Porcine xenograft transplantation raises concerns in humans about the risk of infection with porcine endogenous retroviruses (PERV) as they are an integral part of the pig genome and are therefore very difficult to exclude. In this study, for the first time, a relationship between the provirus genes sequences and released virions from pig cell line and the embedded sequence of this retrovirus in infected human cells was analyzed. PERV infection of human cells HEK-293 and HeLa and detection of PERV in pig PK-15 cells and supernatant were assessed by QPCR or RT-QPCR using primers specific for envA, envB, gag, pol genes and LTR region. Sequence analysis was performed at the DNA level and changes in the amino acid sequence were deduced in silico. Fifty nucleotide substitutions (45 in pol, 3 in gag and one each in envA and envB) were detected and most of these were heterozygous (42), which were present mainly in PK-15 cells. Our results show that sequence of the pol gene and the Pol protein is less conserved compared to the other PERV genes and PERV with some polymorphisms were not released from pig cells or/and do not infect human cells. PERV virions with a homozygous allele system were released from PK-15 cells, although their sequence replicated on the basis of the heterozygous PERV provirus sequence in PK-15. The newly discovered selective transduction of human cells with PERV will be helpful in studying the characteristics and genetic variability of the retrovirus genes to ensure safe xenotransplantation. Keywords: PERV; porcine endogenous retroviruses; infection; genetic polymorphism; xenotransplantation.