Isótipos de anticorpos específicos a Toxoplasma gondii presentes em amostras de leite humano: uma ferramenta para o diagnóstico de toxoplasmose aguda

Abstract

Toxoplasmosis is a zoonosis caused by the intracellular parasite Toxoplasma gondii, which infects different hosts including up to a third of the world s human population and may cause severe damage to the fetus in congenital infection. Maternal breastfeeding is the most natural and safe way to feed a newborn, with the ability to provide good development of the infant s immune system. All immunoglobulin isotypes are present in human breast milk, mainly in the colostrum, with systemic or local source. There are several pieces of evidence showing that breastfeeding protects the infant against a wide range of diseases, but few efforts have been directed to identifying the protecting action of human milk against parasitic infections, including T. gondii. Due to the importance of breastfeeding and to the high prevalence of toxoplasmosis, this study was conducted in order to detect and evaluate the presence of specific T. gondii IgG, IgM and IgA antibodies in paired serum and colostrum samples. The study was carried out on 289 puerperal women from Clinical Hospital of Universidade Federal de Uberlândia (mean age 24.8 years, range 14 43 years). Their serum and colostrum samples were analyzed by ELISA and immunoblotting assays against soluble antigens from T. gondii. ELISA tests showed reactivity for anti-T. gondii IgG, IgM and IgA, respectively, in 136 (47.0%), 20 (6.9%), 8 (2.8%) serum samples and in 133 (46.0%), 23 (7.9%), 8 (2.8%) colostrum samples. Also, it was observed significant correlation rates between anti-T. gondii antibodies levels in serum and colostrum samples. Immunoblotting assays showed that it was possible to detect IgG, IgM and IgA antibodies specific to different antigens of T. gondii in serum as well as colostrum. IgG present in serum and colostrum recognized more antigenic fractions compared to the IgM and IgA, and seric IgG always detected more antigenic fractions than IgG in colostrum from the same patient. In contrast, specific IgA antibodies present in colostrum recognized a higher number of antigens than IgA present in serum from the same patient. Furthermore we have shown that 60 kDa antigenic fraction may be a good marker to diagnose acute toxoplasmosis infection, because it was recognizes frequently by low avidity IgG antibodies in both samples; and 39 kDa antigenic fraction may be a marker to diagnose congenital toxoplasmosis. Our results showed a significant association between T. gondii-specific antibodies present in serum and in milk samples from the patients, demonstrating that it is possible to diagnose toxoplasmosis using human milk, a noninvasive way to obtain biological samples.