Exploring the adaptive role of genomic instability in Trypanosoma cruzi.
Trypanosoma cruzi is a protozoan that causes Chagas disease, a fatal parasitic disease spread by an insect vector called a kissing bug. T. cruzi infects seven million people in Latin America and seventeen million are thought to be at risk of infection. Migration of infected individuals to Europe and North America has transferred Chagas disease outside its traditional range, accounting for c.500,000 additional cases globally. In Europe and America, a risk of congenital and transfusional transmission exists, and infected individuals represent a significant challenge for public health services.
Chagas disease is the most important parasitic in Latin America, killing 12,000 people every year. To provide context, malaria in the region kills a fraction of that number (200-400 annually). Infection with T. cruzi in Chagas disease patients is life-long. Drug treatments are limited, often ineffective at clearing parasite infection, and almost always ineffective at alleviating debilitating chronic symptoms (heart disease, GI tract abnormalities). Despite the impact of Chagas disease on human health, relatively little is known about its biology by comparison to other related human parasites - T. brucei (agent of sleeping sickness) and Leishmania (agent of Leishmaniasis). Important knowledge gaps exist around how T. cruzi adapts to environmental stressors. Addressing theses gaps could shed light on how the parasite avoids host immunity to establish persistent infections in its host, as well as how it survives drug treatment.
DNA sequencing of T. cruzi isolates by members of our consortium and others reveals a genome in a constant state of re-arrangement. The number, sizes, copy number and composition of T. cruzi chromosomes can vary substantially between closely related isolates, as well as, based on pilot data we now present, from individual human infections sampled at different time points. The adaptive value of such genomic re-arrangements may hold the key to understanding, and addressing, many intractable aspects of T. cruzi biology. In this proposal we leverage advances in genomics, genetic manipulation, animal disease models, as well as a world-class research team to understand how T. cruzi genomic re-arrangements may underpin long term survival in the mammalian host as well as parasite resistance to frontline and next generation drugs. Using single cell genomics, we will link genomic re-arrangements to drug resistance and then, via genetic manipulation, attempt to interrupt the machinery that enables such re-arrangements to occur. We will then undertake a series of incisive experiments to link parasite genomic re-arrangements to survival under immune pressure in mouse models and confirm these via observations in a cohort of Ecuadorian Chagas disease patients. Experiments in mammals will focus on re-arrangements among families of genes expressed on the parasite cell surface. The temporal dynamics of parasite genomic changes within immune-competent hosts will be followed and compared to the those in the absence of a functioning immune system to detect signatures of immune avoidance via antigenic shift.
The experiments proposed in this research program are vital basic science precursors to improved drug design and the lab groundwork for future T. cruzi vaccine development, ultimately improving health outcomes for the millions affected by Chagas disease.