Abstract
We detected anti-human small nuclear ribonucleoprotein (snRNP) autoantibodies in chagasic patients by different immunological methods using HeLa snRNPs. ELISA with Trypanosoma cruzi total lysate antigen or HeLa human U small nuclear ribonucleoproteins (UsnRNPs) followed by incubation with sera from chronic chagasic and non-chagasic cardiac patients was used to screen and compare serum reactivity. Western blot analysis using a T. cruzi total cell extract was also performed in order to select some sera for Western blot and immunoprecipitation assays with HeLa nuclear extract. ELISA showed that 73 and 95% of chronic chagasic sera reacted with HeLa UsnRNPs and T. cruzi antigens, respectively. The Western blot assay demonstrated that non-chagasic cardiac sera reacted with high molecular weight proteins present in T. cruzi total extract, probably explaining the 31% reactivity found by ELISA. However, these sera reacted weakly with HeLa UsnRNPs, in contrast to the chagasic sera, which showed autoantibodies with human Sm (from Stefanie Smith, the first patient in whom this activity was identified) proteins (B/B', D1, D2, D3, E, F, and G UsnRNP). Immunoprecipitation reactions using HeLa nuclear extracts confirmed the reactivity of chagasic sera and human UsnRNA/RNPs, while the other sera reacted weakly only with U1snRNP. These findings agree with previously reported data, thus supporting the idea of the presence of autoimmune antibodies in chagasic patients. Interestingly, non-chagasic cardiac sera also showed reactivity with T. cruzi antigen and HeLa UsnRNPs, which suggests that individuals with heart disease of unknown etiology may develop autoimmune antibodies at any time. The detection of UsnRNP autoantibodies in chagasic patients might contribute to our understanding of how they develop upon initial T. cruzi infection.
Highlights
In Brazil and Latin America, Chagas’ disease still represents a serious social and medical problem since this endemic disease affects about 8 millions of mostly poor inhabitants living under precarious housing conditions
The detection of U small nuclear ribonucleoproteins (UsnRNPs) autoantibodies in chagasic patients might contribute to our understanding of how they develop upon initial T. cruzi infection
Eighty-five sera from non-chagasic cardiac individuals and 133 sera from chagasic cardiac patients were analyzed by enzyme-linked immunosorbent assay (ELISA) using T. cruzi antigen and assessed for reactivity using a chagasic serum sample with a high degree of reactivity as positive control
Summary
In Brazil and Latin America, Chagas’ disease still represents a serious social and medical problem since this endemic disease affects about 8 millions of mostly poor inhabitants living under precarious housing conditions. The disease has three phases: acute, latent and chronic. In the acute phase, characterized by high levels of parasitemia, cases may range from asymptomatic to oligosymptomatic and to serious and even fatal, death occurs in less than 3.5% of chagasic individuals. This phase is characterized by exponential parasite growth, triggering an intense immunological response. The latent phase follows the acute one and precedes the chronic one for about 10 to 20 years. At the end of the chronic phase, the worst clinical manifestations appear, with the occurrence of cutaneous eruptions, megaesophagus and megacolon, cardiomegaly, and occasionally hepatosplenomegaly
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