Rommel J Gestuveo, Rhys Parry, Laura B Dickson, Sebastian Lequime, Vattipally B Sreenu, Matthew J Arnold, Alexander A Khromykh, Esther Schnettler, Louis Lambrechts, Margus Varjak, Alain Kohl
Aedes aegypti mosquitoes that transmit human-pathogenic viruses rely on the exogenous small interfering RNA (exo-siRNA) pathway as part of antiviral responses. This pathway is triggered by virus-derived double-stranded RNA (dsRNA) produced during viral replication that is then cleaved by Dicer 2 (Dcr2) into virus-derived small interfering RNAs (vsiRNAs). These vsiRNAs target viral RNA, leading to suppression of viral replication. The importance of Dcr2 in this pathway has been intensely studied in the Drosophila melanogaster model but is largely lacking in mosquitoes. Here, we have identified conserved and functionally relevant amino acids in the helicase and RNase III domains of Ae. aegypti Dcr2 that are important in its silencing activity and antiviral responses against Semliki Forest virus (SFV). Small RNA sequencing of SFV-infected mosquito cells with functional or mutated Dcr2 gave new insights into the nature and origin of vsiRNAs. The findings of this study, together with the different molecular tools we have previously developed to investigate the exo-siRNA pathway of mosquito cells, have started to uncover important properties of Dcr2 that could be valuable in understanding mosquito-arbovirus interactions and potentially in developing or assisting vector control strategies.
(in press)
Matthew J. Arnold, Laura M. Bergner, Haris Malik, Nardus Mollentze, Daniel G. Streicker, and Simon A. Babayan
Knowledge of viral infection in marine mammals, a group of organisms uniquely threatened by human activity, is almost exclusively restricted to the pathology and epidemiology of a few endemic, pathogenic viruses. Studies at the level of entire viral communities are now possible and can identify the ecological and evolutionary factors that shape patterns of viral infection more broadly and, in turn, how changes to populations and environments could impact on the prevalence and diversity of viruses. In this chapter, I applied shotgun metatranscriptomic sequencing to species, age, and sex separated pools comprising 238 tissue samples from 134 individual animals from 15 marine mammal species collected as part of a routine strandings response programme in Scotland. I identified viral sequences in almost all sequencing pools,forming more than 120 distinct viral taxonomic units. Formulating these as a virus-host network revealed patterns of virus sharing structured by host taxonomy, with viral communities of seals differing from those of cetaceans. Despite frequent sharing among seals and among cetaceans, I observed only one probable case of virus sharing between the two groups. Host taxonomy predicted viral community composition, with host species explaining around half of the variation between pools, reflecting the connected nature of the virus host network. In contrast, generalised linear models of viral richness showed no difference based on host taxonomy. Instead, host age was
the most important factor, with viral communities in juveniles roughly twice as rich as those of adults or neonates. Overall, these results shed light on patterns of viral diversity specific to marine mammals and reveal commonalities with other systems, providing key context for future disease surveillance and control strategies.