Evaluation of Colostrum As an Alternative Biological Sample for the Diagnosis of Human Congenital Toxoplasmosis

Background: Toxoplasmosis is a zoonosis caused by Toxoplasma gondii, an intracellular protozoan parasite able to infect a wide range of hosts, including humans. Congenital infection can cause severe damage to the fetus. Thus, it is important to detect antibodies against the parasite to confirm clinical manifestations. Considering that all immunoglobulin isotypes may be present in biological samples from newborns and their mothers, this study aimed to evaluate the ability to diagnose recent toxoplasmosis by using colostrum, as an alternative noninvasive way to obtain biological samples, as well as to determine correlation rates between antibodies from serum samples to detect IgG, IgM and IgA isotypes against T. gondii.

Methods: A total of 289 puerperal women from Clinical Hospital of Federal University of Uberlândia (mean age: 24.8 years, range: 14 - 43 years) took part in this study. Serum and colostrum samples from these patients were analyzed using ELISA and immunoblotting assays for soluble antigens from T. gondii.

Results: ELISA immunoassays with serum samples showed reactivity in 47.0, 6.9 and 2.8 % of samples to anti-T. gondii IgG, IgM and IgA, respectively, in comparison with colostrum samples, which showed reactivity in 46.0, 7.9 and 2.8 % of samples to the same isotypes. Also, significant correlation rates of anti-T. gondii antibody levels between serum and colostrum samples were observed. Interestingly, reactivity to IgM and/or IgA in colostrum and/or serum confirmed clinical manifestations of congenital toxoplasmosis in three newborns. Immunoblotting assays showed that it is possible to detect IgG, IgM and IgA antibodies against various antigens of T. gondii in serum and colostrum samples. IgG antibodies in serum and colostrum samples recognized more antigenic fractions than IgM and IgA antibodies. Serum IgG detected more antigenic fractions than IgG antibodies present in the colostrum of the same patient. In contrast, specific IgA present in colostrum recognized a higher number of antigens than IgA present in serum samples of the same patient.

Conclusions: Overall, the results show that it is important to investigate the occurrence of congenital toxoplasmosis, even at puerperal period. Furthermore, this study demonstrates that T. gondii-specific IgG, IgM and IgA antibodies in serum and colostrum samples from puerperal women may be detected with a significant correlation, suggesting that colostrum may also be used as an alternative biological sample to efficiently diagnose recent human toxoplasmosis.