Vector competence and immune response of Aedes aegypti for Ebinur Lake virus, a newly classified mosquito-borne orthobunyavirus

The global impact of mosquito-borne diseases has increased significantly over recent decades. Ebinur Lake virus (EBIV), a newly classified orthobunyavirus, is reported to be highly pathogenic in adult mice. The evaluation of vector competence is essential for predicting the arbovirus transmission risk. Here, Aedes aegypti was applied to evaluate EBIV infection and dissemination in mosquitos. Our experiments indicated that Ae. aegypti had the possibility to spread EBIV (with a transmission rate of up to 11.8% at 14 days post-infection) through biting, with the highest viral dose in a single mosquito's saliva reaching 6.3 plaque-forming units. The highest infection, dissemination and ovary infection rates were 70%, 42.9%, and 29.4%, respectively. The high viral infection rates in Ae. aegypti ovaries imply the possibility of EBIV vertical transmission. Ae. aegypti was highly susceptible to intrathoracic infection and the saliva-positive rate reached 90% at 10 days post-infection. Transcriptomic analysis revealed Toll and Imd signaling pathways were implicated in the mosquito's defensive response to EBIV infection. Defensin C and chitinase 10 were continuously down-regulated in mosquitoes infected via intrathoracic inoculation of EBIV. Comprehensive analysis of the vector competence of Ae. aegypti for EBIV in laboratory has indicated the potential risk of EBIV transmission through mosquitoes. Moreover, our findings support a complex interplay between EBIV and the immune system of mosquito, which could affect its vector competence. Author summary Aedes aegypti, the major vector of numerous clinically important arboviruses such as dengue virus, is frequently used in studies of vector competence for arboviruses. Our findings imply that Ae. aegypti can get infected with EBIV following either oral feeding or intrathoracic injection, posing a risk of viral transmission. After oral infection, EBIV was able to enter saliva when the viral titer in the gut exceeded a threshold. Remarkably, the salivapositive rates in mosquitoes infected by intrathoracic injection were greater than those infected by oral feeding. The results of oral feeding and intrathoracic injection indicate that the midgut escape barrier (MEB) is the principal barrier to EBIV infection in Ae. aegypti. According to our analysis of the changes in gene expression after infection, we also found that the expression of some immune-related genes changed during early viral infection, whereas the expression of mosquito genes involved in metabolism showed significant differences at late stage of virus infection.

Automated summary

The global impact of mosquito-borne diseases has increased in recent decades. This study found that Aedes aegypti mosquitoes have the potential to spread Ebinur Lake virus (EBIV) through biting, with a transmission rate of up to 11.8%. The study also revealed a complex interplay between EBIV and the mosquito's immune system, which could affect its vector competence.