In an epidemic of gastrointestinal illness strongly associated with swimming at a recreational park in Macomb County, Michigan, in July, 1979, the authors demonstrated the value of serologic testing to detect Norwalk virus infection. Rises in antibody titer to Norwalk virus were noted in all 11 individuals tested. Electron microscopy on stools from 20 ill individuals revealed only one with Norwalk virus-like particles. This particle was shown by radioimmunoassay and immune electron microscopy not to be Norwalk virus and not to have stimulated detectable antibodies in this individual. These results not only indicate that electron microscopy is insensitive in detecting Norwalk virus, but that it has the potential to mislead. A low rate of respiratory symptoms was associated with gastrointestinal illness in this Norwalk virus outbreak. The route of exposure might have been important for this. The outbreak was also noteworthy in that, although there was evidence of familial clusters of resistance, a very high percentage of the population was proved to be susceptible to the Norwalk virus.

A2/I957 influenza neuraminidase (mucopolysaccharide N-acetylneuraminylhydrolase, EC 3.2.1.18) was purified i5-fold from a recombinant virus, with about 25~/o overall yield of enzymic activity. Neuraminidase contained glucosamine, and a high proportion of serine and threonine. The partial specific volume was o.713 cm3/g. Reduced neuraminidase was isotopically labeled in vitro by reaction with iodoE14Clacetamide. When carboxamidomethylated in the absence of urea, enzymically inactive labeled material was obtained with a maximum size similar to native neuraminidase. When carboxamidomethylated in the presence of 6 M urea, labeled, dissociated subunits were obtained that did not associate or regain enzymic activity on removal of urea. The molecular weight of dissociated subunits was determined by sedimentationdiffusion methods as 50 000-54 ooo, and by sodium dodecyl sulfate-acrylamide gel electrophoresis as about 50 ooo. Thus native neuraminidase (tool. wt. about 200 ooo) is probably a tetramer. Neuraminidase contained about 21 cysteine residues per subunit. These appear to be present as disulfide bonds in the native enzyme.

No abstract

No abstract

No abstract