Abstract
Exposure of transmissible gastroenteritis virus of pigs to unheated normal heterotypic serum resulted in a drop in infectivity, an effect which was lost after heating the serum to 56 degrees C for 30 min or by treatments inactivating complement. Analysis of virus proteins, RNA and lipids, and centrifugation studies showed little difference between inactivated and control virus, but electron microscopy of negatively stained particles after treatment with serum revealed holes in the virus envelope, characteristic of those caused by complement in the presence of antibody.