Arthropods harbour a rich microbiota in their gut that influences different aspects of their biology, including development, reproduction and immune responses. Mosquitoes can transmit flaviviruses like dengue virus (DENV) and Zika virus (ZIKV) to humans, and infections present as fever episodes that can potentially progress into severe and fatal illnesses. Outbreaks of mosquito-borne flavivirus diseases are a global concern for public health. Control measures typically involve mosquito elimination with insecticides, a strategy that poses risks to both the environment and human health. In addition, this approach can lead to the emergence of insecticide-resistant mosquitoes, further complicating the situation. New, sustainable and effective methods are urgently needed to control mosquito-borne diseases. Previous reports indicated that the microbiota in the mosquito gut can influence virus transmission. Thus, the interaction between the mosquito gut and viruses could be leveraged as a target for controlling flaviviruses. In this study, Zhang et al. identified a bacterium from the gut of Aedes albopictus mosquitoes that protected them from infection with DENV and ZIKV.
What are the mechanisms underlying the impairment of flavivirus by Rosenbergiella sp. YN46? The authors determined that a glucose dehydrogenase secreted by the bacteria was responsible for inhibiting DENV2 and ZIKV infection in A. albopictus and A. aegypti. A polyclonal anti-glucose dehydrogenase antiserum allowed the mosquitoes to become infected, and a Rosenbergiella sp. YN46 knockout mutant of the glucose dehydrogenase gene did not protect the mosquitoes against DENV2 and ZIKV infection. The authors further demonstrated that the glucose dehydrogenase secreted by the bacterial commensal converted glucose into gluconic acid, acidifying the mosquito’s gut lumen below pH 6.5. Such acidity irreversibly changed the conformation of flavivirus E protein, which mediates viral entry into the host cell, thus inhibiting flavivirus infection in the mosquito gut. To understand the dengue epidemiological implications of Rosenbergiella sp. YN46, the authors analysed its prevalence in mosquitoes from dengue-endemic and low dengue-incidence areas. The symbiont was more prevalent in the guts of mosquitoes of low-dengue-incidence cities. Last, the authors performed semi-field experiments (that is, studies conducted in facilities that simulate the natural field) and found that Rosenbergiella sp. YN46 exhibited effective transstadial transmission in field mosquitoes, and the bacterium blocked the transmission of DENV2 by newly emerged adult mosquitoes.
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