HTLV-2 Encoded Antisense Protein APH-2 Suppresses HIV-1 Replication

Antisense protein of Human T-cell Leukemia Virus Type 2 (HTLV-2), also called APH-2, negatively regulates the HTLV-2 and helps the virus to maintain latency via scheming the transcription. Despite the remarkable occurrence of HTLV-2/HIV-1 co-infection, the role of APH-2 influencing HIV-1 replication kinetics is poorly understood and needs investigation. In this study, we investigated the plausible role of APH-2 regulating HIV-1 replication. Herein, we report that the overexpression of APH-2 not only hampered the release of HIV-1 pNL4.3 from 293T cells in a dose-dependent manner but also affected the cellular gag expression. A similar and consistent effect of APH-2 overexpression was also observed in case of HIV-1 gag expression vector HXB2 pGag-EGFP. APH-2 overexpression also inhibited the ability of HIV-1 Tat to transactivate the HIV-1 LTR-driven expression of luciferase. Furthermore, the introduction of mutations in the IXXLL motif at the N-terminal domain of APH-2 reverted the inhibitory effect on HIV-1 Tat-mediated transcription, suggesting the possible role of this motif towards the downregulation of Tat-mediated transactivation. Overall, these findings indicate that the HTLV-2 APH-2 may affect the HIV-1 replication at multiple levels by (a) inhibiting the Tat-mediated transactivation and (b) hampering the virus release by affecting the cellular gag expression.