Inhibition of Malaria Infection in Transgenic Anopheline Mosquitoes Lacking Salivary Gland Cells

Abstract

Malaria is an important global public health challenge, and is transmitted by anopheline mosquitoes during blood feeding. Mosquito vector control is one of the most effective methods to control malaria, and population replacement with genetically engineered mosquitoes to block its transmission is expected to become a new vector control strategy. The salivary glands are an effective target tissue for the expression of molecules that kill or inactivate malaria parasites. Moreover, salivary gland cells express a large number of molecules that facilitate blood feeding and parasite transmission to hosts. In the present study, we adapted a functional deficiency system in specific tissues by inducing cell death using the mouse Bcl-2-associated X protein (Bax) to the Asian malaria vector mosquito, Anopheles stephensi. We applied this technique to salivary gland cells, and produced a transgenic strain containing extremely low amounts of saliva. Although probing times for feeding on mice were longer in transgenic mosquitoes than in wild-type mosquitoes, transgenic mosquitoes still successfully ingested blood. Transgenic mosquitoes also exhibited a significant reduction in oocyst formation in the midgut in a rodent malaria model. These results indicate that mosquito saliva plays an important role in malaria infection in the midgut of anopheline mosquitoes. The dysfunction in the salivary glands enabled the inhibition of malaria transmission from hosts to mosquito midguts. Therefore, salivary components have potential in the development of new drugs or genetically engineered mosquitoes for malaria control.

Anopheline antiplatelet protein from mosquito saliva regulates blood feeding behavior

“…We next examined the ingested blood meal size of the TG and WT mosquitoes after 10 min of blood feeding. The abdomen of each fed mosquito was homogenized and total hemoglobin was quantified with a colorimetric assay 24 . The blood volume ingested by the TG mosquitoes was significantly reduced compared with the WT mosquitoes when fed on mice (Fig.…”

“…It has been reported that transgenic An. stephensi mosquitoes producing extremely low amounts of saliva enabled to ingest blood and the resulting phenotype showed a significant reduction in the ability to transmit malaria parasites and salivary glands homogenate exhibited reduced exflagellation in vitro 24 . This raises the possibility of the development of a saliva protein-based vaccine that targets malaria transmission stages 29 .…”

Current vector research challenges in the greater Mekong subregion for dengue, Malaria, and Other Vector-Borne Diseases: A report from a multisectoral workshop March 2019

“…However, there are promising strategies, including targeting genes, that result in a reduction of transmission of a pathogen either from the human to the mosquito or vice versa. Additionally, other approaches involve promoting or activating mosquito immune responses against infecting arboviruses that would alter transmission capabilities [105][106][107][108]. Biological control methods, such as Wolbachia infection of A. aegypti, are aimed at reducing the competence of vectors and have reduced dengue incidence in the same areas as field trials in Australia and Indonesia, with documented success in arbovirus control in Colombian releases; and controlled release of Wolbachia-induced sterile males reduced the A. aegypti populations in targeted areas in Florida [109][110][111].…”

“…However, there are promising strategies, including targeting genes, that result in a reduction of transmission of a pathogen either from the human to the mosquito or vice versa. Additionally, other approaches involve promoting or activating mosquito immune responses against infecting arboviruses that would alter transmission capabilities [ 105 – 108 ]. Biological control methods, such as Wolbachia infection of A .…”

A standard photomap of the ovarian nurse cell chromosomes for the dominant malaria vector in Europe and Middle East Anopheles sacharovi

“…The genomics era offers new opportunities for the development of modern genome-based strategies for vector control [ 24 , 25 ] including the CRISPR/Cas9-based gene-drive technologies [ 26 ]. Following the major malaria vector in Africa Anopheles gambiae [ 27 ], the genomes for other malaria mosquitoes have been sequenced [ 28 – 30 ].…”