Partial genome sequence of murine gammaherpesvirus 72 and its analysis.

Murine gammaherpesvirus 68 (MHV-68)-infected mouse is a well known model for studies of Epstein-Barr virus (EBV)-related lymphoproliferative diseases (LPD). Murine gammaherpesvirus 72 (MHV-72) has been considered a close relative of MHV-68 but its replication in murine mammary gland cells and kinetics of infection of mice were found to be different. Pathological studies of a long-term-infection of mice revealed a similar or higher malignancy development rate in MHV-72-infected mice as compared with that of MHV-68. Previous comparison of MHV-72 with MHV-68 revealed their diversity in M3, MK3, and M7 genes encoding the chemokine-binding protein, immune evasion protein and glycoprotein 150, respectively. In this study, a portion (22,899 bp) of MHV-72 genome sequence was determined, analyzed and compared with that of MHV-68. Nucleotide sequences of 13 structural and 6 non-structural genes of MHV-72 and deduced amino acid sequences revealed their identity to those of MHV-72 except for differences in 9 nucleotides and 8 amino acids, occurring in 5 genes and their proteins. Due to these differences, 4 structural proteins encoded by ORF20, ORF26, ORF48, and ORF52, respectively, and a non-structural protein encoded by ORF4, all of MHV-72, are predicted to have altered hydrophilicity and surface exposure in comparison with their MHV-68 counterparts. These differences obviously contribute to some different pathogenetical features of these viruses and could explain the reduced immunogenicity of MHV-72 in relation to MHV-68, allowing MHV-72 to escape the host immune surveillance.