A recent study from our lab showed that, in vitro, microbiomes containing higher levels of T. sanguinis induced more elevated frequencies of HLA-DR+CD38+CD4+ T cells, a marker of chronic activation, when whole microbiome bacterial isolates were cultured with PBMCs [2], suggesting a potential mechanistic relationship between T. sanguinis and T cell activation in the gut with untreated HIV infection. Here, CD38 is linked to HIV infectious disease.