Strategy for introduction of foreign genes into field populations of Chagas disease vectors

Abstract

Paratransgenesis, a strategy for control of certain arthropod-borne infectious diseases, involves expression of disease transmission-blocking molecules by genetically altered symbiotic bacteria of insect vectors. Field use of this approach relies on a method for dispersal of genetically transformed bacteria to their host insects. Rhodococcus rhodnii, a symbiotic bacterium of the Chagas disease vector, Rhodnius prolixus (Stal), has been transformed genetically to express several molecules. Here we report a strategy for dispersal of genetically altered R. rhodnii to target populations of R. prolixus that uses a synthetic substrate termed CRUZIGARD. This preparation mimics natural feces of R. prolixus and, when impregnated with genetically altered symbiotic bacteria, simulates the natural coprophagic method of symbiont dispersal used by the reduviid bug. CRUZIGARD laden with genetically altered symbionts was applied monthly to closed cages of R. prolixus nymphs. Uptake and retention of the recombinant bacteria was demonstrated under laboratory conditions and simulated field conditions in which competing environmental microbes were present. In the simulated field study conducted in Guatemala, nearly 50% of R. prolixus nymphs exposed to bacterialaden CRUZIGARD retained the transgenic microbes throughout their development. In these paratransgenic insects, the genetically altered symbionts comprised nearly 95% of the bacterial colony forming units. No adverse effects of CRUZIGARD on insect development and fecundity were noted. CRUZIGARD represents a potentially powerful method for dispersal of recombinant symbiotic bacteria among field populations of the Chagas disease vector, R. prolixus.