Fighting Arbovirus Transmission: Natural and Engineered Control of Vector Competence in Aedes Mosquitoes

Abstract

Control of aedine mosquito vectors, either by mosquito population reduction or replacement with refractory mosquitoes, may play an essential role in the fight against arboviral diseases. In this review, we will focus on the development and application of biological approaches, both natural or engineered, to limit mosquito vector competence for arboviruses. The study of mosquito antiviral immunity has led to the identification of a number of host response mechanisms and proteins that are required to control arbovirus replication in mosquitoes, though more factors influencing vector competence are likely to be discovered. We will discuss key aspects of these pathways as targets either for selection of naturally resistant mosquito populations or for mosquito genetic manipulation. Moreover, we will consider the use of endosymbiotic bacteria such as Wolbachia, which in some cases have proven to be remarkably efficient in disrupting arbovirus transmission by mosquitoes, but also the use of naturally occurring insect-specific viruses that may interfere with arboviruses in mosquito vectors. Finally, we will discuss the use of paratransgenesis as well as entomopathogenic fungi, which are also proposed strategies to control vector competence.

Keywords: Aedes; antiviral defences; arbovirus; bacteria; insect-specific viruses; mosquito engineering; paratransgenesis; vector competence; vector control.

Figure 1

Wolbachia induced cytoplasmic incompatibility (CI) by infection. Wolbachia are spread and maintained in Aedes populations through a process known as CI which can be present in two distinct forms. Unidirectional CI involves infected females being able to successfully mate with both uninfected males in addition to those infected with the same or similar strains of Wolbachia. Bidirectional CI occurs in males and females infected with two different strains of Wolbachia which are unable to produce viable offspring. Both forms of CI result in females infected with Wolbachia having a fitness advantage. Circles indicate viable offspring and are color coded to demonstrate infection status. CI indicates where no viable offspring are produced.

Figure 2

Schematic representation of the Gal4-UAS system. In a first line, the driver line, the yeast transcriptional activation factor Gal4 is under the control of a promoter directing the expression in the tissues/cells of interest. In the other line, the responder line, the transgene of interest is expressed under the control of the upstream activation sequence (UAS). As transcription of the transgene requires the presence of Gal4, the transgene is silent in the parental responder line. When the driver line and the responder lines are crossed, the transgene is then expressed according to the Gal4 pattern.

Figure 3

Summary of the currently proposed natural and engineered strategies to decrease mosquito competence for arboviruses.