Background
In the gut, early HIV-1 (HIV) infection is associated with high HIV replication, CD4 T cell death, and microbial translocation. Among HIV proteins, Vpr remains enigmatic. In vitro, Vpr is linked to cell cycle arrest, DNA damage, apoptosis, and HIV replication in myeloid cells. Consistent Vpr phenotypes are lacking in CD4 T cells (CD4 Ts) when mitogen-activated blood cells or cell lines are utilized. These data are incongruous with Vpr being packaged in virions as it should exert influence early in infection, where CD4 Ts, particularly in the gut, are critical. To study interactions between primary gut T cells, transmitted/founder (TF) HIV, and translocating enteric bacteria ex vivo, we developed the Lamina Propria Aggregate Culture (LPAC) model. We previously demonstrated bacteria enhance HIV infection and contribute to HIV-mediated CD4 T cell death by inducing Granzyme B (GZB). Here, we investigated if Vpr plays a role in HIV replication and death in gut CD4 Ts using the physiologically-relevant LPAC model.
Methods
Jejunal LP mononuclear cells (n=8 donors) were infected with TF HIV (CH040) wildtype (WT), Vpr-deleted (ΔVpr), or mock in the presence or absence of commensal Escherichia coli lysate (10μg/ml). At 4 dpi, infection (p24), GZB, and total CD4 T cell counts were determined by flow cytometry. Infectious titer in supernatants was determined by TZM-bl assay.
Results
In the absence of bacteria, ΔVpr replicated to significantly lower levels than WT, with an 8.3-fold (p<0.05) reduction in the frequency of p24+ CD4 Ts and 7.4-fold (p<0.01) reduction in infectious titer. The lack of ΔVpr replication significantly rescued CD4 Ts from HIV-mediated death, with 8.9% depletion for ΔVpr versus 38.5% for WT (p<0.05). In the presence of E. coli, WT and ΔVpr virus had no significant difference in cellular infection levels or infectious titers. However, ΔVpr induced significantly lower levels of CD4 T cell depletion relative to WT (20.8% versus 42.3%, p<0.05). Total and HIV p24hi CD4 Ts from ΔVpr-infected cultures had lower levels of GZB versus WT.
Conclusions
Our findings demonstrate that Vpr is critical for robust HIV replication and depletion of gut CD4 T cells. In the context of microbial exposure, Vpr was dispensable for gut CD4 T cell replication, but still contributed to death, possibly by upregulating GZB expression. These data underscore Vpr as an essential component of the HIV life cycle in gut CD4 T cells and highlight novel functional attributes of HIV-Vpr in gut pathogenesis.
Table or Figure
