Studies on the inhibitory activities of human serum lipoproteins for Japanese encephalitis virus.

Human serum lipoproteins were purified by ultracentrifuging and their concentrations adjusted as required to be within the normal male/female serum range for all assays. The activities in inhibition of hemagglutination (HAI) for Japanese encephalitis virus were--low density lipoprotein (LDL) greater than very low density lipoprotein (VLDL) greater than high density lipoprotein (HDL). Heating (56 degrees C/30 minutes) caused the LDL titer to fall and freeze-thawing (20 degrees C/room temperature) the VLDL titer to rise slightly, possibly as a result of alteration in lipoprotein structure. The additon of lipoprotein depleted serum appeared to dampen these effects and there was no nett change in titer when it was added to a lipoprotein mixture. Similarly, unfractionated normal serum showed no significant change in titer after these treatments. The lipoproteins lacked significant virus neutralizing (VN) activity and this remained so in spite of fluctuations in HAI titer after heating and freeze-thawing.