SUMMARYThe polypeptides of purified preparations of the coronavirus responsible for transmissible gastroenteritis of pigs have been examined by polyacrylamide gel electrophoresis. Four major polypeptides, VPI (mol. wt. 2ooooo), VP2 (5oooo), VP3 (3D ODD) and VP4 (28 5oo) and two minor polypeptides, VPIa 0o5ooo) and VP~b (80 5oo) have been reproducibly demonstrated in the virion, of which VPI, VP3 and VP4 contain carbohydrate. Treatment of the virion with the proteolytic enzyme bromelain removes the surface projections and VPI, thus identifying this glycopolypeptide as the major structural component of the projection.

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SUMMARYExposure of purified transmissible gastroenteritis virus, a porcine coronavirus, to non-ionic detergents resulted in the removal of the surface projections and > 98 % of the virus lipid. Virus RNA was associated with a subviral particle which had a sedimentation coefficient of 65olS, compared with 495 S for the intact virion, and which banded in Cs2SO4 gradients at 1.295 g/ml. Negatively stained preparations of subviral particles were shown by electron microscopy to contain spherical particles of 6o to 7o nm diam., similar in appearance to those derived from oncornaviruses.Polyacrylamide gel electrophoresis of the polypeptides from isolated subviral particles showed that these structures contained three of the four major virus structural proteins, the arginine-rich polypeptide VP2 and the two membrane glycopolypeptides VP3 and 4. The detergent-liberated surface projections, composed of a single species of sulphated glycopolypeptide, VPr, were isolated by rate-zonal centrifugation through sucrose gradients followed by precipitation with ammonium sulphate in the presence of bovine serum albumin.

Garwes, D.J., Lucas, M.H., Higgins, D.A., Pike, B.V. and Cartwright, S.F., 1978/1979. Antigenicity of structural components from porcine transmissible gastroenteritis virus. Vet. Microbiol., Pregnant sows were inoculated with inactivated transmissible gastroenteritis virus and with preparations of virus surface projections and subviral particles derived by detergent treatment of the virus. Neutralising antibody was demonstrated in serum and colostrum from animals that received whole virus or preparations of surface projections whereas subviral particles failed to stimulate neutralising antibody formation. Similar results were obtained with serum from rabbits inoculated with whole virus and structural components. All three preparations stimulated the formation of agglutinating antibodies, as demonstrated by sedimentation analysis and filtration studies with radiolabelled virus.The immunoglobulin classes responsible for neutralising antibody activity in sows inoculated by the intramarnmary route were examined. In each case where the immunoglobulin class was determined, IgG was found. One sow that received surface projections also had IgA with neutralising activity in her colostrum. In contrast, infection of sows with live whole virus resulted in neutralising antibody of the IgG, IgM and IgA classes.