Characterization of porcine endogenous retrovirus γ pro-pol nucleotide sequences

Endogenous retroviral sequences in the pig genome (PERV) represent a potential infectious risk in xenotransplantation. All known infectious PERV have been asssigned to the PERV γ1 family, consisting of the subfamilies A, B, and C. The aim of the study was the concise examination of PERV γ by the analysis of the retroviral pro-pol sequences. The analysis of 52 pro-pol clones amplified in this study revealed eight PERV γ families. In addition to four already-described families (γ1, γ4, γ5, γ6), four novel families (γ7, γ8, γ9, γ10) were identified. Quantitative analysis of the novel PERV γ sequences in selected breeds revealed variations in the endogenous retroviral load. Open reading frames (ORF) in the amplified proviral fragment were only found for PERV γ1. In addition, novel ORF-containing PERV γ1 clones consisting of hybrid sequences were revealed. Sequence comparison from published full-length PERV γ1 clones of the PERV subfamilies A, B, and C resulted in a lack of strict correlation of the classification of pro-pol and env. The results indicated the occurrence of causative recombination events between retroviral genomes. Thus, our study on PERV γ provides new data for the evaluation and selection of pigs intended to be used in xenotransplantation.