Control of HIV-1 replication in vitro by vaccine-induced human CD8+ T cells through conserved subdominant Pol epitopes

Abstract

ObjectiveThe specificity of CD8+ T cells is critical for early control of founder/transmitted and reactivated HIV-1. To tackle HIV-1 variability and escape, we designed vaccine immunogen HIVconsv assembled from 14 highly conserved regions of mainly Gag and Pol proteins. When administered to HIV-1-negative human volunteers in trial HIV-CORE 002, HIVconsv vaccines elicited CD8+ effector T cells which inhibited replication of up to 8 HIV-1 isolates in autologous CD4+ cells. This inhibition correlated with interferon-γ production in response to Gag and Pol peptide pools, but direct evidence of the inhibitory specificity was missing. Here, we aimed to define through recognition of which epitopes these effectors inhibit HIV-1 replication.DesignCD8+ T-cells from the 3 broadest HIV-1 inhibitors out of 23 vaccine recipients were expanded in culture by Gag or Pol peptide restimulation and tested in viral inhibition assay (VIA) using HIV-1 clade B and A isolates.MethodsFrozen PBMCs were expanded first using peptide pools from Gag or Pol conserved regions and tested on HIV-1-infected cells in VIA or by individual peptides for their effector functions. Single peptide specificities responsible for inhibition of HIV-1 replication were then confirmed by single-peptide expanded effectors tested on HIV-1-infected cells.ResultsWe formally demonstrated that the vaccine-elicited inhibitory human CD8+ T cells recognized conserved epitopes of both Pol and Gag proteins. We defined 7 minimum epitopes, of which 3 were novel, presumably naturally subdominant. The effectors were oligofunctional producing several cytokines and chemokines and killing peptide-pulsed target cells.ConclusionsThese results implicate the use of functionally conserved regions of Pol in addition to the widely used Gag for T-cell vaccine design. Proportion of volunteers developing these effectors and their frequency in circulating PBMC are separate issues, which can be addressed, if needed, by more efficient vector and regimen delivery of conserved immunogens.

Ehrlichia ruminantium antigens and peptides induce cytotoxic T cell responses in vitro

“…Furthermore, conserved epitopes of influenza A virus were shown to induce protective immunity mediated by influenza specific B-and T cells [41]. In addition, vaccine-induced human CD8 + T cells through conserved subdominant Pol epitopes were able to control HIV-1 replication in vitro [42]. This knowledge complements our data that these epitopes may be useful in the design of a subunit vaccine.…”

Defining the HLA class I‐associated viral antigen repertoire from HIV‐1‐infected human cells

“…Underrepresentation of Pol‐derived peptides from primary infected CD4 + cells was notable and concurred with some previous reports , these peptides may be less abundantly presented on HLA‐I molecules in infected cells compared to Gag‐derived peptides. However, the number of vaccine‐elicited Pol‐specific CD8 + effectors has been shown to correlate with inhibition of HIV‐1 replication in autologous cells at least equally to Gag‐specific responses . Thirty‐two percent of the eluted peptides were not recognized in subjects used in this study that were naturally infected with HIV‐1.…”

Strategies for inducing effective neutralizing antibody responses against HIV-1

“…First, HIVconsv vaccines that include one or several isolated PTEs corresponding to functionally and structurally conserved subdominant regions of the viral proteins [131,134]. In clinical trials, these immunogens re-focused T cell immune responses to conserved epitopes [135,136]. Other mosaic sequences encode for viral proteins that contain as many PTEs as possible while trying to preserve a native-like conformation.…”