Multiple groups of novel retroviral genomes in pigs and related species

In view of the concern over potential infection hazards in the use of porci ne tissues and organs for xenotransplantation to humans, we investigated th e diversity of porcine endogenous retrovirus (PERV) genomes in the DNA of d omestic pigs and related species. In addition to the three known envelope s ubgroups of infectious gamma retroviruses (PERV-A, -B, and -C), classed tog ether here as PERV group yl, four novel groups of gamma retrovirus (gamma2 to gamma5) and four novel groups of beta retrovirus (beta1 to beta4) genome s were detected in pig DNA using generic and specific PCR primers. PCR quan tification indicated that the retroviral genome copy number in the Landrace x Duroc F-1 hybrid pig ranged from 2 (beta2 and gamma5) to approximately 5 0 (yl). The gamma1, gamma2, and beta4 genomes were transcribed into RNA in adult kidney tissue, Apart from gamma1, the retroviral genomes are not know n to be infectious, and sequencing of a small number of amplified genome fr agments revealed stop codons in putative open reading frames in several cas es. Analysis of DNA from wild boar and other species of Old World pigs (Sui dae) and New World peccaries (Tayassuidae) showed that one retrovirus group , beta2, was common to all species tested, while the others were present am ong all Old World species but absent from New World species. The PERV-C sub group of gamma1 genomes segregated among domestic pigs and were absent from two African species (red river hog and warthog). Thus domestic swine and t heir phylogenetic relatives harbor multiple groups of hitherto undescribed PERV genomes.