To investigate the role of the signal sequences of herpes simplex virus 1 (HSV-1) gK on virus replication and viral pathogenesis, we constructed recombinant viruses with or without mutations within the signal sequences of gK. These recombinant viruses expressed two additional copies of the mutated (MgK) or native (NgK) form of the gK gene in place of the latency-associated transcript with a myc epitope tag to facilitate detection at their 3= ends. The replication of MgK virus was similar to that of NgK both in vitro and in vivo, as well as in the trigeminal ganglia (TG) of latently infected mice. The levels of gB and gK transcripts in the corneas, TG, and brains of infected mice on days 3 and 5 postinfection were markedly virus and time dependent, as well as tissue specific. Mutation in the signal sequence of gK in MgK virus blocked cell surface expression of gK-myc in rabbit skin cells, increased 50% lethal dose, and decreased corneal scarring in ocularly infected mice compared to the NgK or revertant (RgK) virus. MgK and NgK viruses, and not the RgK virus, showed a reduced extent of explant reactivation at the lower dose of ocular infection but not at the higher dose. However, the time of reactivation was not affected by overexpression of the different forms of gK. Taken together, these results strongly suggest that the 8mer peptide (ITAYGLVL) within the signal sequence of gK promotes cell surface expression of gK in infected cells and ocular pathogenesis in infected mice.
IMPORTANCEIn this study, we show for the first time that mutations within the signal sequence of gK blocked cell surface expression of inserted recombinant gK in vitro. Furthermore, this blockage in cell surface expression was correlated with higher 50% lethal dose and less corneal scarring in vivo. Thus, these studies point to a key role for the 8mer within the signal sequence of gK in HSV-1-induced pathogenicity.
Herpes simplex virus 1 (HSV-1) infections are among the most frequent serious viral eye infections in the United States and are a major cause of virus-induced blindness (1-3). It is estimated that 70 to 90% of American adults have antibodies to HSV-1 and/or HSV-2 and ca. 25% of these individuals have clinical symptoms upon routine clinical inquiry. HSV-1 is responsible for Ͼ90% of ocular HSV infections (1, 2, 4-7). HSV-1-induced corneal scarring (CS), also broadly referred to as herpes stromal keratitis (HSK), can lead to blindness. Furthermore, HSV-1 is the leading cause of corneal blindness due to an infectious agent in developed countries (1, 2, 4-7). In addition to necrotizing HSK, ocular infection with HSV-1 can cause eye disease ranging in severity from blepharitis, conjunctivitis, and dendritic keratitis to disciform stromal edema (4, 7-11). In the United States, approximately 30,000 people per year suffer recurrent ocular HSV episodes, requiring doctor visits, medication, and in severe cases, corneal transplants.Although it is well established that HSV-1-induced CS is due to immune responses to the virus, the exact...