While considerable developments have been made in treating Immunodeficiency Virus (HIV) infection, many aspects of its interactions with host factors remain an area of considerable research interest toward the hope of developing a cure. HIV is a retrovirus that enters host immune cells via recognition of transmembrane ligands (i.e. CD4, CCR5, CXC4) by viral envelope (gp41, gp120), allowing then for membrane fusion and subsequent virion production and/or genome integration. The complexity of managing treatment of a virus integrated into immune cell genomes presents unique therapeutic and research challenges which have long stymied complete viral clearance and necessitate continued basic science research.

Previous transcriptomic studies identified altered Annexin A5 (AnxA5) expression in T cell lines with varying susceptibility to HIV-1. AnxA5 is a member of the Ca+2-dependent, PtdSer-binding Annexin family of proteins. AnxA5 is demonstrably involved in the induction of membrane curvature, endocytic vesicle formation, shielding procoagulant enzymes from activation, and attenuating the proapoptotic innate immune response; however, its role in HIV infection remains unclear.

To study the potential interactions between AnxA5 and HIV, infections in the context of AnxA5 overexpression and stable knockdown were performed by plasmid or short-hairpin RNA (shRNA) expression, respectively. Exogenous overexpression of AnxA5 slightly increased the susceptibility of HEK293T cells to infection versus control cells. Knockdown of AnxA5 resulted in a 3-fold reduction of infection relative to scramble shRNA control cells. Combined, these data suggest that AnxA5 is a positive factor for HIV infection.

It was also found that virus production from the AnxA5 knockdown cells was reduced 2-fold. Moreover, the infectivity of virus produced from the shAnxA5 cells was reduced 3-fold compared to virus produced from control cells. These data suggest AnxA5 expression is required for virus production. Notably, reconstitution of AnxA5 expression in the knockdown HEK293T-shAnxA5 cell lines did not fully reconstitute HIV susceptibility. This suggests either the potential of off-target effects of shRNA knockdown or the potential that reconstitution of expression by exogenous ectopic plasmid was insufficient to restore the original subcellular expression profile of AnxA5.

Overall, these data identify AnxA5 as a cellular factor potentially involved in HIV replication. Further in vitro and in vivo studies are needed to elucidate the mechanism and clinical implications of this host-viral interaction.