Study of herpes simplex virus type 1 populations obtained from recurrences and primary infections

HSV-1 clinical isolates with unique in vivo and in vitro phenotypes and insight into genomic differences

Strain-specific factors contribute in significant but undefined ways to the variable incidence of herpes simplex virus (HSV) recrudescence. Studies that investigate these strain-specific factors are needed. Here, we used qPCR, in vitro assays, and genomic sequencing to identify important relationships between in vitro and clinical phenotypes of unique HSV-1 clinical isolates. Nine HSV-1 isolates from individuals displaying varying reactivation patterns were studied. Isolates associated with frequent recurrent herpes labialis (RHL) (1) displayed higher rates of viral shedding in the oral cavity than those associated with rare RHL and (2) tended to replicate more efficiently at 33 °C than 39 °C. HSV-1 isolates also displayed a more stable phenotype during propagation in U2OS cells than in Vero cells. Draft genome sequences of four isolates and one variant spanning 95.6 to 97.2 % of the genome were achieved, and whole-genome alignment demonstrated that the majority of these isolates clustered with known North American/European isolates. These findings revealed procedures that could help identify unique genotypes and phenotypes associated with HSV-1 isolates, which can be important for determining viral factors critical for regulating HSV-1 reactivation.

Intrastrain variants of herpes simplex virus type 1 isolated from a neonate with fatal disseminated infection differ in the ICP34.5 gene, glycoprotein processing, and neuroinvasiveness

Two intrastrain variants of herpes simplex virus type 1 (HSV-1) were isolated from a newborn with fatal disseminated infection. A small-plaque-producing variant (SP7) was the predominant virus (>99%) in the brain, and a large-plaque-producing variant (LP5) was the predominant virus (>99%) in the lung and gastrointestinal tract. EcoRI and BamHI restriction fragment patterns indicated that SP7 and LP5 are related strains. The large-plaque variants produced plaques similar in size to those produced by HSV-1 KOS. Unlike LP5 or KOS, SP7 was highly cell associated and processing of glycoprotein C and glycoprotein D was limited to precursor forms in infected Vero cells. The large-plaque phenotype from KOS could be transferred into SP7 by cotransfection of plasmids containing the EK or JK EcoRI fragment or a 3-kb plasmid with the UL34.5 gene of HSV-1 KOS together with SP7 DNA. PCR analysis using primers from within the ICP34.5 gene indicated differences for SP7, LP5, and KOS. Sequencing data indicated two sets of deletions in the UL34.5 gene that distinguish SP7 from LP5. Both SP7 and LP5 variants were neurovirulent (lethal following intracranial inoculation of young BALB/c mice); however, the LP5 variant was much less able to cause lethal neuroinvasive disease (footpad inoculation) whereas KOS caused no disease. Passage of SP7 selected for viruses (SLP-5 and SLP-10) which were attenuated for lethal neuroinvasive disease, were not cell-associated, and differed in the UL34.5 gene. UL34.5 from SLP-5 or SLP-10 resembled that of KOS. These findings support a role for UL34.5 in promoting virus egress and for neuroinvasive disease.

A block in glycoprotein processing correlates with small plaque morphology and virion targetting to cell-cell junctions for an oral and an anal strain of herpes simplex virus type-1

The characteristics of two clinical isolates of HSV-1 obtained from an oral (424) and an anal (490) lesion were compared with the highly passaged KOS strain. In contrast to KOS, the clinical isolates produced small plaques, were more cell-associated and the predominant viral glycoprotein species for gC and gD in infected cell lysates was the precursor, high mannose glycoform. Total virus production in Vero cells was equivalent for the three virus strains in one-step growths. Pulse-chase studies of glycoprotein C processing showed a reduction in rate at 7.5 h post infection and a significant block in processing at 10.5 h post infection for 424 and 490 but not KOS. Similar results were obtained for gD. The significant reduction in glycoprotein processing for 424 and 490 suggests a block in transport of viral glycoproteins or virions to and through the Golgi apparatus. Extracellular virions and the cell surface, prior to cell lysis, contained the processed gC glycoform suggesting a competent cellular glycan processing system. Upon co-infection of 424 or 490 with KOS or a gC- KOS strain, gC was processed to levels equivalent to KOS indicating that 424 and 490 are not inhibitory but that an activity(s) encoded by KOS facilitates maturation of gC from 424 and 490. Unlike KOS infected Vero cells, virion-containing vacuoles were observed in the cytoplasm at 12 h p.i. and extracellular virions were concentrated at cell-cell junctions of 424 or 490 infected cells but not in the perinuclear region. These results suggest that intracellular transport of viral glycoproteins and virions in 424 and 490 infected cells is different from KOS infected cells. The reduced level of viral glycoprotein maturation, virus release, cell surface presence and presence of virions at cell-cell junctions are consistent with small plaque production in tissue culture cells.

Restriction endonuclease patterns of herpes simplex virus DNA: subtyping of HSV-1 and HSV-2 strains from genital and nongenital lesions

Herpes simplex type 1 (HSV-1) and type 2 (HSV-2) isolates from genital and nongenital infections were submitted to restriction endonuclease analysis for possible genomic changes in relation with the adaptation of the virus to a new site on the body. HSV-1 and HSV-2 strains were successfully divided into two subgroups using the Hin c II restriction enzyme. No correlation was found, however, between the proposed genomic subtypes H1A, H1B, H2A and H2B, and the genital or nongenital origin of the HSV strains.

Experimental keratitis in rabbits by human HSV-1 variants: prevention and treatment

The efficacy of different therapies and vaccine preparations was assessed for treating or preventing herpetic ocular keratitis induced by experimental inoculation in rabbits with two HSV-1 variants that display different pathogenetic potential. Early administration of acyclovir (ACV) promoted fast healing and prevented neurologic involvements: alpha-interferon (alpha-IFN) was less efficient than ACV; combined therapy with both drugs increased the antiviral effects. In an attempt to prevent the disease, rabbits were vaccinated with a slightly pathogenic HSV-1 variant or with a secreted form of an engineered HSV-1 glycoprotein gB (gB-1s) and were subsequently challenged with a highly pathogenic HSV-1 variant. Immunization of rabbits with gB-1s was much more efficient than immunization with live virus in reducing the severity of herpetic keratitis and in preventing CNS disease.

Further characterization of virus obtained from herpes simplex virus type 1 recurrences and primary infections. Influence of the temperature of incubation upon glycoprotein synthesis and virus release. Brief report

The virus contained in clinical isolates of herpes simplex virus type 1 (HSV-1) which have not undergone previous in vitro passages (new isolates) differs from HSV-1 prototype strains with respect to infected cell glycoprotein pattern, and, most probably efficiency of virus egress at 37 degrees C. The differences can be abolished by lowering the temperature of incubation to 33 degrees C. A few tissue culture passages cause the conversion of the original virus to a virus undistinguishable from HSV-1 prototype strains with respect to the parameters mentioned above.