Immune Response of Larvae to Infection with the Nematobacterial Complex .

Entomopathogenic nematodes have been proposed as biological agents for the control of , an invasive pest of small-stone and soft-skinned fruits. Larvae of the fly are susceptible to infection but the reaction of immune defenses of the host are unknown. To determine the immune response, larvae were infected with and to evaluate the effector mechanisms of both humoral and cellular processes. The symbiont bacteria presented an inhibitory effect on the phenoloxidase cascade with a low level of melanization. Besides, activated the synthesis of putative antimicrobial peptides on the hemolymph of infected larvae. However, those peptides presented a lower antimicrobial activity compared to hemolymph from larvae infected with non-symbiont bacteria. avoided also the phagocytosis response of hemocytes. During in vitro and in vivo assays, was not encapsulated by cells, unless the cuticle was damaged with a lipase-treatment. Hemocyte counts confirmed differentiation of lamellocytes in the early phase of infection despite the unrecognition of the nematodes. Both and avoided the cellular defenses of larvae and depressed the humoral response. These results confirmed the potential of entomopathogenic nematodes to control