B.J. Ruck

Virus particles in epithelial cells of duodenal mucosa from children with acute non-bacterial gastroenteritis.

Abstract Electron microscopy of duodenal mucosa from nine children with acute non-bacterial gastroenteritis revealed virus particles in epithelial cells from six patients. The morphology of the virus particles was identical in each of the six children. The virus belonged to the orbivirus group. No virus particles were observed in duodenal mucosa obtained from three of these children after clinical recovery. This orbivirus is believed to have been an important cause of sporadic gastroenteritis in children in Melbourne during the 3 months of the survey.

DETECTION OF A NEW VIRUS BY ELECTRON MICROSCOPY OF FÆCAL EXTRACTS FROM CHILDREN WITH ACUTE GASTROENTERITIS

Abstract Electron microscopy of negatively stained faecal extracts revealed particles resembling orbiviruses in 11 of 14 children with acute non-bacterial gastroenteritis. No such particles were observed in faecal extracts from 9 control children. The method of differential centrifugation for extraction of faeces is simple, quick, and more sensitive than duodenol biopsy for detecting the virus. Combining results from duodenal mucosa and faeces, orbivirus particles were observed by electron microscopy in 81% of children with sporadic gastroenteritis in Melbourne.

IS LACTASE THE RECEPTOR AND UNCOATING ENZYME FOR INFANTILE ENTERITIS (ROTA) VIRUSES

Rotaviruses are now regarded as important causes of diarrhoea in man, cattle, pigs, mice, and possibly other animals. Characteristically, disease occurs in newborn and young animals, and infection seems limited to the differentiated gut epithelial cells. The major surface polypeptide of the calf scours rotavirus is glycosylated, and highly purified beta-galactosidase (lactase) interacts with the virus in vitro causing removal of the outer shell of the capsid (uncoating). It is suggested that lactase present in the brush border of the intestinal epithelial cell performs a similar function in vivo by acting as a combined receptor and uncoating enzyme for the rotavirus. This hypothesis is consistent with the observations that rotaviruses seem to infect only gut epithelial cells, and that infant animals, whose lactase concentrations are generally higher than those of adult animals, seem more susceptible to rotavirus infections. Implications of the hypothesis include possible new approaches to laboratory cultivation of rotaviruses, which should be more successful in cells selected for surface lactase activity, and the suggestion that the epidemiology of human rotavirus infections may be influenced by the fact that different ethnic groups have different lactase levels (and hence lactose intolerance) in adulthood.