Enzymatic treatment transforms trypomastigotes of Trypanosoma cruzi into activators of alternative complement pathway and potentiates their uptake by macrophages.

Abstract

In the absence of bound antibody, trypomastigote bloodstream forms of Trypanosoma cruzi fail to activate the alternative complement pathway. We now demonstrate that treatment with trypsin and, to a lesser extent, with sialidase converts these protozoa into activators of the pathway, as judged by their lysis in normal sera or sera genetically deficientin fourth or second component of complement (C4 or C2) and their Mg2+-dependent consumption of C3 as measured by crossed immunoelectrophoresis. In addition, after pretreatment with enzyme and incubation in C5-deficient serum, trypomastigotes were shown to possess both C3 and properdin factor B (B) on their surface as judged by immunofluorescence. Requirement for the late components C5-C9 was suggested by the failure of C5-deficient sera to lyse trypsin-treated parasiteL The inability to activate the alternative complement pathway was regained by these organisms after incubation in vitro. This restoration of insusceptibility was inhibited when puromycin was included in the culture medium. Treatment of the trypomastigotes with trypsin also potentiated their uptake by mouse peritoneal macrophages without apparent interference with their capacity to differentiate and multiply inside the cell. These findings suggest that untreated trypomastigotes normally escape recognition by the alternative pathway in vivo because of the presence on their surface of trypsin-and sialidase-sensitive regulatory molecules, the expression of which is dependent on protein synthesis.Infection with Trypanosoma cruzi is initiated by trypomastigotes which differentiate from epimastigotes in the gut of the insect vector (1). Epimastigotes are lysed by normal serum (2) through the activation of the alternative complement pathway (ACP) (3). In contrast, trypomastigotes obtained from cultures (3) or from the blood of irradiated mice (4) are resistant to ACP lysis in the absence of antibody. Therefore, the differentiation of epimastigotes into trypomastigotes is apparently accompanied by a modification of the parasite surface that renders it resistant to ACP lysis.It has been demonstrated that cells activating ACP have membrane components that protect the activated form of third component of complement (C3b) deposited on their surface from inactivation by C3b inactivator (C3bINA) and f31H and that stabilize C3 convertase (C3bBb) from dissociation by /31H (5). Removal ofmembrane sialic acid residues from sheep erythrocytes by sialidase enables these cells to activate ACP (6, 7) and makes them susceptible to phagocytosis by human monocytes (8). In addition, coupling with heparin glycosaminoglycan impairs the ability of zymosan to activate the ACP (9).We have studied whether regulatory mechanisms similar to those described above explain the inability of T. cruzi trypomastigotes to activate the ACP. Our results demonstrate that trypomastigotes treated with trypsin or sialidase become able to activate ACP and are lysed. The trypsin-treated trypomastigotes recover resistance to ACP lysis within 6 ...

Infectivity of amastigotes of Trypanosoma cruzi

“…As described before, trypomastigotes were not while all epimastigotes were readly lysed. It had been shown previously that treat ment of bloodstream trypomastigotes with trip sin renders them susceptible to complementmediated lysis (KIPNIS et al 12 ). Our experi ments confirmed these observations but showed that the same trypsin treatment did not inter fere with the resistance of amastigotes to the lysis induced by guinea pig serum (Table II).…”

“…Treatment of the amastigotes with trypsin did not increase their ingestion by macrophages. It has been shown that trypsinization increases the uptake of bloodstream trypomastigotes by macrophages (ARAUJO JORGE & SOUZAKIPNIS et al 12 ; NOGUEIRA et al"). It is possible that the procedures used for the obtention of the amastigotes from the spleen interfered with the surface components of the parasites rendering them susceptible to ingestion by the macrophages.…”

Receptor for immunoglobulin Fc on pathogenic but not on nonpathogenic protozoa of the Trypanosomatidae.

“…cruzi, promoting ingestion by mouse macrophages. In addition, Kipnis et al (37) found that T. cruzi trypomastigotes, which do not activate complement by the alternative pathway, acquire the ability to do so after trypsinization.…”

Identification of carbohydrates on the surface membrane of pathogenic and nonpathogenic piscine haemoflagellates, Cryptobia salmositica, C. bullocki and C. catostomi (Kinetoplastida)

“…1993) also contributed significantly to their negative surface charge. Surface-exposed sialic acids were assumed to play important roles as biological masks (Schauer et al 1983) which protect T. cruzi blood forms from complement-mediated lysis (Kipnis et al 1981) a n d phagocytosis by macrophages (Araujo-Jorge & De Souza 1984).…”