Polydnavirus infection inhibits translation of specific growth-associated host proteins

Abstract

The wasp Campoletis sonorensis injects a polydnavirus (CsPDV) along with its egg during parasitization of Heliothis virescens larvae. CsPDV protects the wasp egg and larvae by selectively disabling the host's cellular immune response, and by altering host physiology, growth, and development. Among the changes in host physiology brought about by CsPDV infection is a rapid, and specific decline in the translation of fat body mRNAs encoding selected major plasma proteins. Translational inhibition of the synthesis of all storage protein monomers, p82 (Riboflavin binding hexamer), and p74/p76 (arylphorin), occurs upon infection with CsPDV. Moreover, the prewandering peak of the plasma enzyme juvenile hormone esterase (JHE) was blocked by CsPDV injection. Northern blotting of fat body mRNA demonstrated that transcript levels of storage proteins were not affected by infection. Plasma titers of the iron binding proteins transferrin (p72) and ferritin (p24/26), and of the plasma juvenile hormone binding protein (p25) were not changed by CsPDV infection. That storage protein and JHE synthesis are translationally suppressed, while the synthesis of other plasma proteins continues apace, suggests that CsPDV infection may lead to translational discrimination among available mRNAs in CsPDV infected fat bodies. The effect of this translational discrimination is to shunt host resources away from larval growth and adult development, which presumably makes them available to the developing endoparasitoid.