Necrotizing chorioretinitis in mice inoculated with herpes simplex virus type 1 with or without glycoprotein C: anterior chamber-associated immune deviation does not persist

Isolation of equine herpesvirus-1 lacking glycoprotein C from a dead neonatal foal in Japan

We isolated a variant equine herpesvirus-1 (EHV-1), strain 5089, from the lung of a dead neonatal foal in Japan and characterized the biological nature of the virus. The virus spread in cultured cells mainly by cell-to-cell infection, unlike wild-type EHV-1, which spreads efficiently as a cell-free virus. The virus titer in cultured supernatant and the intracellular virus titer were low compared to those of wild-type EHV-1. Heparin treatment of the virus had no effect on viral infectivity in cell culture. Glycoprotein C (gC) was not detected by Western blotting and fluorescent antibody tests in 5089 virions and 5089-infected cells, respectively. RT-PCR analysis revealed that the expression level of 5089 gC mRNA was reduced considerably compared to that of wild-type EHV-1. Sequencing analysis of the 5089 gC coding region showed a point mutation in the promoter region of the gC open reading frame. However, the mutation did not affect the promoter activity. These results suggested that the lack of gC in 5089 virions might be one of the reasons for spread of the virus by cell-to-cell infection and that gC mRNA expression might not be activated efficiently due to factors other than the mutation in the gC promoter region.

Pathogenicity of glycoprotein C-deficient herpes simplex virus 1 strain TN-1 which encodes truncated glycoprotein C

A clinical isolate of herpes simplex virus 1 (TN-1) from a stromal keratitis patient was found to be defective in the glycoprotein C (gC) gene (UL44), thus resulting in the production of truncated gC upon infection. To study the pathogenetic role of truncated gC, we prepared a recombinant LTN-8 derived from TN-1 with deletions of the 1.5 kilobase pairs of the gC gene including the initiation codon. A penetration assay revealed LTN-8 to be less efficient in its penetration ability than TN-1, the laboratory strain KOS and RTN-1-20-3, a recombinant derived from TN-1 with the KOS gC gene. The penetration of LTN-8 was facilitated by the addition of TN-1-infected culture medium. TN-1 virus preparations had no hemagglutinating activity. However, the animals infected with TN-1 did develop hemagglutination inhibition (HI) antibodies. The LTN-8-infected animals did not develop HI antibodies. The pathogenicity in BALB/c mice following either corneal, intraperitoneal or intracerebral inoculation did not significantly differ among TN-1, RTN-1-20-3 or LTN-8. Our results indicate that truncated gC was sufficient for the induction of HI antibodies and was also able to facilitate penetration in vitro. Although truncated gC might be a virulence factor acting as a decoy, both truncated gC and intact gC had little effect on the outcome following intracerebral, intraperitoneal or corneal inoculation.