Further Studies on Porcine Enteroviruses Isolated at Cambridge: I.—Infections in SPF Pigs and the Preparation of Monospecific Antisera

Abstract

SUMMARY To enable more critical serological studies to be undertaken with various porcine enteroviruses, attempts were made to produce monospecific antisera to 13 selected strains. Each selected strain was cloned 3 times by the plaque technique and then used to infect 2 first-generation specif c pathogen free (SPF) pigs. Before inoculation, faecal samples from these pigs were examined for the presence of cytopathogenic agents and blood samples were tested for antibodies against porcine enteroviruses. Elaborate precautions were taken to prevent accidental contamination. Most of the pigs were killed 2 or 3 weeks after infection. All the selected strains before and after triple-cloning were tested by cross-neutralization tests in tissue culture against sera already available and against the new sera. Each new serum was checked also against an early passage of the selected strain as near as possible to the original isolation. Virus recovered from the faeces and tissues of each serum-producing pig was tested against sera already available. The results of all these tests indicated that, in relation to the porcine enteroviruses, the new sera were monospecific. It appeared probable that the pre-cloning sample of one selected strain, F59, had comprised a number of viruses, at least one of which was eliminated by the cloning procedure. All the selected strains multiplied in the lower portions of the intestinal tract and were excreted in the faeces. In addition to the Talfan and T80 viruses, which are known to produce polioencephalomyelitis, the enterovirus, F59, produced mild lesions of polio-encephalomyeiitis.