Detailed mapping of determinants within the porcine endogenous retrovirus envelope surface unit identifies critical residues for human cell infection within the proline-rich region.
Replication-competent porcine endogenous retroviruses (PERVs) are either human cell tropic (PERV-A and PERV-B) or non-human cell tropic (PERV-C). We previously demonstrated that PERV in vitro cell tropism is modulated by 2 residues within the C terminus of SU and that the PERV receptor binding domain (RBD) extends beyond the variable regions A and B (VRA and VRB, respectively), to include the proline rich-region (PRR) of SU (M. Gemeniano et al., Virology 346:108-117, 2000; T. Argaw et al., J. Virol. 82:7483-7489, 2008). The present study aimed to identify the specific elements within the PERV RBD that interact with the C-terminal elements of SU to facilitate human cell infection. We constructed a series of chimeric and mutated envelopes between PERV-A and PERV-C and using pseudotyped retroviral vectors to map the human cell tropism-determining sequences within the PERV RBD. We show that the PRR from PERV-A is both necessary and sufficient to allow human cell infection when substituted into the homologous region of the PERV-C envelope carrying two C-terminal amino acid substitutions shown to influence human cell tropism, Q374R and I412V (PERV-Crv). Furthermore, substitution of a single amino acid residue in the PRR of the non-human-tropic PERV-Crv envelope allows vectors carrying this envelope to infect human cells. Receptor interference assays showed that these modified PERV-C envelopes do not bind either of the human PERV-A receptors, suggesting the presence of a distinct human PERV-C receptor. Finally, vectors carrying these modified PERV-C envelopes infect primary human endothelial cells, a cell type likely to be exposed to PERV in clinical use of certain porcine xenotransplantation products.
Gene Transfer and Immunogenicity Branch, Division of Cellular and Gene Therapies, Center for Biologics Evaluation and Research, FDA, Bethesda, Maryland, USA.
Takele
T
Argaw
Carolyn A
CA
Wilson
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D020077:Endogenous Retroviruses / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D017988:Gammaretrovirus / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D015686:Gene Products, env / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D011392:Proline / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D013552:Swine / Q000821:virology*; D056189:Viral Tropism; D053586:Virus Internalization
D015686:Gene Products, env; D011392:Proline