Host Adaptation of aWolbachiaStrain after Long-Term Serial Passage in Mosquito Cell Lines

Abstract

The horizontal transfer of the bacterium Wolbachia pipientis between invertebrate hosts hinges on the ability of Wolbachia to adapt to new intracellular environments. The experimental transfer of Wolbachia between distantly related host species often results in the loss of infection, presumably due to an inability of Wolbachia to adapt quickly to the new host. To examine the process of adaptation to a novel host, we transferred a life-shortening Wolbachia strain, wMelPop, from the fruit fly Drosophila melanogaster into a cell line derived from the mosquito Aedes albopictus. After long-term serial passage in this cell line, we transferred the mosquito-adapted wMelPop into cell lines derived from two other mosquito species, Aedes aegypti and Anopheles gambiae. After a prolonged period of serial passage in mosquito cell lines, wMelPop was reintroduced into its native host, D. melanogaster, by embryonic microinjection. The cell line-adapted wMelPop strains were characterized by a loss of infectivity when reintroduced into the original host, grew to decreased densities, and had reduced abilities to cause life-shortening infection and cytoplasmic incompatibility compared to the original strain. We interpret these shifts in phenotype as evidence for genetic adaptation to the mosquito intracellular environment. The use of cell lines to preadapt Wolbachia to novel hosts is suggested as a possible strategy to improve the success of transinfection in novel target insect species.

Wolbachia Strain wAlbB Enhances Infection by the Rodent Malaria Parasite Plasmodium berghei in Anopheles gambiae Mosquitoes

“…Both Wolbachia strains were cultured in Anopheles gambiae cells: wAlbB was cultured in Sua5B cells while wMelPop was cultured in Mos55 cells (25,31). Wolbachia was extracted from cells as previously described (31).…”

Body Size and Wing Shape Measurements as Quality Indicators of Aedes aegypti Mosquitoes Destined for Field Release

“…A variety of quality indicators have been proposed and developed for such insect systems including measures of body size. 11,12 Aedes aegypti, a highly anthropophilic mosquito species, 13,14 and the primary vector of dengue virus, 15 has been successfully infected with Wolbachia 2, 16 and released in the field. 1 The prospects of using this approach to reduce dengue transmission 2,[17][18][19] and/or reduce adult life span 20 may lead to largescale releases of these mosquitoes akin to releases being undertaken with other biocontrol agents.…”

Increased locomotor activity and metabolism ofAedes aegyptiinfected with a life-shortening strain ofWolbachia pipientis

“…Unlike most other Wolbachia infections, wMelPop acts more like a traditional bacterial pathogen than an intracellular symbiont. Insects infected with wMelPop survive roughly half as long as uninfected counterparts and premature death is thought to be caused by bacterial over-replication leading to local cell rupture and tissue damage (McGraw et al, 2002;McMeniman et al, 2008;Min and Benzer, 1997;Reynolds et al, 2003). Recently, the mosquito disease vector Aedes aegypti was artificially infected with this strain of Wolbachia as the first step in developing a biocontrol strategy.…”