Wolbachia strain wAlbB blocks replication of flaviviruses and alphaviruses in mosquito cell culture

O’Mezie Ekwudu,Gregor J Devine,John G Aaskov,Francesca D Frentiu

doi:10.1186/s13071-020-3936-3

Abstract

BackgroundWolbachia pipientis are bacterial endosymbionts of arthropods currently being implemented as biocontrol agents to reduce the global burden of arboviral diseases. Some strains of Wolbachia, when introduced into Aedes aegypti mosquitoes, reduce or block the replication of RNA viruses pathogenic to humans. The wAlbB strain of Wolbachia was originally isolated from Aedes albopictus, and when transinfected into Ae. aegypti, persists in mosquitoes under high temperature conditions longer than other strains. The utility of wAlbB to block a broad spectrum of RNA viruses has received limited attention. Here we test the ability of wAlbB to reduce or block the replication of a range of Flavivirus and Alphavirus species in cell culture.MethodsThe C6/36 mosquito cell line was stably infected with the wAlbB strain using the shell-vial technique. The replication of dengue, West Nile and three strains of Zika (genus Flavivirus), and Ross River, Barmah Forest and Sindbis (genus Alphavirus) viruses was compared in wAlbB-infected cells with Wolbachia-free controls. Infectious virus titres were determined using either immunofocus or plaque assays. A general linear model was used to test for significant differences in replication between flaviviruses and alphaviruses.ResultsTitres of all viruses were significantly reduced in cell cultures infected with wAlbB versus Wolbachia-free controls. The magnitude of reduction in virus yields varied among virus species and, within species, also among the strains utilized.ConclusionOur results suggest that wAlbB infection of arthropods could be used to reduce transmission of a wide range of pathogenic RNA viruses.

Highlights

Wolbachia pipientis are bacterial endosymbionts of arthropods currently being implemented as biocontrol agents to reduce the global burden of arboviral diseases
Wolbachia strain wAlbB blocks Flavivirus replication in vitro All flaviviruses tested replicated to lower titres in C6/36.wAlbB cells compared to Wolbachia-free C6/36 controls, regardless of multiplicities of infection (MOI)
Titres of West Nile virus (WNVKUN) were reduced by almost 5 logs, at later time points during infection (6–8 dpi) (Fig. 2d–f ), virus remained detectable until the end of the experiment

Summary

Introduction

Wolbachia pipientis are bacterial endosymbionts of arthropods currently being implemented as biocontrol agents to reduce the global burden of arboviral diseases. Some strains of Wolbachia, when introduced into Aedes aegypti mosquitoes, reduce or block the replication of RNA viruses pathogenic to humans. Sindbis virus (SINV) infections are associated with a rash and mild fever in humans and have caused disease outbreaks in northern Europe [10, 11]. When transinfected into Aedes aegypti mosquitoes, some Wolbachia strains block the replication and transmission of viruses such as dengue, Zika and chikungunya (CHIKV) [17,18,19,20,21,22]. The pathogen-blocking ability of Wolbachia has resulted in this biocontrol agent being trialled in the field in at least 12 countries (http://www.worldmosquitoprogram.org), with the aim of making native mosquito populations refractory to arbovirus transmission [22,23,24]

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Conclusion