T cell function in the blood and gastrointestinal mucosa in HIV-1 infection

Abstract

Despite many efforts, HIV-1 infection remains a global health problem; an effective vaccine would provide the best chance of controlling the pandemic. Recently, HIV vaccine research has been focusing on the gut mucosal immune system and early immunological events, which may set the stage for the later appearance of clinical immunodeficiency. This thesis describes a method to obtain mucosal tissue, isolate mucosal mononuclear cells (MMC) and study degranulation and intracellular cytokine memory responses using polychromatic flow cytometry. Consistent and reproducible data were generated by adhering to validated Standard Operating Protocols (SOPs). Qualification of such methods is essential for use in vaccine clinical trials. Differences between the magnitude of single CD8 cytokine and degranulation responses between blood and gut were seen; however, the quality of T cell responses at the single cell level was remarkably similar in both compartments. Differences between small bowel and colon were also described and introduce another layer of complexity in the interpretation of mucosal responses to HIV-1. Differences in memory phenotypes and function between blood and gut, in addition to small and large bowel allow for better characterization of the cytotoxic potential of CD8+ and CD4+ T cells against HIV-1 infected cell targets. Finally, a significant positive correlation between IFNγ and degranulation responses were seen with the frequencies of central memory and granzyme B-containing CD8+ in the mucosa, but not in the blood. A better understanding of memory responses and cytotoxic potential against HIV-1 targets will be important in vaccine research; it may also help reshaping the current practice of empirically and unselectively fast-tracking potential immunogens to large-scale trials.