Silkworm plasmatocytes are more resistant than other hemocyte morphotypes to Bombyx mori nucleopolyhedrovirus infection

[Display omitted] ► We developed a novel reporter BmNPV and examined the NPV tropism in hemocytes. ► Silkworm plasmatocytes are more resistant than other hemocyte morphotypes to BmNPV infection. ► BmNPV infection progressed slowly in silkworm spherulocytes. Differences in the viral susceptibility of multiple insect hemocyte morphotypes have not been investigated to date. In this study, a Bombyx mori nucleopolyhedrovirus (BmNPV) derivative possessing a Drosophila hsp70 promoter-driven green fluorescent protein (GFP) gene was used to observe NPV tropism of B. mori larval hemocytes. The experiments clearly revealed that there were fewer GFP-positive plasmatocytes than those observed in other types of hemocytes, such as granulocytes, oenocytoids, and spherulocytes, when infected via the intrahemocoelic or oral route. Our results indicate that silkworm plasmatocytes are more resistant than other hemocyte morphotypes to BmNPV infection.