Anti-HIV CD4+ and CD8+ assay allows rapid estimation of anti-HIV T cell response

A rapid assay that allows detection of anti-HIV CD4+ and CD8+ T cells in whole blood is described by German researchers in the December 1st issue of AIDS. According to the report, the assay may be useful for monitoring clinical trials and vaccination studies. Dr. Andreas Meyerhans from the University of Saarland in Homburg and colleagues explain that the ability to characterize and quantify antibody-mediated immune responses is commonplace. They note, however, that analysis of cellular immune responses is performed only in specialized laboratories because of the need for extensive sample preparation or characterization of human leukocyte antigens or epitopes.

In the present study, the authors describe a whole blood assay that allows the simultaneous quantification and characterization of HIV-specific CD4+ and CD8+ T cell responses. The study team stimulated whole blood from 33 HIV-infected individuals with the HIV-1 structural protein Pr55 Gag for 6 hours, and assessed intracellular cytokine production by flow cytometry.

The study team found that, compared with solubilised Pr55 Gag, virus-like particles containing Pr55 Gag protein were significantly more efficient in stimulating HIV-1-specific CD4+ and, particularly, CD8+ T cell responses. According to the paper, “simultaneous analysis of CD8+ and CD4+ cells revealed that a cellular HIV-1-specific gag-specific immune response was detectable in all tested HIV-infected individuals not receiving antiretroviral therapy.” In addition, HIV-1-specific CD8+ T cells were present at a significantly higher frequency than were CD4+ T cells.

The investigators also found that continuous antiretroviral therapy resulted in a significant reduction in the numbers of HIIV-gag-specific CD4+ and, particularly, CD8+ T cells. In light of their findings, Dr. Meyerhan’s team concludes that the “assay provides a rapid estimate of the total antiviral T cell resources.” They add that the test may be efficiently used to monitor the success of immuno-therapeutic combination therapy or vaccination studies.