Genetics and pathogenesis of Chagas disease megaoesophagus: identification rare pathogenic variants and investigation of their functional impact

• Grant number: 19/22858-3
• Support type: Regular Research Grants
• Duration: September 01, 2020 - August 31, 2022
• Field of knowledge: Biological Sciences - Immunology - Applied Immunology
• Principal Investigator: Edecio Cunha Neto
• Grantee: Edecio Cunha Neto
• Home Institution: Faculdade de Medicina (FM). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Assoc. researchers: Amanda Farage Frade Barros ; Aurelie Cobat ; Christophe Chevillard ; Eduardo Shigueo Kitano ; Francisco Carlos Bernal da Costa Seguro ; Ivan Cecconello ; Jorge Elias Kalil Filho ; Rafael Ribeiro Almeida

Abstract

Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, affects 5-8 million people worldwide. Only a fraction of infected patients develop chronic cardiac or digestive disease. The factors underlying the differential susceptibility to developing either of the symptomatic forms of chronic Chagas disease are incompletely understood. During the chronic phase of infection, 30% of Chagas disease patients develop life-threatening chronic Chagas disease cardiomyopathy (CCC) and 10% develop debilitating gastrointestinal motility disorders, including dilation of esophagus and/or colon (megaesophagus and megacolon) secondary to degeneration of the myoenteric neurons, requiring surgical correction. A significant mononuclear inflammatory infiltrate is found both the esophageal myoenteric plexus of Chagas meagaesophagus patients and myocardium of CCC patients, with abundant local production of IFN-gamma and TNF-alpha and prominent mitochondrial dysfunction in CCC myoardium. A group of patients develop both the cardiac and digestive forms of digestive disease. Indeed, the majority of infected patients (ca. 60%), remain asymptomatic, in the so-called indeterminate form of Chagas disease (ASY). A genetic component to disease susceptibility has been documented in CCC, with familial aggregation and several reports of association with common host genetic variants. However, little is known about the role of genetics in susceptibility to Chagasic megaesophagus. The study of rare genetic variants can provide clues to pathogenesis,and has been increasingly used in polygenic diseases. Our group pioneered the study of rare genetic variants in Chagas disease, analyzing nuclear families with multiple CCC/ASY cases using whole exome sequencing (WES). We found that most heterozygous pathogenic variants associated to CCC cases and absent in ASY patients were in mitochondrial and inflammatory genes; 5/6 families displayed CCC-specific mitochondrial variants. Significantly, patients with genetic mitochodriopathies - homozygous pathogenic rare variants in mitochondrial genes - have drastic mitochondrial dysfunction and energetic impairment in tissues of high energetic demand like neurons and muscle. Up to 40% of such patients develop cardiomyopathy, conduction defects or arrhythmia, and impairment of the autonomous nervous system, and 15% develop digestive motility symptoms including megaesophagus and megacolon due to denervation and destruction of myoenteric neurons. The striking similarity of the nature and prevalence of cardiac and digestive disorders in mitochondriopathies with those observed in Chagas disease support the possibility that heterozygous mutations affecting mitochondrial function may play a role in differential development of both CCC and megaesophagus. IFN-gamma and TNF-alpha, produced systemically and locally by the mononuclear inflammatory cells, are known inducers of mitochondrial dysfunction. Our working hypothesis is that heterozygous mitochondrial pathogenic gene variants are frequent among chagasic megaesophagus patients, and cells bearing such heterozygous pathogenic mitochondrial variants will have increased susceptibility to IFN-³/ TNF-±-induced mitochondrial damage and cell death, processes that could ultimately lead to esophageal plexus denervation and megaesophagus. We here propose to test the hypothesis by assessing the frequency of rare pathogenic genetic variants in patients with chagasic megaesophagus and the indeterminate form, as well as to perform a mechanistic study to assess whether cells carrying such genetic variants are more susceptible to IFN-gamma/ TNF-alpha-induced mitochondrial damage and cell death than those from non-carriers. (AU)