Impacts of fungal entomopathogens on survival and immune responses of Aedes albopictus and Culex pipiens mosquitoes in the context of native Wolbachia infections

Abstract

Microbial control of mosquitoes via the use of symbiotic or pathogenic microbes, such as Wolbachia and entomopathogenic fungi, are promising alternatives to synthetic insecticides to tackle the rapid increase in insecticide resistance and vector-borne disease outbreaks. This study evaluated the susceptibility and host responses of two important mosquito vectors, Ae. albopictus and Cx. pipiens, that naturally carry Wolbachia, to infections by entomopathogenic fungi. Our study indicated that while Wolbachia presence did not provide a protective advantage against entomopathogenic fungal infection, it nevertheless influenced the bacterial / fungal load and the expression of select anti-microbial effectors and phenoloxidase cascade genes in mosquitoes. Furthermore, although host responses from Ae. albopictus and Cx. pipiens were mostly similar, we observed contrasting phenotypes with regards to susceptibility and immune responses to fungal entomopathogenic infection in these two mosquitoes. This study provides new insights into the intricate multipartite interaction between the mosquito host, its native symbiont and pathogenic microbes that might be employed to control mosquito populations.

Genetics and immunity of Anopheles response to the entomopathogenic fungus Metarhizium anisopliae overlap with immunity to Plasmodium

“…Other studies performed on Aedes aegypti mosquitoes showed that the entomopathogenic fungus B. bassiana interacts with the gut microbiota to accelerate mosquito death 37 , and induces a decrease of reactive oxygen species (ROS) activity that result in an increase of the gut microbiota 38 . However, the endosymbiont Wolbachia in Aedes mosquitoes did not provide a protective advantage against entomopathogenic fungal infection 39 . We previously showed that APL1 shapes the enteric bacterial consortium in Anopheles 40 .…”

Wolbachiaenhances the survival ofDrosophilainfected with fungal pathogens

“…However, comparatively little attention has been given to the potential for Wolbachia to interact with other types of pathogens, including fungi. Prior research gave contrasting results either suggesting there was a Wolbachia-fungal infection interaction 72,75 or not 71,73,74 . However, these previous studies were performed in different contexts with many different variables between them.…”

“…Conversely, a third study on infection of female spider mites in topical contact with B. bassiana or Metarhizium fungal pathogens indicated that Wolbachia may actually increase mortality of the host with fungal infection 73 . A fourth investigated the effect of Wolbachia on injection with two Beauveria pathogens on Aedes albopictus and Culex pipiens mosquitoes 74 . This study found no enhancement in host survival with the symbiont, but reported some putative differences in host immune gene expression and reduced fungal load in some contexts.…”

Wolbachia infection in native populations of Blattella germanica and Periplaneta americana

“…Also, Wolbachia presence did not provide a protective advantage against entomopathogenic fungi, Beauveria bassiana and B . brongniartii , in two important mosquito vectors, Aedes albopictus and Culex pipiens that naturally carry Wolbachia [ 71 ]. Taken together these results plus high microbial loads, we suggest that presence of Wolbachia supergroup F may not provide protection in the German cockroach species.…”