The induction of systemic and mucosal immune responses to antigen-adjuvant compositions administered into the skin: alterations in the migratory properties of dendritic cells appears to be important for stimulating mucosal immunity

Effects of oil-based adjuvants on the immune response of pigs after dermal administration of antigen and evaluation of the immunization level after a subsequent Actinobacillus pleuropneumoniae challenge in pigs

Route of vaccine delivery can greatly impact the immunogenicity, efficacy and safety of the vaccine. Four groups of piglets were immunised transdermally (t.d.), intradermally (i.d.) or intramuscularly (i.m.) with the same doses of antigen in combination with a water-in-oil-in-water emulsion adjuvant Montanide™ ISA 201 VG or with a microemulsion adjuvant Montanide™ IMS 1313 VG N ST (Seppic, France). The last group was left without vaccination as a control group. All animals were subsequently exposed to the infection induced by Actinobacillus pleuropneumoniae (App). The immune response was evaluated with respect to the intensity of systemic and mucosal antibody formation, their isotype characterisation and rate of cell-mediated immunity. These findings were compared with the intensity of adverse local reactions and level of protection in experimental challenge. Monitoring of the local reaction at the injection site after each administration showed that microemulsion adjuvant IMS 1313 was less reactogenic than the water-in-oil-in-water emulsion ISA 201. In terms of efficacy, both dermal administrations were less immunogenic than the i.m route. The i.m. injection induced higher anti-App9 IgG and IgM titres. Nevertheless, IgG1 and IgG2 isotypes analysis revealed a close immunological profile between i.m. and i.d. routes. The concentration of IFN-γ from peripheral blood after in vitro restimulation with the specific antigen was only increased in the i.m. group at the day of challenge (D35) and two weeks after (D49). Interestingly, the smallest gross pulmonary lesions were observed in the i.d. vaccinated group (3.4%) compared to the control group (39.4%) and to groups with other routes of administration. Taken together, these results suggest that i.d. administration of vaccines is a promising approach. Even the i.d. vaccine was more reactogenic and slightly less immunogenic than the i.m. vaccine, its protection effectiveness seemed to be superior.

Stimulating immunoglobulin response by intramuscular delivery of exopolysaccharides-adjuvanted mannheimiosis vaccine in goats

Background and Aim

Pneumonic mannheimiosis (PM) is a common respiratory bacterial disease among small ruminants. Despite numerous management methods, vaccination remains a suitable strategy to combat or reduce PM in goats and sheep. Thus, a study was conducted in Malaysia to evaluate the immunogenicity of exopolysaccharide-adjuvanted Mannheimia haemolytica A2 vaccine (EPS-MHA2) under laboratory and field conditions for its potential use as an efficient vaccine against PM.

Materials and Methods

This study induced immunoglobulin (Ig) responses following intramuscular (IM) delivery of the EPS-MHA2 vaccine on 12 goats for about 7 months. Goats were divided into three groups, with three goats per group, and they were vaccinated intramuscularly as follows: Group 1 was vaccinated with an adjuvanted vaccine prepared from formalin-killed M. haemolytica serotypes A2 and EPS excipient; Group 2 was vaccinated with formalin-killed M. haemolytica seed only, whereas Group 3 was injected with phosphate-buffered saline (PBS) as the negative control. Measures of specific immunity included serum IgM, IgG, and IgA as well as bronchoalveolar lavage fluid secretory IgA and the size and number of the bronchus-associated lymphoid tissue (BALT).

Results

From the 1^st day of vaccination, Groups 1 and 2 showed a significant (p < 0.05) increase in serum IgM, IgG, and IgA levels. However, the antibodies started to decline 5-week post-vaccination, indicating that the booster dose was necessary. On the second exposure to the same vaccine (booster), the level of antibodies showed a significant increase (p < 0.05), particularly IgG. All groups were challenged intratracheally by virulent MHA2 2 weeks after the decline of second antibodies on the administration of booster. All goats were euthanatized and necropsied 4-week post-challenge. The number and size of the BALT in Group 1 goats significantly increased compared with those in Group 2 and the unvaccinated control. Bacteriological parameters were evaluated, in which MHA2 was reisolated successfully from lung samples in Group 3. The IgA level produced by the group vaccinated with EPS-MHA2 was significantly (p < 0.001) higher than that the MHA2 vaccine and PBS groups. All data obtained were analyzed statistically using a one-way analysis of variance. The results indicate that IM injection of EPS-MHA2 vaccine significantly enhanced the immune response against MHA2.

Conclusion

Therefore, the addition of EPS to MHA2 (EPS-MHA2 vaccine) can effectively protect goats from lethal mannheimiosis infection. Factors such as the ideal concentration of EPS should be further studied to verify its application potential as a vaccine adjuvant, and the extraction of EPS from different microalgae species should be further investigated. This study showed a novel and exciting set of data and a vaccination system, in which the suppressive effects of mannheimiosis may be further investigated.

Intradermal fractional-dose inactivated polio vaccine (fIPV) adjuvanted with double mutant Enterotoxigenic Escherichia coli heat labile toxin (dmLT) is well-tolerated and augments a systemic immune response to all three poliovirus serotypes in a randomized placebo-controlled trial

Eradication of poliomyelitis globally is constrained by fecal shedding of live polioviruses, both wild-type and vaccine-derived strains, into the environment. Although inactivated polio vaccines (IPV) effectively protect the recipient from clinical poliomyelitis, fecal shedding of live virus still occurs following infection with either wildtype or vaccine-derived strains of poliovirus. In the drive to eliminate the last cases of polio globally, improvements in both oral polio vaccines (OPV) (to prevent reversion to virulence) and injectable polio vaccines (to improve mucosal immunity and prevent viral shedding) are underway. The E. coli labile toxin with two or "double" attenuating mutations (dmLT) may boost immunologic responses to IPV, including at mucosal sites. We performed a double-blinded phase I controlled clinical trial to evaluate safety, tolerability, as well as systemic and mucosal immunogenicity of IPV adjuvanted with dmLT, given as a fractional (1/5th) dose intradermally (fIPV-dmLT). Twenty-nine volunteers with no past exposure to OPV were randomized to a single dose of fIPV-dmLT or fIPV alone. fIPV-dmLT was well tolerated, although three subjects had mild but persistent induration and hyperpigmentation at the injection site. A ≥ 4-fold rise in serotype-specific neutralizing antibody (SNA) titers to all three serotypes was seen in 84% of subjects receiving fIPV-dmLT vs. 50% of volunteers receiving IPV alone. SNA titers were higher in the dmLT-adjuvanted group, but only differences in serotype 1 were significant. Mucosal immune responses, as measured by polio serotype specific fecal IgA were minimal in both groups and differences were not seen. fIPV-dmLT may offer a benefit over IPV alone. Beyond NAB responses protecting the individual, studies demonstrating the ability of fIPV-dmLT to prevent viral shedding are necessary. Studies employing controlled human infection models, using monovalent OPV post-vaccine are ongoing. Studies specifically in children may also be necessary and additional biomarkers of mucosal immune responses in this population are needed. Clinicaltrials.gov Identifer: NCT03922061.

The Immunomodulatory Function of Vitamin D, with Particular Reference to SARS-CoV-2

Vaccines are the only way to reduce the morbidity associated to SARS-CoV-2 infection. The appearance of new mutations urges us to increase the effectiveness of vaccines as a complementary alternative. In this context, the use of adjuvant strategies has improved the effectiveness of different vaccines against virus infections such as dengue, influenza, and common cold. Recent reports on patients infected by COVID-19 reveal that low levels of circulating vitamin D correlate with a severe respiratory insufficiency. The immunomodulatory activity of this micronutrient attenuates the synthesis of pro-inflammatory cytokines and at the same time, increases antibody production. Therefore, the present review proposes the use of vitamin D as adjuvant micronutrient to increase the efficacy of vaccines against SARS-CoV-2 infection.

Immunization with recombinant protein Ag43::UpaH with alum and 1,25(OH)2D3 adjuvants significantly protects Balb/C mice against urinary tract infection caused by uropathogenic Escherichia coli

The majority of urinary tract infections (UTIs) are caused by uropathogenic Escherichia coli (UPEC). Designing a vaccine will certainly reduce the occurrence of infection and antibiotic resistance of the isolates. Antigen 43 (Ag43) and autotransporter H (UpaH) have been associated with the virulence of UPEC. In the present study, the efficacy of different formulations of a hybrid protein composed of Ag43 and UpaH with and without alum and 1,25(OH)2D3 (Vitamin D3) adjuvants were evaluated in mice model. A significant increase in IgG and cellular responses was developed against Ag43::UpaH as compared to the control mice. The addition of alum or a mixture of alum and Vitamin D3 to the protein significantly enhanced the serum IgG responses and tended to remain in a steady state until 6 months. In addition, the mentioned formulations produced significant amounts of IgG1, IL-4, and IL-17 as compared to the fusion protein alone. In addition to the mentioned formulations, the combination of protein with Vitamin D3 also resulted in significantly higher serum IgA and IFN-γ levels as compared to the fusion protein alone. Mice immunized with fusion plus alum and formulation protein admixed with both alum and Vitamin D3 significantly reduced the bacterial load in the bladders and kidneys of mice as compared to the control. In this study, for the first time, the ability of a novel hybrid protein in combination with adjuvants alum and Vitamin D3 was evaluated against UPEC. Our results indicated that fusion Ag43::UpaH admixed with alum and Vitamin D3 could be a promising candidate against UTIs.

Transcutaneous Vaccination with Conjugate Typhoid Vaccine Vi-DT Induces Systemic, Mucosal, and Memory Anti-Polysaccharide Responses

Transcutaneous vaccination can induce both mucosal and systemic immune responses. However, there are few data on anti-polysaccharide responses following transcutaneous vaccination of polysaccharides, despite the role that anti-polysaccharide responses play in protecting against intestinal mucosal and respiratory pathogens. Whether transcutaneous vaccination with a conjugate polysaccharide vaccine would be able to induce memory responses is also unknown. To address this, we transcutaneously vaccinated mice with virulence antigen (Vi) polysaccharide of Salmonella enterica serovar Typhi (the cause of typhoid fever), either in unconjugated or conjugated form (the latter as a Vi-DT conjugate). We also assessed the ability of the immunoadjuvant cholera toxin to impact responses following vaccination. We found that presenting Vi in a conjugate versus nonconjugate form transcutaneously resulted in comparable serum IgG responses but higher serum and lamina propria lymphocyte IgA anti-Vi responses, as well as increased IgG memory responses. The addition of immunoadjuvant did not further increase these responses; however, it boosted fecal IgA and serum IgG anti-Vi responses. Our results suggest that transcutaneous vaccination of a conjugate vaccine can induce systemic as well as enhanced mucosal and memory B-cell anti-polysaccharide responses.

Protection against neonatal enteric colibacillosis employing E. Coli-derived outer membrane vesicles in formulation and without vitamin D3

OBJECTIVE

Enterotoxigenic Escherichia Coli (ETEC) is the cause of diarrhea and even death in humans and offspring of animals. Outer membrane vesicles (OMVs) of the ETEC was prepared and its potential as a vaccine candidate against enteric colibacillosis in neonatal mice was evaluated. Dam mice intradermally injected with ETEC-derived OMVs and OMVs plus an active form of vitamin D3 (avD3). Mucosal and systemic immune responses in mice and passive immunity protection against ETEC lethality in their offspring was investigated.

RESULTS

Immunization of adult mice via ETEC-derived OMV alone and in formulation with avD3 protect offspring from ETEC-induced lethality. Nevertheless, avD3 did not indicate a positive effect on mucosal and systemic immune responses. Only the combination of OMV plus avD3 elicited a significant (P < 0.05) increase in the level of specific IgA antibodies in serum.

Mucosal and systemic responses of immunogenic vaccines candidates against enteric Escherichia coli infections in ruminants: A review

Innumerable Escherichia coli of animal origin are identified, which are of economic significance, likewise, cattle, sheep and goats are the carrier of enterohaemorrhagic E. coli, which are less pathogenic, and can spread to people by way of direct contact and through the contamination of foodstuff or portable drinking water, causing serious illness. The immunization of ruminants has been carried out for ages and is largely acknowledged as the most economical and maintainable process of monitoring E. coli infection in ruminants. Yet, only a limited number of E. coli vaccines are obtainable. Mucosal surfaces are the most important ingress for E. coli and thus mucosal immune responses function as the primary means of fortification. Largely contemporary vaccination processes are done by parenteral administration and merely limited number of E. coli vaccines are inoculated via mucosal itinerary, due to its decreased efficacy. Nevertheless, aiming at maximal mucosal partitions to stimulate defensive immunity at both mucosal compartments and systemic site epitomises a prodigious task. Enormous determinations are involved in order to improve on novel mucosal E. coli vaccines candidate by choosing apposite antigens with potent immunogenicity, manipulating novel mucosal itineraries of inoculation and choosing immune-inducing adjuvants. The target of E. coli mucosal vaccines is to stimulate a comprehensive, effective and defensive immunity by specifically counteracting the antibodies at mucosal linings and by the stimulation of cellular immunity. Furthermore, effective E. coli mucosal vaccine would make vaccination measures stress-free and appropriate for large number of inoculation. On account of contemporary advancement in proteomics, metagenomics, metabolomics and transcriptomics research, a comprehensive appraisal of the immeasurable genes and proteins that were divulged by a bacterium is now in easy reach. Moreover, there exist marvellous prospects in this bourgeoning technologies in comprehending the host bacteria affiliation. Accordingly, the flourishing knowledge could massively guarantee to the progression of immunogenic vaccines against E. coli infections in both humans and animals. This review highlight and expounds on the current prominence of mucosal and systemic immunogenic vaccines for the prevention of E. coli infections in ruminants.

Multigenic DNA vaccine induces protective cross-reactive T cell responses against heterologous influenza virus in nonhuman primates

Recent avian and swine-origin influenza virus outbreaks illustrate the ongoing threat of influenza pandemics. We investigated immunogenicity and protective efficacy of a multi-antigen (MA) universal influenza DNA vaccine consisting of HA, M2, and NP antigens in cynomolgus macaques. Following challenge with a heterologous pandemic H1N1 strain, vaccinated animals exhibited significantly lower viral loads and more rapid viral clearance when compared to unvaccinated controls. The MA DNA vaccine induced robust serum and mucosal antibody responses but these high antibody titers were not broadly neutralizing. In contrast, the vaccine induced broadly-reactive NP specific T cell responses that cross-reacted with the challenge virus and inversely correlated with lower viral loads and inflammation. These results demonstrate that a MA DNA vaccine that induces strong cross-reactive T cell responses can, independent of neutralizing antibody, mediate significant cross-protection in a nonhuman primate model and further supports development as an effective approach to induce broad protection against circulating and emerging influenza strains.

Microneedle delivery of trivalent influenza vaccine to the skin induces long-term cross-protection

A painless self-immunization method with effective and broad cross-protection is urgently needed to prevent infections against newly emerging influenza viruses. In this study, we investigated the cross-protection efficacy of trivalent influenza vaccine containing inactivated A/PR/8/34 (H1N1), A/Hong Kong/68 (H3N2) and B/Lee/40 after skin vaccination using microneedle patches coated with this vaccine. Microneedle vaccination of mice in the skin provided 100% protection against lethal challenges with heterologous pandemic strain influenza A/California/04/09, heterogeneous A/Philippines/2/82 and B/Victoria/287 viruses 8 months after boost immunization. Cross-reactive serum IgG antibody responses against heterologous influenza viruses A/California/04/09, A/Philippines/2/82 and B/Victoria/287 were induced at high levels. Hemagglutination inhibition titers were also maintained at high levels against these heterogeneous viruses. Microneedle vaccination induced substantial levels of cross-reactive IgG antibody responses in the lung and cellular immune responses, as well as cross-reactive antibody-secreting plasma cells in the spleen. Viral loads in the lung were significantly (p < 0.05) reduced. All mice survived after viral challenges. These results indicate that skin vaccination with trivalent vaccine using a microneedle array could provide protection against seasonal epidemic or new pandemic strain of influenza viruses.

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.

A Novel Prime and Boost Regimen of HIV Virus-Like Particles with TLR4 Adjuvant MPLA Induces Th1 Oriented Immune Responses against HIV

HIV virus-like particles (VLPs) present the HIV envelope protein in its native conformation, providing an ideal vaccine antigen. To enhance the immunogenicity of the VLP vaccine, we sought to improve upon two components; the route of administration and the additional adjuvant. Using HIV VLPs, we evaluated sub-cheek as a novel route of vaccine administration when combined with other conventional routes of immunization. Of five combinations of distinct prime and boost sequences, which included sub-cheek, intranasal, and intradermal routes of administration, intranasal prime and sub-cheek boost (IN+SC) resulted in the highest HIV-specific IgG titers among the groups tested. Using the IN+SC regimen we tested the adjuvant VesiVax Conjugatable Adjuvant Lipid Vesicles (CALV) + monophosphoryl lipid A (MPLA) at MPLA concentrations of 0, 7.5, 12.5, and 25 μg/dose in combination with our VLPs. Mice that received 12.5 or 25 μg/dose MPLA had the highest concentrations of Env-specific IgG2c (20.7 and 18.4 μg/ml respectively), which represents a Th1 type of immune response in C57BL/6 mice. This was in sharp contrast to mice which received 0 or 7.5 μg MPLA adjuvant (6.05 and 5.68 μg/ml of IgG2c respectively). In contrast to IgG2c, MPLA had minor effects on Env-specific IgG1; therefore, 12.5 and 25 μg/dose of MPLA induced the optimal IgG1/IgG2c ratio of 1.3. Additionally, the percentage of germinal center B cells increased significantly from 15.4% in the control group to 31.9% in the CALV + 25 μg MPLA group. These mice also had significantly more IL-2 and less IL-4 Env-specific CD8⁺ T cells than controls, correlating with an increased percentage of Env-specific central memory CD4⁺ and CD8⁺ T cells. Our study shows the strong potential of IN+SC as an efficacious route of administration and the effectiveness of VLPs combined with MPLA adjuvant to induce Env specific Th1-oriented HIV-specific immune responses.

Effect of vaccine administration modality on immunogenicity and efficacy

The many factors impacting the efficacy of a vaccine can be broadly divided into three categories: features of the vaccine itself, including immunogen design, vaccine type, formulation, adjuvant and dosing; individual variations among vaccine recipients and vaccine administration-related parameters. While much literature exists related to vaccines, and recently systems biology has started to dissect the impact of individual subject variation on vaccine efficacy, few studies have focused on the role of vaccine administration-related parameters on vaccine efficacy. Parenteral and mucosal vaccinations are traditional approaches for licensed vaccines; novel vaccine delivery approaches, including needless injection and adjuvant formulations, are being developed to further improve vaccine safety and efficacy. This review provides a brief summary of vaccine administration-related factors, including vaccination approach, delivery route and method of administration, to gain a better understanding of their potential impact on the safety and immunogenicity of candidate vaccines.

Animal models for cutaneous vaccine delivery

Main challenges in skin vaccination are overcoming the stratum corneum (SC) barrier and targeting the antigen presenting cells (APC) in the epidermis and the dermis. For this purpose many delivery techniques are being developed. In vivo immunogenicity and safety studies in animals are mandatory before moving to clinical trials. However, the results obtained in animals may or may not be predictive for humans. Knowledge about differences and similarities in skin architecture and immunology within a species and between species is crucial. In this review, we discuss variables, including skin morphology, skin barrier function, mechanical properties, site of application and immunology, which should be taken into account when designing animal studies for vaccination via the skin in order to support the translation to clinical trial outcomes.

Inducing dose sparing with inactivated polio virus formulated in adjuvant CAF01

The development of new low cost inactivated polio virus based vaccines (IPV) is a high priority, and will be required to eradicate polio. In addition, such a vaccine constitutes the only realistic polio vaccine in the post-eradication era. One way to reduce the cost of a vaccine is to increase immunogenicity by use of adjuvants. The CAF01 adjuvant has previously been shown to be a safe and potent adjuvant with several antigens, and here we show that in mice IPV formulated with CAF01 induced increased systemic protective immunity measured by binding and neutralization antibody titers in serum. CAF01 also influenced the kinetics of both the cellular and humoral response against IPV to produce a faster, as well as a stronger, response, dominated by IgG2a, IgG2b, and IgG2c isotypes as well as IPV specific T cells secreting IFN-γ/IL-2. Finally, as intestinal immunity is also a priority of polio vaccines, we present a vaccine strategy based on simultaneous priming at an intradermal and an intramuscular site that generate intestinal immune responses against polio virus. Taken together, the IPV-CAF01 formulation constitutes a new promising vaccine against polio with the ability to generate strong humoral and cellular immunity against the polio virus.

Membrane-bound IL-12 and IL-23 serve as potent mucosal adjuvants when co-presented on whole inactivated influenza vaccines

BACKGROUND

Potent and safe adjuvants are needed to improve the efficacy of parenteral and mucosal vaccines. Cytokines, chemokines and growth factors have all proven to be effective immunomodulatory adjuvants when administered with a variety of antigens. We have previously evaluated the efficacy of membrane-anchored interleukins (IL) such as IL-2 and IL-4 co-presented as Cytokine-bearing Influenza Vaccines (CYT-IVACs) using a mouse model of influenza challenge.

FINDINGS

Here, we describe studies evaluating the parenteral and mucosal adjuvanticity of membrane-bound IL-12 and IL-23 CYT-IVACs in young adult mice. Mucosal immunization using IL-12 and IL-23 bearing whole influenza virus vaccine (WIV) was more effective at eliciting virus-specific nasal IgA and reducing viral lung burden following challenge compared to control WIV vaccinated animals. Both IL-12 and IL-23 bearing WIV elicited the highest anti-viral IgA levels in serum and nasal washes.

CONCLUSIONS

This study highlights for the first time the mucosal adjuvant potential of IL-12 and IL-23 CYT-IVAC formulations in eliciting mucosal immune responses and reducing viral lung burden. The co-presentation of immunomodulators in direct context with viral antigen in whole inactivated viral vaccines may provide a means to significantly lower the dose of vaccine required for protection.

Delivering vaccines into the skin without needles and syringes

The skin is a highly accessible organ and due to the presence of powerful antigen-presenting cells in the epidermis, it functions as an immune barrier. This makes the skin an attractive route for potential delivery of vaccines by painless and user-friendly methods without the requirement of needles and syringes. This article reviews current attempts to administer vaccines into the skin and discusses some of the scientific issues related to the emerging delivery technologies.

Long-term protective immunity from an influenza virus-like particle vaccine administered with a microneedle patch

Skin vaccination with influenza virus-like particles (VLPs) using microneedles has been shown to induce protection similar to or better than that induced by intramuscular immunization. In this study, we examined the long-term protective efficacy of influenza (H1N1 A/PR/8/34) VLPs after skin vaccination using microneedle patches coated with the vaccine. Microneedle vaccination of mice in the skin induced 100% protection against lethal challenge infection with influenza A/PR/8/34 virus 14 months after a single vaccine dose. Influenza virus-specific total IgG response and hemagglutination inhibition (HAI) titers were maintained at high levels for over 1 year after microneedle vaccination. Microneedle vaccination also induced substantial levels of lung IgG and IgA antibody responses, and antibody-secreting plasma cells from spleen and bone marrow, as well as conferring effective control of lung viral loads, resulting in complete protection 14 months after vaccination. These strong and long-lasting immune responses were enabled in part by stabilization of the vaccine by formulation with trehalose during microneedle patch fabrication. Administration of the stabilized vaccine using microneedles was especially effective at enabling strong recall responses measured 4 days after lethal virus challenge, including increased HAI and antibody-secreting cells in the spleen and reduced viral titer and inflammatory response in the lung. The results in this study indicate that skin vaccination with VLP vaccine using a microneedle patch provides long-term protection against influenza in mice.

Nasal and skin delivery of IC31(®)-adjuvanted recombinant HSV-2 gD protein confers protection against genital herpes

Genital herpes caused by herpes simplex virus type 2 (HSV-2) remains the leading cause of genital ulcers worldwide. Given the disappointing results of the recent genital herpes vaccine trials in humans, development of novel vaccine strategies capable of eliciting protective mucosal and systemic immune responses to HSV-2 is urgently required. Here we tested the ability of the adjuvant IC31(®) in combination with HSV-2 glycoprotein D (gD) used through intranasal (i.n.), intradermal (i.d.), or subcutaneous (s.c.) immunization routes for induction of protective immunity against genital herpes infection in C57BL/6 mice. Immunization with gD plus IC31(®) through all three routes of immunization developed elevated gD-specific serum antibody responses with HSV-2 neutralizing activity. Whereas the skin routes promoted the induction of a mixed IgG2c/IgG1 isotype profile, the i.n. route only elicited IgG1 antibodies. All immunization routes were able to induce gD-specific IgG antibody responses in the vaginas of mice immunized with IC31(®)-adjuvanted gD. Although specific lymphoproliferative responses were observed in splenocytes from mice of most groups vaccinated with IC31(®)-adjuvanted gD, only i.d. immunization resulted in a significant splenic IFN-γ response. Further, immunization with gD plus IC31(®) conferred 80-100% protection against an otherwise lethal vaginal HSV-2 challenge with amelioration of viral replication and disease severity in the vagina. These results warrant further exploration of IC31(®) for induction of protective immunity against genital herpes and other sexually transmitted infections.

Transcutaneous vaccination via laser microporation

Driven by constantly increasing knowledge about skin immunology, vaccine delivery via the cutaneous route has recently gained renewed interest. Considering its richness in immunocompetent cells, targeting antigens to the skin is considered to be more effective than intramuscular or subcutaneous injections. However, circumvention of the superficial layer of the skin, the stratum corneum, represents the major challenge for cutaneous immunization. An optimal delivery method has to be effective and reliable, but also highly adaptable to specific demands, should avoid the use of hypodermic needles and the requirement of specially trained healthcare workers. The P.L.E.A.S.E.® (Precise Laser Epidermal System) device employed in this study for creation of aqueous micropores in the skin fulfills these prerequisites by combining the precision of its laser scanning technology with the flexibility to vary the number, density and the depth of the micropores in a user-friendly manner. We investigated the potential of transcutaneous immunization via laser-generated micropores for induction of specific immune responses and compared the outcomes to conventional subcutaneous injection. By targeting different layers of the skin we were able to bias polarization of T cells, which could be modulated by addition of adjuvants. The P.L.E.A.S.E.® device represents a highly effective and versatile platform for transcutaneous vaccination.

Therapeutic DNA vaccine induces broad T cell responses in the gut and sustained protection from viral rebound and AIDS in SIV-infected rhesus macaques

Immunotherapies that induce durable immune control of chronic HIV infection may eliminate the need for life-long dependence on drugs. We investigated a DNA vaccine formulated with a novel genetic adjuvant that stimulates immune responses in the blood and gut for the ability to improve therapy in rhesus macaques chronically infected with SIV. Using the SIV-macaque model for AIDS, we show that epidermal co-delivery of plasmids expressing SIV Gag, RT, Nef and Env, and the mucosal adjuvant, heat-labile E. coli enterotoxin (LT), during antiretroviral therapy (ART) induced a substantial 2-4-log fold reduction in mean virus burden in both the gut and blood when compared to unvaccinated controls and provided durable protection from viral rebound and disease progression after the drug was discontinued. This effect was associated with significant increases in IFN-γ T cell responses in both the blood and gut and SIV-specific CD8+ T cells with dual TNF-α and cytolytic effector functions in the blood. Importantly, a broader specificity in the T cell response seen in the gut, but not the blood, significantly correlated with a reduction in virus production in mucosal tissues and a lower virus burden in plasma. We conclude that immunizing with vaccines that induce immune responses in mucosal gut tissue could reduce residual viral reservoirs during drug therapy and improve long-term treatment of HIV infection in humans.

Clinical evaluation of intradermal vaccination against porcine enzootic pneumonia (Mycoplasma hyopneumoniae)

The aim of the present study was to investigate the efficacy of single-dose intradermal vaccination against Mycoplasma hyopneumoniae on a commercial swine unit. A total of 1051 healthy suckling piglets of 28±3 days of age were randomly assigned to one of three experimental groups: (a) intradermal: 346 piglets vaccinated intradermally (Porcilis M Hyo ID Once, Intervet SPAH), (b) intramuscular : 351 piglets vaccinated intramuscularly (Porcilis M1 Intervet SPAH) and (c) controls: 354 piglets injected with a placebo (adjuvant only). Performance parameters such as average daily weight gain (ADG), as well as health parameters and lung lesion scores were monitored from four weeks of age until slaughter. The improvement in ADG over the controls, during the finishing phase, was 27 g/day for the intradermal group and 17 g/day for the intramuscular group. Both intradermal and intramuscular vaccinations were effective in reducing clinical signs and lung lesions caused by M hyopneumoniae. Compared with the controls, approximately 10.4 per cent fewer clinical cases were diagnosed in the intradermal group, and 6 per cent fewer in the intramuscular group, during the finishing period. In conclusion, performance results were better in the vaccinated groups than in the control group, while intradermal vaccination afforded greater protection than intramuscular vaccination, especially with regard to morbidity, lung lesion and pleuritis scores.

Immunomodulatory properties of vitamins, flavonoids and plant oils and their potential as vaccine adjuvants and delivery systems

INTRODUCTION

During the past century, vaccinologists have attempted to mimic pathogens in their immune-enhancing capacity. This led to the development of life-saving vaccines based on live attenuated viruses, bacteria and toxoids. Hence, intense research in vaccine adjuvant discovery has focused on toll like receptors, mutant toxins and viral and bacterial vectors. Nutritive components such as vitamins and select polyphenols also possess immunomodulating properties without the potential toxic and adverse side effects of agents that mimic danger signals.

AREAS COVERED

This review pertains to immunomodulatory properties of nutritive components, that is vitamins A, C, D, E, flavonoids and plant oils, as potential vaccine adjuvants and delivery systems, covering Pubmed publication searches from 1980 through 2011.

EXPERT OPINION

This relatively unexplored field of the potential of nutritive components as vaccine adjuvants holds great promise to promote the development of effective and above all safe vaccines. Hence the future focus should be placed on enhancing their efficacy, mainly through novel approaches in designing structural derivatives, formulations, delivery systems and routes of administration. As safety has been the major issue in development of novel vaccines, this new approach will probably result in new discoveries in designing safe and effective vaccines.

Exploiting mucosal surfaces for the development of mucosal vaccines

Mucosal immunity covers a variety of mucosal surfaces susceptible to different pathogens. This review highlights the diversity of mucosal tissues and the unique microenvironments in which an immune response is generated. It argues that tissue-specific factors present throughout mucosal tissues and lymph nodes determine the differentiation into IgA-producing B cells, which in turn determines their migration patterns. Mucosal immunity can therefore be induced when antigen is delivered at any mucosal tissue without the need for specific 'mucosal adjuvants' or targeting to specialised lymphoid structures. Non-oral vaccination strategies directed at alternative and more accessible mucosal tissue sites, may provide new avenues for both mucosal and systemic immunization, and will be greatly facilitated by the use of large animal models.

Distinctive immunomodulatory and inflammatory properties of the Escherichia coli type II heat-labile enterotoxin LT-IIa and its B pentamer following intradermal administration

The type I and type II heat-labile enterotoxins (LT-I and LT-II) are strong mucosal adjuvants when they are coadministered with soluble antigens. Nonetheless, data on the parenteral adjuvant activities of LT-II are still limited. Particularly, no previous study has evaluated the adjuvant effects and induced inflammatory reactions of LT-II holotoxins or their B pentameric subunits after delivery via the intradermal (i.d.) route to mice. In the present report, the adjuvant and local skin inflammatory effects of LT-IIa and its B subunit pentamer (LT-IIaB(5)) were determined. When coadministered with ovalbumin (OVA), LT-IIa and, to a lesser extent, LT-IIaB(5) exhibited serum IgG adjuvant effects. In addition, LT-IIa but not LT-IIaB(5) induced T cell-specific anti-OVA responses, particularly in respect to induction of antigen-specific cytotoxic CD8(+) T cell responses. LT-IIa and LT-IIaB(5) induced differential tissue permeability and local inflammatory reactions after i.d. injection. Of particular interest was the reduced or complete lack of local reactions, such as edema and tissue induration, in mice i.d. inoculated with LT-IIa and LT-IIaB(5,) respectively, compared with mice immunized with LT-I. In conclusion, the present results show that LT-IIa and, to a lesser extent, LT-IIaB(5) exert adjuvant effects when they are delivered via the i.d. route. In addition, the low inflammatory effects of LT-IIa and LT-IIaB(5) in comparison to those of LT-I support the usefulness of LT-IIa and LT-IIaB(5) as parenterally delivered vaccine adjuvants.

Programming the magnitude and persistence of antibody responses with innate immunity

Many successful vaccines induce persistent antibody responses that can last a lifetime. The mechanisms by which they do so remain unclear, but emerging evidence indicates that they activate dendritic cells via Toll-like receptors (TLRs). For example, the yellow fever vaccine YF-17D, one of the most successful empiric vaccines ever developed, activates dendritic cells via multiple TLRs to stimulate proinflammatory cytokines. Triggering specific combinations of TLRs in dendritic cells can induce synergistic production of cytokines, which results in enhanced T-cell responses, but its impact on antibody responses remain unknown. Learning the critical parameters of innate immunity that program such antibody responses remains a major challenge in vaccinology. Here we demonstrate that immunization of mice with synthetic nanoparticles containing antigens plus ligands that signal through TLR4 and TLR7 induces synergistic increases in antigen-specific, neutralizing antibodies compared to immunization with nanoparticles containing antigens plus a single TLR ligand. Consistent with this there was enhanced persistence of germinal centres and of plasma-cell responses, which persisted in the lymph nodes for >1.5 years. Surprisingly, there was no enhancement of the early short-lived plasma-cell response relative to that observed with single TLR ligands. Molecular profiling of activated B cells, isolated 7 days after immunization, indicated that there was early programming towards B-cell memory. Antibody responses were dependent on direct triggering of both TLRs on B cells and dendritic cells, as well as on T-cell help. Immunization protected completely against lethal avian and swine influenza virus strains in mice, and induced robust immunity against pandemic H1N1 influenza in rhesus macaques.

Mucosal immunity and HIV-1 infection: applications for mucosal AIDS vaccine development

Natural transmission of human immunodeficiency virus type 1 (HIV-1) occurs through gastrointestinal and vaginal mucosa. These mucosal tissues are major reservoirs for initial HIV replication and amplification, and the sites of rapid CD4(+) T cell depletion. In both HIV-infected humans and SIV-infected macaques, massive loss of CD4(+) CCR5(+) memory T cells occurs in the gut and vaginal mucosa within the first 10-14 days of infection. Induction of local HIV-specific immune responses by vaccines may facilitate effective control of HIV or SIV replication at these sites. Vaccines that induce mucosal responses, in particular CD8(+) cytotoxic T lymphocytes (CTL), have controlled viral replication at mucosal sites and curtailed systemic dissemination. Thus, there is strong justification for development of next generation vaccines that induce mucosal immune effectors against HIV-1 including CD8(+) CTL, CD4(+) T helper cells and secretory IgA. In addition, further understanding of local innate mechanisms that impact early viral replication will greatly inform future vaccine development. In this review, we examine the current knowledge concerning mucosal AIDS vaccine development. Moreover, we propose immunization strategies that may be able to elicit an effective immune response that can protect against AIDS as well as other mucosal infections.

Adjuvants and delivery systems in veterinary vaccinology: current state and future developments

Modern adjuvants should induce strong and balanced immune responses, and it is often desirable to induce specific types of immunity. As an example, efficient Th1-immunity-inducing adjuvants are highly in demand. Such adjuvants promote good cell-mediated immunity against subunit vaccines that have low immunogenicity themselves. The development of such adjuvants may take advantage of the increased knowledge of the molecular mechanisms and factors controlling these responses. However, knowledge of such molecular details of immune mechanisms is relatively scarce for species other than humans and laboratory rodents, and in addition, there are special considerations pertaining to the use of adjuvants in veterinary animals, such as production and companion animals. With a focus on veterinary animals, this review highlights a number of approaches being pursued, including cytokines, CpG oligonucleotides, microparticles and liposomes.

CpG oligodeoxynucleotide promotes protective immunity in the enteric mucosa and suppresses enterotoxigenic E. coli in the weaning piglets

CpG oligodeoxynucleotide (CpG ODN) has been described as an effective activator of the innate immune system, with potential to protect against infection caused by a range of pathogens in a non-specific manner. We therefore investigated if intranasal (IN), oral (OR)-mucosal, and intramuscular (IM)-systemic administrations of CpG ODN without antigen codelivery could all enhance innate immunity in the enteric mucosa and control the extent of enterotoxigenic Escherichia coli (ETEC) infection in weaning piglets. Here our data showed that CpG ODN dosed by IN, OR or IM routes protected weaning piglets against a subsequent challenge with ETEC. The level of protection was greater when CpG ODN was administered IN and OR than IM, demonstrating a clear relationship between the route of CpG dosing and protection. IN and OR treatments with CpG ODN reduced bacterial load in the phases at days 3-5 post challenge. The CXC chemokine (CXCL10 and CXCL11) and CC chemokine (CCL4 and CCL5) mRNA expressions were elevated in the intestinal tissues from animals treated IN or OR with CpG ODN compared to untreated controls. Significantly enhanced mRNA expressions for cathelicidins (PR-39 and protegrin-1), but moderately for β-defensin (pBD1 and pBD2), were observed in IN or OR CpG-treatments. Also, significant production of cytokines (IL-12, IFN-γ, and MCP-1) and F4-specific antibodies (IgG/IgA) was detected in intestinal washings following IN and OR CpG-treatments. In contrast, IM delivery induced marked production of sera F4-specific antibodies. It was possible that these chemokines, cytokines, cathelicidins and antibodies played a role in the clearance of ETEC. These findings suggested that IN or OR administration of CpG ODN without antigen codelivery might represent a valuable strategy for induction of innate immunity against ETEC infection.

Immune-modifying properties of topical vitamin D: Focus on dendritic cells and T cells

Topical creams containing the active form of vitamin D (1,25-dihydroxyvitamin D3; 1,25(OH)2D3) or analogues of this compound are currently used with some success to treat skin conditions including psoriasis and vitiligo. As well as targeting inflammatory processes in the skin, topical application of 1,25(OH)2D3 also affects the function of immune cells in the skin and draining lymph nodes. Topically applied 1,25(OH)2D3 reduces the number of dendritic cells in the skin, resulting in suppressed immunity and in particular reduced contact hypersensitivity (CHS) responses. Topical 1,25(OH)2D3 may also promote the migration of dendritic cells from the skin to the draining lymph nodes. Skin application of 1,25(OH)2D3 prevented the inflammatory effects of UVB irradiation on lymph node hypertrophy, when cell numbers were examined 4 days after skin treatment. In contrast, when 1,25(OH)2D3 was applied to UVB irradiated skin, there was no reversal in the suppression of CHS responses caused by UVB irradiation. Instead, 1,25(OH)2D3 had an additive effect with UVB to suppress CHS responses to a greater degree than UVB alone. In these studies, 1,25(OH)2D3 was applied to the treated skin of BALB/c mice immediately following UVB irradiation. Finally, topical 1,25(OH)2D3 also enhanced the number and suppressive activity of CD4+CD25+ regulatory T cells in the lymphatic tissue draining skin.

GM-CSF increases mucosal and systemic immunogenicity of an H1N1 influenza DNA vaccine administered into the epidermis of non-human primates

Background

The recent H5N1 avian and H1N1 swine-origin influenza virus outbreaks reaffirm that the threat of a world-wide influenza pandemic is both real and ever-present. Vaccination is still considered the best strategy for protection against influenza virus infection but a significant challenge is to identify new vaccine approaches that offer accelerated production, broader protection against drifted and shifted strains, and the capacity to elicit anti-viral immune responses in the respiratory tract at the site of viral entry. As a safe alternative to live attenuated vaccines, the mucosal and systemic immunogenicity of an H1N1 influenza (A/New Caledonia/20/99) HA DNA vaccine administered by particle-mediated epidermal delivery (PMED or gene gun) was analyzed in rhesus macaques.

Methodology/Principal Findings

Macaques were immunized at weeks 0, 8, and 16 using a disposable single-shot particle-mediated delivery device designed for clinical use that delivers plasmid DNA directly into cells of the epidermis. Significant levels of hemagglutination inhibiting (HI) antibodies and cytokine-secreting HA-specific T cells were observed in the periphery of macaques following 1–3 doses of the PMED HA DNA vaccine. In addition, HA DNA vaccination induced detectable levels of HA-specific mucosal antibodies and T cells in the lung and gut-associated lymphoid tissues of vaccinated macaques. Importantly, co-delivery of a DNA encoding the rhesus macaque GM-CSF gene was found to significantly enhance both the systemic and mucosal immunogenicity of the HA DNA vaccine.

Conclusions/Significance

These results provide strong support for the development of a particle-mediated epidermal DNA vaccine for protection against respiratory pathogens such as influenza and demonstrate, for the first time, the ability of skin-delivered GM-CSF to serve as an effective mucosal adjuvant for vaccine induction of immune responses in the gut and respiratory tract.

Adjuvanted influenza vaccine administered intradermally elicits robust long-term immune responses that confer protection from lethal challenge

Background

The respiratory illnesses caused by influenza virus can be dramatically reduced by vaccination. The current trivalent inactivated influenza vaccine is effective in eliciting systemic virus-specific antibodies sufficient to control viral replication. However, influenza protection generated after parenteral immunization could be improved by the induction of mucosal immune responses.

Methodology/Principal Findings

Transcutaneous immunization, a non-invasive vaccine delivery method, was used to investigate the quality, duration and effectiveness of the immune responses induced in the presence of inactivated influenza virus co-administered with retinoic acid or oleic acid. We observed an increased migration of dendritic cells to the draining lymph nodes after dermal vaccination. Here we demonstrate that this route of vaccine delivery in combination with certain immunomodulators can induce potent immune responses that result in long-term protective immunity. Additionally, mice vaccinated with inactivated virus in combination with retinoic acid show an enhanced sIgA antibody response, increased number of antibody secreting cells in the mucosal tissues, and protection from a higher influenza lethal dose.

Conclusions/Significance

The present study demonstrates that transdermal administration of inactivated virus in combination with immunomodulators stimulates dendritic cell migration, results in long-lived systemic and mucosal responses that confer effective protective immunity.

Intradermal vaccination with influenza virus-like particles by using microneedles induces protection superior to that with intramuscular immunization

Influenza virus-like particles (VLPs) are a promising cell culture-based vaccine, and the skin is considered an attractive immunization site. In this study, we examined the immunogenicity and protective efficacy of influenza VLPs (H1N1 A/PR/8/34) after skin vaccination using vaccine dried on solid microneedle arrays. Coating of microneedles with influenza VLPs using an unstabilized formulation was found to decrease hemagglutinin (HA) activity, whereas inclusion of trehalose disaccharide preserved the HA activity of influenza VLP vaccines after microneedles were coated. Microneedle vaccination of mice in the skin with a single dose of stabilized influenza VLPs induced 100% protection against challenge infection with a high lethal dose. In contrast, unstabilized influenza VLPs, as well as intramuscularly injected vaccines, provided inferior immunity and only partial protection (</=40%). The stabilized microneedle vaccination group showed IgG2a levels that were 1 order of magnitude higher than those of other groups and had the lowest lung viral titers after challenge. Also, levels of recall immune responses, including hemagglutination inhibition titers, neutralizing antibodies, and antibody-secreting plasma cells, were significantly higher after skin vaccination with stabilized formulations. Therefore, our results indicate that HA stabilization, combined with vaccination via the skin using a vaccine formulated as a solid microneedle patch, confers protection superior to that with intramuscular injection and enables potential dose-sparing effects which are reflected by pronounced increases in rapid recall immune responses against influenza virus.

Characterisation of the protective immune response following subcutaneous vaccination of susceptible mice against Trichuris muris

Trichuris muris is a laboratory model for the human whipworm Trichuris trichiura which infects approximately 1 billion people in tropical and sub-tropical countries. The development of a vaccine would control trichuriasis by promoting the acquisition of immunity during childhood, thereby reducing faecal egg output by the community into their environment. Resistance to T. muris, defined as expulsion of the parasite prior to patency, requires the development of a T helper 2 (Th2) response during a primary infection. To our knowledge this is the first study to describe the protective immune response in the peripheral lymph nodes (PLN), mesenteric lymph nodes (MLN) and colonic mucosa following s.c. vaccination against T. muris. Susceptible AKR mice were either vaccinated with T. muris excretory–secretory product (ES) in incomplete Freund’s adjuvant (IFA) (ES/IFA) or injected with PBS in IFA (PBS/IFA) and for protection experiments were infected with embryonated infective T. muris eggs 10 days later. The ES/IFA vaccine induced the proliferation of PLN cells and their production of Th2 cytokines and the Th1-associated cytokine IFN-γ. Following a challenge infection, the ES/IFA vaccination offered susceptible mice complete protection. While MLN-derived IFN-γ was produced by infected mice following either ES/IFA vaccination or PBS/IFA, the protection of susceptible mice by ES/IFA was characterised by the production of MLN-derived Th2 cytokines. Goblet cell hyperplasia and the influx and alternative activation of macrophages were observed locally in the gut post-challenge infection. The rate of epithelial turnover did not appear to be increased by vaccination, suggesting that there are differences in the mechanisms of expulsion between ‘natural resistance’ and ‘vaccinated resistance’. High levels of serum IgG1 and cell-bound IgG1 in the colon of mice protected by the ES/IFA vaccine suggest that antibody may be involved in vaccination-induced worm expulsion.

Prospects for developing an effective particle-mediated DNA vaccine against influenza

Vaccine strategies capable of conferring broad protection against both seasonal and pandemic strains of influenza are urgently needed. DNA vaccines are an attractive choice owing to their capacity to induce robust humoral and cellular immune responses at low doses and because they can be developed and manufactured rapidly to more effectively meet the threat of an influenza epidemic or pandemic. Particle-mediated epidermal delivery (PMED), or the gene gun, is a DNA vaccine delivery technology shown to induce protective levels of antibody and T-cell responses in animals and humans against a wide variety of diseases, including influenza. This review focuses on current advances toward the development of an effective PMED DNA vaccine against influenza, including strategies to enhance vaccine immunogenicity, the potential for PMED-based DNA vaccines to improve protection in the vulnerable elderly population, and the prospects for a vaccine capable of providing cross-protection against both seasonal and pandemic strains of influenza.

Construction of a New Fusion Anti-caries DNA Vaccine

Mutans streptococci (MS) are generally considered to be the principal etiological agent of dental caries. MS have two important virulence factors: cell- surface protein PAc and glucosyltransferases (GTFs). GTFs have two functional domains: an N-terminal catalytic sucrose-binding domain (CAT) and a C-terminal glucan-binding domain (GLU). A fusion anti-caries DNA vaccine, pGJA-P/VAX, encoding two important antigenic domains, PAc and GLU, of S. mutans, was successful in reducing the levels of dental caries caused by S. mutans in gnotobiotic animals. However, its protective effect against S. sobrinus infection proved to be weak. Does the DNA vaccine need an antigen of S. sobrinus to enhance its ability to inhibit infection? To answer this question, in this study, we cloned the catalytic ( cat) fragment of S. sobrinus gtf-I, which demonstrated its ability to inhibit water-insoluble glucan synthesis by S. sobrinus, into pGJA-P/VAX to produce a new anti-caries DNA vaccine.

TLR-induced local metabolism of vitamin D3 plays an important role in the diversification of adaptive immune responses

The addition of monophosphoryl lipid A, a minimally toxic derivative of LPS, to nonmucosally administered vaccines induced both systemic and mucosal immune responses to coadministered Ags. This was dependent on an up-regulated expression of 1alpha-hydroxylase (CYP27B1, 1alphaOHase), the enzyme that converts 25-hydroxycholecalciferol, a circulating inactive metabolite of vitamin D(3), into 1,25(OH)2D(3) (calcitriol). In response to locally produced calcitriol, myeloid dendritic cells (DCs) migrated from cutaneous vaccination sites into multiple secondary lymphoid organs, including classical inductive sites of mucosal immunity, where they effectively stimulated B and T cell immune responses. The endogenous production of calcitriol by monophosphoryl lipid A-stimulated DCs appeared to be Toll-IL-1R domain-containing adapter-inducing IFN-beta-dependent, mediated through a type 1 IFN-induced expression of 1alphaOHase. Responsiveness to calcitriol was essential to promote the trafficking of mobilized DCs to nondraining lymphoid organs. Collectively, these studies help to expand our understanding of the physiologically important roles played by locally metabolized vitamin D(3) in the initiation and diversification of adaptive immune responses. The influences of locally produced calcitriol on the migration of activated DCs from sites of vaccination/infection into both draining and nondraining lymphoid organs create a condition whereby Ag-responsive B and T cells residing in multiple lymphoid organs are able to simultaneously engage in the induction of adaptive immune responses to peripherally administered Ags as if they were responding to an infection of peripheral or mucosal tissues they were designed to protect.

After injection into the striatum, in vitro-differentiated microglia- and bone marrow-derived dendritic cells can leave the central nervous system via the blood stream

The prototypic migratory trail of tissue-resident dendritic cells (DCs) is via lymphatic drainage. Since the central nervous system (CNS) lacks classical lymphatic vessels, and antigens and cells injected into both the CNS and cerebrospinal fluid have been found in deep cervical lymph nodes, it was thought that CNS-derived DCs exclusively used the cerebrospinal fluid pathway to exit from tissues. It has become evident, however, that DCs found in peripheral organs can also leave tissues via the blood stream. To study whether DCs derived from microglia and bone marrow can also use this route of emigration from the CNS, we performed a series of experiments in which we injected genetically labeled DCs into the striata of rats. We show here that these cells migrated from the injection site to the perivascular space, integrated into the endothelial lining of the CNS vasculature, and were then present in the lumen of CNS blood vessels days after the injection. Moreover, we also found these cells in both mesenteric lymph nodes and spleens. Hence, microglia- and bone marrow-derived DCs can leave the CNS via the blood stream.

Comparison of different doses of antigen for intradermal administration in pigs: the Actinobacillus pleuropneumoniae model

The intensity of antibody responses and level of protection against challenge infection induced by Actinobacillus pleuropneumoniae (APP) were compared in piglets vaccinated intramuscularly with different vaccination doses of a subunit vaccine. Secondary antibody responses to APP exotoxins induced by the intradermally administered diluted vaccines did not differ from those induced by undiluted vaccines administered either intradermally or intramuscularly. The level of protection measured by the clinical course of challenge infection to the extent of lung lesions was significantly higher in animals vaccinated with a three-time diluted vaccine in comparison with animals that were administered intramuscularly or intradermally with the most concentrated or the most diluted vaccines.

Antibody association with HER-2/neu-targeted vaccine enhances CD8 T cell responses in mice through Fc-mediated activation of DCs

The pathogenic nature of cancer is attributed, at least in part, to the ability of tumors cells to induce systemic and local mechanisms of immune tolerance. However, we previously reported that tumor-free survival in up to 100% of tolerized HER-2/neu transgenic mice can be achieved by administration of neu-specific mAb concurrently with a HER-2/neu-expressing, GM-CSF-secreting whole cell vaccine. In this report, we show that one mechanism of improved antitumor activity induced by the combination of these 2 neu-targeted interventions was enhanced Fc-mediated activation of APCs. Specifically, in vivo studies demonstrated localization of radiolabeled neu-specific mAb at the vaccine site. Subsequently, increased accumulation of neu-specific mAb at the vaccine-draining lymph node correlated with increased vaccine cell uptake by DCs in vivo. This led to enhancement of CD8(+) neu-specific T cell function in terms of proliferation, cytokine production, and central memory development. Thus, the administration of a neu-specific mAb with a neu-targeted GM-CSF-secreting tumor vaccine enhanced induction of neu-specific CD8(+) T cells through Fc-mediated activation of DCs. This multimodality attack on the same tumor antigen may have the potential to overcome tolerance to self antigens and weaken the immunosuppressive networks within the tumor microenvironment.

TLR ligands that stimulate the metabolism of vitamin D3 in activated murine dendritic cells can function as effective mucosal adjuvants to subcutaneously administered vaccines

Cathelicidin production by human myeloid cells stimulated through toll-like receptor (TLR) 2/1, the migration of human CD8+ T cells to inflamed skin sites, and the ability of murine dendritic cells (DCs) to migrate from skin sites of vaccination to mucosal lymphoid organs all occur via calcitriol-dependent mechanisms. Herein, we report that murine DCs exposed to TLR3/TLR4 ligands upregulate their expression of 1 alpha-hydroxylase, the enzyme that converts circulating 25(OH)D3 to calcitriol, the active form of vitamin D3. TLR3/TLR4 ligands injected subcutaneously affect DC migration in vivo, allowing their trafficking to both draining and non-draining systemic and mucosal lymphoid organs. Subcutaneously delivered vaccines containing TLR3/TLR4 ligands and antigen stimulate the induction of both systemic and mucosal immune responses. Vaccines containing TLR9 ligands fail to stimulate 1 alpha-hydroxylase protein expression, are incapable of redirecting DC migration into Peyer's patches and do not induce mucosal immune responses. These findings support a hypothesis that active metabolites of vitamin D3 produced locally are able to affect various aspects of innate and acquired immune responses.

Roles of adjuvant and route of vaccination in antibody response and protection engendered by a synthetic matrix protein 2-based influenza A virus vaccine in the mouse

Background

The M2 ectodomain (M2e) of influenza A virus (IAV) strains that have circulated in humans during the past 90 years shows remarkably little structural diversity. Since M2e-specific antibodies (Abs) are capable of restricting IAV replication in vivo but are present only at minimal concentration in human sera, efforts are being made to develop a M2e-specific vaccine. We are exploring a synthetic multiple antigenic peptide (MAP) vaccine and here report on the role of adjuvants (cholera toxin and immunostimulatory oligodeoxynucleotide) and route of immunization on Ab response and strength of protection.

Results

Independent of adjuvants and immunization route, on average 87% of the M2e-MAP-induced Abs were specific for M2e peptide and a variable fraction of these M2e(pep)-specific Abs (average 15%) cross-reacted with presumably native M2e expressed by M2-transfected cells. The titer of these cross-reactive M2e(pep-nat)-specific Abs in sera of parenterally immunized mice displayed a sigmoidal relation to level of protection, with EC₅₀ of ~20 μg Ab/ml serum, though experiments with passive M2e(pep-nat) Abs indicated that serum Abs did not fully account for protection in parenterally vaccinated mice, particularly in upper airways. Intranasal vaccination engendered stronger protection and a higher proportion of G2a Abs than parenteral vaccination, and the strength of protection failed to correlate with M2e(pep-nat)-specific serum Ab titers, suggesting a role of airway-associated immunity in protection of intranasally vaccinated mice. Intranasal administration of M2e-MAP without adjuvant engendered no response but coadministration with infectious IAV slightly enhanced the M2e(pep-nat) Ab response and protection compared to vaccination with IAV or adjuvanted M2e-MAP alone.

Conclusion

M2e-MAP is an effective immunogen as ~15% of the total M2e-MAP-induced Ab response is of desired specificity. While M2e(pep-nat)-specific serum Abs have an important role in restricting virus replication in trachea and lung, M2e-specific T cells and/or locally produced Abs contribute to protection in upper airways. Intranasal vaccination is preferable to parenteral vaccination, presumably because of induction of local protective immunity by the former route. Intranasal coadministration of M2e-MAP with infectious IAV merits further investigation in view of its potential applicability to human vaccination with live attenuated IAV.

In Vitro Induction of Mucosa-Type Dendritic Cells by All-Trans Retinoic Acid

Efficient induction of mucosal immunity usually employs nasal or oral vaccination while parenteral immunization generally is ineffective at generating mucosal immune responses. This relates to the unique ability of resident mucosal dendritic cells (DC) to induce IgA switching and to imprint mucosa-specific homing receptors on lymphocytes. Based on the well-established plasticity of the DC system, this study sought to investigate whether peripheral DC could be modulated toward "mucosa-type" DC by treatment with immunomodulatory, and therefore potentially adjuvant-like, factors. In this study, we show that monocyte-derived DCs pretreated with the vitamin A derivative all-trans retinoic acid (RA) indeed acquired several attributes characteristic of mucosal DC: secretion of TGF-beta and IL-6 and the capacity to augment mucosal homing receptor expression and IgA responses in cocultured lymphocytes. Addition of a TGF-beta-neutralizing Ab to cocultures significantly inhibited alpha4beta7 integrin, but not CCR9 mRNA expression by the lymphocytes. Both alpha4beta7 integrin and CCR9 mRNA expression, but not IgA production, were suppressed in the presence of a RA receptor antagonist. None of the observed effects on the lymphocytes were influenced by citral, a retinal dehydrogenase inhibitor, arguing against a role for de novo-synthesized RA. Collectively, our findings identified a novel role for RA as a mucosal immune modulator targeting DC. Our results further demonstrate that DC can act as efficient carriers of RA at least in vitro. Consequently, RA targeting of DC shows potential for promoting vaccine-induced mucosal immune responses via a parenteral route of immunization.

Clarification of how HIV-1 DNA and protein immunizations may be better used to obtain HIV-1-specific mucosal and systemic immunity

More focused research on a mucosal HIV-1 vaccine is needed urgently. An increasing amount of collected data, using heterologous multimodality prime-booster strategies, suggest that an efficient and protective HIV-1 vaccine must generate broad, long-lasting HIV-specific CD8(+) cytotoxic T-lymphocyte and neutralizing antibody responses. In the mucosa, these responses would be most effective if a preferential stimulus of HIV-1 neutralizing secretory immunoglobulin A and G were obtained. The attractive property of mucosal immunization is the obtained mucosal and systemic immunity, whereas systemic immunization induces a more limited immunity, predominantly in systemic sites. These objectives will require new vaccine regimens, such as multiclade HIV DNA and protein vaccines (nef, tat, gag and env expressed in DNA plasmids) delivered onto mucosal surfaces with needle-free delivery methods, such as nasal drop, as well as oral and rectal/vaginal delivery, and should merit clinical trials.