Keywords
1. Myxozoan parasite immunity
2. Sphaerospora molnari infection
3. Common carp immune response
4. Presporogonic development in fish
5. Fish-parasite co-evolution
Recent scientific advancements in understanding host-parasite interactions have led to breakthroughs in the field of aquaculture health management. A cornerstone study recently shed light on the dynamics of cellular and humoral immune responses in common carp (Cyprinus carpio) against the myxozoan parasite Sphaerospora molnari. Published in ‘Parasites & Vectors’ with the DOI: 10.1186/s13071-019-3462-3, the paper is a product of extensive research by an international group of scientists, aimed at decoding the early proliferative stages of myxozoans and their expansion within the fish hosts before spore formation.
The study, backed by strong funding from the European Commission’s Horizon 2020 program and grants from Czech agencies (Grantová Agentura České Republiky and Technologická Agentura České Republiky), was conducted over a span of 63 days in a controlled laboratory setting. The collaborative effort was spearheaded by experts from the Institute of Parasitology, Biology Centre of the Czech Academy of Sciences, and the Faculty of Fisheries and Protection of Waters at the University of South Bohemia, among others from Wageningen University & Research.
Sphaerospora molnari is a pervasive parasite in central Europe known for causing sphaerosporosis, an ailment that affects the skin and gills of common carp. Previous studies have been limited by seasonal availability of the life-cycle stages of these parasites; however, this research overcame that limitation by establishing a laboratory model that could study the parasite year-round. Through their work, the researchers provided an unprecedented look into the kinetics of presporogonic development of S. molnari, cataloging a symbiotic dance between the invasive parasite and the carp’s immune system.
The scientists isolated the motile and dividing stages of S. molnari from infected carp blood and introduced them into healthy carp to monitor the infection’s progression and associated immune responses. Their observations indicated an incredibly rapid parasite clearance from the peritoneal cavity — less than 40 hours post-infection. This was followed by a covert period of infection where moderate pro-inflammatory responses were noted for about 1-2 weeks. Once this period was over, parasite multiplication in the blood peaked at 28 days post-infection (dpi), triggering a massive response from lymphocytes.
Interestingly, a dramatic shift was observed in the host’s immune reaction with up to a 1456-fold expression increase of the anti-inflammatory cytokine IL-10, alongside a significant augmentation in the expression of IgM transcripts and an increase in the number of IgM+ B cells. This alternating sequence from inflammation to anti-inflammatory reactions suggests a complex interplay as the carp’s immune system adjusts to the invading parasite.
The research also brings new insights into the co-evolutionary adaptation mechanisms between early metazoans such as Cnidaria, from which myxozoans descend, and the basic vertebrate immune systems as represented by fish. These findings are not just crucial from a biological perspective, but they could pave the way for developing more effective strategies for managing parasitic diseases in aquaculture, potentially safeguarding a critical food supply.
The wealth of data from this investigation extends the knowledge on host-parasite interaction and offers novel perspectives on the evolution of host adaptation and parasite immune evasion strategies. The multidimensional analysis that includes the cellular count, cytokine profiling, and immunoglobulin expression, will be instrumental in shaping future interventions against myxozoan infections.
The original study is supported by an array of peer-reviewed literature that provides context and foundation to these findings. These include works that explore the evolution of the innate and adaptive arms of immune systems, studies on fish immune response to myxozoans, and articles that outline the complex life cycles of these parasites.
This landmark study emphasizes the importance of integrative approaches in combating diseases within the aquatic food industry. As researchers continue to unravel the layers of immune system complexity in the common carp, their work contributes substantially to the conservation of aquaculture across the globe.
References
1. Holzer, A. S., Bartošová-Sojková, P., Born-Torrijos, A., Lövy, A., Hartigan, A., Fiala, I. (2018). The joint evolution of the Myxozoa and their alternate hosts: a cnidarian recipe for success and vast biodiversity. Molecular Biology, 27(8), 1651-1666. DOI: 10.1186/s13071-019-3462-3
2. Tort, L., Balasch, J. C., Mackenzie, S. (2003). Fish immune system: A crossroads between innate and adaptive responses. Inmunología, 22(3), 277-286.
3. Sitjà-Bobadilla, A., Schmidt-Posthaus, H., Wahli, T., Holland, J. W., Secombes, C. J. (2015). Fish immune responses to Myxozoa. In: Myxozoan Evolution, Ecology and Development (pp. 253-280). Springer, Cham.
4. Atkinson, S. D., Bartholomew, J. L., Lotan, T. (2018). Myxozoans: ancient metazoan parasites find a home in phylum Cnidaria. Zoology, 129, 66-68. DOI: 10.1016/j.zool.2018.06.004
5. Gibson, A. K., Stoy, K. S., Gelarden, I. A., Penley, M. J., Lively, C. M., Morran, L. T. (2015). The evolution of reduced antagonism—A role for host-parasite coevolution. Evolution, 69(11), 2820-2830. DOI: 10.1111/evo.12779
Note to Editors
The study provides a landmark overview of the immune responses in common carp to parasite infections and will be relevant to researchers in the fields of molecular biology, aquaculture health management, evolutionary biology, and conservation. For any additional information or interviews with the authors, please refer to the contact details provided alongside the original publication.