Phosphatidyl-serine inhibition of OC43 and NCDCV coronavirus infectivity

Human OC43 and bovine neonatal calf diarrhoea coronavirus (NCDCV) are known to be inhibited by non-antibody factors present in sera of different mammalian species, including man and cattle. Such an inhibitor is also present in fetal calf serum generally used for growing and maintaining cell cultures, thus influencing the viral infectivity titer. Previous reports refer to the effectiveness of phospholipase C treatment in eliminating the inhibiting activity. In order to detect the compound possibly involved in coronavirus growth inhibition (among the phospholipids naturally present in mammalian sera), we tested several phospholipids with hemagglutino-inhibition test and plaque reduction assay. Only phosphatidyl-serine seemed to be effective on Coronavirus OC43 and NCDCV, as detected by plaque-reduction assay, but not by hemagglutino-inhibition test.