Vaccine-induced IFNγ + CD4 T cells migrate to and persist in mucosal tissue and negatively associate with protection against SIV.

ABSTRACT Trimeric HIV-1 envelope (Env) immunogens are attractive due to their ability to display quaternary epitopes targeted by broadly neutralizing antibodies (bNAbs) while obscuring unfavorable epitopes. Results from the RV144 trial highlighted the importance of vaccine-induced HIV-1 Env V1V2-directed antibodies, with key regions of the V2 loop as targets for vaccine-mediated protection. We recently reported that a trimeric JRFL-gp120 immunogen, generated by inserting an N-terminal trimerization domain in the V1 loop region of a cyclically permuted gp120 (cycP-gp120), induces neutralizing activity against multiple tier-2 HIV-1 isolates in guinea pigs in a DNA prime/protein boost approach. Here, we tested the immunogenicity of cycP-gp120 in a protein prime/boost approach in rabbits and as a booster immunization to DNA/modified vaccinia Ankara (MVA)-vaccinated rabbits and rhesus macaques. In rabbits, two cycP-gp120 protein immunizations induced 100-fold higher titers of high-avidity gp120-specific IgG than two gp120 immunizations, with four total gp120 immunizations being required to induce comparable titers. cycP-gp120 also induced markedly enhanced neutralizing activity against tier-1A and -1B HIV-1 isolates, substantially higher binding and breadth to gp70-V1V2 scaffolds derived from a multiclade panel of global HIV-1 isolates, and antibodies targeting key regions of the V2-loop region associated with reduced risk of infection in RV144. Similarly, boosting MVA- or DNA/MVA-primed rabbits or rhesus macaques with cycP-gp120 showed a robust expansion of gp70-V1V2-specific IgG, neutralization breadth to tier-1B HIV-1 isolates, and antibody-dependent cellular cytotoxicity activity. These results demonstrate that cycP-gp120 serves as a robust HIV Env immunogen that induces broad anti-V1V2 antibodies and promotes neutralization breadth against HIV-1. IMPORTANCE Recent focus in HIV-1 vaccine development has been the design of trimeric HIV-1 Env immunogens that closely resemble native HIV-1 Env, with a major goal being the induction of bNAbs. While the generation of bNAbs is considered a gold standard in vaccine-induced antibody responses, results from the RV144 trial showed that nonneutralizing antibodies directed toward the V1V2 loop of HIV-1 gp120, specifically the V2 loop region, were associated with decreased risk of infection, demonstrating the need for the development of Env immunogens that induce a broad anti-V1V2 antibody response. In this study, we show that a novel trimeric gp120 protein, cycP-gp120, generates high titers of high-avidity and broadly cross-reactive anti-V1V2 antibodies, a result not found in animals immunized with monomeric gp120. These results reveal the potential of cycP-gp120 as a vaccine candidate to induce antibodies associated with reduced risk of HIV-1 infection in humans.

A gradually built up immune response specifies protection against Simian Immunodeficiency Virus infection in Rhesus Macaques

Background. In this study, we analyzed the protective efficacy of a simian immunodeficiency virus (SIV) macaque 239 (SIVmac239) analogue of the clinically tested GOVX-B11 deoxyribonucleic acid (DNA)/modified vaccinia Ankara (MVA) human immunodeficiency virus vaccine. Methods. The tested vaccine used a DNA immunogen mutated to mimic the human vaccine and a regimen with DNA deliveries at weeks 0 and 8 and MVA deliveries at weeks 16 and 32. Twelve weekly rectal challenges with 0.3 animal infectious doses of SIV sootey mangabey E660 (SIVsmE660) were administered starting at 6 months after the last immunization. Results. Over the first 6 rectal exposures to SIVsmE660, <10-year-old tripartite motif-containing protein 5 (TRIM5)α-permissive rhesus macaques showed an 80% reduction in per-exposure risk of infection as opposed to a 46% reduction in animals over 10 years old; and, over the 12 challenges, they showed a 72% as opposed to a 10% reduction. Analyses of elicited immune responses suggested that higher antibody responses in the younger animals had played a role in protection. Conclusions. The simian analogue of the GOVX-B11 HIV provided strong protection against repeated rectal challenges in young adult macaques.

Due to the majority of HIV/SIV transmissions occurring via the mucosal route, a mucosal vaccine that generates immune responses along the genitorectal tract may provide the tools needed to combat HIV/SIV in its earliest stages of infection. We recently demonstrated that an orally delivered mucosal vaccine based around the probiotic bacterium Lactococcus lactis expressing HIV/SIV antigens fused to a cell wall anchored Group A Streptococcus (GAS) pilus induces a strong systemic and mucosal immunity in mice. To test the mechanisms behind immunogenicity, we gavaged mice and examined the activation level of various dendritic cells in the intestinal Peyer’s patches and found increased activation of CD11b+CD8− DC compared to wild-type L. lactis, indicating some inherent adjuvant activity of the GAS pilus. As there is evidence that GAS pilus specific antibodies may aid in the protection from GAS infection, we evaluated the ability of our L. lactis vectors to generate these pilus-targeting antibodies. We observed a strong induction of GAS-pilus specific antibodies in both mice and rhesus macaques orally immunized with our L. lactis vectors. We were unable to detect antibody responses generated against the backbone L. lactis bacterium, underlining the immunodominance of the GAS pilus in these vectors. These data suggest that these constructs may serve a dual role in generating protective immune responses against HIV and GAS infections.

The induction of a potent humoral and cellular immune response in mucosal tissue is important for the development of an effective HIV vaccine. Most of the current HIV vaccines under development use the i.m. route for immunization, which is relatively poor in generating potent and long-lived mucosal immune responses. In this article, we explore the ability of an oral vaccination with a probiotic organism, Lactococcus lactis, to elicit HIV-specific immune responses in the mucosal and systemic compartments of BALB/c mice. We expressed the HIV-1 Gag-p24 on the tip of the T3 pilus of Streptococcus pyogenes as a fusion to the Cpa protein (LL-Gag). After four monthly LL-Gag oral immunizations, we observed strong Gag-specific IgG and IgA responses in serum, feces, and vaginal secretions. However, the Gag-specific CD8 T cell responses in the blood were at or below our detection limit. After an i.m. modified vaccinia Ankara/Gag boost, we observed robust Gag-specific CD8 T cell responses both in systemic and in mucosal tissues, including intraepithelial and lamina propria lymphocytes of the small intestine, Peyer’s patches, and mesenteric lymph nodes. Consistent with strong immunogenicity, the LL-Gag induced activation of CD11c+ CD11b+ dendritic cells in the Peyer’s patches after oral immunization. Our results demonstrate that oral immunization with L. lactis expressing an Ag on the tip of the group A Streptococcus pilus serves as an excellent vaccine platform to induce strong mucosal humoral and cellular immunity against HIV.

Glycosylation is the most abundant post-translational polypeptide chain modification in nature. Although carbohydrate modification of protein antigens from many microbial pathogens constitutes important components of B cell epitopes, the role in T cell immunity is not completely understood. Here, using ELISPOT and polychromatic flow cytometry, we show that O-mannosylation of the adhesin, Apa, of Mycobacterium tuberculosis (Mtb) is crucial for its T cell antigenicity in humans and mice after infection. However, subunit vaccination with both mannosylated and non-mannosylated Apa induced a comparable magnitude and quality of T cell response and imparted similar levels of protection against Mtb challenge in mice. Both forms equally improved waning BCG vaccine-induced protection in elderly mice after subunit boosting. Thus, O-mannosylation of Apa is required for antigenicity but appears to be dispensable for its immunogenicity and protective efficacy in mice. These results have implications for the development of subunit vaccines using post-translationally modified proteins such as glycoproteins against infectious diseases like tuberculosis.

Background The induction of a potent humoral and cellular immune response both in the peripheral and mucosal tissues is important for the development of an effective HIV vaccine. The present study explores the ability of a Lactococcus lactis (L. lactis), a probiotic organism, based oral vaccine to elicit HIV-specific immune responses in the mucosal and systemic compartments of mice and rhesus monkeys.

Chandipura virus (CHPV) has emerged as an important pediatric encephalitis-causing pathogen with very high mortality in India. No specific vaccine or treatment is available till date. We attempted to prepare a candidate vaccine employing recombinant CHPV Glycoprotein (rGp). The Glycoprotein gene (G-gene) of CHPV was expressed using Baculovirus expression system. The rGp was purified by HPLC and used for mice immunization, 3 doses, and 4 weeks apart. One microgram rGp was found to be optimum. Sero-conversion was observed as early as 2nd week by detecting anti-CHPV IgG antibodies. Antibody titres were immunogen-concentration dependent. Intracerebral challenge of the immunized mice with 100 LD50 of the homologous strain demonstrated 90% protection. In in vitro neutralization, antibodies from the immunized mice were able to neutralize heterologous viruses. There was 60% T cell proliferation observed against rGp in immunized mice. The study shows that rGp induces both arms of immune response and represents an ideal vaccine candidate for further evaluations.