Abstract
The 3 major lipoprotein fractions of human serum were investigated for their ability to inhibit the haemagglutination of 24 different togaviruses including rubella virus and arboviruses from 5 antigenic groups. All viruses were inhibited by the 3 fractions and this was most evident with low and very low density lipoproteins; inhibitory activity appeared to be associated with the lipid part of the lipoproteins. When artificial dispersions of the lipids cholesterol, cholesteryl ester and triglyceride were emulsified with egg lecithin three categories of inhibitory activity were observed which were independent of virus antigenic grouping -- category 1, no activity; category 2, activity confined to cholesterol and category 3, activity for cholesterol and to a lesser extent the other lipids.