Larval secretions of parasitoid wasps are new effectors that impair host immune defences

Parasitoid wasps belong to a remarkably successful group of biological control agents. To ensure effective parasitism, parasitoid wasps have evolved various effectors to modulate host immune responses, such as venom, PDVs and teratocytes. However, little information is available for wasp larval secretions. Here, we applied the Drosophila parasitoids Leptopilina boulardi and L. heterotoma as a study model to investigate the larval secreted components and the potential molecules manipulating host immune responses. We obtained 388 and 30 larval secreted proteins from L. boulardi and L. heterotoma, respectively. These results were consistent with the fact that L. boulardi larvae encounter more severe immune challenges in comparison with L. heterotoma. We further revealed that parasitoid wasps have evolved specialized secreted proteins to inhibit host melanization responses via serpins, as well as a group of metalloproteases may contribute to impairing host encapsulation responses. Our findings provide the evidence that larval secretions of parasitoid wasps are new effectors and further uncover their potential roles in manipulating host immune responses.