Options for the pharmacotherapy of toxoplasmosis during pregnancy

Long-Term Outcomes in Children with Congenital Toxoplasmosis-A Systematic Review

Even in the absence of manifestations at birth, children with congenital toxoplasmosis (CT) may develop serious long-term sequelae later in life. This systematic review aims to present the current state of knowledge to base an informed decision on how to optimally manage these pregnancies and children. For this, a systematic literature search was performed on 28 July 2022 in PubMed, CENTRAL, ClinicalTrials.gov, Google Scholar and Scopus to identify all prospective and retrospective studies on congenital toxoplasmosis and its long-term outcomes that were evaluated by the authors. We included 31 research papers from several countries. Virulent parasite strains, low socioeconomic status and any delay of treatment seem to contribute to a worse outcome, whereas an early diagnosis of CT as a consequence of prenatal screening may be beneficial. The rate of ocular lesions in treated children increases over time to 30% in European and over 70% in South American children and can be considerably reduced by early treatment in the first year of life. After treatment, new neurological manifestations are not reported, while ocular recurrences are observed in more than 50% of patients, with a mild to moderate impact on quality of life in European cohorts when compared to a significantly reduced quality of life in the more severely affected South American children. Though CT is rare and less severe in Europe when compared with South America, antenatal screening is the only effective way to diagnose and treat affected individuals at the earliest possible time in order to reduce the burden of disease and achieve satisfying outcomes.

Development of a murine vertical transmission model for Toxoplasma gondii oocyst infection and studies on the efficacy of bumped kinase inhibitor (BKI)-1294 and the naphthoquinone buparvaquone against congenital toxoplasmosis

Objectives

Establishment of a mouse model for congenital toxoplasmosis based on oral infection with oocysts from Toxoplasma gondii ME49 and its application for investigating chemotherapeutic options against congenital toxoplasmosis.

Methods

CD1 mice were mated, orally infected with 5, 25, 100, 500 or 2000 oocysts and monitored for clinical signs and survival of dams and pups until 4 weeks post partum . The parasite burden in infected mice was quantified by real-time PCR in lungs, brains and, in the case of surviving pups, also in eyes. Seroconversion was assessed by ELISA. T. gondii cysts in brain were identified by immunofluorescence. In a second experiment, pregnant CD1 mice challenged with 20 oocysts/mouse were treated with buparvaquone or the calcium-dependent protein kinase 1 inhibitor bumped kinase inhibitor (BKI)-1294 and the outcome of infection was analysed.

Results

T. gondii DNA was detected in the brain of all infected animals, irrespective of the infection dose. Seroconversion occurred at 3 weeks post-infection. Most pups born to infected dams died within 1 week post partum , but a small fraction survived until the end of the experiment. T. gondii DNA was detected in the brain of all survivors and half of them exhibited ocular infection. Chemotherapy with both compounds led to dramatically increased numbers of surviving pups and reduced cerebral infection. Most efficient were treatments with BKI-1294, with 100% survivors and only 7% brain-positive pups.

Conclusions

BKI-1294 and buparvaquone exert excellent activities against transplacental transmission in pregnant mice.

Fitness of Toxoplasma gondii is not related to DHFR single-nucleotide polymorphism during congenital toxoplasmosis

Factors that regulate the pathogenesis of Toxoplasma gondii in humans are poorly understood. When acquired during pregnancy, toxoplasmosis can be disastrous, leading to fetal loss or conversely to subclinical disease. In congenitally infected infants, evolution is highly unpredictable. Genotype based virulence patterns have been described in mice, but in humans this classification does not correlate with the gravity of the disease. Mutations on DHFR-TS loci have recently been reported to confer T. gondii fitness cost. In this study, we investigated the relationship between the virulence of the parasite, as measured by clinical outcome in the fetus or newborn, fitness, as measured by parasitic load in amniotic fluid, and allelic polymorphism in DHFR. Six cases of severe congenital toxoplasmosis and 23 cases of mild congenital infections were included in the study. Quantitative PCR was performed to evaluate total T. gondii DNA load in amniotic fluid and detection of mutations was carried out with a LightCycler using hybridisation probes. Parasitic load was significantly higher in severe infections than in mild diseases. Among isolates from severe or non-severe cases of congenital toxoplasmosis, no polymorphism could be detected at loci 36, 83 or 245 of the DHFR gene. The virulent RH strain presented the same melting temperature as the non-virulent PRU strain for codons 36, 83 and 245. Only mutated clones, M2M3 and M2M4 with allelic replacement at these positions, displayed different profiles allowing a clear distinction between wild and mutant types. We concluded that the DHFR gene mutations we investigated do not regulate T. gondii fitness in humans.

Treatments for toxoplasmosis in pregnancy

BACKGROUND

Toxoplasmosis is a widespread parasitic disease and usually causes no symptoms. However, infection of pregnant women may cause congenital infection, resulting potentially in mental retardation and blindness in the infant.

OBJECTIVES

The objective of this review was to assess whether or not treating toxoplasmosis in pregnancy reduces the risk of congenital toxoplasma infection and improves infant outcomes.

SEARCH STRATEGY

The Cochrane Pregnancy and Childbirth Group trials register was searched. An electronic search was performed using the key words 'congenital and toxoplasmosis' on the following databases: MEDLINE (1966-07/1997), Embase (1993-07/1997), Pascal (French) (1990-1997), Biological Abstracts (1993-1995) and the Cochrane Controlled Trials Register. There was also contact with experts in the field, including those in the European Research Network on Congenital Toxoplasmosis.

SELECTION CRITERIA

Randomised controlled trials of antibiotic treatment versus no treatment of pregnant women with proven or likely acute Toxoplasma infection, with outcomes in the children reported. We also inspected relevant reports of less robust experimental studies in which there were (non randomly allocated) control groups, although it was not planned to include such data in the primary analysis.

DATA COLLECTION AND ANALYSIS

Reports of possibly eligible studies were scrutinised by two investigators.

MAIN RESULTS

Out of the 2591 papers identified, none met the inclusion criteria.

REVIEWER'S CONCLUSIONS

Despite the large number of studies performed over the last three decades we still do not know whether antenatal treatment in women with presumed toxoplasmosis reduces the congenital transmission of Toxoplasma gondii. Screening is expensive, so we need to evaluate the effects of treatment, and the impact of screening programmes. In countries where screening or treatment is not routine, these technologies should not be introduced outside the context of a carefully controlled trial.