Nonhuman Primate IFITM Proteins Are Potent Inhibitors of HIV and SIV

June Nonhuman Primate IFITM Proteins Are Potent Inhibitors of HIV and SIV Jordan Wilkins 0 1 Yi-Min Zheng 0 1 Jingyou Yu 0 1 Chen Liang 1 Shan-Lu Liu 0 1 0 Department of Molecular Microbiology and Immunology, Bond Life Sciences Center, University of Missouri , Columbia , Missouri, United States of America, 2 Lady Davis Institute, Jewish General Hospital , Montreal, Quebec , Canada , 3 Departments of Medicine, Microbiology & Immunology, McGill University , Montreal, Quebec , Canada 1 Editor: Aftab A. Ansari, Emory University School of Medicine , UNITED STATES Interferon-induced transmembrane (IFITM) proteins are potent antiviral factors shown to restrict the infection of many enveloped viruses, including HIV. Here we report cloning and characterization of a panel of nonhuman primate IFITMs. We show that, similar to human IFITM, nonhuman primate IFITM proteins inhibit HIV and other primate lentiviruses. While some nonhuman primate IFITM proteins are more potent than human counterparts to inhibit HIV-1, they are generally not effective against HIV-2 similar to that of human IFITMs. Notably, depending on SIV strains and also IFITM species tested, nonhuman primate IFITM proteins exhibit distinct activities against SIVs; no correlation was found to support the notion that IFITM proteins are most active in non-natural primate hosts. Consistent with our recent findings for human IFITMs, nonhuman primate IFITM proteins interact with HIV-1 Env and strongly act in viral producer cells to impair viral infectivity and block cell-to-cell transmission. Accordingly, knockdown of primate IFITM3 increases HIV-1 replication in nohuman primate cells. Interestingly, analysis of DNA sequences of human and nonhuman primate IFITMs suggest that IFITM proteins have been undergoing purifying selection, rather than positive selection typical for cellular restriction factors. Overall, our study reveals some new and unexpected features of IFITMs in restricting primate lentiviruses, which enhances our understanding of virus-host interaction and AIDS pathogenesis. - OPEN ACCESS Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Funding: This work was supported by a grant from NIH to SLL (R01 AI112381) and a grant from Canadian Institutes of Health Research to CL (MOP133479). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. Introduction Following detection of pathogen-associated molecular patterns (PAMPs), cells produce and secrete interferon [ 1, 2 ]. Interferons are cytokines that upregulate the expression of hundreds of interferon-stimulated genes (ISGs) and represent one of the cells first lines of defense against viruses [3]. Several ISGs have been characterized with antiviral activity, including Tetherin, TRIM5α, APOBEC3G, SAMHD1, and MxB [ 4–11 ]. The interferon-induced transmembrane (IFITM) proteins are a subset of ISGs known to restrict several enveloped viruses including, but not limited to, influenza A virus (IAV), dengue virus, Ebola virus, SARS coronavirus, hepatitis C virus (HCV), Jaagsiekte sheep retrovirus (JSRV) and human immunodeficiency virus (HIV) [ 12–19 ]. In humans, five IFITM isoforms have been discovered thus far [ 20 ]. IFITM5 is found in osteoblasts and functions in bone mineralization while IFITM10 has an unknown function [ 21, 22 ]. The remaining three members (IFITM1, 2, and 3) have been characterized with antiviral activity [ 20, 23 ]. The IFITM proteins are localized to both the plasma membrane and the endosomal membranes where they are thought to restrict viral entry by directly modulating cell membranes or antagonizing components of the viral structure [ 19, 24–29 ]. While the exact topology of IFITMs remains unclear, studies have suggested that the IFITMs have full or partial membrane-spanning regions, with the N-terminus and a conserved central region on the cytosolic side and the C-terminus being extracellular [ 26, 30, 31 ]. The N-terminus of human IFITM2 and IFITM3 contain an additional 20 or 21 amino acids, respectively, compared to IFITM1. This extended N-terminal region contains a tyrosine residue (Y20) that is important for IFITM localization and their antiviral activity [ 32–34 ]. Recently, the PPxY motif of IFITM3 was discovered to interact with the NEDD4 E3 ligase that causes IFITM3 ubiquitination [ 35 ]. Cysteine residues C71, C72, and C105 in IFITM3, which are also conserved in IFITM1 and IFITM2, are palmitoylated and contribute to its antiviral function [ 24, 31 ]. Two phenylalanine residues (F75 and F78) in IFITM3 mediate interaction amongst the IFITMs, increasing IFITM3 antiviral properties [36]. Interestingly, IFITM proteins have also been shown to promote infection or replication of some viruses, although the underlying mechanisms remain to be de (...truncated)