SIMIAN SARCOMA-ASSOCIATED VIRUS FAILS TO INFECT CHINESE-HAMSTER CELLSDESPITE THE PRESENCE OF FUNCTIONAL GIBBON APE LEUKEMIA-VIRUS RECEPTORS

We have sequenced the envelope genes from each of the five members of the gibbon ape leukemia virus (GALV) family of type C retroviruses. Fo ur of the GALVs, including GALV strain SEATO (GALV-S), were originally isolated from gibbon apes, whereas the fifth member of this family, s imian sarcoma-associated virus (SSAV), was isolated from a woolly monk ey and shares 78% amino acid identity with GALV-S, To determine whethe r these viruses have identical host ranges, we evaluated the susceptib ility of several tell lines to either GALV-S or SSAV infection. GALV-S and SSAV have the same host range with the exception of Chinese hamst er lung E36 cells, which are susceptible to GALV-S but not SSAV. We us ed retroviral vectors that differ only in their envelope composition ( e.g., they contain either SSAV or GALV-S envelope protein) to show tha t the envelope of SSAV restricts entry into E36 cells. Although unable to infect E36 cells, SSAV infects GALV-resistant murine cells express ing the E36-derived viral receptor, HaPit2. These results suggest that the receptors present on E36 cells function for SSAV. We have constru cted several vectors containing GALV-S/SSAV chimeric envelope proteins to map the region of the SSAV envelope that blocks infection of E36 c ells. Vectors bearing chimeric envelopes comprised of the N-terminal r egion of the GALV-S SU protein and the C-terminal region of SSAV infec t E36 cells, whereas vectors containing the N-terminal portion of the SSAV SU protein and C-terminal portion of GALV-S fail to infect E36 ce lls. This finding indicates that the region of the SSAV envelope prote in responsible for restricting SSAV infection of E36 cells lies within its amino-terminal region.