The investigation of toxoplasma infection associated with pregnancy

Congenital toxoplasmosis: late pregnancy infections detected by neonatal screening and maternal serological testing at delivery

The first aim of this study was to determine the prevalence of congenital toxoplasmosis in newborn infants treated by the public health system in Porto Alegre, a city in southern Brazil, using neonatal screening for Toxoplasma gondii-specific IgM. The second aim was to investigate whether the cases detected by this approach could have been identified by the prenatal screening for antibodies to T. gondii that was performed in the same population. A fluorometric assay was used to analyse T. gondii-specific IgM in filter paper specimens obtained from newborn infants for routine screening for metabolic diseases. When the specific IgM was positive, serum samples from the infant and the mother were requested for confirmatory serological testing, and the infant underwent clinical examination. Among 10 000 infants screened for T. gondii-specific IgM, seven filter paper samples were positive, and congenital toxoplasmosis was confirmed in six patients. The prevalence of IgM specific for T. gondii was 6/10 000 [95% CI 2/10 000, 13/10 000]. One infected infant had already been identified in the maternity ward before birth, three had been identified by maternal serology at delivery, and two infants with congenital toxoplasmosis were identified solely through neonatal screening. Although four mothers of the patients with congenital toxoplasmosis received prenatal care, and three mothers had one or two serological tests for T. gondii-specific antibodies (one at first trimester, one at first and second trimesters, and the other at second and third trimesters), they were not identified during pregnancy as infected. Neonatal screening identified cases of infection not detected by obtaining only one or two serum samples from pregnant women for T. gondii serology, mainly when infection was acquired and transmitted in late pregnancy. Maternal serology at delivery and neonatal screening were especially useful in the identification of infants with congenital toxoplasmosis when the mother did not receive regular prenatal serological testing or prenatal care.

Newborn screening for congenital toxoplasmosis: feasible, but benefits are not established

Perspective on the paper by Schmidt et al (see page 661)

Cytokines involved in Toxoplasmic encephalitis

Reactivation of cerebral toxoplasmosis occurs in approximately 30% of acquired immune deficiency syndrome (AIDS) patients who are seropositive for Toxoplasma gondii and a change in the levels of cytokines during this relapse is observed. Several cytokines are able to initiate meningeal inflammation and may play a role in the immunopathogenesis of the disease. The induction of a type 1 inflammatory cytokine response is a key event in the initiation of immunity to T. gondii. Interleukin (IL)-10 production in infected brain facilitates the persistence of parasites by down-regulating the intracerebral immune response. The in vivo and in vitro models are very numerous and this may explain the heterogeneity of the results. The role of gamma interferon is important because it is the principal mediator inducing a host resistance against T. gondii. Several cytokines stimulating or decreasing interferon (IFN)-gamma levels are reported. The particular case of AIDS patients whose humoral response is altered, is studied.

Value of prenatal diagnosis and early postnatal diagnosis of congenital toxoplasmosis: retrospective study of 110 cases

We reviewed the files of 110 women with Toxoplasma seroconversion during pregnancy. Prenatal diagnosis was attempted for 94 women by amniotic fluid sampling. Toxoplasma gondii was detected by PCR, with or without tissue culture and mouse inoculation. The early neonatal diagnostic procedure included placental testing by PCR and/or mouse inoculation, cord blood serological testing, and comparison of maternal and newborn antibodies by Western blotting (WB). Serological follow-up of the infants was conducted during the first year of life or until the diagnosis of congenital toxoplasmosis (CT) could be ruled out. Congenital infection was diagnosed in 27 individuals (20 live births) in the prenatal and/or neonatal period. The sensitivity and specificity of prenatal diagnosis were 81 and 100%, respectively. Placental examination was positive for 66.7% of individuals with CT and was always negative for neonates without CT. Cord blood serology detected immunoglobulin M (IgM) and/or IgA in 80% of infected newborns, with respective specificities of 91.2 and 87.7%. By WB we detected bands on IgG and IgM blots recognized by the newborn serum but not by the maternal serum (neosynthesized IgG and/or IgM) for 88.2% of infected infants within the first 2 months of life with a specificity of 100%. Early postnatal diagnosis was negative for 2 of the 20 neonates with CT. Both of these newborns had a negative prenatal diagnosis and were asymptomatic, suggesting a very low parasite load. In conclusion, despite the use of advanced methods, some cases of congenital toxoplasmosis cannot be detected early, which underlines the importance of careful follow-up of newborns who are at risk.