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Clin. Vaccine Immunol. doi:10.1128/CVI.00069-08
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Reverse ELISA using monoclonal antibodies against SAG1-related sequence, SAG2A and p97 antigens from Toxoplasma gondii for detection of specific IgG, IgM and IgA antibodies in human sera

Laboratory of Immunoparasitology, and Laboratory of Molecular Biology, Institute of Biomedical Sciences, Federal University of Uberlândia, Uberlândia, MG, Brazil; and Division of Microbiology and Immunology, Federal University of Tocantins, Brazil

^* To whom correspondence should be addressed. Email: jrmineo{at}ufu.br.

	Abstract

The present study aimed to evaluate the performance of three monoclonal antibodies (mAbs) in reverse ELISAs to detect IgG, IgM and IgA antibodies anti-Toxoplasma gondii in 175 serum samples from patients at different stages of T. gondii infection defined by both serological and clinical criteria, as follows: recent (n=45), transient (n=40) and chronic (n=55), as well as seronegative subjects (n=35) The results were compared with those obtained by indirect ELISA using soluble Toxoplasma total antigen (STAg). Our data demonstrated that mAb A3A4 recognizes a conformational epitope in SAG1-related sequence (SRS) antigens, while A4D12 and 1B8 recognize linear epitopes defined as SAG2A surface antigen and p97 cytoplasmatic antigen, respectively. Reverse ELISA-IgG using A3A4 or A4D12 mAbs was highly correlated with indirect ELISA-IgG anti-STAg, whereas only A4D12 reverse ELISA showed high correlation with indirect ELISA for IgM and IgA isotypes. To our knowledge, this is the first report analyzing the performance of a reverse ELISA for simultaneous detection of IgG, IgM and IgA isotypes towards native SAG2A, SRS and p97 molecules from STAg, using a panel of human sera from patients with recent and chronic toxoplasmosis. Thus, reverse ELISA based on the capture of native SAG2A and SRS antigens of STAg by mAbs could be an additional approach to strength the helpfulness of serological tests assessing the stage of infection, particularly in combination with highly sensitive and specific assays that are frequently used nowadays for diagnosis of toxoplasmosis during pregnancy or congenital infection in newborns.