Background: Crimean-Congo haemorrhagic fever (CCHF) is a severe disease for humans caused by CCHF orthonairovirus (CCHFV), a class 4 pathogen. Ticks of the genus Hyalomma are the viral reservoir and they represent the main vector. CCHFV can be transmitted to its hosts during the tick blood feeding. We have previously shown that CCHFV can persistently infect Hyalomma-derived tick cell lines without any cytopathic effect. However, the mechanism allowing the establishment of a persistent viral infection in ticks is still unknown. It has been recently reported that Hazara orthonairovirus (HAZV) can be used as a BSL-2 viral model instead of CCHFV to study viral/vector interaction. The aim of our study is to elucidate the mechanism allowing the establishment of the CCHFV persistent infection in ticks by using HAZV as a model. Methods: We used classical and molecular methods applied to virology to characterize the establishment of the HAZV persistent infection in two Hyalomma anatolicum-derived cell lines, Hae/CTVM8 and Hae/CTVM9. Results and Conclusions: As for CCHFV, we showed that HAZV persistently infects tick cells without any sign of cytopathic effect, and that cells can be cultured for more than one year. The persistent infection is established in roughly 15 days post-infection and viral titer is maintained at lower level with prospect to the earlier time points. Interestingly, short viral derived DNA forms (vDNAs) start to be detected in parallel with the beginning of viral replication and are maintained in persistently infected cells. Experiments with the antiretroviral drug AZT suggest that vDNAs are produced by a retrotranscripatse activity; furthermore we collected evidence that vDNAs are not integrated, and seem to be involved in downregulation of viral replication by promoting cell survival. In conclusion, vDNA synthesis might represent a strategy to control the replication of RNA viruses in ticks, as recently demonstrated in insect, allowing the persistent infection in viral vectors.

The persistent infection of tick cells by Hazara orthonairovirus is mediated by virus-derived DNA forms.

M. V. Salvati;C. Del Vecchio;C. Parolin;A. Calistri;G. Palù;C. Salata.
2019

Abstract

Background: Crimean-Congo haemorrhagic fever (CCHF) is a severe disease for humans caused by CCHF orthonairovirus (CCHFV), a class 4 pathogen. Ticks of the genus Hyalomma are the viral reservoir and they represent the main vector. CCHFV can be transmitted to its hosts during the tick blood feeding. We have previously shown that CCHFV can persistently infect Hyalomma-derived tick cell lines without any cytopathic effect. However, the mechanism allowing the establishment of a persistent viral infection in ticks is still unknown. It has been recently reported that Hazara orthonairovirus (HAZV) can be used as a BSL-2 viral model instead of CCHFV to study viral/vector interaction. The aim of our study is to elucidate the mechanism allowing the establishment of the CCHFV persistent infection in ticks by using HAZV as a model. Methods: We used classical and molecular methods applied to virology to characterize the establishment of the HAZV persistent infection in two Hyalomma anatolicum-derived cell lines, Hae/CTVM8 and Hae/CTVM9. Results and Conclusions: As for CCHFV, we showed that HAZV persistently infects tick cells without any sign of cytopathic effect, and that cells can be cultured for more than one year. The persistent infection is established in roughly 15 days post-infection and viral titer is maintained at lower level with prospect to the earlier time points. Interestingly, short viral derived DNA forms (vDNAs) start to be detected in parallel with the beginning of viral replication and are maintained in persistently infected cells. Experiments with the antiretroviral drug AZT suggest that vDNAs are produced by a retrotranscripatse activity; furthermore we collected evidence that vDNAs are not integrated, and seem to be involved in downregulation of viral replication by promoting cell survival. In conclusion, vDNA synthesis might represent a strategy to control the replication of RNA viruses in ticks, as recently demonstrated in insect, allowing the persistent infection in viral vectors.
2019
Abstracs Book
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/3308224
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