Wolbachia-mediated arbovirus inhibition in Aedes mosquitoes

Herd, Christie (2019) Wolbachia-mediated arbovirus inhibition in Aedes mosquitoes. PhD thesis, University of Glasgow.

Abstract

Currently, Aedes aegypti mosquitoes carrying Wolbachia strains wMel and wAlbB, both of which provide good levels of arbovirus transmission inhibition, are being used in field releases for dengue control. Other strains ofWolbachia might provide even stronger virus transmission inhibition in Ae. aegypti. wAu and wAlbA were transinfected into Ae. aegypti and fitness traits were characterised, as well as the ability to block arbovirus replication and transmission. These data reveal that while wAu provides complete viral blockage of dengue and Zika virus, it has a detrimental effect on fitness with reduced adult longevity and egg survival. Interestingly, although wAlbA reached a high density in the Ae. aegypti host, no pathogen inhibition was observed following challenge with Semliki Forest Virus.

The suitability of wMel, wAu and wAlbB-infected Ae. aegypti for field releases was examined by exposing larvae to higher temperatures that can occur in the field. An experimental temperature cycle was based on water temperatures recorded from larval breeding sites in Trinidad and environmental temperature in Malaysia. Larvae were exposed to these temperatures, or the normal insectary rearing temperatures, and the impact this had on Wolbachia density was assessed. Data revealed wMel and wAu were not stable following heattreatment, with drops in whole-body and ovary density, leading to reductions in maternal transmission rate. On the other hand, wAlbB remained stable following heat-treatment. Heat-treated mosquitoes were then challenged with Semliki Forest virus, revealing no significant loss of the pathogen-inhibition phenotype.

Aedes cell lines infected with the high-density wMelPop and wAu Wolbachia strains were used to investigate the mechanism of Wolbachiamediated pathogen inhibition. One hypothesis is that transinfection of Wolbachia into novel hosts primes the immune system against viruses by inducing oxidative stress. While Ae. aegypti (Aag2) wMelPop cells showed evidence of oxidative stress, Ae. albopictus (Aa23) wAu did not, yet both are strong blockers of arboviruses. Gene transcription assays indicated that wMelPop is interfering with the expression of protein chaperones that are involved in the folding of proteins in the endoplasmic reticulum (ER). This indicates Wolbachia may be modifying the ER and thereby preventing incoming virus from completing replication.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: Q Science > QR Microbiology > QR355 Virology
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Infection & Immunity > Centre for Virus Research
• Supervisor's Name: Sinkins, Prof. Steven
• Date of Award: 2019
• Embargo Date: 19 February 2022
• Depositing User: Mrs Marie Cairney
• Unique ID: glathesis:2019-41026
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 19 Feb 2019 10:24
• Last Modified: 18 Apr 2024 08:30
• Thesis DOI: 10.5525/gla.thesis.41026
• URI: https://theses.gla.ac.uk/id/eprint/41026

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