Prevention of retinochoroiditis in congenital toxoplasmosis: Europe versus South America

Pediatric Posterior Infectious Uveitis

PURPOSE

To describe the most important cause of infectious posterior uveitis in pediatric patients.

METHODS

Review of the literature.

RESULTS

The most important causes of infectious uveitis in pediatric patients are: cat-scratch disease, toxocariasis, tuberculosis, viral diseases and toxoplasmosis. Ocular manifestations include retinitis, neuroretinitis, choroidal granulomas, peripheral granulomas and posterior pole granulomas.

CONCLUSION

Infectious posterior uveitis is a challenging subject and should be considered in the differential diagnosis of any posterior uveitis in children. Infectious uveitis must be excluded before initiating immunosuppressive therapy.

Clinical and Serological Characteristics of Ocular Toxoplasmosis in the Democratic Republic of Congo

PURPOSE

To describe demographic data, clinical features, and serological profiles in a cohort of Congolese patients with ocular toxoplasmosis (OT).

METHOD

Cross-sectional study, carried out between March 2020 and July 2021 in two ophthalmic clinics in Kinshasa.

RESULTS

The study comprised 95 participants with OT. Fifty-three patients were male (55.8%). The mean age at presentation was 35.6 ± 14.1 years (range 8-69 years); 71 had active OT (74.7%), among them, 33 had primary OT (46.5%), and 38 had recurrences (53.5%). At presentation, 51 patients (53.7%) had visual impairment (VA < 6/18). Retinochoroidal lesions were located in the central retina in 60 patients (63.1%). Patients with primary OT tend to have higher IgG levels than those with recurrent OT (P = .01).

CONCLUSION

We report the largest cohort of patients with OT in sub-Saharan Africa. In our setting, most patients had recurrent OT with multiple, extensive, and central retinochoroidal lesions.

Variation in CD8 T cell IFNγ differentiation to strains of Toxoplasma gondii is characterized by small effect QTLs with contribution from ROP16

Introduction

Toxoplasma gondii induces a strong CD8 T cell response characterized by the secretion of IFNγ that promotes host survival during infection. The initiation of CD8 T cell IFNγ responses in vitro differs widely between clonal lineage strains of T. gondii, in which type I strains are low inducers, while types II and III strains are high inducers. We hypothesized this phenotype is due to a polymorphic "Regulator Of CD8 T cell Response" (ROCTR).

Methods

Therefore, we screened F1 progeny from genetic crosses between the clonal lineage strains to identify ROCTR. Naïve antigen-specific CD8 T cells (T57) isolated from transnuclear mice, which are specific for the endogenous and vacuolar TGD057 antigen, were measured for their ability to become activated, transcribe Ifng and produce IFNγ in response to T. gondii infected macrophages.

Results

Genetic mapping returned four non-interacting quantitative trait loci (QTL) with small effect on T. gondii chromosomes (chr) VIIb-VIII, X and XII. These loci encompass multiple gene candidates highlighted by ROP16 (chrVIIb-VIII), GRA35 (chrX), TgNSM (chrX), and a pair of uncharacterized NTPases (chrXII), whose locus we report to be significantly truncated in the type I RH background. Although none of the chromosome X and XII candidates bore evidence for regulating CD8 T cell IFNγ responses, type I variants of ROP16 lowered Ifng transcription early after T cell activation. During our search for ROCTR, we also noted the parasitophorous vacuole membrane (PVM) targeting factor for dense granules (GRAs), GRA43, repressed the response suggesting PVM-associated GRAs are important for CD8 T cell activation. Furthermore, RIPK3 expression in macrophages was an absolute requirement for CD8 T cell IFNγ differentiation implicating the necroptosis pathway in T cell immunity to T. gondii.

Discussion

Collectively, our data suggest that while CD8 T cell IFNγ production to T. gondii strains vary dramatically, it is not controlled by a single polymorphism with strong effect. However, early in the differentiation process, polymorphisms in ROP16 can regulate commitment of responding CD8 T cells to IFNγ production which may have bearing on immunity to T. gondii.

Human toxoplasmosis in Mozambique: gaps in knowledge and research opportunities

Toxoplasmosis is a parasitic zoonotic disease caused by Toxoplasma gondii that afflicts humans worldwide and wild and domestic warm-blooded animals. In immunocompetent individuals, the acute phase of infection presents transient low or mild symptoms that remain unnoticed. In immunocompromised patients, T. gondii is a life-threatening opportunistic infection, which can result from the reactivation of latent infection or primary infection. Moreover, congenital toxoplasmosis, which results from the transplacental passage of tachyzoites into the fetus during a pregnant primary infection, can lead to miscarriage, stillbirth, or ocular and neurologic disease, and neurocognitive deficits in the newborns. Thus, the present review aims to address the current knowledge of T. gondii infection and toxoplasmosis in Africa and especially in Mozambique, stressing the importance of identifying risk factors and promote awareness among the health care providers and population, assessing the gaps in knowledge and define research priorities. In Mozambique, and in general in southern African countries, clinical disease and epidemiological data have not yet been entirely addressed in addition to the implications of T. gondii infection in immunocompetent individuals, in pregnant women, and its relation with neuropsychiatric disorders. The main gaps in knowledge in Mozambique include lack of awareness of the disease, lack of diagnostic methods in health facilities, lack of genetic data, and lack of control strategies.

Ocular Toxoplasmosis in Africa: A Narrative Review of the Literature

PURPOSE

To present a narrative review about ocular toxoplasmosis epidemiology, disease burden and prevalent African parasitic strains.

METHODS

An initial search for MeSH terms was conducted with a posterior advanced search in two electronic databases. Full text reading was performed.

RESULTS

Animal African studies have identified Toxoplasma gondii type II, type III, Africa 1, and Africa 3 strains. Seroprevalence varies from 6.4% to 74.5%. Nevertheless, there is a scarcity of epidemiology and serotyping information about ocular toxoplasmosis. African studies have demonstrated that uveitis patients present high frequencies of ocular toxoplasmosis. There is a lack of studies describing specific clinical characteristics, which can be related, to environmental and socioeconomic factors, parasite serotype and genotype, and genetic susceptibility of the host.

CONCLUSION

As Toxoplasma gondii has more virulent strains in the Southern hemisphere, it is relevant to determine African strain types and the correlation between the infecting strains and the clinical manifestations.

Antibiotic treatment for ocular toxoplasmosis: a systematic review and meta-analysis: study protocol

BACKGROUND

Ocular toxoplasmosis (OT) is the most common cause of posterior uveitis, leading to visual impairment in a high proportion of patients. Antibiotics and corticosteroids lower the risk of permanent visual impairment by reducing the size of the retinochoroidal scar, the risk of recurrence, and the severity and duration of acute symptoms. Although OT is a very common cause of infectious posterior uveitis, its treatment remains controversial. Through our systematic review and meta-analysis, we aim to provide the best possible evidence-based information on the safety and effectiveness of the different antibiotic regimes for OT.

METHODS

This systematic review protocol has been developed based on PRISMA-P guidelines for reporting systematic reviews evaluating health care interventions. We will include all published and unpublished randomized controlled trials (RCTs) comparing different antibiotics used for the treatment of OT. We will consider changes in visual acuity, number of recurrences, improvement or worsening of ocular inflammation, size of lesion, and adverse effects as our outcomes. Screening, data extraction, and quality assessment will be undertaken by two reviewers with disagreements resolved through discussion. Studies that compared antibiotics with placebo will be excluded. The reviews will be assessed for quality and relevance. We will assess the risk of bias in five domains according to Cochrane group's tool. The type of data will dictate measures of treatment effect. We will use a random-effects model to calculate our meta-analysis, as eligible studies represent clinically varied populations of participants.

DISCUSSION

The strength of our study will lie in the exhaustive and systematic nature of the literature search, as well as in its methods for assessing quality and analyzing RCT data. Considering the controversial efficacy of the treatment for OT, our study will contribute to improving the existing evidence on the effectiveness of different antibiotics. Future studies may be conducted to increase physicians' awareness of antibiotic therapies, improving the health of patients with OT.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42018085468.

Congenital toxoplasmosis: an in-depth density-equalizing mapping analysis to explore its global research architecture

BACKGROUND

Toxoplasmosis endangers the unborn child if its infectious agent--toxoplasma gondii--is transmitted transplacentally during pregnancy. Although this condition occurs in all parts of the world and represents a major public health burden, no detailed knowledge on the global research architecture of congenital toxoplasmosis is available thus far. Hence, it was the aim of this study to assess the related global research activity over the past 110 years.

METHODS

We employed the NewQIS platform, which combines established scientometric and socioeconomic analysis tools with novel visualizing techniques such as density equalizing mapping projections.

RESULTS

In the Web of Science, 13,044 congenital toxoplasmosis-related items published between 1900 and 2012 were identified. These were issued by 26,483 authors originating from 125 countries. The US was the dominating nation (38.7 % of total scientific output), followed by France (10.9 %) and Great Britain (9.2 %). The US also led the ranking in regards to semi-qualitative parameters (total citations, country-specific h-indices and citation rates). When research activity was related to economic figures, the ratio of total toxoplasmosis publications to the total GDP listed Switzerland first with an average of 589.35 toxoplasmosis-related publications per GDP in 1000 Bio US-$, followed by France (545.16), the UK (486.13) and Brazil (431.84) and the US (311.11). The relation of toxoplasmosis-specific publications to the economic power indicator GDP per capita in 1000 US-$ revealed that the US was ranked first with 97.65 toxoplasmosis-related publications/GDP per capita in 1000 US-$, followed by Brazil (85.95). Subject area analysis indicated a relative shortage of studies that addressed pharmacological or public health aspects of congenital toxoplasmosis.

CONCLUSIONS

This study is the first in-depth approach to sketch a global picture of the congenital toxoplasmosis research architecture. In contrast to other fields of biomedical research, not only high-income countries play a major role regarding congenital toxoplasmosis research but also countries such as Brazil that have a high incidence of congenital toxoplasmosis.

Toxoplasma gondii superinfection and virulence during secondary infection correlate with the exact ROP5/ROP18 allelic combination

The intracellular parasite Toxoplasma gondii infects a wide variety of vertebrate species globally. Infection in most hosts causes a lifelong chronic infection and generates immunological memory responses that protect the host against new infections. In regions where the organism is endemic, multiple exposures to T. gondii likely occur with great frequency, yet little is known about the interaction between a chronically infected host and the parasite strains from these areas. A widely used model to explore secondary infection entails challenge of chronically infected or vaccinated mice with the highly virulent type I RH strain. Here, we show that although vaccinated or chronically infected C57BL/6 mice are protected against the type I RH strain, they are not protected against challenge with most strains prevalent in South America or another type I strain, GT1. Genetic and genomic analyses implicated the parasite-secreted rhoptry effectors ROP5 and ROP18, which antagonize the host’s gamma interferon-induced immunity-regulated GTPases (IRGs), as primary requirements for virulence during secondary infection. ROP5 and ROP18 promoted parasite superinfection in the brains of challenged survivors. We hypothesize that superinfection may be an important mechanism to generate T. gondii strain diversity, simply because two parasite strains would be present in a single meal consumed by the feline definitive host. Superinfection may drive the genetic diversity of Toxoplasma strains in South America, where most isolates are IRG resistant, compared to North America, where most strains are IRG susceptible and are derived from a few clonal lineages. In summary, ROP5 and ROP18 promote Toxoplasma virulence during reinfection.

Toxoplasma gondii is a widespread parasite of warm-blooded animals and currently infects one-third of the human population. A long-standing assumption in the field is that prior exposure to this parasite protects the host from subsequent reexposure, due to the generation of protective immunological memory. However, this assumption is based on clinical data and mouse models that analyze infections with strains common to Europe and North America. In contrast, we found that the majority of strains sampled from around the world, in particular those from South America, were able to kill or reinfect the brains of hosts previously exposed to T. gondii. The T. gondii virulence factors ROP5 and ROP18, which inhibit key host effectors that mediate parasite killing, were required for these phenotypes. We speculate that these results underpin clinical observations that pregnant women previously exposed to Toxoplasma can develop congenital infection upon reexposure to South American strains.

Plasma microRNAs are promising novel biomarkers for the early detection of Toxoplasma gondii infection

Background

MicroRNAs (miRNAs) have been shown to be present in plasma, which are remarkably stable, and have been suggested as disease biomarkers. Toxoplasma gondii (T. gondii) is a protozoan parasite that is infective to a wide range of animals and human beings. Previous studies have found that the parasite generated a large number of miRNAs during proliferation and it is known that the spectrum of miRNA expression in the infected hosts is pathogen-specific. To date, there are no reports regarding the application of microRNAs as biomarkers for the early detection of T. gondii infection.

Methods

In this study, we investigated the expression patterns of 414 murine miRNAs and tested their expression levels in the plasma after T. gondii infection by real-time PCR, with an ultimate purpose of identifying infection-related miRNAs. Three miRNAs in particular, exhibiting prominently elevated expressions, were further validated in a large number of infected mice. The Toxoplasma infection-specific miRNAs were confirmed by comparing their expression levels with those of mice infected with Plasmodium berghei, P. yoelii, P. chabaudi, Cryptosporidium parvum, Mouse hepatitis virus, and Staphylococcus aureus.

Results

Among the 414 miRNA candidates identified by a real-time PCR array, 71 were found to be up-regulated in the plasma of T. gondii infected mice. Three of those miRNAs (mmu-miR-712-3p, mmu-miR-511-5p and mmu-miR-217-5p) were prominently expressed in mice infected by both the RH and ME49 strains of T. gondii. Additionally, the elevated expression of these miRNAs was Toxoplasma-specific.

Conclusions

The levels of the three miRNAs, mmu-miR-712-3p, mmu-miR-511-5p and mmu-miR-217-5p miRNAs, were found specifically up-regulated in plasma of mice after T. gondii infection.

[Role of systematic ophthalmological screening for congenital toxoplasmosis: epidemiological study of an Alsatian cohort from 1990 to 2011]

INTRODUCTION

Ophthalmologic complications of congenital toxoplasmosis, such as retino-choroiditis, are particularly feared. Any child with confirmed congenital toxoplasmosis is systematically treated and followed regularly with multiple fundus examinations. The goal of our study is to describe the management and monitoring of a cohort of patients with congenital toxoplasmosis in Alsace, and the impact of this disease in terms of parental anxiety using a standardized questionnaire.

MATERIALS AND METHODS

Our study recorded 35 children with congenital toxoplasmosis, born between 1990 and 2011 in Alsace. All patients were followed by an ophthalmologist. A standardized questionnaire concerning the experience of pregnancy and post-natal follow-up was administered to the parents.

RESULTS

At birth, retinochoroiditis was detected in 2 of the 35 children, and only one child developed chorioretinitis detected during follow-up monitoring (follow-up ranged from 1 to 22 years). Brain abnormalities were noted in 3 children at birth; none of them have presented with chorioretinitis to this day. An average score of 15 out of 23 was found by our standardized questionnaire, reflecting significant anxiety due to congenital toxoplasmosis.

DISCUSSION

Parental anxiety due to congenital toxoplasmosis is obvious, as demonstrated by our standardized questionnaire. Follow-up, directed by comprehensive pediatric examination at birth, including fundus examination, and good information on functional signs of ocular toxoplasmosis may improve screening, so as to avoid impact on visual function.

Ophthalmic outcomes of congenital toxoplasmosis followed until adolescence

BACKGROUND

Congenital toxoplasmosis (CT) can elicit severe damage to several organs, especially the eye, and may be manifested at birth or later. We assessed the long-term ocular prognosis in a cohort of congenitally infected children treated according to a standardized protocol and monitored for up to 22 years.

METHODS

This prospective study included confirmed cases of CT, which were identified by obligatory antenatal screening at the Lyon (France) reference center between 1987 and 2008. Data obtained through ocular examinations were recorded on a standardized form and confirmed by an independent external committee. Risk factors for retinochoroiditis were identified by using a multivariable Cox model and a flexible model that accounted for changes in the factor effects during follow-up.

RESULTS

A total of 477 of 485 infected live-born children were followed for a median of 10.5 years (75th percentile: 15.0 years). During the follow-up, 142 patients (29.8%) manifested at least 1 ocular lesion. Lesions were unilateral in 98 individuals (69.0%) and caused no vision loss in 80.6%. Lesions were first manifested at a median age of 3.1 (0.0-20.7) years. In 48 (33.8%) of the children, recurrences or new ocular lesions occurred up to 12 years after the appearance of the first lesion. Early maternal infection and confirmation of CT in children, prematurity, and nonocular CT lesions at baseline were associated with a higher risk of retinochoroiditis.

CONCLUSIONS

Although the consequences of CT are rarely severe in treated children, regular postnatal monitoring is nevertheless justified because of the lifelong persisting risk of new ocular manifestations.

Severe South American ocular toxoplasmosis is associated with decreased Ifn-γ/Il-17a and increased Il-6/Il-13 intraocular levels

In a cross sectional study, 19 French and 23 Colombian cases of confirmed active ocular toxoplasmosis (OT) were evaluated. The objective was to compare clinical, parasitological and immunological responses and relate them to the infecting strains. A complete ocular examination was performed in each patient. The infecting strain was characterized by genotyping when intraocular Toxoplasma DNA was detectable, as well as by peptide-specific serotyping for each patient. To characterize the immune response, we assessed Toxoplasma protein recognition patterns by intraocular antibodies and the intraocular profile of cytokines, chemokines and growth factors. Significant differences were found for size of active lesions, unilateral macular involvement, unilateral visual impairment, vitreous inflammation, synechiae, and vasculitis, with higher values observed throughout for Colombian patients. Multilocus PCR-DNA sequence genotyping was only successful in three Colombian patients revealing one type I and two atypical strains. The Colombian OT patients possessed heterogeneous atypical serotypes whereas the French were uniformly reactive to type II strain peptides. The protein patterns recognized by intraocular antibodies and the cytokine patterns were strikingly different between the two populations. Intraocular IFN-γ and IL-17 expression was lower, while higher levels of IL-13 and IL-6 were detected in aqueous humor of Colombian patients. Our results are consistent with the hypothesis that South American strains may cause more severe OT due to an inhibition of the protective effect of IFN-γ.

It is not only the cat that did it: how to prevent and treat congenital toxoplasmosis

The apicomplexan parasite Toxoplasma gondii was discovered a little over one hundred years ago and was soon recognized as a pathogen responsible for congenital infection. But detailed understanding of its epidemiology emerged only after 1970 with the discovery of its life cycle. In the last ten years, high resolution molecular tools have allowed the characterization of various strain types with different virulence patterns, and current studies are exploring the distribution of these different genotypes. In parallel, sophisticated diagnostic tools have been developed and awareness of disease burden has led some European countries with high prevalence rates to implement screening of pregnant women. In this article, the screening options and therapies used to prevent congenital toxoplasmosis are dissected in the light of recent data from cohort studies and other epidemiological data.

[Congenital toxoplasmosis: long-term ophthalmologic follow-up praised by patients]

INTRODUCTION

Ocular lesions of congenital toxoplasmosis may occur and relapse unpredictably even a long time after birth. There is no consensus concerning the necessity or timing of ophthalmologic follow-up for these patients. We surveyed adults with congenital toxoplasmosis followed regularly since birth, in order to learn their perceptions of this follow-up. The goal of this study was to provide doctors with patient-reported information on how they perceived the long-term monitoring of their disease.

METHODS

Enrolled patients were given a two-question questionnaire addressing the way they perceived the long-term follow-up and their attitudes toward continuing it. Eligible patients had to be 18 years or older and to have undergone ophthalmologic follow-ups, including funduscopy, every year since birth. The last ophthalmologic examination had to be within one year of the patient's inclusion in the study.

RESULTS

Of the 102 patients finally included in the study, 98% stated that the follow-up was useful and 92% reassuring. Among the 11% of patients who found the follow-ups frightening, the proportion of patients with low visual acuity and low score on the visual function test was significantly higher than among the others. All patients except two wished to continue with regular follow-up.

CONCLUSION

Without general agreement or guidelines on how patients with congenital toxoplasmosis should be monitored, the patient's wishes are important in making a decision. Our study brought out a clear fact; the majority of patients found long-term follow-up useful and reassuring and wished to continue.

Therapy for ocular toxoplasmosis

PURPOSE

To review current evidence for the treatment of ocular toxoplasmosis (OT).

DESIGN

Narrative review and expert recommendations.

METHODS

Meta-analysis and selected original articles from the medical literature were reviewed critically. Expert recommendations were analyzed.

RESULTS

Numerous observational studies suggest a benefit of short-term antimicrobial therapy for toxoplasmic retinochoroiditis in immunocompetent patients, although its efficacy has not been proven in randomized clinical trials. A randomized clinical trial revealed that intermittent trimethoprim/sulfamethoxazole treatment could decrease the rate of recurrence in high-risk patients. Intravitreal injection of clindamycin and dexamethasone was an acceptable alternative to the classic treatment for OT in a randomized clinical trial.

CONCLUSIONS

Opinions about therapy differ and controversy remains about its type, efficacy, and length. Intravitreal therapy may be promising for OT. A recent description of the presence of parasitemia in patients with active and inactive ocular toxoplasmosis raises new questions that need to be explored.

Long-term ocular outcome in congenital toxoplasmosis: a prospective cohort of treated children

OBJECTIVES

Congenital toxoplasmosis remains a public health problem throughout the world. Long-term longitudinal studies are still needed to argument controversial screening and treatment strategies and to enable to accurately counsel parents.

METHODS

We conducted a prospective cohort study over 16 years in Marseilles, France. Seronegative pregnant women underwent monthly serological testing. Children were treated antenatally with rovamycine as soon as maternal infection was detected and with pyrimethamine and sulfadoxine in case of positive Toxoplasma PCR on amniotic fluid. Postnatal treatment with pyrimethamine and sulfadoxine was systematically prescribed for one year and possibly continued at the physician discretion.

RESULTS

127 children were included. 24 children (18.9%) presented ocular lesions causing visual impairment in eight cases. Eleven children (8.7%) presented with ocular lesions at birth, mostly macular. Sixteen children (12.6%) developed ocular lesions during follow-up, mostly peripheral. The first ocular lesion could occur as late as 12 years after birth. No significant risk factor of chorioretinitis was identified including gestational age at infection, type of antenatal treatment and shorter postnatal treatment.

CONCLUSIONS

These results confirm the overall good prognosis of congenital toxoplasmosis in Europe but highlight though a low risk of late ocular manifestation. Chorioretinitis affected 18.9% of children suffering from congenital toxoplasmosis despite antenatal and neonatal screening associated with early treatment. Long-standing follow-up is needed because first lesion can occur as late as 12 years after birth. Late lesions were less often macular but nevertheless caused sometimes visual impairment.