Comparison of M and N gene sequences distinguishes variation amongst equine arteritis virus isolates

cDNA copies of the M and N genes of equine arteritis virus (EAV) isolates were synthesized by reverse transcription followed by polymerase chain reaction amplification. The cDNA was subjected to a cycle sequencing strategy using Taq polymerase, and the nucleotide and derived amino acid sequences of 10 virus isolates were compared. The M and N genes of all isolates had the same initiation and termination sites as the prototype Bucyrus strain and the encoded proteins were conserved between viruses. Comparison of nucleotide sequence homologies and phylogenetic tree analysis implied the existence of three EAV variants originating from the U.S.A. (Bucyrus), Austria (Vienna) and Switzerland (Bibuna), and suggested that RNA recombination between EAV isolates may have occurred.