Immunolocalization and characterization of the low molecular weight antigen (4–5 kDa) ofToxoplasma gondiithat elicits an early IgM response upon primary infection

Abstract

A striking feature of toxoplasmic seroconversion is the prominent and early IgM response to a low molecular weight antigen of 4-5 kDa. Two different monoclonal antibodies directed against the 4-5 kDa antigen have been generated and used to characterize this molecule. Using these monoclonal antibodies, we could demonstrate the surface localization of the low M(r) antigen by immunofluorescence and immuno-electron microscopy assays. By immunoblotting, we observed that one of the monoclonal antibodies was unable to recognize the 4-5 kDa antigen in tachyzoites propagated in cell culture, indicating an epitope variability between Toxoplasma gondii tachyzoites grown in vivo and in vitro. We discuss the implications of this latter finding in the design of diagnostic reagents.

Molecular structure of the “low molecular weight antigen” of Toxoplasma gondii: a glucose α1-4 N-acetylgalactosamine makes free glycosyl-phosphatidylinositols highly immunogenic

“…GalNAc b1-4-linked to the ®rst mannose is a common structural feature in vertebrate GPI-protein anchors Mehlert et al, 1994;Nakano et al, 1994), and therefore, their presence on host molecules might induce tolerance to this structure. The two monoclonal antibodies previously described, to recognize the low molecular weight antigen (Striepen et al, 1992;Tomavo et al, 1994), show a more restricted pattern of recognized glycolipids. Both monoclonals react only with GPIs containing a terminal ethanolamine phosphate.…”

“…Puri®ed glycolipid species were spotted onto reinforced nitrocellulose sheets and dried. Blotted glycolipids were probed with a polyclonal anti-Toxoplasma rabbit serum, sera from human cases of acute toxoplasmosis and two monoclonal antibodies mAb T54E10 and mAb T33F12; previously described to be speci®c for the low molecular weight antigen (Striepen et al, 1992;Tomavo et al, 1994). Four glycolipids, namely glycolipids I, II, IV and V, were consistently detected by antibodies present in rabbit and human sera reactive against T. gondii ( Figure 1).…”

“…Nitrocellulose strips were dried at 37 C and blocked with 5% (w/v) defatted dry milk in Trisbuffered saline (15 mM Tris-HCl, (pH 8), 140 mM NaCl, 0.05% w/v Tween 20). Blots were incubated with a polyclonal anti-Toxoplasma rabbit serum, sera from patients suffering from acute toxoplasmosis (a kind gift from Dr B. Fortier, Lille) and monoclonal antibodies (mAb) T33F12 and T54E10 directed against the low molecular weight antigen of T. gondii (Tomavo et al, 1994), at a 1:100 dilution. After washing, blots were incubated with an appropriate anti-Ig-conjugate and reacted with substrate using the supplier's protocols.…”

Immunoglobulin M (IgM)-Glycoinositolphospholipid Enzyme-Linked Immunosorbent Assay: an Immunoenzymatic Assay for Discrimination between Patients with Acute Toxoplasmosis and Those with Persistent Parasite-Specific IgM Antibodies

“…Therefore, the diagnosis of recent toxoplasmosis in gravid women is of great importance. The identification of most acute cases of toxoplasmosis in humans is based on detection and measurement of parasite-specific immunoglobulin M (IgM) in sera from the patients by indirect immunofluorescence assay (IFA) and immunosorbent capture enzyme-linked immunosorbent assay (capture ELISA) (4,5,16,19,20,28,29). The IFAs have high specificity but lower sensitivity, leading to false-negative results (19).…”

T. gondii Infection Acquired during Pregnancy and/or after Birth may be Responsible for Development of both Type 1 and 2 Diabetes Mellitus

“…In mice with chronic phase of infection, cold water stress caused strong antibody response manifesting as the 5-kDa antigen on the surface of tachyzoites (not present in bradyzoite preparations), with significant diagnostic potential [731]. A similar protein (4-5kDa) was identified in human serum samples that reacted with IgM upon primary infection with the parasite [732]. Otherwise it is known that B cells (responsible for the production of antibodies) play an important role in resistance to persistent T. gondii infection, especially in the brain and lung [733].…”