Serum lipoproteins as inhibitors of haemafflutination by rubella virus.

The role of serum lipoproteins as non-antibody-like inhibitors of haemagglutination for rubella virus was investigated. Dissociation of lipoproteins into their respective lipid and protein components significantly reduced their inhibitory titre. This reduction was more prominent with the protein component. When mixtures of pure lipids were tested for their haemagglutination inhibitory activities, no inhibition was observed. Sonication of the three major lipoprotein fractions significantly increased the inhibitory activities of low density lipoproteins (LDL) and very low density lipoproteins (VLDL) but not high density lipoproteins (HDL). Succinylation, acetylation, and methylation of the lipoproteins did not appear to affect their inhibitory titre. On the other hand, phospholipase A treatment significantly increased the inhibitory properties of all lipoproteins fractions. These results are discussed in terms of the possible mechanisms by which the lipoproteins interact with the rubella haemagglutinins.