A real time biomolecular interaction assay system involving an optical sensor was applied to the quantitative analysis of the binding of herpes simplex virus type 1 (HSV-1) to Vero cells, and the neutralization antibody titer against this virus with a commercially available sulfonated human immunoglobulin preparation. The ELISA assay appeared to be more sensitive for detecting gB and gD antibodies. Preparation of recombinant amplicon vector particles by transfection of amplicon and superinfection of helper virus into cells, and harvesting of packaged particles, is also delineated. Ibuprofen also directly inhibited the replication of herpes simplex virus in trigeminal ganglia and Vero cell monolayers, which indicates that the drug reduced the recovery of reactivated viral titers from explanted ganglia with latent virus by acting on the replication process rather than on the reactivation mechanism in vitro. An increased titer of antibody to gD seemed to be associated with a reduced number of recurrent episodes and to a reduced number of days with recurrent lesions. All 16 specimens analyzed were PCR positive with primer set 1; 15 of 16 were also positive with primer set 2, with the HSV type identified for all specimens (7 were HSV-1 and 8 were HSV-2). Stevens, J.
Virol. Use of this quantitative assay should allow further investigation into the relationship of the immune response to these important targets and the clinical course of HSV disease. To study this further, we isolated an RS6-derived herpes simplex virus intertypic recombinant (R13-1) which has a genetic defect within this area. After inoculation into mouse brains, R13-1 was found to be approximately 10,000-fold less neurovirulent than either the wild-type type 1 or type 2 parental virus. However, R13-1 replicated in the mouse brain to titers resembling those of the wild-type parents. Further comparisons with wild-type counterparts indicated that R13-1 expressed equivalent levels of the enzyme thymidine kinase and replicated to intermediate levels in primary mouse embryo fibroblasts maintained at the normal body temperature for mice. Using marker rescue techniques combined with in vivo selection, we found that recombination between unit-length R13-1 DNA and a cloned type 1 DNA fragment spanning the region from 0.11 to 0.14 map units (EcoRI-d, 0.079 to 0.192 map units) generated viruses with a wild-type neurovirulence phenotype.
To further refine the genomic region of interest, we performed marker rescue experiments using two EcoRI-d subclones, EcoRI/BamHI dc (0.079 to 0.143 map units) and BamHI/EcoRI and (0.143 to 0.192 map units), representing the left and right halves of the EcoRI d fragment, respectively. In these experiments the EcoRI/BamHI dc clone, but not the BamHI/EcoRI ad clone, yielded recombinant viruses exhibiting wild-type neurovirulence. These results show that at least one herpes simplex virus gene function associated with neurovirulence is located within a 9.1-kilobase region at 0.079 to 0.143 map units of the viral genome. Perhaps more significantly, the results indicate that this neurovirulence property functions independently of high-titer virus replication in the brain.