Identification of the murine cytomegalovirus glycoprotein B gene and its expression by recombinant vaccinia virus

The gene encoding glycoprotein B (gB) of murine cytomegalovirus
(MCMV) strain Smith was identified, sequenced, and expressed by
recombinant vaccinia virus. The gB gene was found adjacent to the
polymerase gene, as it is in the genome of human cytomegalovirus
(HCMV). The open reading frame consists of 2,784 nucleotides
capable of encoding a protein of 928 amino acids. Comparison with
gB homologs of other herpesviruses revealed a high degree of
homology. The similarity between the MCMV gB and the HCMV gB is
most prominent, since 45% of the amino acids are identical. In
addition, all cysteine residues are at homologous positions,
indicating a similar tertiary structure of the two proteins. In
contrast to HCMV, the MCMV gB mRNA is a true late transcript. A
recombinant vaccinia virus expressing the MCMV gB gene has been
constructed (Vac-gB). Antibodies raised against the Vac-gB
recombinant precipitated proteins of 130, 105, and 52 kDa from
MCMV-infected cells. The identity of the MCMV gB with the major
envelope glycoprotein of MCMV described by Loh et al. was shown (L.
C. Loh, N. Balachandran, and L. F. Qualtiere, Virology 166:206-216,
1988). Immunization of mice with the Vac-gB recombinant gave rise
to neutralizing antibodies.