Early diagnosis of congenital toxoplasmosis in newborn infants using IgG subclasses against two Toxoplasma gondii recombinant proteins

• Published in: Memórias do Instituto Oswaldo Cruz Vol. 107; no. 3; pp. 342 - 347
• Main Authors: e Silva, Carlos Henryque de Souza, de Andrade, Gláucia Queiroz, Januário, José Nélio, Carneiro, Ana Carolina de Aguiar Vasconcelos, Carneiro, Mariangela, Vasconcelos-Santos, Daniel Vitor, Vitor, Ricardo Wagner de Almeida
• Format: Journal Article
• Language: English
• Published: Brazil Fundação Oswaldo Cruz, Fiocruz 01-05-2012; Instituto Oswaldo Cruz, Ministério da Saúde; Fundação Oswaldo Cruz (FIOCRUZ)
• Subjects: Antibodies, Protozoan - blood; Antibodies, Protozoan - immunology; Antigens, Protozoan - immunology; Blood; congenital toxoplasmosis; congenital toxoplasmosis - ELISA - recombinant proteins - IgG subclasses; Early Diagnosis; ELISA; Enzyme-Linked Immunosorbent Assay; Filter paper; Humans; IgG subclasses; Immunoglobulin G; Immunoglobulin G - blood; Immunoglobulin G - immunology; Immunoglobulin M; Infant, Newborn; Infants; Neonates; Optical density; PARASITOLOGY; Predictive Value of Tests; Prospective Studies; recombinant proteins; Recombinant Proteins - blood; Reproducibility of Results; Sensitivity and Specificity; Toxoplasma - immunology; Toxoplasma gondii; Toxoplasmosis; Toxoplasmosis, Congenital - diagnosis; Toxoplasmosis, Congenital - immunology; TROPICAL MEDICINE; recombinant proteins; congenital toxoplasmosis; IgG subclasses; ELISA
• ISSN: 1678-8060; 0074-0276; 1678-8060; 0074-0276
• DOI: 10.1590/s0074-02762012000300008

The aim of this work was to evaluate the utility of ELISA-based testing
of total IgG (IgGt) antibodies and its subclasses (IgG1, IgG2, IgG3 and
IgG4) against soluble (STAg) and recombinant (rSAG1 and rMIC3) antigens
of Toxoplasma gondii for diagnosing congenital toxoplasmosis. Sera
from 217 newborns initially testing positive for specific IgM in filter
paper dried blood spots were tested for specific IgM and IgG by
ELFA-VIDAS®. Congenital toxoplasmosis was confirmed in 175 and
ruled out in 42 infants. The validity of the ELISA tests was determined
using the persistence of IgG antibodies (ELFA-VIDAS® kit) at the
end of 12 months, which is considered the reference test for the
diagnosis of congenital toxoplasmosis. The frequency of positivity with
IgGt against STAg, rSAG1 and rMIC3 was found in 97.2%, 96.3% and 80.2%,
respectively, of the newborns with confirmed congenital toxoplasmosis.
IgG1 reacted with all three antigens, while IgG3 and IgG4 reacted
preferentially with rMIC3. Higher mean values of reactivity (sample
optical density/cut-off) were found for all subclasses when using
rMIC3. All of the antigens showed high sensitivity and low specificity
in detecting anti-T. gondii IgGt and IgG1 and low sensitivity and high
specificity in detecting IgG3 and IgG4. In conclusion, the combined
detection of IgG antibody subclasses against recombinant toxoplasmic
antigens may be useful for the early diagnosis of congenital
toxoplasmosis.