Identification of the structural proteins of turkey enteric coronavirus

Abstract

Coronaviruses in the intestinal contents of turkey poults from Quebec flocks with outbreaks of enteritis were detected by electron microscopy. Five isolates were serially propagated in embryonic turkey eggs by inoculation of clarified intestinal contents into the amniotic cavity. Viral particles contained in the intestinal contents of infected embryos were purified by differential and isopycnic centrifugation in sucrose gradients. Intact virions present in fractions of densities 1.18 to 1.20 g/ml were precipitated with trichloroacetic acid and the protein content was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. At least seven polypeptides with molecular weights ranging from 27,000 to 180,000 were regularly detected after electrophoresis of SDS-solubilized virions. Homologous rabbit antisera to turkey coronaviruses and pooled sera from convalescent turkeys immunochemically stained five polypeptides of apparent molecular weights of 95,000, 72-75,000, 66,000, 52,000 and 27,000. A further polypeptide with a molecular weight of 140,000 appeared in the absence of 2-mercaptoethanol and probably represents a dimer of the 66,000 polypeptide. One Quebec isolate differed from the Minnesota strain by two of its polypeptides, but no antigenic variations could be demonstrated amongst the various isolates either by immuno-electron microscopy, hemagglutination inhibition, or enzyme immuno assays on nitrocellulose.