CROI 2016 Abstract eBook

Abstract Listing

Oral Abstracts

creates an opportunity for activated NK cells to target and kill latently infected primary T cells. We further hypothesized that broadly neutralizing antibodies (bnAb) recognizing the HIV envelope would be capable of mediating ADCC to target a wide range of HIV proviruses. Novel assays for NK cell effector function have been developed using both primary cell models of HIV latency and patient cells. For the primary cell models loss of HIV GFP expression and delivery of granzyme B are measured by flow cytometry. For patient cells loss of inducible cell-associated HIV mRNA and proviral DNA is measured using highly sensitive next generation sequencing readouts. When NK cells were cocultured with cells expressing IL-21, we observed dramatic NK cell expansion and enhancement of cytotoxicity against reactivated latently infected primary T cells. Using this protocol we are able to expand large numbers of highly cytotoxic NK cells that maintain their specificity for killing of infected cells and their ability to mediate ADCC. Importantly, this protocol is able to efficiently expand and activate NK cells from HIV + donors. We have identified a combination of the histone deacetylase inhibitor (HDACi) Panobinostat with the PKC agonist Bryostatin or the combination of IL-15 with the HDACi SAHA as regimens that can optimally reactivate HIV‑1 while inducing minimal changes in cell surface expression profiles. Coculture of NK cells with infected primary T cells led to preferential killing of reactivated cells. We have identified at least one anti-Env antibody that can strongly mediate ADCC and enhance selectivity of killing reactivated HIV-1-infected CD4 + T cells while sparing uninfected cells. This antibody demonstrates ADCC activity at both low antibody and low NK cell to target cell ratios. We have also identified three more anti-Env antibodies that can enhance ADCC. Enhancing NK cell activity may represent an important new approach to virus eradication. We are optimizing protocols that can be rapidly translated into the clinic that involve proviral and NK cell reactivation and enhancement of killing by ADCC. 181 Exposing Env: A New Strategy to Target HIV-1–Infected Cells by ADCC Andrés Finzi , CRCHUM, Montreal, QC, Canada Prevention of HIV-1 transmission and progression likely requires approaches that can specifically eliminate HIV-1-infected cells. There is increasing evidence supporting a role of Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC) in controlling HIV-1 transmission and disease progression. However, Env epitopes targeted by antibodies effective at mediating ADCC are poorly exposed on the unliganded HIV-1 envelope glycoprotein (Env) trimer. Indeed, HIV-1 has evolved a sophisticated mechanism to avoid exposure of ADCC-mediating Env epitopes by downregulating CD4 and by limiting the amount of Env at the cell surface. We observed that interaction of Env with the CD4 receptor was required for efficient exposure of ADCC-mediating Env epitopes. In that context, HIV-1-infected cells presenting HIV-1 Env in the CD4-bound conformation were found to be preferentially targeted by ADCC-mediating antibodies present in HIV+ sera. We therefore tested the capacity of rationally-designed CD4-mimetic compounds (CD4mc) to promote the CD4- bound conformation of Env and thereby sensitize HIV-1-infected cells to ADCC. We observed that certain CD4mc were able to induce the CD4-bound conformation of Env, thus enhancing the susceptibility of HIV-1-infected cells to ADCC. Of note, the ADCC-mediating activity in HIV+ sera appears to be mainly directed against the gp120 inner domain. Upon testing a panel of anti-Env antibodies we found that the anti-cluster A class mediated the most robust ADCC response. These antibodies bound Env with a unique angle of approach resulting in optimal Fc exposure. Thus, allowing for efficient engagement by Fcγ receptors present on effector cells. Altogether, our data suggest that forcing Env to expose highly-conserved epitopes, recognized by antibodies present in the sera of HIV-1-infected individuals, might represent a new approach for HIV eradication strategies.

Protection from ADCC

ADCC response

CD4

Env

Deletion of Nef andVpu

BST-2

Vpu

Nef

CD4-mimetics

Oral Abstracts

Vpu

Nef

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CROI 2016