Variability in the structural polypeptides of herpes simplex virus 1 strains: potential application in molecular epidemiology

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Abstract
This paper reports on the variability of structural polypeptides of 53 strains of herpes simplex virus 1 isolated from Italy, Uganda, South Africa, and various locations in the United States. Most strains were passaged a limited number of times at low multiplicity outside the human host; a few strains were characterized by numberous passages at variable multiplicities in cell culture and experimental animals. The acrylamide gel electrophoresis of polypeptides from purified virions revealed seven variable polypeptides. Virion polypeptides (VP) 7, 11, 13, 14, 15.2 and 23 were present in at least two isotypic forms characterized by fast and slow electrophoretic mobilities. VP8 could not be detected in three strains. In addition, VP13, 15.2, and 23 in some strains were either absent or comigrated with other polypeptides. A variety of tests showed that the variability in electrophoretic mobility of polypeptides was reproducible and could not be attributed to artifacts of purification, solubilization, or electrophoresis. Attempts to classify the strains on the basis of electrophoretic mobility of five or all seven variable polypeptides yielded 14 and 19 groups, respectively. The bulk of the strains (41 to 53) fell into six groups. Not all possible permutations of variable polypeptides were observed. Comparison of early and late passages of laboratory strains showed that in the few instances tested the variability could not be attributed to the propagation of the virus outside the human host. Clustering of strains on the basis of country of origin was not observed. Some clustering of isolates on the basis of site of isolation was observed, and the data do suggest that further analyses of isolates for evidence of a correlation between the site of localization on the human body and the structural polypeptides might be useful. Electrophoretic characterization of structural polypeptides has the potential of becoming a powerful tool for epidemiological studies of herpes simplex virus infections.