THE EQUINE HERPESVIRUS-1 GLYCOPROTEIN GP21 22A, THE HERPES-SIMPLEX VIRUS TYPE-1 GM HOMOLOG, IS INVOLVED IN VIRUS PENETRATION AND CELL-TO-CELL SPREAD OF VIRIONS/

Experiments to analyze the function of the equine herpesvirus 1 (EHV-1 ) glycoprotein gM homolog were conducted. To this end, an Rk(13) cell line (TCgM) that stably expressed EHV-1 gM was constructed. Proteins w ith apparent M(r)s of 46,000 to 48,000 and 50,000 to 55,000 were detec ted in TCgM cells with specific anti-gM antibodies, and the gM protein pattern was indistinguishable from that in cells infected with EHV-1 strain RacL11, A viral mutant (L11 Delta gM) bearing an Escherichia co li lacZ gene inserted into the EHV-I strain RacL11 gM gene (open readi ng frame 52) was purified, and cells infected with L11 Delta gM did no t contain detectable gM. L11 Delta gM exhibited approximately 100-fold lower titers and a more than 2-fold reduction in plaque size relative to wild-type EHV-1 when grown and titrated on noncomplementing cells. Viral titers were reduced only 10-fold when L11 Delta gM was grown on the complementing cell line TCgM and titrated on noncomplementing cel ls. L11 Delta gM also exhibited slower penetration kinetics compared w ith those of the parental EHV-I RacL11. It is concluded that EHV-1 gM plays important roles in the penetration of virus into the target cell and in spread of EHV-I from cell to cell.