Transinfection: a method to investigate Wolbachia-host interactions and control arthropod-borne disease

Abstract

The bacterial endosymbiont Wolbachia manipulates arthropod host biology in numerous ways, including sex ratio distortion and differential offspring survival. These bacteria infect a vast array of arthropods, some of which pose serious agricultural and human health threats. Wolbachia-mediated phenotypes such as cytoplasmic incompatibility and/or pathogen interference can be used for vector and disease control; however, many medically important vectors and important agricultural species are uninfected or are infected with strains of Wolbachia that do not elicit phenotypes desirable for disease or pest control. The ability to transfer strains of Wolbachia into new hosts (transinfection) can create novel Wolbachia-host associations. Transinfection has two primary benefits. First, Wolbachia-host interactions can be examined to tease apart the influence of the host and bacteria on phenotypes. Second, desirable phenotypes induced by Wolbachia in a particular insect can be transferred to another recipient host. This can allow the manipulation of insect populations that transmit pathogens or detrimentally affect agriculture. As such, transinfection is a valuable tool to explore Wolbachia biology and control arthropod-borne disease. The present review summarizes what is currently known about Wolbachia transinfection methods and applications. We also provide a comprehensive list of published successful and unsuccessful Wolbachia transinfection attempts.

Keywords: Wolbachia; arthropod-borne disease; arthropods; horizontal transmission; insects; microinjection; pathogen interference; reproductive manipulation; symbionts; transinfection.

Figure 1

Comparison of adult and embryonic microinjection for stable line development. When microinjected into adults (A), Wolbachia needs to (1) avoid the immune response, (2) compete with the native microbiota, and (3) infect the germline to be vertically transferred to the next generations. To infect the germline (B), Wolbachia must traverse through both the muscular epithelium (4) and the peritoneal sheath (5), then the follicular epithelium of the ovary to enter the ovarian follicles. The bacterium may enter the germarium infecting the germline stem cell niche (I) or the somatic stem cell niche (II) or directly infect the ovarian follicle (III). Embryonic microinjection localizes Wolbachia directly within the developing embryo before pole cell development (C). The germline develops and becomes infected with Wolbachia. This process bypasses the barriers to germline infection that the bacterium encounters during adult microinjection. The possible outcomes of infection are compared for adult and embryonic microinjection (below). For both processes, germline infection is critical for vertical transmission of Wolbachia, and both approaches require selection for development of a stable line.