Retinoic acid reduces the yield of herpes simplex virus in Vero cells and alters the N-glycosylation of viral envelope proteins.

Treatment of Vero cells with all-trans-retinoic acid (RA) decreased the production of infectious herpes simplex virus (HSV) by 1000-10000-fold when compared with control cultures. Levels of total HSV envelope glycoproteins gB, gC and gD produced following RA treatment, were comparable with those found in control cultures. Following 24 h of RA treatment, lower molecular weight variants of gB, gC and gD were produced in addition to the typical molecular mass of each protein found in control samples. Between 24 and 48 h of RA treatment, the proportion of the lower molecular mass variants increased. When control and RA treated samples were incubated with peptide N-glycosidase F (PNGase F), which removes N-glycosylated sugars, the molecular weights of the respective gB, gC and gD proteins produced were comparable in both the groups, indicating that RA did not alter the primary sequence of viral proteins during protein synthesis or increase viral protein proteolysis. RA treatment increased [3H]mannose incorporation into glycoproteins in HSV infected cells but did not change [3H]glucosamine incorporation. We conclude that RA treatment does not reduce the synthesis of three major viral envelope glycoproteins but alters their N-glycosylation and postulate that the inhibitory effect of RA is related to its action on N-glycosylation.