Directly Infected Resting CD4+T Cells Can Produce HIV Gag without Spreading Infection in a Model of HIV Latency

Abstract

Despite the effectiveness of highly active antiretroviral therapy (HAART) in treating individuals infected with HIV, HAART is not a cure. A latent reservoir, composed mainly of resting CD4+T cells, drives viral rebound once therapy is stopped. Understanding the formation and maintenance of latently infected cells could provide clues to eradicating this reservoir. However, there have been discrepancies regarding the susceptibility of resting cells to HIV infection in vitro and in vivo . As we have previously shown that resting CD4+T cells are susceptible to HIV integration, we asked whether these cells were capable of producing viral proteins and if so, why resting cells were incapable of supporting productive infection. To answer this question, we spinoculated resting CD4+T cells with or without prior stimulation, and measured integration, transcription, and translation of viral proteins. We found that resting cells were capable of producing HIV Gag without supporting spreading infection. This block corresponded with low HIV envelope levels both at the level of protein and RNA and was not an artifact of spinoculation. The defect was reversed upon stimulation with IL-7 or CD3/28 beads. Thus, a population of latent cells can produce viral proteins without resulting in spreading infection. These results have implications for therapies targeting the latent reservoir and suggest that some latent cells could be cleared by a robust immune response.

Cyclin T1 and CDK9 T-Loop Phosphorylation Are Downregulated during Establishment of HIV-1 Latency in Primary Resting Memory CD4+T Cells

“…The HIV-1 latent reservoir in memory CD4 ϩ T cells is believed to be generated when activated CD4 ϩ T cells are infected as they are making the transition to a resting memory phenotype (4), although infection of resting cells can also occur (42,43). As the infected cells revert to a metabolically quiescent state, productive transcription of the integrated provirus is shut down (44).…”

Exploring the Potential of Monoclonal Antibody Therapeutics for HIV-1 Eradication

“…Along these lines, previous studies using anti-CD3/28 and interleukin (IL)-7 treatment resulted in Env expression, 59 supporting the possibility that this target can be induced. However, it remains unclear to what extent Env may be expressed on LRAreactivated cells, and specifically which Env epitopes may be expressed most broadly on reactivated cells.…”

“…However, it remains unclear to what extent Env may be expressed on LRAreactivated cells, and specifically which Env epitopes may be expressed most broadly on reactivated cells. Interestingly, in an in vitro resting latency model, negligible levels of Env were detectable in resting cells 59 and ex vivo virion production with LRAs remains elusive, 22 suggesting that much work is necessary to define whether Env is a viable target and consequently which epitopes may serve as the best targets.…”

Pharmacologic HIV-1 Nef blockade promotes CD8 T cell–mediated elimination of latently HIV-1–infected cells in vitro

“…Overall, HIV-1 Gag + cell median frequency was 1.7% in medium alone compared with median 6.2% cells stimulated with IL-15 for 6 days in HAART (P = 0.008). Few HIV-1 Gag + cells are detected in infected cultures without any stimulation, and such HIV-1 Gag-producing resting HIV-1-infected CD4 T cells have previously been reported (39). Furthermore, such resting HIV-1 Gag + T cells are also detected in vivo in the PBMC of donors on suppressive HAART (9)(10)(11).…”

“…HIV-1 Gag-expressing resting CD4 T cells have been described in nonspreading infection (39), and importantly, these cells can be targeted for clearance by autologous CD8 T cells in in vitro assays (10). The degree to which these in vitro latently infected cells were eliminated by CD8 T cells inversely correlated with the size of the in vivo reservoir (10), suggesting that CD8 T cell-mediated in vitro elimination would be physiologically relevant if tested clinically.…”