Chagas disease, a parasitic disease endemic to South and Central America, is caused by the protozoan Trypanosoma cruzi and transmitted to humans via the feces of triatomine bugs. It affects approximately 8–11 million people, results in 50,000 deaths and accounts for the loss of 500,000 disability-adjusted life-years annually . Cases of Chagas disease have expanded globally, and are now reported in the Americas, Europe, Australia and Asia due to emigration of infected individuals from endemic parts of the world .
Chagas disease manifests in three distinct phases - acute, indeterminate and chronic. Infected individuals present in an initial acute phase that develops into a chronic phase in 20-40% of the patients. The chronic phase is characterized by the development of lesions in the nervous tissue of the heart, intestine and esophagus that result in progressive organ enlargement with potentially fatal complications. Patients who do not progress to the chronic phase of the disease exist in an indeterminate phase . The two drugs used worldwide in the treatment of Chagas disease, benznidazole and nifurtimox, are effective only against the acute stage of the disease . These treatments are marred by their many side effects including bone marrow toxicity, neural toxicity and severe nausea and vomiting . Moreover, strains of T. cruzi that are resistant to both drugs have emerged and resistance to one drug is usually coupled with resistance to the other .
Several efforts have been undertaken to control transmission of the disease to human populations from triatomine vectors. These transmission-prevention programs include insecticide-based campaigns, housing improvements, health education and blood donor screening programs . Much of the success of transmission-control stems from the Southern Cone , Central American  and Andean Pact Initiatives . These strategies have had considerable success in interrupting vectorial transmission and have reduced new cases of the disease in many countries. However, the wide use of insecticides has created resistant triatomine populations . Furthermore, large-scale vector eradication programs have suffered due to funding issues in countries such as Argentina . The reduced effectiveness of insecticide-based programs in peridomestic habitats has resulted in incomplete eradication of the vector. Re-emergence of Chagas disease is an immediate threat. The need for new methods of disease control are highlighted by the emergence of drug resistant T. cruzi, toxic side-effects of available drug treatments, the inability to treat chronic disease, insecticide resistance in target vector populations and ineffectiveness of the insecticide-based approach in eliminating the disease
Paratransgenesis is an alternative approach under development to reduce transmission of vector-borne diseases by eliminating carriage of pathogens by their arthropod vector hosts . The strategy focuses on understanding the microbial flora of the insect host at the developmental locus of the pathogen and genetically transforming selected bacteria to produce molecules that disrupt the target pathogen. Thus the bacteria act as a carrier or delivery agent – a Trojan horse – for the anti-pathogen molecules . We developed the paratransgenic strategy to control Chagas disease transmission by triatomine bugs over 10 years ago . In this strategy, the relationship between an important vector, Rhodnius prolixus, and its gut symbiont, Rhodococcus rhodnii, was exploited to disrupt the transmission of T. cruzi. R. rhodnii is a nocardiform actinomycete that aids R. prolixus with vitamin metabolism after its blood meal . These actinomycetes, obtained through coprophagy, are essential for the survival of the triatomine bugs. Aposymbiotic nymphs of R. prolixus do not reach sexual maturity . Because of its symbiotic association and proximity to the infective trypomastigote form of T. cruzi in the insect hindgut, R. rhodnii serves as an ideal organism for application in paratransgenesis . We initially demonstrated that genetically engineered R. rhodnii that expressed an anti-trypanosomal peptide, cecropin A, when introduced into R. prolixus, resulted in elimination or significant reduction of T. cruzi in experimentally infected bugs . More recent in vitro studies have shown that several anti-microbial peptides (AMPs) are even more effective at targeting T. cruzi when used in combination . This opens up the possibility of using multiple molecules synergistically to eliminate vector carriage of the parasite.
In this study, we investigate the potential role of endoglucanases as anti-trypanosomal agents. The surface of T. cruzi is covered by a thick coat of mucin-like glycoproteins. Many of these glycoproteins are developmentally regulated and have been proposed to play a role in the binding of the cell body and the flagellum of T. cruzi to the membrane surface of the vector gut, an integral step in T. cruzi maturation . We hypothesize that disruption of the glycoconjugates by endoglucanases could arrest parasite development in the vector and abort the transmission cycle. Arthrobacter luteus lyticase is a complex endoglucanase consisting of β-1,3-glucanase and alkaline protease that degrades β-1,3 and 1–6 glycosidic linkages . We previously demonstrated that purified lyticase from Arthrobacter was highly effective at lysing T. cruzi in vitro. Here we report that recombinant Arthrobacter luteus β-1,3-glucanase expressed via R. rhodnii effectively kills T. cruzi Sylvio II strain, suggesting that this molecule may be a powerful addition to the arsenal of effector molecules for paratransgenic control of Chagas disease.