Investigating multiple factors affecting the successful infection and transmission of arboviruses

Widlake, Emma

Abstract

Arboviruses are arthropod-borne viruses that cycle between a vertebrate host and an arthropod vector. This disparate life cycle involves adapting to two alternate animals and the differing tissues and systems within them. A range of factors influence the ability of a mosquito to transmit a virus, including internal factors such as mosquito immunity, the mosquito microbiota and the mutation rate of the virus itself, and external factors such as exposure to agricultural chemicals and warming global temperatures. I looked at several factors affecting the establishment of infection and transmission of arboviruses. Three low-fidelity mutants of Venezuelan Equine Encephalitis Virus (VEEV), which produce a higher mutation rate than the wild-type virus, were previously identified as unable to successfully infect mosquitoes. To understand why these low-fidelity mutants were attenuated, I serially passaged wildtype VEEV and the three low-fidelity mutants in a new cell culture model designed to replicate bottlenecks within arbovirus transmission. This would enable us to understand why the low-fidelity mutants were attenuated in previous in vivo mosquito and mouse infections. Furthermore, we wanted to see if the low-fidelity nature changed the RNAi response, a key antiviral immune response within mosquitoes. We looked to see if the RNAi response was different for TC83_3X (a low-fidelity mutant) compared to the parent TC83 VEEV-vaccine strain using in vitro cell culture experiments and RNA sequencing. Finally, I wanted to understand the impact of external factors on vector competence, given many factors will act on wild mosquito populations. I determined if two agricultural chemicals, glyphosate and triticonazole, or exposure to the insect-specific virus Negevirus (NEGV), altered the vector competence of Aedes aegypti for Chikungunya virus (CHIKV) or Zika virus (ZIKV). To summarise the results, we found that the previously seen attenuation of the three low-fidelity VEEV variants is likely due to their inability to traverse bottlenecks associated with mosquito infection, and that the RNAi response did not differ between parent TC83 and low-fidelity TC83_3X. Both Glyphosate and Triticonazole slightly reduced the vector competence of A. aegypti for both CHIKV and ZIKV whilst exposure to NEGV increased the percentage of the mosquito population infected with both viruses. However, NEGV exposure reduced the percentage of infected mosquitoes with dissemination, which may subsequently reduce the likelihood of transmission due to lower likelihood of infectious virus reaching mosquito salivary glands. Our work covered a range of internal and external factors and identified their influence on vector competence. This has greater implications for our understanding of the establishment of arboviral infection and their transmission.

Citation

Widlake, E. (2024). Investigating multiple factors affecting the successful infection and transmission of arboviruses. (Thesis). Keele University. Retrieved from https://keele-repository.worktribe.com/output/850302

• Thesis Type: Thesis
• Deposit Date: Jun 14, 2024
• Publicly Available Date: Jun 20, 2024
• Public URL: https://keele-repository.worktribe.com/output/850302
• Award Date: 2024-06