Nonhuman Primate IFITM Proteins Are Potent Inhibitors of HIV and SIV

Wilkins, Jordan; Zheng, Yi-Min; Yu, Jingyou; Liang, Chen; Liu, Shan-Lu

Recently, our lab demonstrated that human IFITM proteins contribute to HIV-1 restriction by antagonizing envelope protein (Env), thereby impairing viral fusion, infectivity and cell-to-cell infection [29] . We sought to ask if association of human IFITM with HIV-1 Env is conserved in OWM IFITMs. Because of its strong inhibition of HIV-1 infectivity (Fig 1) , we chose L'Hoest's IFITMs to represent OWM. We co-transfected 293T cells with HIV-1 NL4.3 and flag-tagged human or L'Hoest's IFITMs, followed by immunoprecipitation using anti-flag beads. Both human and OWM IFITM3 proteins were capable of interacting with HIV-1 Env in a dose-dependent manner, showing that IFITM-envelope interaction has been evolutionarily conserved (Fig 3A) . When we compared the band intensity ratios between immunoprecipitated HIV-1 Env gp41 and flag-IFITM3, we found an approximate 20% increase in OWM IFITM3 interaction with HIV-1 Env compared to that with human IFITM3 (Fig 3B) ; this was despite the relatively low levels of Env expression in the OWM IFITM3-expressing cells as compared to cells expressing human IFITM3 (Fig 3A; see gp120 and gp41 blots). Human IFITM1 had no significant interaction HIV-1 Env (Fig 3A) . Both human and OWM IFITM3 proteins inhibited the processing of Env precursor into gp120 and gp41 (Fig 3A, top panel) , whereas the IFITM1 protein downregulated the expression of HIV-1 Env and Gag at higher doses of transfection (Fig 3A; see gp41 and p24 blots) similar to our recent study [29] . These results demonstrate that Env interaction with IFITMs, as well as their effects on Env processing, are evolutionarily conserved among human and nonhuman primates species and that the increased interaction between L'Hoest's IFITM3 and HIV-1 Env somewhat correlates with the enhanced antiviral effect.