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.

Arbovirus infections in reptiles: studies on the presence of Japanese encephalitis virus antibody in the plasma of the turtle, Trionyx sinensis.

This study was undertaken to examine further the natural infection of poikilothermic animals e.g. turtles, to Japanese encephalitis (JE) virus. Plasma samples from 75 soft-shelled fresh water turtles (Trionyx sinensis Wiegman) from China were examined in virus neutralization (VN) and hemagglutination inhibition (HAI) tests for the presence of specific antibody. The total incidence of antibody detected by either test to a titer of 10 or greater was 89% while 77% and 60% were positive by VN and HAI tests, respectively. Forty-one per cent were jointly positive by both tests. Mean HAI and VN titers were similar and showed no obvious differences between spring/summer and autumn/winter seasons. The HAI reactivity was associated with a 7S component for both seasons. The significance of this inhibition in the serology of poikilothermic hosts and the possible behaviour of T. sinensis in the natural history of JE virus is briefly considered.