Perfil de imunoglobulinas G e suas subclasses em recém-nascidos comtoxoplasmose congênita em Minas Gerais, Brasil

Abstract

Toxoplasma gondii has medical and veterinary importance, being an opportunistic pathogen in immunocompromised patients and fetuses of mothers recently infected. From November/2006 to May/2007 220 newborns positive for IgM anti-T. gondii and their mothers were identified from 146,307 screened babies, participants of the Newborn Screening State Program in Minas Gerais. Toxoplasmosis was confirmed in 190 children with persistence of IgG antibody until the 12th month of life, while 45 had congenital toxoplasmosis discarded. The aim of this study was to establish a comparison between the results of the ELISA test in newborns with congenital toxoplasmosis when T. gondii soluble antigens (STAg) and recombinants (rSAG1 and rMIC3) were employed, comparing serology of mothers and their newborns. In addition, it was studied the association of IgG subclasses and clinical signs. One hundred seventy five children among the 190 with confirmed congenital toxoplasmosis and 42 among the 45 with negative diagnosis were evaluated. The proportion of reactive samples of newborns infected and uninfected ones were different when performing ELISA using ecombinant antigens. All the antigens showed high sensitivity and low specificity for detecting total IgG and IgG1 anti-T. gondii in children with congenital toxoplasmosis and low sensitivity and high specificity to detect IgG3 and IgG4. Difference in the proportion of newborn infected with non-infected mothers and newborns infected with non-infected mothers was observed, demonstrating the production of anti-T. gondii by infected fetus during pregnancy. It was observed greater chance to detect total IgG anti-T. gondii by ELISA in children without ocular lesions when compared with children with active and cicatrized lesions, while detection of IgG2 and IgG4 anti-T. gondii was related to ocular lesion when compared with children without damage. Relationship between ELISA and cases of neurological disorders was observed for IgG2 and IgG4 anti-T. gondii, while IgG3 was related to children with no neurological deficits. Based on these results, it can be affirmed that recombinant antigens in conjunction with subclasses of IgG antibodies detection are important indirect diagnostic tools capable of predicting the potential alterations found in newborns with congenital toxoplasmosis