[Show abstract][Hide abstract] ABSTRACT: Developing a vaccine that overcomes the diversity of HIV-1 is likely to require a strategy that directs antibody (Ab) responses toward conserved regions of the viral Envelope (Env). However, the generation of neutralizing Abs (NAbs) targeting these regions through vaccination has proven to be difficult. One conserved region of particular interest is the membrane proximal external region (MPER) of Env located within the gp41 ectodomain. In order to direct the immune response to this region, the MPER and gp41 ectodomain were expressed separately as N-terminal fusions to the E2 protein of Geobacillus stearothermophilus. The E2 protein acts as a scaffold by self-assembling into 60-mer particles, displaying up to 60 copies of the fused target on the surface. Rabbits were immunized with E2 particles displaying MPER and/or the gp41 ectodomain in conjunction with DNA encoding full-length gp160. Only vaccines including E2 particles displaying MPER elicited MPER-specific Ab responses. NAbs were elicited after two immunizations that largely targeted the V3 loop. To overcome V3 immunodominance in the DNA component, E2 particles displaying MPER were used in conjunction with gp160 DNA lacking hypervariable regions V2, V3, or combined V1V2V3. All rabbits had HIV binding Ab responses and NAbs following the second vaccination. Using HIV-2/HIV-1 MPER chimeric viruses as targets, NAbs were detected in 12/16 rabbits after three immunizations. Low levels of NAbs specific for Tier 1 and 2 viruses were observed in all groups. This study provides evidence that co-immunizing E2 particles displaying MPER and gp160 DNA can focus Ab responses toward conserved regions of Env.
PLoS ONE 12/2014; 9(12):e113463. DOI:10.1371/journal.pone.0113463 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: SHIV models for HIV infection have been widely used in passive studies with HIV neutralizing antibodies (NAbs) to test for protection against infection. However, because SHIV-infected adult macaques often rapidly control plasma viremia and any resulting pathogenesis is minor, the model has been unsuitable for studying the impact of antibodies on pathogenesis in infected animals. We found that SHIVSF162P3 infection in one month-old rhesus macaques results not only in high persistent plasma viremia but also leads to very rapid disease progression within 12-16 weeks. In this model, passive transfer of high doses of neutralizing IgG (SHIVIG) prevents infection. Here, we show that at lower doses SHIVIG reduces both plasma and PBMC-associated viremia and mitigates pathogenesis in infected animals. Moreover, production of endogenous NAbs correlated with lower set-point viremia and 100% survival of infected animals. New SHIV models are needed in order to investigate whether passively transferred antibodies or antibodies elicited by vaccination that fall short of providing sterilizing immunity impact disease progression or influence immune responses. The one month-old rhesus macaque SHIV model of infection provides a new tool to investigate the effects of antibodies on viral replication and clearance, mechanisms of B cell maintenance and the induction of adaptive immunity in disease progression.
Journal of Virology 07/2013; 87(19). DOI:10.1128/JVI.00049-13 · 4.44 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To obtain proof of concept for HIV vaccines, we generated recombinant multimeric particles displaying the HIV-1 Envelope (Env) third hypervariable region (V3) as an N-terminal fusion protein on the E2 subunit of the pyruvate dehydrogenase complex of Geobacillus stearothermophilus. The E2 scaffold self-assembles into a 60-mer core that is 24 nm in diameter, with a molecular weight of 1.5 MDa, similar to a virus like particle with up to 60 copies of a heterologous protein accessible on the surface. Env(V3)-E2 multimers were tested alone and in combination with Env(gp160) DNA in mice and rabbits. Following two or more co-immunizations with Env(V3)-E2 and Env gp160 DNA, all 18 rabbits developed potent autologous neutralizing antibodies specific for V3 in six weeks. These neutralizing antibodies were sustained for 16 weeks without boosting, and comparable responses were obtained when lipopolysaccharide, a contaminant from expression in E. coli, was removed. Co-immunizations of Env(V3)-E2 and DNA expressing gp160 elicited moderate CD8-specific responses and Env-specific antibodies in mice. Co-immunization with DNA and E2 was superior to individual or sequential vaccination with these components in eliciting both neutralizing antibodies in rabbits and CD8(+) T cell responses in mice. Co-immunization with DNA and multimeric E2 scaffolds appears to offer a highly effective means of eliciting rapid, specific, and sustained immune responses that may be a useful approach for other vaccine targets.
PLoS ONE 02/2012; 7(2):e31464. DOI:10.1371/journal.pone.0031464 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Maternal HIV-1-specific antibodies are efficiently transferred to newborns, but their role in disease control is unknown. We administered neutralizing IgG, including the human neutralizing monoclonal IgG1b12, at levels insufficient to block infection, to six newborn macaques before oral challenge with simian-HIV strain SF162P3 (SHIV(SF162P3)). All of the macaques rapidly developed neutralizing antibodies and had significantly reduced plasma viremia for six months. These studies support the use of neutralizing antibodies in enhancing B cell responses and viral control in perinatal settings.
Nature medicine 10/2010; 16(10):1117-9. DOI:10.1038/nm.2233 · 27.36 Impact Factor