgA responses or protective mucosal immunity. Nevertheless, currently licensed systemic vaccines do provide effective protection against mucosal pathogens such as influenza viruses and Streptococcus pneumoniae. However, whether systemic immunization induces protective mucosal immunity remains a controversial topic. Here we reviewed the current literature and discussed the potential of systemic routes of immunization for the induction of mucosal immunity.

Immune responses to the O-specific polysaccharide antigen in children who received a killed oral cholera vaccine compared to responses following natural cholera infection in Bangladesh

Current oral cholera vaccines induce lower levels of protective efficacy and shorter durations of protection in young children than in adults. Immunity against cholera is serogroup specific, and immune responses to Vibrio cholerae lipopolysaccharide (LPS), the antigen that mediates serogroup-specific responses, are associated with protection against disease. Despite this, responses against V. cholerae O-specific polysaccharide (OSP), a key component of the LPS responsible for specificity, have not been characterized in children. Here, we report a comparison of polysaccharide antibody responses in children from a region in Bangladesh where cholera is endemic, including infants (6 to 23 months, n = 15), young children (24 to 59 months, n = 14), and older children (5 to 15 years, n = 23) who received two doses of a killed oral cholera vaccine 14 days apart. We found that infants and young children receiving the vaccine did not mount an IgG, IgA, or IgM antibody response to V. cholerae OSP or LPS, whereas older children showed significant responses. In comparison to the vaccinees, young children with wild-type V. cholerae O1 Ogawa infection did mount significant antibody responses against OSP and LPS. We also demonstrated that OSP responses correlated with age in vaccinees, but not in cholera patients, reflecting the ability of even young children with wild-type cholera to develop OSP responses. These differences might contribute to the lower efficacy of protection rendered by vaccination than by wild-type disease in young children and suggest that efforts to improve lipopolysaccharide-specific responses might be critical for achieving optimal cholera vaccine efficacy in this younger age group.

Transcutaneous immunization: an overview of advantages, disease targets, vaccines, and delivery technologies

Skin is an immunologically active tissue composed of specialized cells and agents that capture and process antigens to confer immune protection. Transcutaneous immunization takes advantage of the skin immune network by inducing a protective immune response against topically applied antigens. This mode of vaccination presents a novel and attractive approach for needle-free immunization that is safe, noninvasive, and overcomes many of the limitations associated with needle-based administrations. In this review we will discuss the developments in the field of transcutaneous immunization in the past decade with special emphasis on disease targets and vaccine delivery technologies. We will also briefly discuss the challenges that need to be overcome to translate early laboratory successes in transcutaneous immunization into the development of effective clinical prophylactics.

Memory B cell and other immune responses in children receiving two doses of an oral killed cholera vaccine compared to responses following natural cholera infection in Bangladesh

Current oral cholera vaccines induce lower protective efficacy and shorter duration of protection against cholera than wild-type infection provides, and this difference is most pronounced in young children. Despite this, there are limited data comparing immune responses in children following wild-type disease versus vaccination, especially with regard to memory responses associated with long-term immunity. Here, we report a comparison of immune responses in young children (2 to 5 years of age; n = 20) and older children (6 to 17 years of age; n = 20) given two doses of an oral killed cholera vaccine containing recombinant cholera toxin B subunit (CtxB) 14 days apart and compare these responses to those induced in similarly aged children recovering from infection with Vibrio cholerae O1 Ogawa in Bangladesh. We found that the two vaccine groups had comparable vibriocidal and lipopolysaccharide (LPS)-specific plasma antibody responses. Vaccinees developed lower levels of IgG memory B cell (MBC) responses against CtxB but no significant MBC responses against LPS. In contrast, children recovering from natural cholera infection developed prominent LPS IgG and IgA MBC responses, as well as CtxB IgG MBC responses. Plasma LPS IgG, IgA, and IgM responses, as well as vibriocidal responses, were also significantly higher in children following disease than after vaccination. Our findings suggest that acute and memory immune responses following oral cholera vaccination in children are significantly lower than those observed following wild-type disease, especially responses targeting LPS. These findings may explain, in part, the lower efficacy of oral cholera vaccination in children.

Transcutaneous immunization with a Vibrio cholerae O1 Ogawa synthetic hexasaccharide conjugate following oral whole-cell cholera vaccination boosts vibriocidal responses and induces protective immunity in mice

A shortcoming of currently available oral cholera vaccines is their induction of relatively short-term protection against cholera compared to that afforded by wild-type disease. We were interested in whether transcutaneous or subcutaneous boosting using a neoglycoconjugate vaccine made from a synthetic terminal hexasaccharide of the O-specific polysaccharide of Vibrio cholerae O1 (Ogawa) coupled to bovine serum albumin as a carrier (CHO-BSA) could boost lipopolysaccharide (LPS)-specific and vibriocidal antibody responses and result in protective immunity following oral priming immunization with whole-cell cholera vaccine. We found that boosting with CHO-BSA with immunoadjuvantative cholera toxin (CT) or Escherichia coli heat-labile toxin (LT) following oral priming with attenuated V. cholerae O1 vaccine strain O395-NT resulted in significant increases in serum anti-V. cholerae LPS IgG, IgM, and IgA (P < 0.01) responses as well as in anti-Ogawa (P < 0.01) and anti-Inaba (P < 0.05) vibriocidal titers in mice. The LPS-specific IgA responses in stool were induced by transcutaneous (P < 0.01) but not subcutaneous immunization. Immune responses following use of CT or LT as an adjuvant were comparable. In a neonatal mouse challenge assay, immune serum from boosted mice was associated with 79% protective efficacy against death. Our results suggest that transcutaneous and subcutaneous boosting with a neoglycoconjugate following oral cholera vaccination may be an effective strategy to prolong protective immune responses against V. cholerae.

Comparison of memory B cell, antibody-secreting cell, and plasma antibody responses in young children, older children, and adults with infection caused by Vibrio cholerae O1 El Tor Ogawa in Bangladesh

Children bear a large component of the global burden of cholera. Despite this, little is known about immune responses to cholera in children, especially those under 5 years of age. Cholera vaccine studies have demonstrated lower long-term protective efficacy in young children than in older children and adults. Memory B cell (MBC) responses may correlate with duration of protection following infection and vaccination. Here we report a comparison of immune responses in young children (3 to 5 years of age; n = 17), older children (6 to 17 years of age; n = 17), and adults (18 to 60 years of age; n = 68) hospitalized with cholera in Dhaka, Bangladesh. We found that young children had lower baseline vibriocidal antibody titers and higher fold increases in titer between day 2 and day 7 than adults. Young children had higher baseline IgG plasma antibody levels to Vibrio cholerae antigens, although the magnitudes of responses at days 7 and 30 were similar across age groups. As a surrogate marker for mucosal immune responses, we assessed day 7 antibody-secreting cell (ASC) responses. These were comparable across age groups, although there was a trend for older age groups to have higher levels of lipopolysaccharide-specific IgA ASC responses. All age groups developed comparable MBC responses to V. cholerae lipopolysaccharide and cholera toxin B subunit at day 30. These findings suggest that young children are able to mount robust vibriocidal, plasma antibody, ASC, and MBC responses against V. cholerae O1, suggesting that under an optimal vaccination strategy, young children could achieve protective efficacy comparable to that induced in adults.

Safety and efficacy of novel dermal and epidermal microneedle delivery systems for rabies vaccination in healthy adults

In the present pilot study, intradermal ID delivery systems with a BD microneedle from 1 to 3mm in length, and epidermal delivery (BD skin abrader) through abraded skin surface relative to standard intramuscular injection were evaluated. Circulating neutralizing antibodies were measured against the rabies virus after the Vero cells rabies vaccine was administered at D0, D7, D21 and D49. This clinical evaluation in 66 healthy volunteers shows that ID delivery using BD microneedle technology of 1/4 the IM antigen dose is safe, efficient and reliable, resulting in a protective seroconversion rate. In contrast, the epidermal delivery route did not produce an immune response against the rabies vaccine.

Transcutaneous immunization with a synthetic hexasaccharide-protein conjugate induces anti-Vibrio cholerae lipopolysaccharide responses in mice

Antibodies specific for Vibrio cholerae lipopolysaccaride (LPS) are common in humans recovering from cholera, and constitute a primary component of the vibriocidal response, a serum complement-mediated bacteriocidal response correlated with protection against cholera. In order to determine whether transcutaneous immunization (TCI) with a V. cholerae neoglycoconjugate (CHO-BSA) comprised of a synthetic terminal hexasaccharide of the O-specific polysaccharide of V. cholerae O1 (Ogawa) conjugated with bovine serum albumin (BSA) could induce anti-V. cholerae LPS and vibriocidal responses, we applied CHO-BSA transcutaneously in the presence or absence of the immune adjuvant cholera toxin (CT) to mice. Transcutaneously applied neoglycoconjugate elicited prominent V. cholerae specific LPS IgG responses in the presence of CT, but not IgM or IgA responses. CT applied on the skin induced strong IgG and IgA serum responses. TCI with neoglycoconjugate did not elicit detectable vibriocidal responses, protection in a mouse challenge assay, or stool anti-V. cholerae IgA responses, irrespective of the presence or absence of CT. Our results suggest that transcutaneously applied synthetic V. cholerae neoglycoconjugate is safe and immunogenic, but predominantly induces systemic LPS responses of the IgG isotype.

Intradermal vaccine delivery: will new delivery systems transform vaccine administration?

There has been a recent resurgence of interest in intradermal vaccine delivery. The physiological advantages of intradermal vaccine delivery have been known for some time, but the difficulties associated with performing an intradermal injection have historically limited its use. New delivery systems currently in development facilitate convenient intradermal vaccination, unlocking the potential advantages of this delivery route, and potentially transforming vaccine delivery.

Transcutaneous immunization by merely prolonging the duration of antigen presence on the skin of mice induces a potent antigen-specific antibody response even in the absence of an adjuvant

Transcutaneous immunization (TCI) is a promising needle-free technique for vaccination. In this method, strong adjuvants, such as the cholera toxin, are generally crucial to elicit a robust immune response. Here, we showed that prolonged antigen presence on the skin of mice during TCI could effectively enhance the immune response. Substantial antigen-specific antibodies were produced in the sera of mice even after non-adjuvanted TCI when the antigen presence was for longer than 16 h. This non-adjuvanted TCI method was applied using the tetanus toxoid, and potent tetanus toxoid-specific antibodies were successfully induced in the sera of mice; they survived a lethal tetanus toxin challenge with no clinical signs. Thus, non-adjuvanted approach might be a possible option for TCI, and this method might improve the safety and practicality of transcutaneous vaccination.

Evaluation of the clinical performance of a new intradermal vaccine administration technique and associated delivery system

The advantages of intradermal (ID) vaccine administration have been well documented but difficulties in performing ID vaccination using existing techniques and equipment have limited it's clinical application. In the present study, a new ID injection technique and associated microinjection system is described and evaluated in a swine and Human models. Clinical investigation models included: injection site imaging (X-ray and 3D ultrasound echography), histological examination of injection sites, fluid injection volume accuracy measurement, subject' perceived pain and local skin reactivity were specifically developed. These evaluations showed that microinjection system can make the practice of ID vaccination easy to perform, reliable and safe, thus setting the stage for broader clinical application of ID vaccine delivery.

Transcutaneous immunization with Clostridium difficile toxoid A induces systemic and mucosal immune responses and toxin A-neutralizing antibodies in mice

Clostridium difficile is the leading cause of nosocomial infectious diarrhea. C. difficile produces two toxins (A and B), and systemic and mucosal anti-toxin A antibodies prevent or limit C. difficile-associated diarrhea. To evaluate whether transcutaneous immunization with formalin-treated C. difficile toxin A (CDA) induces systemic and mucosal anti-CDA immune responses, we transcutaneously immunized three cohorts of mice with CDA with or without immunoadjuvantative cholera toxin (CT) on days 0, 14, 28, and 42. Mice transcutaneously immunized with CDA and CT developed prominent anti-CDA and anti-CT immunoglobulin G (IgG) and IgA responses in serum and anti-CDA and anti-CT IgA responses in stool. Sera from immunized mice were able to neutralize C. difficile toxin A activity in an in vitro cell culture assay. CDA itself demonstrated adjuvant activity and enhanced both serum and stool anti-CT IgA responses. Our results suggest that transcutaneous immunization with CDA toxoid may be a feasible immunization strategy against C. difficile, an important cause of morbidity and mortality against which current preventative strategies are failing.

Analysis of strategies to successfully vaccinate infants in developing countries against enterotoxigenic E. coli (ETEC) disease

Enterotoxigenic Escherichia coli (ETEC) is the most common bacterial cause of diarrhoea in the world, annually affecting up to 400,000,000 children under 5 years of age living in developing countries (DCs). Although ETEC possesses numerous antigens, the relatively conserved colonization factor (CF) antigens and the heat labile enterotoxin (LT) have been associated with protection and most vaccine candidates have exploited these antigens. A safe and effective vaccine against ETEC is a feasible goal as supported by the acquisition of protective immunity. The success of an ETEC vaccine targeting infants and children in DCs will depend on a combination of maximally antigenic vaccine preparations and regimens for their delivery which will produce optimal immune responses to these antigens. Vaccine candidates having a high priority for accelerated development and clinical testing for eventual use in infants would include inactivated ETEC or Shigella hybrids expressing ETEC antigens as well as attenuated ETEC strains which express the major CF antigens and LT toxin B-subunit, as well as attenuated Shigella, Vibrio cholerae and Salmonella typhi hybrids engineered to deliver antigens of ETEC. Candidates for an ETEC vaccine would have to meet the minimal requirement of providing at least 50% protection against severe disease in DCs during the first 2 years of life. The critical roadblock to achieving this goal has not been the science as much as the lack of a sufficiently funded and focused effort to bring it to realization. However, a Product Development Partnership to overcome this hurdle could accelerate the time lines towards when control of ETEC disease in DCs is substantially closer.

Transcutaneous immunization with toxin-coregulated pilin A induces protective immunity against Vibrio cholerae O1 El Tor challenge in mice

Toxin-coregulated pilin A (TcpA) is the main structural subunit of a type IV bundle-forming pilus of Vibrio cholerae, the cause of cholera. Toxin-coregulated pilus is involved in formation of microcolonies of V. cholerae at the intestinal surface, and strains of V. cholerae deficient in TcpA are attenuated and unable to colonize intestinal surfaces. Anti-TcpA immunity is common in humans recovering from cholera in Bangladesh, and immunization against TcpA is protective in murine V. cholerae models. To evaluate whether transcutaneously applied TcpA is immunogenic, we transcutaneously immunized mice with 100 mug of TcpA or TcpA with an immunoadjuvant (cholera toxin [CT], 50 mug) on days 0, 19, and 40. Mice immunized with TcpA alone did not develop anti-TcpA responses. Mice that received transcutaneously applied TcpA and CT developed prominent anti-TcpA immunoglobulin G (IgG) serum responses but minimal anti-TcpA IgA. Transcutaneous immunization with CT induced prominent IgG and IgA anti-CT serum responses. In an infant mouse model, offspring born to dams transcutaneously immunized either with TcpA and CT or with CT alone were challenged with 10(6) CFU (one 50% lethal dose) wild-type V. cholerae O1 El Tor strain N16961. At 48 h, mice born to females transcutaneously immunized with CT alone had 36% +/- 10% (mean +/- standard error of the mean) survival, while mice born to females transcutaneously immunized with TcpA and CT had 69% +/- 6% survival (P < 0.001). Our results suggest that transcutaneous immunization with TcpA and an immunoadjuvant induces protective anti-TcpA immune responses. Anti-TcpA responses may contribute to an optimal cholera vaccine.

Neuraminidase pharmacophore model derived from diverse classes of inhibitors

A three-dimensional pharmacophore model was developed based on 22 currently available inhibitors, which were carefully selected with great diversity in both molecular structure and bioactivity, for discovering new potent neuraminidase (NA) inhibitors to fight against avian influenza virus. The best hypothesis (Hypo1), consisting of five features, namely, one positive ionizable group, one negative ionizable group, one hydrophobic point, and two hydrogen-bond donors, has a correlation coefficient of 0.902, a root mean square deviation of 1.392, and a cost difference of 72.88, suggesting that a highly predictive pharmacophore model was successfully obtained. The application of the model shows great success in predicting the activities of 88 known NA inhibitors in our test set with a correlation coefficient of 0.818 with a cross-validation of 98% confidence level. Accordingly, our model should be reliable in identifying structurally diverse compounds with desired biological activity.

Adjuvants modulating mucosal immune responses or directing systemic responses towards the mucosa

In developing veterinary mucosal vaccines and vaccination strategies, mucosal adjuvants are one of the key players for inducing protective immune responses. Most of the mucosal adjuvants seem to exert their effect via binding to a receptor/or target cells and these properties were used to classify the mucosal adjuvants reviewed in the present paper: (1) ganglioside receptor-binding toxins (cholera toxin, LT enterotoxin, their B subunits and mutants); (2) surface immunoglobulin binding complex CTA1-DD; (3) TLR4 binding lipopolysaccharide; (4) TLR2-binding muramyl dipeptide; (5) Mannose receptor-binding mannan; (6) Dectin-1-binding ss 1,3/1,6 glucans; (7) TLR9-binding CpG-oligodeoxynucleotides; (8) Cytokines and chemokines; (9) Antigen-presenting cell targeting ISCOMATRIX and ISCOM. In addition, attention is given to two adjuvants able to prime the mucosal immune system following a systemic immunization, namely 1alpha, 25(OH)2D3 and cholera toxin.

Considerations for development of whole cell bacterial vaccines to prevent diarrheal diseases in children in developing countries

Enteric pathogens constitute a major pediatric threat in the developing world through their impact on morbidity and mortality, physical and cognitive development and cause and effect relationship with malnutrition. Although many bacterial pathogens can cause diarrheal diseases, a group of less than 10 including Shigella spp., enterotoxigenic Escherichia coli (ETEC), Vibrio cholerae, and possibly, Campylobacter jejuni account for a significant percentage of these diseases in developing countries. Rotavirus is also a major cause of diarrheal diseases. Vaccines against these agents offer a potentially effective control measure against these diseases, but safe, practical, and effective vaccines for many of these agents have yet to be realized. Many vaccine development approaches are under investigation, but the one that is currently most advanced and that has been most widely applied to enteric pathogens is the use of orally administered live or killed whole pathogen preparations. If inactivated, these vaccines will probably be administered as multiple doses with approximately 10(10) to 10(11) total particles per dose, but they are relatively safe for oral administration. Further, they may not require a buffer for delivery and can be stored in liquid formulations. Fewer doses may be required for some live attenuated pathogen vaccines, but a buffer will most likely be required for oral delivery and the product must be stored in a dried formulation. Also, safety becomes more of a concern with live pathogens depending on the degree of attenuation, host immunocompetence, and the total number and kinds of attenuated pathogens which may be present in a combined agent vaccine. Both live and killed whole pathogen vaccines can be immunogenic and have the possibility to serve as vectors for other antigens. Although many organisms and serotypes are clinically important, by exploiting antigenic cross reactivity and using some pathogen components as vectors for cloned antigens of other pathogens, it could be possible to induce immunity against major enteric pathogens/serotypes with <10 whole pathogen components in a multi-agent vaccine. Safe and effective mucosal adjuvants may in the future be useful in whole pathogen vaccines, but they do not seem to be essential for immunization. Further, dietary supplements such as zinc, mixed routes of delivery and new regimens are under study which may in the future enhance further the effectiveness of the whole pathogen vaccines which now seem realizable in the near term. For this to happen, however, a coordinated and committed effort is necessary now to address the immunologic, regulatory, manufacturing, testing and implementation issues which will be involved in the realization of this important product to benefit children's health worldwide.

Cholera toxin B-subunit gene enhances mucosal immunoglobulin A, Th1-type, and CD8+ cytotoxic responses when coadministered intradermally with a DNA vaccine

A plasmid vector encoding the cholera toxin B subunit (pCtB) was evaluated as an intradermal genetic adjuvant for a model DNA vaccine expressing the human papillomavirus type 16 L1 capsid gene (p16L1) in mice. p16L1 was coadministered with plasmid pCtB or commercial polypeptide CtB as a positive control. Coadministration of pCtB induced a significant increment of specific anti-L1 immunoglobulin A (IgA) antibodies in cervical secretions (P < 0.05) and fecal extracts (P < 0.005). Additionally, coadministration of pCtB enhanced the production of interleukin-2 and gamma interferon by spleen cells but did not affect the production of interleukin-4, suggesting a Th1-type helper response. Furthermore, improved CD8+ T-cell-mediated cytotoxic activity was observed in mice vaccinated with the DNA vaccine with pCtB as an adjuvant. This adjuvant effect was comparable to that induced by the CtB polypeptide. These results indicate that intradermal coadministration of pCtB is an adequate means to enhance the mucosa-, Th1-, and CD8(+)-mediated cytotoxic responses induced by a DNA vaccine.

Starch microparticles as an adjuvant in immunisation: effect of route of administration on the immune response in mice

This paper describes the effects on the development of an immune response by changing the route of administration of a new vaccine adjuvant, starch microparticles with human serum albumin (HSA) as a model antigen. The model vaccine was administered to mice by oral, subcutaneous and intramuscular routes in various combinations and both the local secretory immunoglobulin antibody (s-IgA) and systemic humoral and cellular (delayed-type hypersensitivity assay (DTH)) responses were followed. The only immunisation regimens inducing a significant s-IgA response were those incorporating oral booster doses. Oral and subcutaneous immunisations had similar effects on the Th1/Th2 balance, as indicated by the IgG subclass ratios and cytokine analyses. However, significant differences between oral and intramuscular immunisations were seen in the IgG subclass ratios. The Th2 influence was stronger after oral primary immunisation than after intramuscular primary immunisation, while oral boosters elicited a comparatively stronger Th1 response than intramuscular boosters. This result was also supported by the DTH analyses. Subcutaneous immunisation induced a stronger Th2 response than intramuscular immunisation, as indicated by subclass ratio and the IgE response. In conclusion, our results show that the profile of an immune response depends on the route of administration, which should be considered when developing new vaccines or new routes of administration.