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Identification and tissue tropism of newly identified iflavirus and negevirus in Glossina morsitans morsitans tsetse flies
Tsetse flies cause major health and economic problems as they transmit trypanosomes causing sleeping sickness in humans (Human African Trypanosomosis, HAT) and nagana in animals (African Animal Trypanosomosis, AAT). A solution to control the spread of these flies and their associated diseases is the Sterile Insect Technique (SIT).
For successful application of SIT it is important to establish and maintain healthy and competitive insect colonies. However, mass production of tsetse is threatened by covert virus infections, such as the Glossina pallidipes salivary gland hypertrophy virus (GpSGHV). This virus infection can switch from a covert asymptomatic to an overt symptomatic state and can cause the collapse of an entire fly-colony. Although the effects of GpSGHV infections can be mitigated, the presence of other covert viruses threaten tsetse mass production. Recently, the research group of Adly Abd Alla (Insect Pest Control Laboratory, IAEA, Austria) demonstrated the presence of an iflavirus and a negevirus, both positive-sense, single-stranded RNA viruses, in tsetse (Glossina) species at the Seibersdorf rearing facility (Insect Pest Control Laboratory, IAEA, Austria). We are currently assessing the prevalence of the iflavirus and negevirus in various tseste species. Our preliminary results demonstrated Glossina pallidipes is a species without iflavirus and negevirus and the species with the highest prevalence is Glossina mositans morsitans. We analyzed the tissue tropism of these viruses in G. m. morsitans to decipher their mode of transmission. To analyze this tissue tropism, we used the Stellaris in situ hybridization technique with fluorescent probes. Our results demonstrate that both viruses can be found in both males and females, in the brain and fat bodies, and also in their reproductive organs (ovaries and testes), as well as in the milk and salivary glands. These findings suggest a potential horizontal transmission route during feeding and/or a vertically way of transmission from parent to offspring. At the Laboratory of Virology of Wageningen University, the Netherlands, I am currently trying to isolate and visualize the virus particles. Afterwards I plan to do infection studies in Glossina pallidipes, the species not naturally carrying iflavirus and negevirus, to get the first information about the effect of these viruses on host fitness.
Legend for lead image:
Virus localisation in Glossina morsitans morsitans: Stellaris rRNA-Fluorescence in situ Hybridization (FISH) in fatbody tissue of female Glossina morsitans morsitans aged 30 days. In blue: Nucleus (Dapi staining (4′,6-diamidino-2-phenylindole)), In green: F-Actin staining (488 phalloidin), In red: Iflavirus, In cyan: Negevirus, Magnification 40x; Please note: Arrow head shows the colocalization between Iflavirus and Negevirus. (picture taken by Dr. Anton Strunov)