Classification of North American porcine enteroviruses: a comparison with European and Japanese strains.

Seventy-two strains of porcine enteroviruses including strains from North America, England, and Japan were compared by cell culture neutralization tests to provide a serological classification of North American strains. From the tests, eight serogroups evolved, with serogroup 8 having a possible three subgroups. There appeared to be some intergroup relationship among certain viruses in groups having the same specific cytopathic effect (CPE) in cell culture. There was no apparent cross-reaction between the group with type II CPE and groups with type I CPE. Antisera produced in nonhost chickens provided a satisfactory antibody source for the tests. It was proposed that satisfactory typing of viruses could be done best by cross-neutralization rather than by one-way neutralization tests. This provided the homologous serum titer as determined in the laboratory conducting the tests which was important where comparisons are made on the basis of per cent of the homologous titer. It was further emphasized that viruses of tissue origin and their antisera have fewer intergroup reactions than viruses of intestinal origin and their antisera. General type strains and specific North American strains were suggested as satisfactory type sera and viruses for seven of the eight groups to facilitate virus identification.