IMMUNOBLOT ASSAY USING EXCRETED-SECRETED ANTIGENS OF TRYPANOSOMA-CRUZI IN SERODIAGNOSIS OF CONGENITAL, ACUTE, AND CHRONIC CHAGAS-DISEASE

Immunoblotting with trypomastigote excreted-secreted antigens (TESA bl ot) of Trypanosoma cruzi was evaluated as a method for diagnosis of ch ronic and acute phases as well as congenital (in newborn children) Cha gas' disease. Serum samples from acute-phase and congenital infections were considered to be positive when they reacted with ladder-like ban ds of 130- to 200-kDa antigens, recognized by immunoglobulin M (IgM) a nd IgG antibodies, while IgG from chronic-phase sera recognized a broa d band antigen of 150 to 160 kDa. Nonchagasic sera were not reactive t o these antigens. The study was carried out on 512 patients, 111 of wh om were nonchagasic but included cases of leishmaniasis or other patho logies, and 401 chagasic patients. The latter group comprised 361 chro nic cases, 36 acute cases, and 4 congenital cases in newborn children. Among the chronic cases, 256 were from areas in which T. cruzi is end emic but which differed widely in the pathogenic expression of T. cruz i infection and in parasitemia levels. These patients at the same time showed a broad range of low, medium, and high reactivity to conventio nal enzyme-linked immunosorbent assays and indirect immunofluorescence serotests for Chagas' disease. For these reasons they may better repr esent the universe of chagasic patients than would a sample of highly reactive sera obtained from chagasic patients in a single area endemic for T. cruzi. All acute and congenital cases showed positivity in the IgM and IgG TESA blots, while chronic cases were 100% positive for Ig G antibodies. In nonchagasic sera, including 30 cases of visceral and muco-cutaneous leishmaniasis, the specificity index was 1.000, and no cross-reactions were observed. The TESA blot thus seems to be useful a s a sensitive and specific diagnostic assay in cases of suspected acut e or congenital T. cruzi infection and as a general confirmatory test for conventional Chagas' disease serology.