Wolbachia transinfection in Aedes aegypti:: A potential gene driver of dengue vectors

The endosymbiotic bacteria in the genus Wolbachia are capable of inducing a wide range of reproductive abnormalities in their hosts, including cytoplasmic incompatibility (Cl), which could lead to the replacement of uninfected host populations with infected ones. Because of this, Wolbachia have attracted considerable interest as a potential mechanism for spreading disease-blocking transgenes through vector populations. Here we report the establishment of double Wolbachia transinfection by direct adult microinjection of Wolbachia from naturally double-infected Aedes albopictus to Aedes aegypti, the most important mosquito vector of infectious viral diseases, and a mosquito in which natural Wolbachia infections are not known to occur. We further demonstrate that incomplete Cl is induced in these double-transinfected mosquitoes. Comparisons of fitness traits between naturally uninfected and transinfected Ae. aegypti lines indicated one significant difference in favor of the latter, namely, an increased number of eggs laid. Levels of Cl expression corresponded to the Wolbachia density. There were large differences in relative Wolbachia density between reproductive and nonreproductive tissues in both Ae. albopictus and transinfected Ae. aegypti, except Malpighian tubule, which implied the preferred establishment of Wolbachia within reproductive tissue. Results from a simulation model confirm that population replacement by transinfected Ae. aegypti is possible over time. The establishment of Wolbachia double infections in Ae. aegypti by direct adult microinjection and the demonstration of Cl expression in this new host suggest that Wolbachia could be experimentally transferred into vector species and could also be used as a gene-driving system to genetically manipulate vector populations.