Scientific Publications by FDA Staff

J Virol 2008 Aug;82(15):7483-91

Identification of residues outside of the receptor binding domain that influence infectivity and tropism of porcine endogenous retrovirus.

Argaw T, Figueroa M, Salomon DR, Wilson CA

Wilson, CA, US FDA, Ctr Biol Evaluat & Res, Gene Transfer & Immunogen Branch, Div Cellular & Gene Therapies, Bldg 29B,Room 5NN22,8800 Rockville Pike, Bethesda, MD 20892 USA US FDA, Ctr Biol Evaluat & Res, Gene Transfer & Immunogen Branch, Div Cellular & Gene Therapies, Bethesda, MD 20892 USA Scripps Res Inst, Dept Mol & Expt Med, La Jolla, CA 93037 USA

Identification of determinants of human tropism of porcine endogenous retrovirus (PERV) is critical to understanding the risk of transmission of PERV to recipients of porcine xenotransplantation products. Previously, we showed that a chimeric envelope cDNA encoding the 360 N-terminal residues of the human-tropic PERV-A SU and the 130 C-terminal residues of the pig-tropic PERV-C SU and all of TM (PERV-A/C) showed a 100-fold decrease in infectivity titer on human cells (Gemeniano M et.al 2006). To identify residues important for human cell infection, we performed site-directed mutagenesis on each of the 9 residues, singly or in combination, that distinguish the C-terminal region of PERV-C from PERV-A. Of the 9 amino acids, two single amino acid substitutions, Q374R and I412V, restored the infectivity of human cells of the chimeric PERV-A/C to titers equivalent to PERV-A. In contrast, PERV A/C mutant envelope Q439P resulted in undetectable infection of human cells and an approximately 1000-fold decrease in control pig cells. Mutation of K441R rescued mutants that carried Q439P suggesting an incompatibility between the proline residue at this position and the presence of KK in the proteolytic cleavage signal. We confirmed this incompatibility with vectors carrying PERV-A envelope mutant R462K that were also rendered non-infectious. Finally, tropism of vectors carrying PERV-C envelope mutatants with only four amino acid changes in the C-terminus of PERV-C envelope, NHRQ436YNRP plus K441R, was shifted to one similar to PERV-A. Our results show an important and previously unrecognized role for infectivity and tropism for residues at the C-terminus of SU.