Differentiation of mouse hepatitis viruses in animal facilities in Japan by use of nucleotide analysis of the nucleocapsid gene

The nucleotide sequences of the coding region of the nucleocapsid (N) gene of 12 mouse hepatitis virus (MHV) strains recently found in animal faciliti es in Japan were analyzed. Nucleotide sequencing was performed directly on polymerase chain reaction (PCR) products amplified by reverse transcription (RT) and polymerase chain reaction (RT-PCR) analysis from fecal samples or isolated viruses. Phylogenetic analysis of these MHV strains along with th ose reported previously indicated that sequence analysis of the N gene was a useful tool for differentiation of MHV strains, although most MHV strains in Japanese facilities were phylogenetically close. Results suggested that interchange of mice infected with MHV among facilities provided opportunit ies of introduction of MHV into otherwise MHV-free facilities and that the source of MHV infection could be traced by use of nucleotide analysis of th e N gene.