Haynes Vaccine Discovery Consortium
OVERVIEW:
The human immune system is capable of producing antibodies against HIV-1 envelope, yet these antibodies that are readily made fail to broadly neutralize a wide spectrum of transmitted/founder viruses. The HIV-1 envelope has several conserved vulnerable regions, but with natural infection and with envelope immunization, the B-cell arm of human and animal immune systems do not recognize these vulnerable envelope regions to make neutralizing antibodies. The researchers in the Haynes-led VDC are determining why broadly reactive neutralizing antibodies are not made, and studying how to design immunogens and adjuvants in vaccine formulations to overcome these roadblocks. Some species of broadly neutralizing anti-HIV-1 antibodies are polyreactive autoantibodies that can be directed at neutralizing viral molecules. The researchers are exploring the role of the immune system in silencing anti-HIV-1 antibodies, a process termed immune tolerance. They are exploring the hypothesis that a successful way to induce broadly reactive neutralizing antibodies to HIV-1 is to vaccinate with novel viral envelop structures reflective of conserved vulnerable envelope regions in formulations that will safely and transiently break tolerance to HIV-1, or to vaccinate with viral epitopes that cross react with host molecules, or with target host molecules that are selectively expressed on the surface of HIV-1 virions and infected cells.
RESEARCH OBJECTIVES:
1. To determine the spectrum of endogenous antigens to which broadly neutralizing antibodies bind, and determine the structure of neutralizing antibody Fab binding to autoantigens and to HIV-1 Env.
2. To develop new immunization strategies to promote survival and expansion of the antibody-producing B cells that produce antibodies against broadly reactive neutralizing determinants on HIV-1 Env.
3. To evaluate the immunogenicity of HIV-2 gp41 membrane proximal external region (MPER) epitopes in HIV-2 infected humans compared to HIV-1 infected subjects, and to determine the breadth, potency and epitope specificity of MPER-directed neutralizing antibodies elicited by natural infection and vaccination.
4. To establish administrative and computational biology cores to facilitate the proposed VDAC studies.
PROGRESS:
The Haynes-led VDC laboratories are developing immunogen formulations that trigger B-cells to produce antibodies. The investigators are determining the origins, development, physiology, and fates of marginal zone, transitional and B cell populations in animal models including mice and non-human primates. Researchers are determining the role of tolerance mechanisms and toll like receptor (TLR) signaling on control of HIV-1 envelope broadly reactive B cell activation.
Another VDC effort involves determining the role of lipid binding anti-HIV antibodies such as anti-phosphatidylserine (PS) autoantibodies to protection from HIV infection. The team has recently found that non-pathogenic anti-lipid antibodies that do not require beta-2-glycoprotein-1 for lipid binding do prevent HIV-1 and SHIVSF162P3 (and all R5 HIVs tested) from infecting peripheral blood mononuclear cells (PBMCs) in vitro. A prototype of non-pathogenic anti-lipid antibodies will be studied in vivo for the ability to protect against R5 SHIV mucosal infection.
Other VDC investigators are developing immunogens that are in native conformations and are being tested for induction of neutralizing antibodies. These include HIV Env immunogens with a spectrum of affinities for binding to broadly reactive neutralizing antibodies, and thermodynamically stable immunogens.
Still other researchers within the VDC have made single chain Fv 4E10 antibodies and whole IgG1 2F5 Mabs with mutations that selectively eliminate gp41 or lipid reactivity. The investigators have demonstrated that both 2F5 and 4E10 require the capacity to bind to lipids to neutralize HIV-1. They will now use the Fvs and Mabs in co-crystallization efforts with trimeric gp120/gp41 constructs to understand exactly how broadly neutralizing antibodies interact with intact virus particles in order to design better vaccine immunogens to induce these types of antibodies.
Another group within the VDC has designed gp41 peptide lipid conjugates that incorporate TLR-ligands as agonists using Envgp41 neutralizing epitopes. The researchers are characterizing the binding kinetics, and thermodynamic properties of immunogenic peptide conjugates.
Researchers within the VDC are characterizing the carbohydrates of HIV-1 Env produced in T cells and macrophages, and determining methods for making these “autoantigens” immunogenic. A researcher is studying the lipid-peptide conjugates for their structures by NMR.
Two collaborators have constructed HIV-1/HIV-2 chimeras with HIV-2 neutralizing determinants in HIV-1 scaffolds, to study the neutralization of HIV-2. Their investigative team has used phage display library technology to isolate monoclonal antibodies from patients with anti-gp41 MPER broadly neutralizing antibodies.
The team has made knock-in mice exploring the lower VH and VL immunoglobulin regions of the broadly neutralizing antibodies, 2F5 and 4E10, and is using these mice to determine tolerance control of expression of these antibodies and as well as using these animals for immunization to determine how best to induce broadly reactive neutralizing antibodies.
Finally, a team at the Tropical Disease Research Laboratory in Ndola, Zambia, has provided the CAVD with PBMCs and plasma from chronically infected subjects for mapping epitopes of broadly neutralizing antibodies for immunogen design.
Products expected to be derived from this VDC:
1. Year 3--Optimized peptide lipid constructs developed for optimal immunizations and neutralizing antibody binding
2. Year 4--Optimized peptide lipid constructs developed with optimal adjuvants; definition of the B cell subsets capable of making Broadly Neutralizing Antibodies by immunizing recombinant mice expressing two broadly neutralizing antibodies
3. Year 5--Preclinical toxicity and other regulatory studies on best immunogen and adjuvants from Year 1 to 3 studies.