Excretory products of the cestode, Schistocephalus solidus, modulate invitro responses of leukocytes from its specific host, the three-spined stickleback (Gasterosteus aculeatus)

Scharsack J.P., Gossens A., Franke F., Kurtz J.

Abstract

Helminth parasites have evolved remarkable strategies to manipulate the immune system of their hosts. During infections of three-spined stickleback (Gasterosteus aculeatus) with the cestode Schistocephalus solidus prominent immunological changes occur, presumably due to manipulative activity of the parasite. We hypothesise that excretory/secretory products of the parasite are involved in the manipulation of the stickleback's immune system and that this may depend on the individual parasite and its origin. We therefore produced S.solidus conditioned cell culture media (SSCM) with parasites from different origins (Norway, Spain and Germany) and exposed head kidney leukocytes (HKL) from un-infected sticklebacks in cell cultures to SSCM. After invitro culture, HKL were subjected to differential cell counts (granulocytes/lymphocytes) by means of flow cytometry. Leukocyte sub-populations were analysed for cell viability and changes in cell morphology. The respiratory burst activity was measured with a luminescence assay. Exposure of HKL to SSCM induced an up-regulation of respiratory burst activity after already 1h, which was still elevated at 24h, but which was in some cases significantly down-regulated after 96h. Respiratory burst was positively correlated with the number of live granulocytes in the culture, suggesting that the respiratory burst activity was changed by SSCM effects on granulocyte viability. After 1h and 24h of HKL culture, no lymphocyte responses to SSCM were detectable, but after 96h lymphocyte viability was significantly decreased with SSCM from Spanish S.solidus. In these cultures, residual lymphocytes increased in size, suggesting that cell death and activation might have occurred in parallel. The highest respiratory burst activity was induced by SSCM from Spanish parasites, in particular when they were grown in sympatric sticklebacks. © 2013 Elsevier Ltd.