The larval saliva of an endoparasitic wasp Pteromalus puparum supresses its host immune responses

Authors: SHI, JIAMIN - Zhejiang University; JIN, HONGXIA - Zhenjiang University; WANG, FANG - Zhenjiang University; Stanley, David; FANG, QI - Zhenjiang University; YE, GONGYIN - Zhenjiang University

Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/23/2022
Publication Date: 7/22/2022
Citation: Shi, J., Jin, H., Wang, F., Stanley, D.W., Fang, Q., Ye, G. 2022. The larval saliva of an endoparasitic wasp Pteromalus puparum supresses its host immune responses. Journal of Insect Physiology. 141. Article 104425. https://doi.org/10.1016/j.jinsphys.2022.104425.
DOI: https://doi.org/10.1016/j.jinsphys.2022.104425

Interpretive Summary: A very large group of wasps are called parasitoids because females deposit their eggs in or on other, host, insect species. Newly hatched larvae feed on host hemolymph as they develop into adults. The adult wasps leave their hosts, which typically die. Host insects evolved immune mechanisms disable parasitoids and parasitoids evolved chemicals and some viruses they inject into hosts with their eggs to disable host immune mechanisms.

Technical Abstract: In the lengthy co-evolution between insects and their animal or plant hosts, insect saliva has evolved various functions to help evade host defenses. Although there is a very large literature on saliva of herbivorous and hematophagous insects, little attention has been focused on the saliva of parasitoid wasps. Some parasitoid species are natural enemies that effectively regulate insect population sizes in nature to the extent that they are applied for biological control of agricultural pests. Here we demonstrate the influence of the parasitoid, Pteromalus puparum, larval saliva on the cellular and humoral immunity its host. Larval saliva increases mortality of hemocytes, insect blood cells, and inhibits hemocyte spreading, a specific cellular immune action. We report that high saliva concentrations act in inhibiting host cellular encapsulation of foreign of foreign invaders. The larval saliva also inhibits the melanization in host hemolymph. The saliva inhibits the growth of some bacterial species, Bacillus subtilis, Staphylococcus aureus and Pseudomonas aeruginosa. This may promote larvae fitness by protecting them from infections. Insight into such functions of parasitic wasp saliva provides a new insight into host-parasitoid relationships and possibly lead to new agricultural pest management technologies.