Abstract
Highly specific and sensitive diagnostic methods are vital for the effective control and treatment of toxoplasmosis. Routine diagnosis is primarily serological because T. gondii infections stimulate persistently high IgG antibody responses. The sensitivity and specificity of methods are crucial factors for the proper diagnosis of toxoplasmosis, primarily dependent on the antigens used in different assays. In the present study, we compared the serodiagnostic performances of three recombinant dense granule antigens, namely, the GRA6, GRA7, and GRA14, to detect IgG antibodies against T. gondii in human sera from the Philippines. Moreover, we evaluated the IgG1, IgG2, IgG3, and IgG4 responses against the different recombinant antigens, which has not been performed previously. Our results revealed that the TgGRA7 has consistently displayed superior diagnostic capability, while TgGRA6 can be a satisfactory alternative antigen among the GRA proteins. Furthermore, IgG1 is the predominant subclass stimulated by the different recombinant antigens. This study’s results provide options to researchers and manufacturers to choose recombinant antigens suitable for their purpose.
Highlights
Toxoplasmosis is known to infect nearly one-third of the world’s human population [1].The accurate detection of T. gondii infection through highly specific and sensitive diagnostic methods is vital for the effective control and treatment of toxoplasmosis [2,3]
We assessed the reactivity of IgG and IgG subclasses (IgG1, IgG2, IgG3, IgG4) in human sera from the Philippines against three recombinant antigens expressed in E. coli as GST-fused (TgGRA7 and TgGRA14) and His-tagged (TgGRA6) proteins through indirect ELISA
For the TgGRA6- and TgGRA14-ELISA, 2 and 16 human serum samples were found below the cut-off values, respectively
Summary
The accurate detection of T. gondii infection through highly specific and sensitive diagnostic methods is vital for the effective control and treatment of toxoplasmosis [2,3]. T. gondii infections in humans are characterized by persistent high IgG antibody titers [4,5]. Routine diagnosis for toxoplasmosis is mainly through detecting specific T. gondii antibodies. The sensitivity and specificity of methods are crucial factors for the proper diagnosis of toxoplasmosis to avoid false-positive and false-negative results. These factors are primarily dependent on the antigens used in different assays. Aside from improving T. gondii diagnosis, differentiating the different phases of infection using recombinant antigens has been widely recognized [6,7]. Among the recombinant antigens that showed outstanding serodiagnostic performance are the SAG1 [8,9,10] and SAG2 [11,12] of the surface antigen (SAG) family; the dense granule (GRA) proteins GRA1 [8], GRA2 [13,14], GRA 3 [9], GRA5 [15], GRA6 [16,17], GRA7 [10,18,19,20], and GRA8 [21,22]; the rhoptry proteins ROP1 [14,23], ROP2 [24], and ROP8 [25]; and MAG1 [26] and MIC2 [9]
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