An evaluation of fusion partner proteins for paratransgenesis in Asaia bogorensis

Abstract

Mosquitoes transmit many pathogens responsible for human diseases, such as malaria which is caused by parasites in the genus Plasmodium. Current strategies to control vector-transmitted diseases are increasingly undermined by mosquito and pathogen resistance, so additional methods of control are required. Paratransgenesis is a method whereby symbiotic bacteria are genetically modified to affect the mosquito’s phenotype by engineering them to deliver effector molecules into the midgut to kill parasites. One paratransgenesis candidate is Asaia bogorensis, a Gram-negative bacterium colonizing the midgut, ovaries, and salivary glands of Anopheles sp. mosquitoes. Previously, engineered Asaia strains using native signals to drive the release of the antimicrobial peptide, scorpine, fused to alkaline phosphatase were successful in significantly suppressing the number of oocysts formed after a blood meal containing P. berghei. However, these strains saw high fitness costs associated with the production of the recombinant protein. Here, we report evaluation of five different partner proteins fused to scorpine that were evaluated for effects on the growth and fitness of the transgenic bacteria. Three of the new partner proteins resulted in significant levels of protein released from the Asaia bacterium while also significantly reducing the prevalence of mosquitoes infected with P. berghei. Two partners performed as well as the previously tested Asaia strain that used alkaline phosphatase in the fitness analyses, but neither exceeded it. It may be that there is a maximum level of fitness and parasite inhibition that can be achieved with scorpine being driven constitutively, and that use of a Plasmodium specific effector molecule in place of scorpine would help to mitigate the stress on the symbionts.

Bacterial diversity on larval and female Mansonia spp. from different localities of Porto Velho, Rondonia, Brazil

“…Asaia is abundant in the salivary glands, reproductive organs, and intestines of different mosquito species [74][75][76] and can colonize other insects [77]. Because of its characteristics, such as stable association, the ability to colonize different tissues, vertical transmission, cultivation, and genetic manipulation, this bacterium is a candidate for paratransgenic malaria control [78]. In the present study, Asaia was abundant in the field collected Mansonia females.…”

Wolbachia and Asaia Distribution among Different Mosquito Vectors Is Affected by Tissue Localization and Host Species

“…Indeed, Asaia may infect most of the members of a population if not all, including all developmental stages and several anatomical districts, thus acclaiming itself as one of the best paratransgenic agents. In this frame, at the laboratory level, paratransgenic strains of Asaia that inhibit malaria transmission have been produced [ 15 , 16 ]. Moreover, Asaia can stimulate the basal level of mosquito immunity to naturally reduce the development of malaria parasite oocysts in Anopheles stephensi , thus expanding its potential in SC approaches, not only through paratransgenesis, but also as a potential effector for insect immune priming [ 17 , 18 ].…”