Nonhuman Primate IFITM Proteins Are Potent Inhibitors of HIV and SIV

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

HIV has adapted various mechanisms to escape host restriction [42] . While it was previously shown that IFITMs from African green monkey (AGM) are capable of restricting both HIV-1 and SIVagm to varying degrees [49] , we further sought to know if the IFITMs from additional nonhuman primates are capable of restricting HIV. To do so, we cloned IFITM1 and IFITM3 from 8 nonhuman primate cell lines belonging to the families Cercopithecidae (old world monkey; OWM) and Hominidae (hominoids), stably expressed them in the CD4+ T cell line SupT1, and tested their ability to restrict HIV (Table 1, Fig 1) . SupT1 cells were infected with HIV-1 (NL4.3 or BH10) or HIV-2 bearing VSV-G in order to achieve efficient infection, and newly produced virus was harvested 48 hours later. Infectivity of newly generated virus was measured using the indicator cell line HeLa-TZM-bl (TZM-bl), which is susceptible to both CXCR4 and CCR5 tropic viruses. Against HIV-1 NL4.3, we found that both human IFITM1 and IFITM3 had less than a two-fold reduction in infectivity, similar to our previous results [50] , while we found up to an approximate 5-and 10-fold reduction in infectivity for the majority of nonhuman primate IFITM1 and IFITM3 tested (Fig 1A) . Against HIV-1-BH10, human IFITM1 resulted in an approximate 4-fold reduction in infectivity while human IFITM3 caused less than a 2-fold reduction (Fig 1B) , again paralleling our previous reports [15, 51] . Notably, nonhuman primate IFITM1 and IFITM3 reduced HIV-1 BH10 infectivity up to 10-and 6-fold, respectively ( Fig 1B) . Interestingly, against HIV-2, we found only a two-fold reduction in infectivity against almost all species of IFITMs ( Fig 1C) . Similar to human IFITMs [29, 32] , nonhuman primate IFITMs did not significantly inhibit release of HIV-1 and HIV-2 from viral producer cells based on their RT activities (data not shown). Western blotting analysis showed that the expression levels of these nonhuman primate IFITMs were approximately comparable to their human counterparts ( Fig 1D) . Altogether, these results suggest that HIV-1 is strongly, but differentially, restricted by IFITMs of nonhuman primate species.