In vitro sensitization of T cells with DC-associated/delivered HIV constructs can induce a polyfunctional CTL response, memory T-cell response, and virus suppression

Abstract

The absence of a suitable animal model for HIV infection is one of the major obstacles to the development of a preventive HIV vaccine. Vaccines showing good response in animal studies may fail in human efficacy trials. We have demonstrated DC-mediated in vitro sensitization of autologous T cells against three HIV constructs. The in vitro sensitized T cells were able to demonstrate a polyfunctional T-cell response, as well as central and effector memory T cells, and virus lysis in a virus inhibition assay, three potentially protective responses. However, none of the constructs could induce all three responses. Also there were variations from volunteer to volunteer. These may be due to genetic and other factors. This study provides evidence of an in vitro system that can be used to assess the immune response against a candidate vaccine, and may also provide the opportunity to modify vaccine constructs to achieve the goal of developing an ideal vaccine.

FIG. 1.

IFN-γ secretion by the sensitized T cells. The antigen-specific IFN-γ secretion was determined using an ELISPOT assay with pools of overlapping peptides from the Gag, Env, protease, integrase, reverse transcriptase, and Nef regions. MEV-, pVAXgag-, and IVC-4-sensitized T-cell responses are shown. The negative controls included MOCK (cells without any stimulation), BCL control, and No cell control, while PHA-P was used as the positive control. The unrelated response was determined against peptides from Yersinia pestis. The responses are plotted as spot-forming units (SFU) per million T cells.

FIG. 2.

The polyfunctional T-cell response. CD8⁺ T cells sensitized with pVAXgag (from all three donors, D-1, D-2, and D-3), and MEV (from donors D-1 and D-3) demonstrated secretion of multiple cytokines in response Gag peptides. The labels in the pie charts indicate the percentages of cells expressing the cytokines.

FIG. 3.

Inhibition of HIV replication by sensitized T cells. The functional ability of the sensitized T cells was determined in an in vitro assay using autologous CD8⁺ T cells using different E:T ratios (three in the case of MEV, and two in the case of pVAXgag and IVC-4). The culture supernatants were collected at three time points (days 3, 7, and 10) and tested for p24 antigen. The virus inhibition is plotted as the percentage of virus inhibition on the y axis. Color images available online at www.liebertonline.com/vim