Human antibody responses to Trypanosoma cruzi 70-kD heat-shock proteins.

Abstract

Heat-shock proteins of the 70-kD (hsp70) family are targets of humoral and cellular immune responses following bacterial or parasitic infections, including Chagas' disease. In the present study, we measured antibodies in human sera reactive with hsp70s from the cytoplasm (cy-hsp70), mitochondrion (mt-hsp70), and endoplasmic reticulum (grp78) of Trypanosoma cruzi. Of the three hsp70s tested, only grp78 detected T. cruzi infection in more than 90% of nontreated (NT) patients, with cy-hsp70 and mt-hsp70 detecting only 78% and 25% of NT patients, respectively. Reactivity of leishmanial sera was 77% with cy-hsp70, 13% with grp78, and 5% with mt-hsp70. Therefore, considering sensitivity and specificity, the best candidate for T. cruzi serodiagnosis is grp78. Combination of grp78 with a T. cruzi 24-kD flagellar calcium binding protein (FCaBP) increased the diagnostic sensitivity from 90% to 97% but increased leishmanial reactivity from 3% to 8%. To determine whether hsp70s are useful for discriminating between cured and noncured patients treated with trypanocidal drugs, we tested sera from treated noncured (TNC) patients and cured patients who have positive conventional serology, termed treated dissociated (TD). The cy-hsp70 and grp78 reacted with 74% and 68% of TNC patient sera, respectively, but these antigens did not discriminate TNC from TD patients (52% and 45% positive, respectively). The mt-hsp70 was detected by sera from few TNC patients (18%) and no TD patients. Although individual hsp70s were not useful for determining the effect of trypanocidal drugs on T. cruzi infection in individual patients, the majority of TNC patient sera (70-80%) reacted with two or three of the hsp70s. In contrast, no TD sera reacted with all three hsp70s, and 40% did not react with any of the hsp70s, indicating that the number of hsp70s detected decreases following successful treatment. Considered together, these results show that grp78 has potential as a diagnostic antigen and that absence of reactivity to all three hsp70s may be indicative of effective treatment.

Use of Full-Length Recombinant Calflagin and Its C Fragment for Improvement of Diagnosis ofTrypanosoma cruziInfection

“…The function of this protein remains largely unknown, but it has been hypothesized that it participates in an acyl-calcium switch system (12), and this proposal is supported by experimental data showing a Ca 2ϩ -dependent conformational change (26). Since it was cloned for the first time, its utility in the diagnosis of T. cruzi infection has been well established (14,18,25,(33)(34)(35), including the possibility of using its gene sequence for PCR diagnosis (31). The rapid reduction of antibodies against calflagin in patients that respond to trypanocidal treatment has also been demonstrated, indicating that calflagin may be used in therapy follow-up (33).…”

“…Interestingly, no Leishmania orthologs have been described up to now. Several studies on the diagnostic profile of this recombinant protein identified its use as a valuable antigen for the serological detection of the infection in the indeterminate phase (14,18,25,34,35) and for therapy evolution follow-up (33). Several works also established that sera from Leishmania spp.-infected individuals have low levels of cross-reactivity with T. cruzi calflagins (14,34,35).…”

Tc45, a dimorphic Trypanosoma cruzi immunogen with variable chromosomal localization, is calreticulin.

“…[1][2][3][4][5][6] Although important contributions have been made to better define their potential role as immunogens or diagnostic tools, no functional characterization has been defined for the majority of the described parasite molecules. [1][2][3][4][5][6][7][8][9][10][11][12][13] The immunological functions of calreticulin in mammals have been delineated to some extent, in particular as a chaperone molecule in the process of antigen presentation to CD8ϩ T cells. Thus, when ␤ 2 -microglobulin binds to the major histocompatibility complex (MHC) class I ␣ chain, the partially folded ␣␤ 2 -microglobulin heterodimer dissociates from calnexin and binds calreticulin.…”

The utility of anti-trypomastigote lytic antibodies for determining cure of Trypanosoma cruzi infections in treated patients: an overview and perspectives

“…The calcium binding protein of low molecular weight (Tc24) also had a good correlation with the CoML test (86%) (Krautz et al 1995). The heat-shock proteins, especially HP70, were proven to be reliable antigens to assess cure after chemotherapy and replaced the CoML test in the followup of treated patients (Krautz et al 1998). These antigens were successfully used in ELISA tests and showed a high correlation with the results of the CoML test when the same sera (from patients treated and cured) were used in parallel (Table V).…”