Resistance of Insect to Pathogenic Viruses

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Nucleopolyhedrovirus (NPV) of the silkworm was inactivated after incubation with the silkworm hemolymph. Inactivation activity was located in the fraction that passed a filter with 5 kd M.W.and inhibitors of that activity existed in the fraction with more than 5Kd. Inactivation activity was retained after heat and protease treatment of the fraction. We also detected that glutathion inactivated NPV and are analyzing inactivation mechanism of NPV by the hemolymph and other compounds.An increase in median lethal dose (LD50) and median lethal time (LT50) values with increased larval age was recorded in bioassay studies of the nucleopolyhedrovirus (NPV) infected Spodoptera litura Fab. larvae. The LD50 values and LT50 increase with increased larval age. Larvae those were more than 11-day-old after hatching was not infected through oral inoculation even at the highest dose of the trial. However, intrahaemocoelic injection of NPV into matured larvae resulted into death due to viral infection indicating a lack of susceptibility possibly due to gut mediated barrier that developed as the larvae approached pupation.