Study of the immune response and intestinal microbiome of Aedes aegypti (Diptera: Culicidae) after challenge with Metarhizium anisopliae
Biological control, Metarhizium, Mosquito vectors, Gene expression, Innate immunity, gut microbiota, Illumina sequencing
Aedes aegypti is one of the main vectors of arboviruses of public health relevance, such as dengue, Zika, and chikungunya, and the limitations associated with the continuous use of chemical insecticides reinforce the need for alternative and more sustainable control strategies, including the use of entomopathogenic fungi. In this context, this study aimed to evaluate the response of A. aegypti larvae to infection by the fungus Metarhizium anisopliae, considering both the modulation of the humoral immune response and potential alterations in the intestinal microbiota. Rockefeller strain larvae at the L2 stage were exposed to conidial suspensions of the M. anisopliae CG 153 isolate at a concentration of 1 × 10⁵ conidia mL⁻¹ and maintained under controlled temperature and humidity conditions. In Chapter 1, after 24 and 48 hours of exposure, intestines, fat bodies, and whole larvae were collected for RNA extraction, cDNA synthesis, and gene expression analysis by RT-qPCR, encompassing genes associated with the innate immune pathways Toll, IMD, and JAK-STAT, as well as antimicrobial peptides. In Chapter 2, the intestinal microbiota was analyzed by next-generation sequencing, followed by filtering, quality control, and data processing steps. The results from Chapter 1 showed that the expression of the evaluated genes exhibited variations dependent on the analyzed tissue and post-infection time, without a homogeneous pattern among the components of the immune pathways, while antimicrobial peptides displayed distinct expression profiles across tissues and time points. Microbial ecology analyses indicated maintenance of richness, diversity, and overall composition of the intestinal microbiota between control and infected groups, with no evident separation of microbial profiles at the analyzed time points. Taken together, the results indicate that larval infection by M. anisopliae is associated with an immune response modulated in a tissue- and time-dependent manner, without expressive alterations in the overall structure of the intestinal microbiota under the experimental conditions evaluated, contributing to the understanding of interactions between A. aegypti and entomopathogenic fungi in the context of biological control.