Differences Between HSV2 and HSV1

Despite their high degree of genomic identity (>80%) (7,8), their significantly different pathology in humans is reflected in differences in the behavior of the virus in animal systems (9,10). An important problem in herpes virology is to understand the molecular basis leading to the different pathologies between HSV-1 and HSV-2. Differences in viral functions as well as in the cellular functions affected by each type of virus could explain these different pathologies. Thus, some viral functions are different in HSV-1 and HSV-2. For instance, whereas in HSV-1 glycoprotein C is the major viral function responsible for virus attachment to cells and glycoprotein B mediates penetration, in HSV-2 glycoprotein B is the major protein involved in both binding and penetration (11). Also, the viral host shutoff activity is much stronger in HSV-2 than in HSV-1 (12). Furthermore, the protein kinase activity associated with ribonucleotide reductase 1 has different ATP requirements in HSV-1 and HSV-2 (13). Cellular functions are also affected differently in HSV-1 and HSV-2 infections. Whereas HSV-1 increases the levels of transcription factors c-Jun (14) and NF-kB (15), HSV-2 increases c-fos transcription (16). The regulation of nitric oxide

Fig. 1. The HSV-2 transcription map determined from the sequence of the HG52 strain. The major features of the viral genome, the open translational reading frames, polyadenylation signals (vertical arrows), and locations of specific 75-base oligonucleotide probes are shown. (Adapted from ref. 8.)

production in epithelial cells is also different, with HSV-2 causing upregulation and HSV-1 downregulation (17). Therefore, to catalog the differences between HSV-1 and HSV-2 and to understand their molecular basis may explain their different pathologies and provide and important knowledge of herpes virology.

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