Molecular characterization of the porcine endogenous retrovirus subclass A and B envelope gene from pigs

Xenotransplantation of porcine organs has the potential to overcome the current critical shortage of allogenic organs for transplantation in humans. However, the existence of porcine endogenous retroviruses (PERVs) presents a problem for the clinical use of xenografts from pigs. In an attempt to understand the molecular characteristics of PERVs, we cloned the PERV env gene from six pig breeds (ie, Berkshire, Duroc, Landrace, Yorkshire, and two types of miniature pigs) in Korea. A total of 141 env clones were isolated and their sequences were analyzed. Phylogenetic analyses of these genes revealed the presence of PERVs, from both classes A and B, in 54% and 46% of the env clones, respectively. Among these clones, 37 isolates had the correct open reading frame (ORF; 27 clones in subclass A and 10 clones in subclass B), while the others had premature termination. These PERV nucleotide sequences can be used in a database for comparisons of PERV distribution among different pig breeds and for monitoring PERV infection using isolates with functional ORFs. Recombinant envelope of subclass A and B with functional ORF was expressed by vaccinia virus systems. Additionally isolated env clones can be used for various experiments, such as PERV control and infectivity tests, and may enhance the understanding of molecular mechanisms through pseudotyped PERV viruses.