Bovine herpesvirus 1 glycoprotein G is required for viral growth by cell-to-cell infection

The bovine herpesvirus 1 (BHV-1) US4 gene encodes glycoprotein G (gG), which is conserved in the majority of alphaherpesviruses. In order to identify the role of BHV-1 gG in the viral infection cycle, a gG minus BHV-1 mutant and its gG-positive revertant were constructed and their growth characteristics in Madin-Darby bovine kidney (MDBK) cells were compared. The gG minus mutant formed smaller plaques than the gG-positive BHV-1 in MDBK cells. When a monolayer culture of MDBK cells was infected with BHV-1 at a low multiplicity of infection and overlaid with semi-solid growth medium, under which adsorption of the mature virion released in the medium was inhibited, gG-positive BHV-1 multiplied, while the growth of the gG negative BHV-1 was severely inhibited. These data suggest that BHV-1 gG functions in direct cell-to-cell transmission mechanism of BHV-1 in tissue culture.