Detection of two novel porcine herpesviruses with high similarity to gammaherpesviruses

Evidence for the existence of porcine gammaherpesviruses was obtained by PCR and sequence analysis. Initially, samples of peripheral blood mononuclear cells (PBMC), spleens, lungs, kidneys and livers of pigs from Germany and Spain were tested with a PCR assay which targets conserved regions of the herpesvirus DNA polymerase gene with degenerate and deoxyinosine-substituted primers. Amplicons of identical sequence were obtained from one spleen and two PBMC samples. This sequence showed a high percentage of identity with the DNA polymerase genes of herpesviruses of the oncogenic subfamily Gammaherpesvirinae. Alignment of amino acid sequences showed the highest identity values with bovine gammaherpesviruses, namely alcelaphine herpesvirus type 1 (68%), ovine herpesvirus type 2 (68%) and bovine lymphotropic herpesvirus (67%). Comparison with pseudorabies virus and porcine cytomegalovirus, which are the only porcine herpesvirus species presently known, showed values of only 41 %. PCR analysis of PBMC (n = 39) and spleen (n = 19) samples from German pigs, using primers specific for the novel sequence, revealed a prevalence of 87 and 95%, respectively. In this analysis, three out of eight spleen samples from Spanish pigs were also positive. Subsequent sequencing of the amplicons revealed the presence of two closely related gammaherpesvirus sequences, differing from each other by 8% at the amino acid level. The putative novel porcine herpesviruses, from which these sequences originated, were tentatively designated porcine lymphotropic herpesvirus type 1 and type 2 (PLHV-1 and PLHV-2). When using pig organs for xenotransplantation, the presence of these viruses has to be considered.