Mario E Camargo
Rua Pombal 133, 01253-010 São Paulo, SP, Brasil
Fax: +55-11-287-2428.
Received 9 June 1999
Accepted 9
August 1999
Code Number:OC99180
Key words: Chagas disease - etiologic diagnosis
The etiologic diagnosis of Chagas disease has presented up to
now a continuous and progressive development, with more and more
precise, sensitive and practical procedures. Since when Carlos
Chagas described Trypanosoma cruzi, and next its role as the
agent of the disease he also discovered and carries his name, a
large amount of research has been done with the purpose of ensuring
its diagnosis.
In this meeting we will have the opportunity and the pleasure of
hearing from experts, and changing experiences, on the present
aspects of this diagnosis, either parasitological, biomolecular or
serological. Complementing coordination on the parasitological
diagnosis in this round-table, by Dr Alejandro Luquetti, I should
like to introduce the presentation on serodiagnosis by Professor
Eufrosina Setsu Umezawa, and following discussions, by summarizing
the main aspects of the work on serodiagnosis which have been
developed at the Instituto de Medicina Tropical de São
Paulo.
Chagas disease serodiagnosis, which started in 1913 with the
complement fixation test described by Guerreiro and Machado, still
presents many problems, a few pertinent to serodiagnosis in
general, as interferring signals and cut-off selection, others
directly related to parasite antigens, as well as to the patients'
humoral responses. The high antigenic complexity of T. cruzi
and its variability in evolutive forms and strains, as well as
antigenic communities with related parasites represent difficulties
in the way of standardizing a universal, reference test, for
serodiagnosis. Antibody response at the same time presents marked
differences along the phases of the disease, adding more complexity
to the problem.
For thirty years or more, at the Serology and Seroepidemiology
Laboratory of the Instituto, Chagas disease serology has been a
constant study subject. Collaboration of colleagues as Sumie
Hoshino Shimizu, Antonio Walter Ferreira, Eufrosina Setsu Umezawa,
Anna Maria Simonsen Stolf, Maria Carolina Soares Guimarães,
Benedito Anselmo Peres, José Roberto Mineo, Katia Primavera,
Tereza Keiko N Sugahara, and myself, plus staff members of other
brazilian and foreign Institutions in North, Central and South
America, allowed for the development and evaluation of new tests,
as immunofluorescence, immunoenzymatic, hemagglutination,
flocculation and immunoblot assays, the study of antigens,
cross-reactions, tests standardizations, as well as the production
of stable and practical reagents. In several developments the
Laboratory was pioneer, as of a practical immunofluorescence assay;
in removing rheumatoid factor interferences in IgM assays; in
developing a stable, liquid reagent for hemagglutination; in the
development of Elisa and Immunoblot assays with T. cruzi
excretion and secretion antigens from trypomastigotes in cell
cultures (TESA). These assays were shown as very sensitive for IgG
and IgM antibodies and furnishing characteristic reactivity
patterns for acute and chronic Chagas disease, while immunoblot
negative for Leishmania antibodies; in developing a Universal
Elisa for Chagas Disease Serodiagnosis, with an association of
T. cruzi recombinant antigens. Produced by Prof. Franco da
Silveira (Molecular Biology, Parasitology, Escola Paulista de
Medicina, São Paulo, Brazil) and by a few foreign centers
(CYTED-D), these recombinant peptides were selected in our
Laboratory according to sensitivity and specificity with a large
number of serum samples from patients of different endemic areas in
Brazil and in several countries in South and Central America. A
careful study was then performed in our Laboratory, with these
recombinants after isotope-labeling, so as to determine and
overcome their competition on coating the plates for Elisa.
In the development of the different tests, association with
epidemiological and clinical researchers has been of paramount
importance, specially with Professors J Rodrigues Coura and MA
Shikanai Yasuda.
In collaboration with the Brazilian Ministry of Health,
seroprevalence of Chagas disease was established in a survey
covering the country, by sampling the population of every
municipality in all states, with the exception of the State of
São Paulo and the Federal District. For this purpose, the
Laboratory produced all the reagents and performed a continuous
test-control of the 14 collaborating laboratories throughout
Brazil, in a work that took about four years. Associated with data
from a parallel triatomine survey, seroprevalence results have been
an indicator for Public Health measures against Chagas disease
natural transmission in Brazil. It has been taken as a model for
similar surveys in other countries where Chagas disease is also
present.
Copyright 1999 Fundacao Oswaldo Cruz - Fiocruz