Toxoplasma-IgM and IgG-avidity in single samples from areas with a high infection rate can determine the risk of mother-to-child transmission

Abstract

SUMMARYAnti-Toxoplasma IgG-avidity was determined in 168 serum samples from IgG-and IgM-positive pregnant women at various times during pregnancy, in order to evaluate the predictive value for risk of mother-to-child transmission in a single sample, taking the limitations of conventional serology into account. The neonatal IgM was considered the serologic marker of transmission. Fluorometric tests for IgG, IgM (immunocapture) and IgG-avidity were performed. Fifty-one of the 128 pregnant women tested gave birth in the hospital and neonatal IgM was obtained. The results showed 32 (62.75%) pregnant women having high avidity, IgM indexes between 0.6 and 2.4, and no infected newborn. Nineteen (37.25%) had low or inconclusive avidity, IgM indexes between 0.6 and 11.9, and five infected newborns and one stillbirth. In two infected newborns and the stillbirth maternal IgM indexes were low and in one infected newborn the only maternal parameter that suggested fetal risk was IgG-avidity. In the present study, IgG-avidity performed in single samples from positive IgM pregnant women helped to determine the risk of transmission at any time during pregnancy, especially when the indexes of the two tests were analysed with respect to gestational age. This model may be less expensive in developing countries where there is a high prevalence of infection than the follow-up of susceptible mothers until childbirth with monthly serology, and it creates a new perspective for the diagnosis of congenital toxoplasmosis.

Seroprevalence and Sources of Toxoplasmosis among Orang Asli (Indigenous) Communities in Peninsular Malaysia

“…IgG avidity has recently been tested in a single serum sample and was found to be effective for diagnosis of acute toxoplasmosis in pregnant women and other adults. 24,25 In this present study, there were no pregnant women involved. Additional study is, therefore, recommended to be carried out on a larger scale, particularly in screening women of reproductive age, to prevent the risk of congenital transmission.…”

Non-association between anti-Toxoplasma gondii antibodies and ABO blood group system

“…Most humans tend to produce high avidity IgG anti-T. gondii antibodies, since contact with the infecting forms of T. gondii also stimulates the development of immune memory (16)(17)(18)(19)(20)(21). Additionally, older individuals seem to be exposed to a greater number of stimuli as well as reinfections by this parasite, without necessarily manifesting the clinical form of the disease.…”

Congenital toxoplasmosis infection in an infant born to an HIV-1-infected mother

“…As other tools for early diagnosis, detection of parasite in amniotic fluid can be accomplished by in vitro culture, animal inoculation and PCR [10]. PCR for detection of T. gondii has revolutionized prenatal diagnosis, avoiding the use of more invasive procedures on the fetus, thanks to its sensitivity, specificity and rapidity [11].…”