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Bombyx mori nucleopolyhedrovirus (BmNPV) causes infection in the silkworm that is often lethal. The infection is hard to prevent, partly because of the nature of the virus particles and partly because of the different strains of B. mori. Titanium dioxide nanoparticles (TiO₂ NPs) have been demonstrated to have antimicrobial properties. The present study investigated whether TiO₂ NPs added to an artificial diet can increase the resistance of B. mori larvae to BmNPV and examined the molecular mechanism behind any resistance shown. The results indicated that ingested TiO₂ NPs decreased reactive oxygen species and NO accumulation in B. mori larvae under BmNPV infection, which in turn led to a decrease in their growth inhibition and mortality. In addition, the TiO₂ NPs significantly promoted the expression of resistance-related genes, including those encoding superoxide dismutase, catalase, glutathione peroxidase, acetylcholine esterase, carboxylesterase, heat shock protein 21, glutathione S transferase o1, P53, and transferring and of genes encoding cytochrome p302 and nitric oxide synthase. These findings are a useful addition to the understanding of the mechanism of BmNPV resistance of B. mori larvae in response to TiO₂ NPs addition. Such information also provides a theoretical basis for the use of TiO₂ NPs in sericulture.

One of the most important agents causing lethal disease in the silkworm is the Bombyx mori nucleopolyhedrovirus (BmNPV), while low-dose rare earths are demonstrated to increase immune capacity in animals. However, very little is known about the effects of added CeCl(3) on decreasing BmNPV infection of silkworm. The present study investigated the effects of added CeCl(3) to an artificial diet on resistance of fifth-instar larvae of silkworm to BmNPV infection. Our findings indicated that added CeCl(3) significantly decreased inhibition of growth and mortality of fifth-instar larvae caused by BmNPV infection. Furthermore, the added CeCl(3) obviously decreased lipid peroxidation level and accumulation of reactive oxygen species such as O(2)(-), H(2)O(2), (·)OH, and NO and increased activities of the antioxidant enzymes including superoxide dismutase, catalase, ascorbate peroxidase, glutathione peroxidase, ascorbate, and glutathione contents in the BmNPV-infected fifth-instar larvae. In addition, the added CeCl(3) could significantly promote acetylcholine esterase activity and attenuate the activity of inducible nitric oxide synthase in the BmNPV-infected fifth-instar larvae. These findings suggested that added CeCl(3) may relieve oxidative damage and neurotoxicity of silkworm caused by BmNPV infection via increasing antioxidant capacity and acetylcholine esterase activity.