# De Novo Expressed Vpr Stimulates HIV-1 Replication in T Cells

## TL;DR

This paper shows that newly produced Vpr, not prepackaged Vpr, mainly boosts HIV-1 replication in T cells.

## Contribution

The study introduces a T cell system to distinguish the roles of virion-associated and de novo expressed Vpr in HIV-1 replication.

## Key findings

- De novo synthesized Vpr has a dominant effect on HIV-1 replication in T cells.
- Virion-associated Vpr likely does not drive replication in proliferating T cells.
- Antagonism of preintegration silencing by Vpr may be more important in non-dividing T cells.

## Abstract

Vpr, a virion-associated accessory virulence factor of HIV-1, promotes virus replication in both T cells and macrophages. Although Vpr’s early activity—antagonism of preintegration silencing and host restriction factors—has been documented, the relative contribution of virion-associated versus de novo expressed Vpr to HIV-1 replication fitness remains unclear. Here, we developed a T cell-based system that genetically separates early and late Vpr functions by combining tetracycline-inducible Vpr expression in CEM.SS T cells with vpr-deficient HIV-1 constructs and Gag p6 mutations that block Vpr packaging. CEM.SS T cells have been shown to recapitulate the positive effect of Vpr on HIV-1 replication observed in activated primary T cells. Using pairwise replication fitness assays under spreading infection conditions, we demonstrate that de novo synthesized Vpr exerts the dominant effect on HIV-1 replication in T cells, while virion-associated Vpr plays a lesser role. Somewhat unexpectedly, our findings reveal that antagonism of preintegration HIV-1 silencing by virion-associated Vpr is unlikely to be the major driver of enhanced HIV-1 replication in proliferating T cells. Instead, this function may play a more prominent role in the infection of non-dividing T cells and/or other cell types.