Transmissible gastroenteritis of swine: Virus-intestinal cell interactions II. Electron microscopy of the epithelium in isolated jejunal loops

Summary

Electron microscopy studies on the morphology of the columnar cells covering the villi in small intestinal loops, which were surgically isolated in 7 day old pigs, showed that the fine structure of those cells is very similar to that in other mammalian species. Upon infection of the loops with TGE virus, virus particles with a diameter of 75 to 88 mμ became visible in the cytoplasm of these absorptive cells. The virus was taken up by pinocytosis, and newly produced particles maturated by budding at smooth cellular membranes particularly in the Golgi apparatus. Cellular morphological changes were first detectable at the microvillar border and appeared to develop concomitantly with virus release. Loss of cells occurred later through desquamation and cell disruption. Atrophied villi were, at 18 hours postinoculation, almost completely covered with newly produced cuboidal cells which ultrastructurally resembled the undifferentiated crypt cells. Gradual differentiation of these cells occured during the following days and at 72 hours postinoculation, they were morphologically similar to normal absorptive cells. A few of the differentiating and differentiated cells were seen to contain virus particles.