HuPAR1 and HuPAR2 function for PERV-A 14/220* infection. HuPAR1 and HuPAR2 C-terminally tagged eGFP constructs were expressed in non-permissive SIRC cells. Stable lines were sorted by eGFP expression to yield cell populations with similar receptor expression levels. PERV pol copy number in 250 ng genomic DNA of infected SIRC/receptor-expressing cell lines was determined to assess receptor function. HuPAR2 PERV pol copy number was normalized by HuPAR1 PERV pol copy number in each experiment and expressed as percent of HuPAR1 function. The average function determined by three individual infection experiments with three replicates each is shown with standard errors. HuPAR2 is 11-fold more functional than HuPAR1 (p < 0.001).