Population bottlenecks and temporal constraints shape dengue virus infection of Aedes aegypti midguts

Arthropod-borne viruses (arboviruses) such as dengue virus pose a significant and growing threat to human health worldwide. Maintained in a transmission cycle between arthropod vectors and vertebrate hosts, arboviruses experience strong bottlenecks during transmission which can drastically alter virus population composition and fitness. In vectors, severe population bottlenecks occur at the initial site of infection, the midgut, yet the specific factors driving this process remain unclear. To investigate these mechanisms, we need a better understanding of early infection events; however, traditional detection methods lack the necessary sensitivity. Recent advances in molecular signal amplification-based methods now make it possible to study these early stages in detail. In this study, we examined early dengue virus 2 (DENV-2) infection of Ae. aegypti midguts using multiple hybridization chain reaction techniques. We demonstrate that these techniques are much more sensitive than the traditional immunofluorescence assay and can reliably detect DENV-2 in mosquito midguts as early as 6 hours post infection. Further, we observed significant bottlenecks as only a handful of virions initiate infection of the midgut. The application of signal amplification strategies now enables critical assessment of the cellular and molecular interactions governing early infection events which could inform the development of novel interventions.