Characterisation of antibody responses in pigs induced by recombinant oncosphere antigens from Taenia solium

Recombinant antigens cloned from the oncosphere life cycle stage of the cestode parasite Taenia solium (T. solium) have been proven to be effective as vaccines for protecting pigs against infections with T. solium. Previous studies have defined three different host protective oncosphere antigens, TSOL18, TSOL16 and TSOL45. In this study, we evaluated the potential for combining the antigens TSOL16 and TSOL18 as a practical vaccine. Firstly, in a laboratory trial, we compared the immunogenicity of the combined antigens (TSOL16/18) versus the immunogenicity of the antigens separately. Secondly, in a field trial, we tested the ability of the TSOL16/18 vaccine to induce detectable antibody responses in animals living under environmental stress and traditionally reared in areas where T. solium cysticercosis is endemic; and finally, we characterised the immune response of the study population. Pigs of 8–16 weeks of age were vaccinated with 200 μg each of TSOL16 and TSOL18, plus 5 mg of Quil-A. Specific total IgG, IgG₁ and IgG₂ antibody responses induced by TSOL16 and TSOL18 were determined with ELISA. The immunogenicity of both antigens was retained in the combined TSOL16/18 vaccine. The combined vaccine TSOL16/18 induced detectable specific anti-TSOL18 antibody responses in 100% (113/113) and specific anti-TSOL16 in 99% (112/113) of the vaccinated animals measured at 2 weeks following the booster vaccination. From the two IgG antibody subtypes analysed we found there was stronger response to IgG₂.     

Immune response and protection elicited by DNA immunisation against Taenia cysticercosis

The study evaluated DNA vaccination in Taenia solium cysticercosis prevention by using cDNA of an antigen (cC1) from T. solium metacestode. pcDNA3-cC1 DNA vaccine was constructed by inserting the cDNA into the eukaryotic expression plasmid pcDNA3. Positive expression of the pcDNA3-cC1 product was confirmed by its transfection into COS7 cell and enzyme-linked immunoabsorbent assay using serum of pigs infected with T. solium metacestode. Immunisation of BALB/c mice with three injections of pcDNA3-cC1 induced antigen-specific immune responses of the Th1 phenotype. Inoculation of new-born pigs induced protection against challenge with T. solium by 73.3% reduction of the metacestode number. Antibodies elicited by DNA immunisation with pcDNA3-cC1 specifically reacted with native cC1 protein, which was mainly restricted to the cyst wall of T. solium metacestode. Positive apoptosis signals were also detected in the cyst wall cells of metacestode slices from pigs immunised with pcDNA3-cC1 by TUNEL staining method. Those suggested that apoptosis played a role in protecting pigs immunised with pcDNA3-cC1 nucleic acid vaccine from pathogen challenge.     

Synthetic peptide vaccine against Taenia solium pig cysticercosis: successful vaccination in a controlled field trial in rural Mexico

Taenia solium cysticercosis seriously affects human health when localised in the central nervous system (CNS) and causes great economic loss in pig husbandry in rural areas of endemic countries. Increasing the resistance to the parasite in the obligatory host pig may help in curbing transmission. Three synthetic peptides based on protein sequences of the murine parasite Taenia crassiceps, which had previously been shown to induce protection in mice against homologous challenge, were tested as a vaccine against T. solium cysticercosis in pigs. Vaccinated and unvaccinated piglets (240 in all) were distributed in pairs among the peasants' households of two rural villages in Mexico in which 14% of the native pigs were cysticercotic. Ten to twelve months later, the effect of vaccination was evaluated at necropsy. Vaccination decreased the total number of T. solium cysticerci (98.7%) and reduced the prevalence (52.6%). The natural challenge conditions used in this field trial strengthen the likelihood of successful transmission control to both pig and human through a large-scale pig vaccination program. We believe this is a major contribution in anticysticercosis vaccine development as these rather simple yet protective peptides are potentially more cost-effective to produce and less variable in results than antigens that are more complex.     

Induction of protection against porcine cysticercosis in growing pigs by DNA vaccination

A DNA vaccine, pcDNA3-B, was developed by using the nucleotide sequence of Taenia solium B antigen and cloning into pcDNA3.1 plasmid. The growing pigs were vaccinated by one intramuscular infection of 200 or 1000 microg pcDNA3-B. The immunization with 1000 microg of pcDNA3-B showed 92.6% protection when the pigs were challenged by T. solium eggs and four of the five pigs vaccinated had no viable cysts. The results provide encouraging information on the use of pcDNA3-B vaccination for the prevention of cysticercosis.     

Vaccination of mice with a cocktail DNA vaccine induces a Th1-type immune response and partial protection against Schistosoma japonicum infection.

Several defined vaccine candidate antigens of Schistosoma japonicum have shown promise in large animal vaccination experiments. However, vaccination of mice in the laboratory with either single recombinant antigens or DNA encoding forms of the individual antigens has so far failed to induce significant protection against S. japonicum cercarial challenge infection as judged by worm reduction, although specific antibodies were generated. This is in contrast to the results achieved using radiation-attenuated vaccines which are highly protective. Even in large animal vaccination experiments, the protection levels obtained with single defined antigens were far below those achieved using the attenuated vaccines. One possible interpretation is that the immune responses induced by single antigen vaccination may not be strong enough to combat the challenging infection. We, therefore, carried out mouse vaccination experiments using a cocktail DNA vaccine comprising four DNA plasmids encoding four different S. japonicum antigens, Sj62, Sj28, Sj23 and Sj14-3-3, respectively. We, also investigated whether co-injection of the mouse IL-12 encoding plasmid with the cocktail DNA vaccine was able to enhance the Th1 responses and hence the protective immunity. Three intramuscular injections of the cocktail DNA vaccine induced a significant Th1-type cellular response with high level of IFN-gamma production by splenocytes upon in vitro stimulation with recombinant antigens. Importantly, significant IgG antibody responses were also induced against crude worm antigens. In two out of three experiments, significant resistance (34-37 and 44-45%, respectively) was demonstrated while another experiment did not show any protection against S. japonicum cercarial challenge infection. Co-injection of the IL-12 encoding DNA did not further enhance these responses, nor the level of resistance, compared with the cocktail DNA alone.     

Protection of pigs against Taenia solium cysticercosis using recombinant antigen or in combination with DNA vaccine

In the present study, we investigated the duration of protection afforded to pigs immunized in two different prime-boost regimens: one is homologus priming and boosting with a protein vaccine, and the other is priming with a DNA vaccine and boosting with the protein vaccine. Groups of pigs that received the same vaccination regimen were then challenged with Taenia solium eggs at 6, 12 or 20 weeks post-immunization (wpi), respectively. The results showed that all vaccinated pigs challenged at 6 or 12 wpi showed significant (P < 0.05) reduction in the development of cysts. When challenged at 20 wpi, pigs primed with the DNA vaccine (pcDNA3-cC1) followed by two boosters of the protein vaccine (GST-cC1) showed significant (P < 0.05) protection against the challenge of T. solium eggs, whereas pigs receiving three injections of the protein vaccine showed no significant protection compared to non-vaccinated controls (P > 0.05). Antibody isotype assays showed that DNA prime-protein boost regimen induced a predominantly IgG2 response, compared to an IgG1 biased response for the protein prime-protein boost regimen. In addition, peripheral blood mononuclear cells (PBMC) obtained from the DNA prime-protein boost group proliferated strongly in response to GST-cC1 protein, and this responsiveness persisted until 20 wpi. Taken together, our data suggest that the use of a prime-boost strategy combining DNA and protein vaccines may be better than protein alone for the longevity of protection against the challenge of T. solium eggs.     

GTL001 and bivalent CyaA-based therapeutic vaccine strategies against human papillomavirus and other tumor-associated antigens induce effector and memory T-cell responses that inhibit tumor growth

GTL001 is a bivalent therapeutic vaccine containing human papillomavirus (HPV) 16 and HPV18 E7 proteins inserted in the Bordetella pertussis adenylate cyclase (CyaA) vector intended to prevent cervical cancer in HPV-infected women with normal cervical cytology or mild abnormalities. To be effective, therapeutic cervical cancer vaccines should induce both a T cell-mediated effector response against HPV-infected cells and a robust CD8⁺ T-cell memory response to prevent potential later infection. We examined the ability of GTL001 and related bivalent CyaA-based vaccines to induce, in parallel, effector and memory CD8⁺ T-cell responses to both vaccine antigens. Intradermal vaccination of C57BL/6 mice with GTL001 adjuvanted with a TLR3 agonist (polyinosinic-polycytidylic acid) or a TLR7 agonist (topical 5% imiquimod cream) induced strong HPV16 E7-specific T-cell responses capable of eradicating HPV16 E7-expressing tumors. Tumor-free mice also had antigen-specific memory T-cell responses that protected them against a subsequent challenge with HPV18 E7-expressing tumor cells. In addition, vaccination with bivalent vaccines containing CyaA-HPV16 E7 and CyaA fused to a tumor-associated antigen (melanoma-specific antigen A3, MAGEA3) or to a non-viral, non-tumor antigen (ovalbumin) eradicated HPV16 E7-expressing tumors and protected against a later challenge with MAGEA3- and ovalbumin-expressing tumor cells, respectively. These results show that CyaA-based bivalent vaccines such as GTL001 can induce both therapeutic and prophylactic anti-tumor T-cell responses. The CyaA platform can be adapted to different antigens and adjuvants, and therefore may be useful for developing other therapeutic vaccines.     

Vaccination of domestic pig with recombinant paramyosin. against Schistosoma japonicum in China

Paramyosin (PM), a myosin-like protein is a major antigen on Schistosoma japonicum (Sj). We reported that passive transfer of a monoclonal IgE SjE18varepsilon.1 which recognizes PM of Sj (SJPM), partially protected mice from challenge infection. In the present study, we developed an experimental model system of schistosomiasis japonica with domestic pigs in China and used it for the evaluation of vaccination with recombinant SJPM (rSJPM). Sixteen-week-old pigs were successfully infected by dermal penetration of 120 cercariae of a domestic strain of Sj (50-60% worm recovery 11 weeks after challenge). The pigs vaccinated with 400 UV attenuated cercariae showed a reduction of worm recovery (53%, p<0.001). The experimental groups were immunized intradermally with rSJPM and alum or TiterMax and were partially protected against the challenge infection (32-35% reduction).     

Protection of pigs against genital Chlamydia trachomatis challenge by parenteral or mucosal DNA immunization

The current study evaluates combined aerosol-vaginal delivery of a MOMP-based Chlamydia trachomatis (serovar E) DNA vaccine in a pig genital challenge model. Most non-replicating antigens are rather poor mucosal immunogens in comparison to replicating antigens. Therefore, a mucosal administered DNA vaccine, which actually mimics a live vaccine, could be promising. Protection was promoted by plasmids encoding the porcine granulocyte macrophage-colony stimulating factor (pcDNA3.1zeo::GM-CSF), the Escherichia coli thermo-labile enterotoxin (LT) subunit A (plasmid PJV2004::LTa) and subunit B (plasmid PJV2005::LTb). Mucosal C. trachomatis DNA vaccination induced significant protection against genital C. trachomatis challenge although the infection could not be eradicated. Intradermal immunization was significantly less efficient in protecting experimentally infected pigs. Protection was correlated with efficient T cell priming and significantly higher serum IgA titers following primo vaccination.     

An enhanced GRA1-GRA7 cocktail DNA vaccine primes anti-Toxoplasma immune responses in pigs

The protozoan parasite Toxoplasma gondii is the causative agent of a worldwide zoonosis and high prevalencies can be found both in animals and humans. An important source of human contamination with T. gondii is the consumption of raw or undercooked meat products. In this study, we evaluated whether DNA vaccination against T. gondii in pigs is able to generate immune responses known to be protective against tissue cyst formation. A GRA1-GRA7 DNA vaccine cocktail was enhanced by codon optimization of the encoding antigens and addition of heat labile enterotoxin expressing vectors as genetic adjuvant. Pigs vaccinated intradermally with this enhanced GRA1-GRA7 DNA vaccine cocktail developed high antibody levels against GRA1, GRA7 and a T. gondii lysate, and lymphocyte proliferation and production of IFN-gamma could be detected in these animals after challenge with the parasite. These results indicate that pigs can be efficiently primed against T. gondii infection by means of a DNA vaccine.     

Incorporation of RG1 epitope concatemers into a self-adjuvanting Flagellin-L2 vaccine broaden durable protection against cutaneous challenge with diverse human papillomavirus genotypes

AimTo achieve durable and broad protection against human papillomaviruses by vaccination with multimers of minor capsid antigen L2 using self-adjuvanting fusions with the toll-like receptor-5 (TLR5) ligand bacterial flagellin (Fla) instead of co-formulation with alum.MethodsFla fusions with L2 protective epitopes comprising residues 11-200, 11-88 and/or 17-38 of a single or multiple HPV types were produced in E. coli and their capacity to activate TLR5 signaling was assessed. Immunogenicity was evaluated serially following administration of 3 intramuscular doses of Fla-L2 multimer without exogenous adjuvant, followed by challenge 1, 3, 6 or 12 months later, and efficacy compared to vaccination with human doses of L1 VLP vaccines (Gardasil and Cervarix) or L2 multimer formulated in alum. Serum antibody responses were assessed by peptide ELISA, in vitro neutralization assays and passive transfer to naïve rabbits in which End-Point Protection Titers (EPPT) were determined using serial dilutions of pooled immune sera collected 1, 3, 6 or 12 months after completing active immunization. Efficacy was assessed by determining wart volume following concurrent challenge at different sites with HPV6/16/18/31/45/58 ‘quasivirions’ containing cottontail rabbit papillomavirus (CRPV) genomes.ResultsVaccination in the absence of exogenous adjuvant with Fla-HPV16 L2 11-200 fusion protein elicited durable protection against HPV16, but limited cross-protection against other HPV types. Peptide mapping data suggested the importance of the 17-38 aa region in conferring immunity. Indeed, addition of L2 residues 17-38 of HPV6/18/31/39/52 to a Fla-HPV16 L2 11-200 or 11-88 elicited broader protection via active or passive immunization, similar to that seen with vaccination with an alum-adjuvanted L2 multimer comprising the aa 11-88 peptides of five or eight genital HPV types.ConclusionsVaccination with flagellin fused L2 multimers provided lasting (>1 year) immunity without the need for an exogenous adjuvant. Inclusion of the L2 amino acid 17-38 region in such multi-HPV type fusions expanded the spectrum of protection.     

Towards a universal vaccine for avian influenza: Protective efficacy of modified Vaccinia virus Ankara and Adenovirus vaccines expressing conserved influenza antigens in chickens challenged with low pathogenic avian influenza virus

Current vaccines targeting surface proteins can drive antigenic variation resulting either in the emergence of more highly pathogenic viruses or of antigenically distinct viruses that escape control by vaccination and thereby persist in the host population. Influenza vaccines typically target the highly mutable surface proteins and do not provide protection against heterologous challenge. Vaccines which induce immune responses against conserved influenza epitopes may confer protection against heterologous challenge. We report here the results of vaccination with recombinant modified Vaccinia virus Ankara (MVA) and Adenovirus (Ad) expressing a fusion construct of nucleoprotein and matrix protein (NP + M1). Prime and boost vaccination regimes were trialled in different ages of chicken and were found to be safe and immunogenic. Interferon-γ (IFN-γ) ELISpot was used to assess the cellular immune response post secondary vaccination. In ovo Ad prime followed by a 4 week post hatch MVA boost was identified as the most immunogenic regime in one outbred and two inbred lines of chicken. Following vaccination, one inbred line (C15I) was challenged with low pathogenic avian influenza (LPAI) H7N7 (A/Turkey/England/1977). Birds receiving a primary vaccination with Ad-NP + M1 and a secondary vaccination with MVA-NP + M1 exhibited reduced cloacal shedding as measured by plaque assay at 7 days post infection compared with birds vaccinated with recombinant viruses containing irrelevant antigen. This preliminary indication of efficacy demonstrates proof of concept in birds; induction of T cell responses in chickens by viral vectors containing internal influenza antigens may be a productive strategy for the development of vaccines to induce heterologous protection against influenza in poultry.     

Protection against hydatid disease induced with the EG95 vaccine is associated with conformational epitopes

This paper describes attempts to map the location of host-protective epitopes of a recombinant vaccine antigen by assessing the ability of truncated regions of the antigen to elicit protective immune responses in sheep. Sheep were immunised with three truncated regions (EG95-1, EG95-2 and EG95-3) of the hydatid vaccine antigen, EG95. These regions overlapped each other and corresponded to amino acids 1-70 (EG95-1), 51-106 (EG95-2) and 89-153 (EG95-3) of the full length recombinant protein. Each region elicited antibody which reacted with the parent antigen, although these reactivities were a small proportion of the level of reactivity generated by immunisation with the full length antigen. Antisera raised against each of the truncated proteins reacted with the native parasite antigen. In vaccination and parasite challenge trials in sheep, none of the truncated regions elicited significant protection against challenge infection or antibody which was lethal to the parasite in vitro. Antibodies from sheep immunised with the combination of all three overlapping truncations elicited a comparatively low but significant level of lysis of the parasite in vitro. These antigens did not inhibit anti-EG95 antibody reactivity with EG95 nor did they inhibit in vitro oncosphere killing induced by anti-EG95 antibodies. These results indicate that the major part of the immune response induced by EG95 vaccination is directed against conformational epitopes and that the host-protective epitope(s) is/are conformational.     

Combined use of two separate but protective vaccine antigens provides protection against Taenia ovis infection in lambs in the presence of protective maternal antibody

Three recombinant Taenia ovis antigens (To45, To16, To18) each induce protective immunity in lambs or ewes against infection with T. ovis metacestodes. The degree and duration of immunity were assessed in lambs born from vaccinated ewes. Treatment group sizes varied, typically not fewer than 5 animals per group. Ewes were immunised with one T. ovis recombinant protein prior to lambing and the degree and duration of passive immunity in their lambs was assessed by challenge infection up to 18 weeks. Lambs were fully protected up to 6 weeks of age but immunity waned from 6 to 12 weeks and there was no protection when lambs were challenged at 15 weeks. Immunisation of lambs with the homologous recombinant antigen was not effective when vaccinations were given when maternal antibody was high. Lambs were effectively immunised in the presence of passively protective antibody when vaccinated with an antigen that was different to that given to ewes. Vaccination of lambs with a combination of two proteins, To16 and To18, was more effective than giving these single antigens and gave a significant reduction of cyst numbers when lambs were challenged 12 months after immunisation. These results indicate that the use of combinations of T. ovis recombinant antigens could enable complete protection of lambs against infection, if a delivery system becomes available that will maintain antibody at protective levels for 12 months. Alternatively, a third injection given at 6 months may promote the anamnestic response to give long lasting protection.     

Efficacy of an AS03A-adjuvanted split H5N1 influenza vaccine against an antigenically distinct low pathogenic H5N1 virus in pigs

We used the pig model of influenza to examine the efficacy of an AS03(A)-adjuvanted split H5N1 (A/Indonesia/05/2005) vaccine against challenge with a low pathogenic (LP) H5N1 avian influenza (AI) virus (duck/Minnesota/1525/1981) with only 85% amino acid homology in its HA1. Influenza seronegative pigs were vaccinated twice intramuscularly with adjuvanted vaccine at 3 antigen doses, unadjuvanted vaccine or placebo. All pigs were challenged 4 weeks after the second vaccination and euthanized 2 days later. After 2 vaccinations, all pigs in the adjuvanted vaccine groups had high hemagglutination inhibiting (HI) antibody titers to the vaccine strain (160-640), and lower antibody titers to the A/Vietnam/1194/04 H5N1 strain and to 2 LP H5 viruses with 90-91% amino acid homology to the vaccine strain (20-160). Eight out of 12 pigs had HI titers (10-20) to the challenge virus immediately before challenge. Neuraminidase inhibiting antibodies to the challenge virus were detected in most pigs (7/12) and virus neutralizing antibodies in all pigs. There was no antigen-dose dependent effect on the antibody response among the pigs immunized with adjuvanted H5N1 vaccines. After challenge, these pigs showed a complete clinical protection, reduced lung lesions and a significant protection against virus replication in the respiratory tract. Though the challenge virus showed only moderate replication efficiency in pigs, our study suggests that AS03(A)-adjuvanted H5N1 vaccine may confer a broader protection than generally assumed. The pros and cons of the pig as an H5N1 challenge model are also discussed.     

A PCV2 vaccine based on genotype 2b is more effective than a 2a-based vaccine to protect against PCV2b or combined PCV2a/2b viremia in pigs with concurrent PCV2, PRRSV and PPV infection

The predominant genotype of porcine circovirus (PCV) in the pig population today is PCV2b yet PCV2a-based commercial vaccines are considered effective in protecting against porcine circovirus associated disease. The objective of this study was to compare the ability of PCV2a- and PCV2b-based vaccines to control PCV2b viremia in a challenge model that mimics the U.S. field situation. Sixty-three pigs were randomly assigned to one of eight groups. Sixteen pigs were vaccinated with an experimental live-attenuated chimeric PCV1-2a vaccine based on genotype 2a and another 16 pigs with a chimeric PCV1-2b vaccine based on genotype 2b. Challenge was done 28 days post vaccination (dpv) using PCV2b (or a combination of PCV2a and PCV2b), porcine reproductive and respiratory syndrome virus (PRRSV), and porcine parvovirus (PPV) to mimic what commonly occurs in the field. The experiment was terminated 21 days post challenge (dpc) or 49 dpv. Pigs vaccinated with the chimeric PCV1-2b vaccine had significantly higher levels of PCV1-2b viremia and shedding of the PCV1-2b vaccine virus in feces and nasal secretions but also a more robust humoral immune response as evidenced by significantly higher ELISA S/P ratios compared to the PCV1-2a vaccination. Regardless of challenge, the PCV1-2b vaccination significantly reduced the prevalence and amount of PCV2 viremia compared to the PCV1-2a vaccination. Interestingly, in the non-vaccinated pigs concurrent PCV2a infection resulted in clinical disease and increased macroscopic lung lesions compared to pigs challenged with PCV2b alone, further supporting the idea that concurrent PCV2a/PCV2b infection is necessary for optimal PCV2 replication.     

Serological and mucosal immune responses after vaccination and infection with FMDV in pigs

The aim of this study was to determine a possible correlation between humoral immune responses shortly after vaccination and protection against foot-and-mouth disease virus (FMDV) infection and to study the serological and mucosal antibody responses after vaccination and infection. We used three groups of ten pigs, one non-vaccinated group, one group vaccinated with a single dose vaccine and one group vaccinated with a four-fold dose vaccine. At 7 days post vaccination, five pigs per group were challenged intra-dermally with FMDV O TAW 3/97 and the remaining pigs of each group were contact-exposed to the inoculated pigs. In each group, virus excretion and number of contact infections were quantified. The serological and mucosal antibody responses were evaluated until 116 days post infection. Vaccination resulted in a significant decrease of virus excretion. Stepwise linear regression analysis of variables from individual vaccinated pigs revealed the virus excretion after challenge to be correlated with neutralising antibody titres at the day of challenge (p<0.01). In serum and OPF samples comparable isotype-specific antibody responses (IgM, IgG and IgA), could be detected after vaccination as well as after infection. Remarkably, the pigs with the highest IgA responses after vaccination were protected against contact exposure. After infection, a long lasting (up to 116dpi) IgA response was seen in the non-vaccinated and to a lesser extent in the single dose vaccinated pigs. The induction of NSP antibodies in the vaccinated pigs after infection was lower and of shorter duration as compared to the non-vaccinated infected pigs. This experiment shows that vaccination can reduce virus excretion in pigs, which will contribute to reduced transmission of FMDV in the field, even if the pigs are not fully protected. Moreover, vaccines that induce local IgA responses may be more effective, which merits further investigation.     

Intranasal immunization with serum opacity factor (SOF) of Streptococcus pyogenes fails to protect mice against lethal mucosal challenge with a heterologous strain

Streptococcus pyogenes is a human pathogen causing invasive and non-invasive diseases, as well as severe sequels, such as rheumatic fever. Several bacterial factors have been proposed as candidate vaccine antigens. Among them, the serum opacity factor (SOF), which was able to confer protective immunity against an intraperitoneal challenge after vaccination by the parenteral route. In an attempt to develop more efficient vaccines, we combined SOF with an additional well-known protective antigen, namely, the fibronectin-binding protein I (SfbI). Intranasal immunization of mice with SOF and SfbI stimulates strong systemic and mucosal immune responses against both antigens. Animals vaccinated with SfbI, alone or in combination with SOF, were also efficiently protected against a lethal challenge with a SOF/SfbI-positive virulent S. pyogenes strain (80% survival). In contrast, those vaccinated with SOF alone were not protected against a mucosal challenge (100% lethality), which mimics more closely natural infections. These results highlight the importance of developing adequate experimental animal models to evaluate vaccine efficiency, according to the selected antigen.     

A mixed Th1/Th2 response elicited by a liposomal formulation of Leishmania vaccine instructs Th1 responses and resistance to Leishmania donovani in susceptible BALB/c mice

In this study, we have developed a vaccine with Leishmania donovani promastigote membrane antigens (leishmanial antigens (LAg)) encapsulated in a liposome carrier formulated with distearyol (DSPC, transition temperature (Tc) = 54 degrees C) derivative of l-alpha-phosphatidyl choline, for immunizing BALB/c mice against progressive visceral leishmaniasis. This formulation could limit hepatosplenomegaly to almost normal levels and conferred strong levels of protection in both liver and spleen against challenge infection. Immunization with liposomal LAg activated peritoneal macrophages for enhanced leishmanicidal activity in association with NO production, and induced antibody as well as T-cell mediated immune responses. Production of both IFN-gamma and IL-4 by splenic T cells, and serum IgG1 and IgG2a, suggest induction of a mixed Th1/Th2 response following immunization. Experimental challenge corresponded with elevated DTH, and mitogen and antigen specific cellular responses. Increased production of NO and IFN-gamma by spleen cells, and down regulation of IL-4, demonstrate that an initial stimulation of a mixed Th1/Th2 response by vaccination instructs Th1 responses and resistance against a progressive infection by L. donovani.     

High-throughput proteomic screening identifies Chlamydia trachomatis antigens that are capable of eliciting T cell and antibody responses that provide protection against vaginal challenge

A comprehensive proteomic screening technology was previously used to characterize T cell responses to Chlamydia trachomatis infection. In this study, we demonstrated that T cells specific for protein antigens identified through this comprehensive technology home to the site of infection after mucosal challenge with C. trachomatis. In addition, T cell responses to these proteins were elicited in multiple genetic backgrounds. Two protein antigens, CT823 and CT144, were evaluated as vaccine candidates. When administered with AbISCO-100 adjuvant, these antigens stimulated potent CD8(+) T cell responses, polyfunctional T(H)1-polarized CD4(+) T cell responses, and high titer protein-specific T(H)1-skewed antibody responses. Vaccination with either antigen with AbISCO-100 provided long-lived protection against intravaginal challenge with C. trachomatis. Adoptive transfer of immune T cells also conferred protection in the challenge model whereas passive transfer of immune serum did not, indicating the critical role for T cell responses in control of this infection. The ability of these antigens to induce potent immune responses and provide long-lived protection in response to challenge provides a basis for the rational design of a C. trachomatis subunit vaccine.