Molecular Markers in Acute and Chronic Phases of Human Toxoplasmosis: Determination of Immunoglobulin G Avidity by Western Blotting

Abstract

We characterized antigenic markers recognized by human serum samples from patients presenting with acute and chronic toxoplasmosis by the determination of immunoglobulin G (IgG) antibody avidity by a Western blot modified technique (avidity immunoblotting) that includes the dissociation of the antigenantibody interaction with 6 or 8 M urea solutions. Human serum samples from 20 patients presenting with recent infection and from 20 patients with chronic infection were analyzed. It was observed that bands p16, p32, p38, p40, p43, p54, p60, p66, and p97 were more frequently recognized by low-avidity IgG in recent infection and by high-avidity IgG in chronic toxoplasmosis. From these antigenic bands, p38 can be characterized as an optimal antigenic marker of low avidity for recent forms of toxoplasmosis due to a significant decrease of their frequencies (from 80 to 0%) after treatment with 6 M urea solutions. The p30 antigen was not considered a good marker to distinguish acute from chronic infection since corresponding IgG antibodies were determined to have high avidity in both phases of the infection. Thus, the avidity immunoblotting assay proved to be a useful tool for determining antigenic markers of recent and chronic phases of Toxoplasma gondii infection.

Seroprevalence of toxoplasmosis, toxocariasis and cysticercosis in a rural settlement, São Paulo State, Brazil

“…Low socioeconomic status is an additional factor contributing to T. gondii infection in Brazilian communities and worldwide. [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]27 There was also a significant increase in infections in females compared to males. This may be a result of women remaining near or inside the house, close to domestic animals, and becoming predisposed to T. gondii infection.…”

“…14,16 Toxoplasma gondii IgG and IgM Toxoplasma gondii IgG and IgM antibodies were detected using ELISA containing T. gondii excretorysecretory antigen (ESA) peptides. 11,20 The ESA peptides chosen were granule protein 1 (GRA-1), which correlates with chronic toxoplasmosis, granule protein 7 (GRA-7) which is detected in acute toxoplasmosis, 21,22 and surface antigen 1 (SAG-1), which is present only in the tachyzoite stage and is a marker of acute toxoplasmosis, 23 based on the methodology described by Araú jo and Ferreira. 11,20…”

High diagnostic efficiency of IgM-ELISA with the use of multiple antigen peptides (MAP1) from T. gondii ESA (SAG-1, GRA-1 and GRA-7), in acute toxoplasmosis

“…Because specific IgM antibodies can persist for several months, or even years in some individuals, following acute infection, interpretation of serological tests might be troublesome when acute Toxoplasmosis is suspected 9 . The diagnosis of chronic stage of infection or of past exposure to T. gondii is made by detection of specific IgG antibodies and the absence of the acute-phase markers IgM and IgA 22 . The currently available commercial tests to detect IgG, IgM and IgA antibodies rely mostly on preparations of crude parasite antigens, i.e.…”

“…So, multiple antigen peptides may be an alternative source of antigens that are characteristic of the acute or chronic stages of the infection, serving as a tool to discriminate the acute/recent toxoplasmosis from chronic stages. The design of MAP chosen for study by above authors consisted of a core 16,22 and surface antigen 1 (SAG-1) present only in the tachyzoite stage and marker of acute toxoplasmosis 2,7,26 . In the present study, we evaluated the diagnostic efficiency of ELISA with the use of SAG1, GRA1 and GRA7 peptides derived from T. gondii ESA, individually and in combined forms as MAP, for the detection of IgG, IgM and IgA antibodies, aiming to establish a profile of acute/recent toxoplasmosis, with a single serum sample.…”

Development and validation of an Enzyme Linked Immunosorbent Assay (ELISA) test for the diagnosis of toxoplasmosis in Sri Lanka

“…Therefore, the diagnosis of toxoplasmosis depends heavily on immunological tests, with detection of Toxoplasma specific IgG, IgM and IgA antibodies [5]. Further low avidity tests, which indicate recently formed immunoglobulin is also now available [6,7]. In Sri Lanka diagnosis of toxoplasmosis is currently done using commercially available Toxoplasma IgG and/or IgM ELISA kits.…”