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Recombinant DNA/MVA/ChAdV-63-elicited T cells specific for conserved regions of the HIV-1 proteome recognize HIV-1 infected cells and suppress HIV-1
© Ahmed et al; licensee BioMed Central Ltd. 2012
Published: 13 September 2012
Currently, immunogenicity assessments of candidate HIV-1 vaccines in human clinical trials rely on the use of peptides for sensitization of target cells. However, employment of HIV-1-infected cells provides more informative and relevant in vitro readouts of HIV-1 recognition.
A viral suppression assay (VSA) was developed to assess CD8+ T cell responses to infected autologous CD4+ targets using HIV-1 p24 levels as measured by flow cytometry and ELISA. In parallel, we also investigated live virus infected cells for re-stimulation of vaccine elicited T cells in an IFN-γ ELISpot assay.
HIV-1 infection kinetics is influenced by the multiplicity of infection (MOI) used to infect autologous CD4+ cells, with rapid kinetics observed at higher MOIs. For HIV-1 BaL optimal infection of autologous CD4+ cells was achieved at MOI of 0.05. In the VSA, HIV-1 BaL virus replication was shown to be sensitive to the chemokines MIP-1α and RANTES added in the absence of effector cells. Pre-activated effector cells indicated increased non-specific background suppression in healthy controls, which was reduced following a prolonged rest before co-culture with autologous CD4+ targets, but led to marked proliferation of the CD8+ T cell effectors. Preliminary investigations in vaccinees show that HIV-1 suppression mediated by CD8+ T cells can be detected in vitro following vaccination and that P24 ELISA has higher sensitivity than flow cytometry. As an alternative to the VSA, an IFN-γ ELISpot assay has also been optimized for the use of autologous HIV-1-infected CD4+ cells. Using both of the above assays, preliminary characterization of T cell responses induced in volunteers receiving pSG2.HIVconsv DNA, MVA.HIVconsv and ChAdV63.HIVconsv vaccines will be shown.
Two assays employing HIV-1 infected target cells were standardised and employed to characterize responses elicited in participants of the HIV-1 vaccine trial HIVCORE002 in Oxford, UK.
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.