Congenital toxoplasmosis—prenatal aspects of Toxoplasma gondii infection

Toxoplasma gondii (T. gondii) is the cause of toxoplasmosis. Primary infection in an immunocompetent person is usually asymptomatic. Serological surveys demonstrate that world-wide exposure to T. gondii is high (30% in US and 50-80% in Europe). Vertical transmission from a recently infected pregnant woman to her fetus may lead to congenital toxoplasmosis. The risk of such transmission increases as primary maternal infection occurs later in pregnancy. However, consequences for the fetus are more severe with transmission closer to conception. The timing of maternal primary infection is, therefore, critically linked to the clinical manifestations of the infection. Fetal infection may result in natural abortion. Often, no apparent symptoms are observed at birth and complications develop only later in life. The laboratory methods of assessing fetal risk of T. gondii infection are serology and direct tests. Screening programs for women at childbearing age or of the newborn, as well as education of the public regarding infection prevention, proved to be cost-effective and reduce the rate of infection. The impact of antiparasytic therapy on vertical transmission from mother to fetus is still controversial. However, specific therapy is recommended to be initiated as soon as infection is diagnosed.

[Acute toxoplasmic perimyocarditis in a 67-year-old HIV-negative woman--a case report]

Acquired toxoplasmosis is a widespread parasitic disease caused by an obligate intracellular protozoan, Toxoplasma gondii. Humans are infected by consuming undercooked or raw meat containing tissue cysts or by ingesting oocysts in food or water contaminated with feline faeces. Most cases of Toxoplasma gondii infections in immunocompetent individuals are asymptomatic. Although acquired toxoplasmosis is usually a mild infection, it may be life-threatening in immunocompromised patients. In this report we present a 67-year-old HIV-negative woman with acute toxoplasmic perimyocarditis, heart failure and with a history of ischemic heart disease, hypertension and dyslipidemia. The diagnosis was based on clinical characteristics, echocardiographic examinations, elevated inflammatory markers and the presence of IgM and IgG antibodies against Toxoplasma gondii. We conclude that Toxoplasma gondii infection should be considered in each case of perimyocarditis with concomitant, significant diagnostic and therapeutic problems, especially in immunocompromised patients. This paper also reviews differential diagnosis of elevated CA 125 serum levels in postmenopausal women.

Alpha CD 2 mAb treatment safely attenuates adoptive transfer colitis

Increased proliferation, defective apoptosis, and cytokine dysregulation of T lymphocytes are thought to be important for the pathogenesis of inflammatory bowel disease. Since these phenomena can be corrected by alpha CD 2 mAb, we asked whether CD2 directed immunotherapy safely prevents and/or ameliorates adoptive transfer colitis. Colitis was induced by transfer of CD4(+) T cell blasts to syngenic RAG 1(-/-) mice or CD 45 RB(high) CD4(+) T cells to SCID mice. The alpha CD 2 mAb 12-15 or rat IgG was given, starting either initially or upon first signs of colitis. Disease activity was assessed by clinical monitoring, microscopic scoring, hemoccult, endoscopy, and blood count analysis. Cytokine production of stimulated LPL was measured by ELISA and cell proliferation by [(3)H]-thymidine incorporation. Parasite control was analyzed in a murine model of infection with Toxoplasma gondii. The alpha CD 2 mAb significantly increased mean survival time when starting at transfer of blasts (survival >35 days: alpha CD 2 69% vs 0% of controls, P<0.001). In the SCID colitis model hematochezia and macroscopic colitis were delayed. When used in established T-cell blast colitis, the benefit was less pronounced, even in combination with dexamethasone (mean survival+/-s.e.m.: alpha CD 2+dexa: 13.5+/-2.9 vs dexa+IgG: 6.3+/-1.0, P<0.05). In the preventive experiment the alpha CD 2 mAb markedly reduced IL-2 secretion and T-cell proliferation. The immune response towards Toxoplasma gondii was not impaired. These studies show for the first time that CD2 directed immunotherapy can attenuate or delay adoptive transfer colitis and ameliorate established colitis. Most likely inhibition of IL-2 secretion and T-cell proliferation are responsible for these effects. Still, immune defence towards T. gondii is maintained.

Treating opportunistic infections among HIV-exposed and infected children: recommendations from CDC, the National Institutes of Health, and the Infectious Diseases Society of America

In 2001, CDC, the National Institutes of Health, and the Infectious Diseases Society of America convened a working group to develop guidelines for therapy of human immunodeficiency virus (HIV)-associated opportunistic infections to serve as a companion to the Guidelines for Prevention of Opportunistic Infections Among HIV-Infected Persons. In recognition of unique considerations related to HIV infection among infants, children, and adolescents, a separate pediatric working group was established. Because HIV-infected women coinfected with opportunistic pathogens might be more likely to transmit these infections to their infants than women without HIV infection, guidelines for treating opportunistic pathogens among children should consider treatment of congentially acquired infections among both HIV-exposed but uninfected children and those with HIV infection. In addition, the natural history of opportunistic infections among HIV-infected children might differ from that among adults. Compared with opportunistic infections among HIV-infected adults, which are often caused by reactivation of pathogens acquired before HIV infection when host immunity was intact, opportunistic infections among children often reflect primary acquisition of the pathogen and, among children with perinatal HIV infection, infection acquired after HIV infection has been established and begun to compromise an already immature immune system. Laboratory diagnosis of opportunistic infections can be more difficult with children. Finally, treatment recommendations should consider differences between adults and children in terms of drug pharmacokinetics, dosing, formulations, administration, and toxicities. This report focuses on treatment of opportunistic infections that are common in HIV-exposed and infected infants, children, and adolescents in the United States.

Incidence of toxoplasmosis in 5532 pregnant women in Crete, Greece: management of 185 cases at risk

OBJECTIVES

To study the incidence of toxoplasmosis in pregnant women in Crete and to test a designed protocol for handling those at risk of delivering congenitally infected infants.

STUDY DESIGN

Pregnant women were screened serologically over a period of 5 years. Cases with suspected acute toxoplasmosis were treated, peripheral blood (PB), and amniotic fluid (AF) tested by polymerase chain reaction (PCR) and culture, and fetuses monitored by ultrasonography. The absence of congenital infection in infants was confirmed by serology and clinical evaluation.

RESULTS

Of the 5532 pregnant women followed, 70.57% remained seronegative, 29.45% were seropositive, and there was direct evidence of seroconversion in six cases. Acute toxoplasmosis was suspected in 185 cases, maternal parasitemia was detected in five cases and positive amniotic fluid in one case. Congenital infection was excluded in all infants followed, based on the absence of ultrasound findings in utero, lack of clinical symptoms at birth, negative Western blotting (WB) at birth and 3 months later, and descending serology for a year.

CONCLUSION

Overall, 29.45% of the pregnant women followed were seropositive, 3.3% with suspected acute toxoplasmosis, and in 0.02% cases there was evidence of maternofetal transmission. The protocol tested allowed differentiation between acute and latent toxoplasmosis, safe management of the cases at risk and assisted in avoidance of unwarranted pregnancy terminations.

Séroconversion toxoplasmique chez la femme enceinte

INTRODUCTION

Since 1992 France has been running a toxoplasmosis prevention program based on the serological detection of infections during pregnancy. In the absence of a consensus, the seroconversions discovered are managed in different ways, varying from one centre to another.

OBJECTIVE

To describe the habits of the specialised centres in France and propose means to reduce the heterogeneity.

METHODS

A survey using a questionnaire mailed to the centres of parasitology in France specialised in the management of toxoplasmosis seroconversion during pregnancy.

RESULTS

All the 30 centres surveyed replied. Five of them do not provide recommendations for treatment and were excluded from analysis. The attitudes of the 25 other centres varied greatly with regard to the indications for therapeutic abortion and amniocentesis, treatment protocols with pyrimethamine and sulfamides, as well as in the frequency of sonographical monitoring.

CONCLUSION

In the absence of National guidelines, the management of seroconversions discovered during the prenatal prevention of congenital toxoplasmosis program is left to the discretion of the specialised centre. This results in variations from one town to the next. This heterogeneity underlines the lack of knowledge on the most efficient and acceptable means of preventing and treating congenital toxoplasmosis. In order to improve this situation, the French parasitologists have launched a program of consensual meetings aimed at harmonising the treatment protocols and identifying the points that require further studies.

Toxoplasmosis

Toxoplasma gondii is a protozoan parasite that infects up to a third of the world's population. Infection is mainly acquired by ingestion of food or water that is contaminated with oocysts shed by cats or by eating undercooked or raw meat containing tissue cysts. Primary infection is usually subclinical but in some patients cervical lymphadenopathy or ocular disease can be present. Infection acquired during pregnancy may cause severe damage to the fetus. In immunocompromised patients, reactivation of latent disease can cause life-threatening encephalitis. Diagnosis of toxoplasmosis can be established by direct detection of the parasite or by serological techniques. The most commonly used therapeutic regimen, and probably the most effective, is the combination of pyrimethamine with sulfadiazine and folinic acid. This Seminar provides an overview and update on management of patients with acute infection, pregnant women who acquire infection during gestation, fetuses or infants who are congenitally infected, those with ocular disease, and immunocompromised individuals. Controversy about the effectiveness of primary and secondary prevention in pregnant women is discussed. Important topics of current and future research are presented.

Opportunistic infections of the CNS in patients with AIDS: diagnosis and management

The CNS is the second most commonly affected organ in patients with AIDS. Many opportunistic infections may involve the brain, but the four most frequent conditions are toxoplasmosis, progressive multifocal leukoencephalopathy (PML), cryptococcosis and cytomegalovirus infection. Although the incidence of these infections among patients with AIDS has decreased in the past years as a consequence of the introduction of highly active antiretroviral therapy (HAART), they remain a major cause of morbidity and mortality in this patient group. This article summarises the clinical manifestations, diagnostic procedures and management strategies for these four conditions. The clinical manifestations are nonspecific and depend on the type and location of the lesions. In clinical practice, the diagnosis of these entities is made with noninvasive methods. Imaging studies, especially magnetic resonance imaging, are very useful for the diagnosis of toxoplasmic encephalitis and PML, although their usefulness for the diagnosis of cryptococcal meningitis and cytomegalovirus infections is lower. The presence of multiple ring-enhancing lesions with surrounding oedema and mass effect is characteristic of toxoplasmosis. The response to antitoxoplasmic therapy, which is usually observed within the first 2 weeks, is also used for diagnostic purposes. Molecular methods applied to the CSF are essential for the diagnosis of PML and cytomegalovirus infections. In addition, the quantification of viral DNA of both JC virus (the causative agent of PML) and cytomegalovirus has prognostic implications and may serve to evaluate the response to therapy. Cryptococcosis may be easily diagnosed by CSF stains and cultures, as well as by the detection of the cryptococcal capsular polysaccharide antigen in the blood and, especially, the CSF. Effective treatments are available for toxoplasmosis and cryptococcosis, although adverse effects are common and some patients may not respond to therapy. In contrast, there is no specific treatment for PML, and the efficacy of anticytomegalovirus therapy is poor and the toxicity significant. HAART has improved the outcome of patients with AIDS who have infections of the CNS, and the initiation of this therapy is mandatory for all patients with such infections, particularly in those conditions for which effective therapy is not available. Lifelong secondary prophylaxis with agents for the opportunistic infections was necessary before the HAART era because the risk of recurrence was very high if only induction therapy was administered. However, today, the discontinuation of secondary prophylaxis in patients treated with HAART who have stably reached a certain immune reconstitution is possible.

[Toxoplasma infections in early pregnancy: consequences and management]

OBJECTIVE

To assess the consequences for the fetus of maternal toxoplasma infection acquired during the first 8 weeks of gestation and to set guidelines on how to manage these maternal infections.

METHODS

Data were prospectively analyzed on 360 pregnancies followed-up in our department due to a toxoplasma infection during the 8 first weeks of pregnancy. Estimates of the risk of fetal infection were based on all cases, including those which could not be followed up until infection was ruled out or confirmed. Severity of infection was estimated based on ultrasound findings during pregnancy, neonatal and long-term postnatal clinical, neurological and ophthalmologic work up.

RESULTS

Out of the 360 included women, 336 gave birth to a live born child: 7 (2%) were infected, 302 (90%) were free of infection and follow-up was insufficient to conclude about the 27 (8%) remaining infants. The estimated risk of fetal infection ranged between 2 and 10% based on live born children and between 3 and 14% when the 24 interrupted pregnancies were included. At their last clinical evaluation at 70 months of age, all 7 children, including the 2 who had inactive peripheral eye lesions and the one who had a unique intracranial calcification were free of any ophthalmologic or neurological impairment.

CONCLUSION

Our study confirms that in the event of a maternal infection during the first 8 weeks of pregnancy the risk of fetal infection is low and results mainly in a spontaneous termination of pregnancy. Future parents should be assured that conversely to a common opinion, the prognosis of congenital toxoplasmosis in live-born children is good. For these early maternal infections as for those acquired later, we recommend immediate treatment with spiramycin, monthly ultrasound surveillance, amniocentesis and treatment with pyrimethamine and sulphamides if the PCR is positive. Abortion should be restricted to cases with ultrasound lesions

Central nervous system infections in individuals with HIV-1 infection

Opportunistic infections of the central nervous system (CNS) are common complications of advanced immunodeficiency in individuals with human immunodeficiency virus type 1 (HIV-1) infection. Neurological disease is the first manifestation of acquired immunodeficiency syndrome (AIDS) in 10% to 20% of symptomatic HIV-1 infection. Prompt diagnosis and treatment of such disorders is critical. Also, in the era of highly active antiretroviral therapy (HAART), these disease states have changed in presentation and epidemiology. Therefore, we review the epidemiology, pathogenesis, clinical features, diagnosis, and management of five common central nervous system disorders in individuals with HIV-1 infection: toxoplasma encephalitis, primary central nervous system lymphoma, cryptococcal meningitis, cytomegalovirus encephalitis, and progressive multifocal leukoencephalopathy.

Toxoplasmosis, an overview with emphasis on ocular involvement

Toxoplasmosis is a common parasitic zoonosis and an important cause of abortions, mental retardation, encephalitis, blindness, and death worldwide. Although a large body of literature has emerged on the subject in the past decades, many questions about the pathogenesis and treatment of the disease remain unanswered. This review aims to provide an overview of the current insights regarding the causative parasite and the mechanisms leading to symptomatic infection with emphasis on ocular toxoplasmosis.

Effects of specific monoclonal antibodies to dense granular proteins on the invasion of Toxoplasma gondii in vitro and in vivo

Although some reports have been published on the protective effect of antibodies to Toxoplasma gondii surface membrane proteins, few address the inhibitory activity of antibodies to dense granular proteins (GRA proteins). Therefore, we performed a series of experiments to evaluate the inhibitory effects of monoclonal antibodies (mAbs) to GRA proteins (GRA2, 28 kDa; GRA6, 32 kDa) and surface membrane protein (SAG1, 30 kDa) on the invasion of T. gondii tachyzoites. Passive immunization of mice with one of three mAbs following challenge with a lethal dose of tachyzoites significantly increased survival compared with results for mice treated with control ascites. The survival times of mice challenged with tachyzoites pretreated with anti-GRA6 or anti-SAG1 mAb were significantly increased. Mice that received tachyzoites pretreated with both mAb and complement had longer survival times than those that received tachyzoites pretreated with mAb alone. Invasion of tachyzoites into fibroblasts and macrophages was significantly inhibited in the anti-GRA2, anti-GRA6 or anti-SAG1 mAb pretreated group. Pretreatment with mAb and complement inhibited invasion of tachyzoites in both fibroblasts and macrophages. These results suggest that specific antibodies to dense-granule molecules may be useful for controlling infection with T. gondii.

Seroprevalence of varicella zoster virus, parvovirus B19 and Toxoplasma gondii in a Melbourne obstetric population: implications for management

At an antenatal clinic at a Melbourne obstetric hospital, 308 women were questioned about a known past history of infection with varicella zoster virus (VZV), human parvovirus B19 and Toxoplasma gondii. Immunoglobulin G (IgG) concentrations were determined for the 3 infectious agents and a recalled history of infection was compared with the presence of specific antibody. Exactly 66% of women recalled being infected with chickenpox (VZV) and 94% showed serological evidence of past exposure. Although 64% of women had parvovirus specific IgG, only one gave a definite history of past parvovirus infection. None of the 23% of women with evidence of previous exposure to Toxoplasma gondii recalled a past infection. The proportion of antenatal women at risk in this study was used to estimate the potential burden of disease from congenital infections in Australia and to examine implications for management of pregnancies complicated by these 3 infections.

Preventing congenital toxoplasmosis

SCOPE OF THE PROBLEM

Toxoplasmosis is caused by infection with the protozoan parasite Toxoplasma gondii. Acute infections in pregnant women can be transmitted to the fetus and cause severe illness (e.g., mental retardation, blindness, and epilepsy). An estimated 400-4,000 cases of congenital toxoplasmosis occur each year in the United States. Of the 750 deaths attributed to toxoplasmosis each year, 375 (50%) are believed to be caused by eating contaminated meat, making toxoplasmosis the third leading cause of foodborne deaths in this country.

ETIOLOGIC FACTORS

Toxoplasma can be transmitted to humans by three principal routes: a) ingestion of raw or inadequately cooked infected meat; b) ingestion of oocysts, an environmentally resistant form of the organism that cats pass in their feces, with exposure of humans occurring through exposure to cat litter or soil (e.g., from gardening or unwashed fruits or vegetables); and c) a newly infected pregnant woman passing the infection to her unborn fetus. RECOMMENDATIONSFOR PREVENTION: Toxoplasma infection can be prevented in large part by a) cooking meat to a safe temperature (i.e., one sufficient to kill Toxoplasma); b) peeling or thoroughly washing fruits and vegetables before eating; c) cleaning cooking surfaces and utensils afterthey have contacted raw meat, poultry, seafood, or unwashed fruits or vegetables; d) pregnant women avoiding changing cat litter or, if no one else is available to change the cat litter, using gloves, then washing hands thoroughly; and e) not feeding raw or undercooked meat to cats and keeping cats inside to prevent acquisition of Toxoplasma by eating infected prey.

RESEARCH AGENDA

Priorities for research were discussed at a national workshop sponsored by CDC in September 1998 and include a) improving estimates of the burden of toxoplasmosis, b) improving diagnostic tests to determine when a person becomes infected with Toxoplasma, and c) determining the applicability of national screening programs.

CONCLUSION

Many cases of congenital toxoplasmosis can be prevented. Specific measures can be taken by women and their health-care providers to decrease the risk for infection during pregnancy and prevent severe illness in newborn infants.

[Toxoplasma gondii]

The authors offered a general view on Toxoplasma gondii from the historical, taxonomic, biological and epidemiological point of view. They also studied the problems of pathogenesis, pathology, clinics, diagnosis, as well as therapy and prevention. (Tab. 1, Ref. 9)