Seroreactivity to and Avidity for Recombinant Antigens in Toxoplasmosis

Abstract

To improve serodiagnostic methods for the diagnosis of acute toxoplasmosis during pregnancy, a new test system has been developed and evaluated based on the use of recombinant antigens. Five recombinant Toxoplasma gondii antigens (ROP1, MAG1, SAG1, GRA7, and GRA8) were cloned in Escherichia coli, purified, and applied directly onto nitrocellulose membranes in a line assay (recomLine Toxoplasma). A panel of 102 sera from 25 pregnant women with supposed recent toxoplasmosis and from two symptomatic children was compared to a panel of 71 sera from individuals with past infection. Both panels were analyzed using a recombinant line assay for immunoglobulin G (IgG), IgM, and IgA antibodies and a reference enzyme-linked immunosorbent assay. Within the IgM-positive samples, antibodies against ROP1 were predominant regardless of the infection state. In IgG analysis a characteristic antibody pattern was found for very recent infections. This pattern changed to a different one during the time course of infection: antibodies against GRA7 and GRA8 were characteristic for very early IgG, whereas antibodies against SAG1 and MAG1 appeared significantly later. These results were further confirmed by determination of the IgG antibody avidity for every single recombinant antigen. In the time course of infection, IgG antibodies against the early recognized antigens matured significantly earlier than those directed against the later antigens did. The IgA patterns did not give reliable information about the infection time points. The data revealed that the recombinant line assay provides valuable information on the actual state of infection, especially during the early infection time points.Toxoplasmosis is caused by the parasite Toxoplasma gondii.

Toxoplasma gondii Recombinant Antigens as Tools for Serodiagnosis of Human Toxoplasmosis: Current Status of Studies

“…Many of these recombinant antigens have been used for the detection of T. gondii-specific antibodies in human serum samples (38). Furthermore, several previous studies have found that recombinant antigens improve the serological diagnosis of toxoplasmosis (15,25,34,(39)(40)(41)(42)(43)(44)(45)(46)(47)(48). However, it is not only the improvement of T. gondii diagnosis with the use of recombinant antigens that is very important but, also, improvement in differentiating between the acute and chronic phase of toxoplasmosis.…”

Toxoplasmosis: IgG Avidity and Its Implication in Serodiagnosis

“…Therefore, detection of GRA7 antibodies would be expected to be a good candidate to use for serodiagnosis. Several rGRA antigens such as rGRA2 (Golkar et al, 2007;HolecGąsior et al, 2009), rGRA6 (Aubert et al, 2000Golkar et al, 2008), rGRA7 (Aubert et al, 2000Pietkiewicz et al, 2004;Pfrepper et al, 2005;Pietkiewicz et al, 2007), and rGRA8 (Pfrepper et al, 2005;Gatkowska et al, 2006;Babaie et al, 2009) have been proposed as markers to indicate acute infections. rGRA4 and rGRA7, but not rROP2, have been shown to be valuable in differentiating acute and chronically infected individuals for both adult and congenital toxoplasmosis (Nigro et al, 2003;Altcheh et al, 2006).…”

The Laboratory Diagnosis in Toxoplasma Infection

“…The dense granule antigen-GRA1, GRA2, GRA4, GRA6, GRA7 and GRA8, rhoptries protein-ROP1 and ROP2, the matrix protein-MAG1, protein micronemes-MIC2, MIC3, MIC4 and MIC5 or the surface antigen-SAG1 and SAG226, were evaluated as diagnostic markers in human beings or animals by ELISA to detect IgG and IgM speciic antibodies [25]. The combinations of recombinant antigens have showed more sensibility and speciicity for the use of only one antigen.…”