Parasitism by Cotesia flavipes induces immunosuppression of Diatraea saccharalis and Eoreuma loftini

A gregarious endoparasitoid wasp, Cotesia flavipes, parasitizes the sugarcane borer, Diatrae saccharalis. During oviposition, the parasitoid wasp Cotesia flavipes injects polydnavirus, venom, and parasitoid eggs into larvae of its lepidopteran host, the sugarcane borer, Diatraea saccharalis. Polydnaviruses (PDVs) suppress the immune system of the host and allow the juvenile parasitoids to develop without being encapsulated by host hemocytes mobilized by the immune system, and eventually leading to death of the host. This study focused on the effect of C. flavipes parasitization on encapsulation immune response and glucose dehydrogenase (GLD) activity of D.saccharalis and Mexican rice borer, Eoreuma loftini. For this purpose, both parasitized and unparasitized larvae were injected with Sephadex A-25 beads, and the number of encapsulated beads was counted. For GLD activity both parasitized and unparasitized larvae were dissected after a definite time and a known amount of the hemolymph was collected and then the activity of the enzyme was measured at 600 nm absorbance. Our Results demonstrated that the percentage of the encapsulated beads in both D. saccharalis and E. loftini was strongly reduced in parasitized larvae compared to unparasitized. Moreover, the GLD activity increased immediately post-oviposition, indicating that virions elicit nonself recognition.