A field study of the immune response to the shed acute phase antigen (SAPA)
of Trypanosoma cruzi was carried out in the locality of Mizque, Cochabamba
department, Bolivia. Schoolchildren (266), with an average of 8.6+/-3.6
years, were surveyed for parasitological and serological diagnosis, as well
as antibodies directed against SAPA using the corresponding recombinant
protein in ELISA. The antibodies against SAPA were shown in 82% of patients
presenting positive serological diagnosis (IgG specific antibodies). The
positive and negative predictive values were 0.88. Antibodies anti-SAPA
were shown in 80.8% of the chagasic patients in the initial stage of the
infection (positive IgM serology and/or positive buffy coat (BC) test) and
in 81.4% of the patients in the indeterminate stage of the infection
(positive IgG serology with negative BC and IgM tests). These results show
that the anti-SAPA response is not only present during the initial stage of
the infection (few months) but extends some years after infection.
