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Daniel I. Bolnick, Sophia Arruda, Christian Polania, Lauren Simonse, Arshad Padhiar, Maria L. Rodgers, and Andrea J. Roth-Monzón: Read the article
Coinfections reveal a complex battle of genetics. Continue reading to discover how parasites not only manipulate but also affect host traits!
Indirect genetic effects occur when genetic differences in one organism influence the traits of another. For instance, parasites produce antigens that can trigger or evade a host’s immune response, with genetic variations among parasites leading to differences in immune reactions across hosts. In a study on host-parasite interactions, researchers from the University of Connecticut have uncovered surprising findings about how coinfecting parasite strains impact their host's immune response. When two or more parasite strains infect the same host, one might expect the host's immune response to match the most dominant parasite. Instead, this study shows that coinfections in threespine stickleback fish can produce an “overdominant effect” where the host’s immune reaction is even stronger than the reaction to either parasite’s antigens alone.
Dr. Daniel I. Bolnick and his team's study focused on the parasitic cestode Schistocephalus solidus, a worm known for its invasive effects on the stickleback fish’s body. The study aimed to see how different parasite genotypes influence host traits, especially under coinfection. Using experiments and theoretical models, the researchers showed that the dominance of parasite indirect genetic effects during coinfections could significantly impact parasite evolution. For instance, coinfections with overdominant immune responses can inhibit the spread of immune-evasive parasite genotypes, potentially reducing gene flow between parasites in different stickleback populations.
The results, published in The American Naturalist, highlight that coinfecting parasites with distinct genetic traits can elicit an immune response greater than any parasite alone could cause. This suggests a new mechanism of immune system interaction under multiple infections. The findings demonstrate that host immune systems can respond more aggressively to multiple parasite genotypes. This has significant implications for understanding how infections influence host immunity and could inform strategies for managing wildlife and human health in environments where infections are prevalent.
In conclusion, the authors found that when multiple genotypes of a species interact with another species, such as parasites infecting a host, they can exert varying levels of influence on the traits of their partner. In a broader context, understanding how the genetic differences in one organism influence the traits of another could provide valuable insights into biomedical challenges, such as how multiple drugs interact to influence a single trait in a host, which is a growing focus in cancer immunotherapy research.
Elvira D’Bastiani is a Brazilian quantitative ecologist focused on understanding the causes and consequences of host-parasite interactions. She is a postdoctoral researcher in the Department of Ecology and Evolutionary Biology at the University of California, Los Angeles (UCLA). When not studying parasite-host interactions, she enjoys engaging in outreach through her Women in Ecology project, playing beach tennis, talking with her family, cooking, and traveling to new places.
