Cytotoxic effects of parasitism and application of venom fromthe endoparasitoid Pimpla turionellae on hemocytes of the hostGalleria mellonella
Özet
In parasitoid species devoid of polydnaviruses and virus-like particles,
venom appears to play a major role in suppression of host immunity.
Venom from the pupal endoparasitoid Pimpla turionellae L. (Hymenoptera: Ichneumonidae) has previously been shown to contain a mixture
of biologically active components, which display potent paralytic, cytotoxic, and cytolytic effects toward lepidopteran and dipteran hosts. The
current study was undertaken to investigate if parasitism and/or envenomation by P. turionellae affects the frequency of apoptotic and necrotic
hemocytes, hemocyte viability and mitotic indices in Galleria mellonella
L. (Lepidoptera: Pyralidae) pupae and larvae. Our study indicates that
parasitism and experimental envenomation of G. mellonella by P. turionellae resulted in markedly different effects on the ratio of apoptotic hemocytes circulating in hemolymph depending on the host developmental
stages. The ratio of early and late apoptotic hemocytes increased in
G. mellonella pupae and larvae upon parasitization and at high doses of
venom when compared to untreated, null and Phosphate Buffered
Saline (PBS) injected controls. In contrast, an increase in necrotic hemocytes was only observed in parasitized pupae at 24 h and no difference
was observed in larvae. The lowest hemocyte viability values were
observed with pupae as 69.87%, 69.80%, and 72.47% at 4, 8, and 24 h
post-parasitism. The ratio of mitotic hemocytes also decreased in pupae
and larvae upon parasitization and at high doses of venom. Staining of
hemocytes with annexin V-FITC revealed green fluorescent ‘halos’ along
the plasma membranes of venom treated cells within 15 min following
exposure to venom. By 1 h post-venom – treatment, the majority of
hemocytes displayed binding of this probe, indicative of early stage
apoptosis. These same hemocytes also displayed a loss of plasma membrane integrity at the same time points as evidenced by accumulation of
propidium iodide in nuclei.
