Annual and Interim Progress Report Summaries
Principal Investigator: Robin Weiss
Project: Vaccine-Induced Protective Cross-Neutralization of HIV-1
Submitted July 31, 2012
The main objective is to design immunogens which elicit antibody protection against HIV-1 infection.
Related to activity 1, the characterization of novel HIV-1 neutralizing monoclonal antibodies (NMAbs), we isolated two extraordinarily broad and potent llama single chain VHH which each strongly neutralize >94% of HIV-1 strains of various subtypes (clades) by interaction with the CD4 binding site (CD4bs) of gp120. Five novel human NMAbs from HIV-1-infected subjects were isolated. HIV-1 mutations resulting in neutralization escape from human and llama NMAbs were characterized.
For activity 2, the selection and characterization of lead immunogens , we produced recombinant trimeric gp140 envelope proteins from six HIV-1 strains and selected CA018 (derived from a CRF_02A/G African isolate) as the most promising immunogen. We used recombinant and alanine scanning libraries to derive enmvelope variants for comparison to our best trimeric gp140 glycoproteins. We adopted an “immunofocussing” method based on gluteraldehyde cross-lining of lysine residues to derive envelope Ags which focus the immune response to the CD4bs.
For passive protection, we used human NMAb HGN194 and its afucosyl and lala mutants and converted HGN194 IgG to IgA to test protection from mucosal challenge by subtype C SHIV (simian-human hybrid virus).
For active immunization, we evaluated potential lead immunogens in small animals using a heterologous DNA prime, protein boost regimen to elicit neutralizing antibodies. We selected CA018 recombinant trimeric envelope gp140 to take forward into a NHP study. We showed that a combination of two non-interefering adjuvants, MF59 and Carbopol 971 (C971) is more potent in eliciting neutralizing antibodies than either adjuvant alone. We have begun to immunize MHC and Trim5α genotyped Rhesus monkeys for a vaccine trial of CA018 gp140 with MF59/C971 adjuvant in comparison to boosts with envelope-based peptides followed by subtype C SHIV challenge.