CROI 2017 Abstract e-Book

Abstract eBook

Poster and Themed Discussion Abstracts

Results: Through screening of 90 plasma samples we observed moderate neutralization among 28 samples (Table: 1). Neutralization potency among viremic non-progressors were significantly higher than typical progressors (p=0.043). Remarkably, we were able to identify 4 elite neutralizers with geometric mean ID[50] titer between 500 and 700 and three of themwere viremic non-progressors. Epitope mapping of those elite neutralizers were not specific to known targets like V2, V3, CD4bs and MPER region. Interestingly, the top most elite neutralizer has neutralized N301A mutant virus with 2.0 fold greater than the wild type. When assessed its CD4bs neutralization activity by treating with RSC3 protein, there was 1.5 fold drops in the ID[50] titer to the untreated plasma. Conclusion: These results demonstrate that viremic non-progressors develop bnAb response and it suggests that provision of CD4 helper T cells is critical for formation of functional germinal centre. This bnAb response was associated with the presence of CD4bs Abs and it is due to viral escape in N301 glycan of V3 region which may expose occluded conserved epitope that facilitating the development of breath among elite neutralizers.

Poster and Themed Discussion Abstracts

246 USING EMPIRIC SATURATION MUTAGENESIS TO IDENTIFY NOVEL ENV TRIMERS FOR VACCINES

Maria Jose Duenas Decamp 1 , Li Jiang 2 , Dan Bolon 1 , Paul Clapham 1 1 Univ of Massachusetts, Worcester, MA, USA, 2 Harvard Univ, Boston, MA, USA

Background: Protective HIV-1 vaccines may need to induce antibodies that neutralize diverse HIV-1. A major target for cross-reacting neutralizing antibodies (nabs) is the CD4 binding site (CD4bs) on the envelope glycoprotein trimer (Env). There is an urgent need to identify novel Env trimers where the CD4bs is optimally displayed without exposing immunogenic sites that induce non-neutralizing antibodies or strain specific nabs. We used a novel saturation mutagenesis approach, EMPIRIC (Exceedingly Meticulous and Parallel Investigation of Randomized Individual Codons) to investigate effects of the CD4 binding loop on trimer structure and identify Env mutants with enhanced exposure of the CD4bs. This region of Env contains (1) CD4 contact sites, (2) residues that modulate trimer opening and (3) sites that influence macrophage-tropism. Here, we describe Env mutants that carry a more exposed CD4bs yet differ in the exposure of the V3 loop at the trimer apex. Methods: Using EMPIRIC, we prepared plasmid libraries for all possible mutations covering the CD4 binding loop region (aas 361-380). Libraries were cloned into LN40 env (from an AIDS patient lymph node) incorporated in a replication competent pNL4.3 chimera. LN40/NL4.3 libraries were transfected into 293T cells and progeny virus rescued. This virus was used to infect PBMCs and the replication fitness of each mutant estimated by deep sequencing progeny virus. Env mutants that conferred wt replication or higher were investigated for their properties via Env+ pseudoviruses using Env mabs via neutralization and a trimer binding assay. Results: Env mutants were identified that carried an exposed CD4bs and a modified trimer apex. These included mutants with substitutions at 373, 375, 377 and 380. Several substitutions at residue 380 resulted in a more exposed CD4bs and a modified trimer apex with an exposed V3 loop. In contrast, while substitutions at residue 375 also resulted in enhanced Env:CD4 interactions, the V3 loop remained occluded. The same observations were made when these substitutions were introduced into another clade B Env and a clade C Env. Conclusion: We identified specific residues in the CD4 binding loop that expose the CD4bs, yet differ in their effects on the trimer apex and V3 loop in clade B and C Envs. Env mutants that enhance the exposure of the CD4bs yet maintain a closed trimer structure with the V3 loop occluded may be desired immunogens for inclusion in vaccines aimed at eliciting CD4bs nabs. 247 OLEANOLIC ACID DERIVATIVE OKS3-019 AS A NOVEL BIFUNCTIONAL HIV-1 ENTRY INHIBITOR Shigeyoshi Harada 1 , Kasumi Ogihara 2 , Yuta Hikichi 1 , Tetsuro Matano 1 , Tetsuo Narumi 2 , Kazuhisa Yoshimura 1 1 Natl Inst of Infectious Diseases, Shinjuku-ku, Tokyo, Japan, 2 Shizuoka Univ, Hamamatsu, Shizuoka, Japan Background: CD4 mimetic small compounds, such as NBD-556, act as a bifunctional entry inhibitor of HIV-1 with respect to both neutralizing antibody activation and entry inhibition. Recently, we have also developed novel bifunctional entry inhibitors that target non-CD4-binding site of HIV-1 based on oleanolic acid derivatives. In this study, we demonstrated the antiviral potency of a selected set of oleanolic acid derivatives. Methods: Oleanolic acids are the common starting material for the synthesis of novel bifunctional entry inhibitors. The susceptibility of the infectious HIV clones to the entry inhibitors and neutralization sensitivity to anti-HIV neutralizing antibodies (NAbs) were determined using the TZM-bl assay. We also examined synergistic effect between the oleanolic acid derivatives (OKS compounds) and seven NAbs targeting different domains in gp120 and gp41 (b12, 2F5, 4E10, 447-52D, KD-247, 2G12 and PG16) .

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CROI 2017