The role of IFN-gamma Elispot assay in HIV vaccine research

The interferon (IFN)-gamma Elispot assay has been widely used as a general screening method for the quantification and characterization of the human immunodeficiency virus (HIV)-specific CD8+ T cell responses. However, the predictive power of this assay has been challenged due to the lack of efficacy of a recently conducted HIV vaccine phase IIb trial, despite induction of robust Elispot responses. This finding plus improvements in multiparameter flow cytometry, which has the potential advantage of simultaneously quantifying numerous parameters, raises questions regarding the future role of IFN-gamma Elispot as a gateway to moving forward with clinical trials of candidate vaccines. However, the IFN-gamma Elispot assay has been, unlike other techniques, evaluated and validated in several proficiency panels and is advantageous in cost-effectively detecting and mapping T-cell responses. Here we present a detailed protocol for a state-of-the-art 3-d IFN-gamma Elispot assay and review further advantages and disadvantages of this method for the characterization of HIV-specific CD8+ T cell responses.