A Neurotoxic Insecticide Promotes Fungal Infection in Aedes aegypti Larvae by Altering the Bacterial Community.

Symbiotic bacteria have a significant impact on the formation of defensive mechanisms against fungal pathogens and insecticides. The microbiome of the mosquito Aedes aegypti has been well studied; however, there are no data on the influence of insecticides and pathogenic fungi on its structure. The fungus Metarhizium robertsii and a neurotoxic insecticide (avermectin complex) interact synergistically, and the colonization of larvae with hyphal bodies is observed after fungal and combined (conidia + avermectins) treatments. The changes in the bacterial communities (16S rRNA) of Ae. aegypti larvae under the influence of fungal infection, avermectin toxicosis, and their combination were studied. In addition, we studied the interactions between the fungus and the predominant cultivable bacteria in vitro and in vivo after the coinfection of the larvae. Avermectins increased the total bacterial load and diversity. The fungus decreased the diversity and insignificantly increased the bacterial load. Importantly, avermectins reduced the relative abundance of Microbacterium (Actinobacteria), which exhibited a strong antagonistic effect towards the fungus in in vitro and in vivo assays. The avermectin treatment led to an increased abundance of Chryseobacterium (Flavobacteria), which exerted a neutral effect on mycosis development. In addition, avermectin treatment led to an elevation of some subdominant bacteria (Pseudomonas) that interacted synergistically with the fungus. We suggest that avermectins change the bacterial community to favor the development of fungal infection.

Genetic determination of the immune response in mice to cells of different histological type.

The intensity of the cellular immune response to strong transplantation antigens of the H-2 complex is related to the histological type of cells taken for immunization. Splenic cells from C3H mice immunized BALB/c mice better than cells of non-lymphoid origin from the same donor. The reverse was observed when, instead of BALB/c mice, C57B1/6 and A/He were used in immunization experiments. Analysis of the inheritance of this immunization pattern studied in mice of the first generation from various crosses between strains (BALB/c, C57B1/6 and A/He) and in mice from backcrosses has demonstrated that this immunization pattern is not inherited as a simple Mendelian character. Therefore, it could be supposed that efficiency of immunological control of cells having different histological types, may be genetically determined.