Characterization and evaluation of approaches to elicit Broadly Reactive Neutralizing Antibodies against HIV-1
Despite 25 years of research, an HIV-1 vaccine remains elusive. Eliciting broadly reactive-neutralizing antibodies (BR-NAbs) against HIV-1 envelope glycoprotein is hindered by high sequence variability, epitope masking, decoy epitopes and low immunogenicity. Accurate assessment of the immunogenic properties of envelope is an important goal towards designing antigens capable of eliciting BR-Nabs. This body of work consists of three projects aimed at characterizing humoral immune responses in HIV-1 infected patients, and evaluation of novel approaches to elicit BR-NAbs. In the first component, five soluble GST-fusion proteins were generated, each encompassing fragments of gp41 ectodomain, an important vaccine target for several BR-NAbs. These proteins allowed characterization of patient antibody response profiles against different regions of gp41, and neutralizing activity was compared among patients with variant responses. We identified several patients who mounted antibodies against epitopes near or overlapping with those targeted by BR-NAbs 2F5 or 4E10, suggesting such antibodies may not be as rare in patients as has previously been thought.
Today, vaccines target either conserved structures common across all viruses, or diverse neutralizing domains to generate a broad polyclonal response. During HIV-1 entry, envelope protein undergoes major conformational changes, exposing conserved epitopes.
In the second project, we generated two transgenic mouse lines expressing human CD4 with or without CCR5 on the surface of murine B-cells. These mice were used to target humoral responses against conserved fusion-intermediate structures of envelope exposed transiently during receptor binding events.
Lastly, we hypothesize that polyclonal antibodies against multiple epitopes from diverse viral strains will exhibit greater breadth of neutralizing activity against HIV-1 isolates than any single immunogen. In this study, a novel technique was established to generate considerable diversity within the hypervariable V3 sequence, representing the majority of circulating subtype B HIV-1 variants. These polyvalent V3 sequences were represented either proportionally or equivalently to the observed frequency of V3 amino acids in primary isolates. This diversity is extensive yet specific, and can be easily manipulated.
Taken together, the panel of soluble gp41-fusion proteins, transgenic mice and polyvalent V3 antigens will be important tools for better understanding humoral immune responses against envelope and for future vaccine development.
School:Case Western Reserve University
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:hiv aids vaccine neutralizing antibodies transgenic mice gp41 polyvalent v3
Date of Publication:01/01/2008