Detection of HumanToxoplasma-Specific Immunoglobulins A, M, and G with a RecombinantToxoplasma gondiiRop2 Protein

Abstract

The Toxoplasma gondii rhoptry protein Rop2 was expressed in Escherichia coli as a fusion protein containing 44 kDa of the 55-kDa mature Rop2, supplied with six histidyl residues at the N-terminal end (Rop2196–561). Humoral response during Toxoplasma infection of humans was analyzed by immunoglobulin G (IgG), IgA, and IgM enzyme-linked immunosorbent assay with Rop2196–561 as the antigen substrate. The analyzed sera were divided according to T. gondii-specific serological tests (IgG, IgA, or IgM indirect immunofluorescence and IgA or IgM immunosorbent agglutination assay) as group A (IgG+ IgA− IgM−;n = 35), group B (IgG+ IgA+IgM+; n = 21), group C (IgG+IgA+ IgM−; n = 5), and group D (IgG+ IgA− IgM+;n = 16). Twenty-six T. gondii-seronegative sera from individuals with other infections were also included (group E). Anti-Rop2 IgG antibodies were detected in 82.8% of group A sera and in 97.6% of the sera with acute-phase marker immunoglobulins (groups B, C, and D). The percentage of IgA antibody reactivity against Rop2196–561 was 17.1% in group A, 50% in group D, and 80.8% in groups B and C. The percentage of IgM antibody reactivity was 0% in groups A and C and 62% in groups B and D. Sera from group E failed to show IgA, IgM, or IgG antibody reactivity. Since T. gondii Rop2 elicits a strong humoral response from an early stage of infection, it is suggested that recombinant Rop2196–561 would be suitable for use in diagnostic systems, in combination with other T. gondii antigens, to detect specific IgG, IgA, and IgM antibodies.

Toxoplasma gondii excretory secretory antigenic proteins of diagnostic potential

“…Thus, presence of IgM antibodies in human serum sample alone is often insufficient for the diagnosis of acute toxoplasmosis. IgA antibodies is considered to be a marker acquired toxoplasmosis because the kinetics of this isotype is faster than that of IgM antibodies, and naturally reacting IgA is not found in seronegative subjects (13).…”

Expression of a cDNA encoding a Toxoplasma gondii protein belonging to the heat-shock 90 family and analysis of its antigenicity

“…These results are similar to those obtained by Mun et al [11] with T. gondii cystic-stage Bag1/Hsp30 protein, which induced protective immunity in mice. By contrast, rRop2 [8] was shown to produce a signi¢cative humoral response early in the infection in both mouse strains (Fig. 3A).…”

“…The plasmid pQE-TgHsp90 produces a recombinant protein with a 6-His tag at the N-terminus (rTgHsp90). Expression and puri¢cation under denaturing conditions were performed as previously described [8].…”

Recombinant Antigens To DetectToxoplasma gondii-Specific Immunoglobulin G and Immunoglobulin M in Human Sera by Enzyme Immunoassay

“…The pattern of immunoreactivity observed by Western blotting with human sera varies with the immunoglobulin class and the stage of infection. Several genes have been cloned that encode T. gondii antigens, as follows: the surface antigens P22 (SAG2) (38,46) and P30 (SAG1) (3,12,24); the dense granule antigens P24 (GRA1) (4), P28 (GRA2) (35,45), P29 (GRA7) (2,9,17), P32 (GRA6) (27,47), and P41 (GRA4) (33,55); the rhoptry antigens P54 (ROP2) (31,51,56) and P66 (ROP1) (25,37); and the B10 (36), P25 (22,55), P35, and P68 antigens (25). These recombinant antigens expressed in bacteria have been used to detect antibodies to the parasite in the serum of humans and animals.…”