Variations of HSV-1 glycoprotein B in human herpes simplex encephalitis

The factors which cause herpes simplex encephalitis (HSE) to occur among herpes simplex virus type 1 (HSV-1) infected humans are not understood. In experimental models, HSV-1 neuroinvasiveness is influenced by amino acid changes in HSV glycoproteins D (gD) or B (gB), which are essential to the virus infectivity and to the induction of host immune responses. To test the possible involvement of these glycoproteins in human HSE, we compared CSF-derived sequences of these genes with those obtained from peripheral HSV-1 isolates. We have previously shown the conservation of gD in 10 HSE samples. Here, we show that the functional domains of gB involved in cell penetration and cell fusion, and the major antigenic domains D2a, D2b and Dd5a were highly conserved. In the gB amino-terminal domain, we distinguished several alleles that were common to HSE and peripheral isolates, and identified in only three out of fifteen HSE cases, a variation that was not encountered in 20 control strains. Overall, there were no striking differences between peripheral and HSE gBs. These results suggest that gB alone may not be responsible for neuroinvasiveness nor human neuropathogenicity.