Induction of cell-mediated immunity during early stages of infection with intracellular protozoa

Toxoplasma gondii and Trypanosoma cruzi are intracellular parasites which, as part of their life cycle, induce a potent cell-mediated immunity (CMI) maintained by Th1 lymphocytes and IFN-g. In both cases, induction of a strong CMI is thought to protect the host against rapid parasite multiplication and consequent pathology and lethality during the acute phase of infection. However, the parasitic infection is not eliminated by the immune system and the vertebrate host serves as a parasite reservoir. In contrast, Leishmania sp, which is a slow growing parasite, appears to evade induction of CMI during early stages of infection as a strategy for surviving in a hostile environment (i.e., inside the macrophages which are their obligatory niche in the vertebrate host). Recent reports show that the initiation of IL-12 synthesis by macrophages during these parasitic infections is a key event in regulating CMI and disease outcome. The studies reviewed here indicate that activation/inhibition of distinct signaling pathways and certain macrophage functions by intracellular protozoa are important events in inducing/modulating the immune response of their vertebrate hosts, allowing parasite and host survival and therefore maintaining parasite life cycles.

Prevalência de toxoplasmose ovina determinada pela reação de Sabin-Feldman em animais de Uruguaiana, RS, Brasil

Determinou-se a prevalência de toxoplasmose ovina em soros de 100 animais, provenientes de Uruguaiana, RS e abatidos em Bragança Paulista, SP, Brasil, através de reação de Sabin-Feldman (RSF). Considerando-se animais positivos aqueles com títulos > ou = 16, obtiveram-se 39% de soro-reagentes, com títulos e percentuais de soropositividade correspondentes a: 16 (66,7%), 64 (23%), 256 (2,6%), 1024 (5,1) e 4000 (2,6%).

Suspected acute toxoplasmosis in pregnant women

OBJECTIVE: To determine the prevalence of reagent serology for suspected acute toxoplasmosis in pregnant women and to describe clinical, laboratory and therapeutic profiles of mothers and their children. METHODS: A retrospective study was conducted with IgM-anti-Toxoplasma gondii-reagent pregnant women and their children who attended the public health system in the state of Paraná, Southern Brazil, from January 2001 to December 2003. Information were obtained from clinical, laboratory (ELISA IgM/IgG) and ultrasonographic data and from interviews with the mothers. To test the homogeneity of the IgM indices in relation to the treatment used, the Pearson's Chi-square test was applied. Comparisons were considered significant at a 5% level. RESULTS: Two hundred and ninety (1.0%) cases of suspected IgM-reagent infection were documented, with a prevalence of 10.7 IgM-reagent women per 1,000 births. Prenatal care started within the first 12 weeks for 214/290; 146/204 were asymptomatic. Frequent complaints included headaches, visual disturbance and myalgia. Ultrasonography revealed abnormalities in 13 of 204 pregnancies. Chemoprophylaxis was administered to 112/227; a single ELISA test supported most decisions to begin treatment. Pregnant women with IgM indices =2.000 tended to be treated more often. Among exposed children, 44/208 were serologically followed up and all were IgG-reagent, and three IgM-reagent cases showed clinical symptoms. CONCLUSIONS: The existence of pregnant women with laboratorially suspected acute toxoplasmosis who were not properly followed up, and of fetuses that were not adequately monitored, shows that basic aspects of the prenatal care are not being systematically observed. There is need of implementing a surveillance system of pregnant women and their children exposed to T. gondii.

Tratamento da retinocoroidite toxoplasmótica com o cloridrato de clindamicina

Com o cloridrato de clindamicina, foram tratados 18 pacientes com retinocoroidite toxoplasmótica. Houve adoção da conduta escolhida em uma ou duas crises de cada doente e ficou patente a capacidade do antibiótico, administrado pela via oral, no sentido de controlar o processo e de promover cicatrização. A tolerância ao medicamento pôde ser considerada satisfatória e, por vezes, recaídas sucederam, mas afigurou-se concreta a possibilidade de incorporar o remédio em apreço ao conjunto de antiparasitários indicados para combater o referido comprometimento ocular devido ao Toxoplasma gondii.

Toxoplasmose em animais silvestres e domésticos da região de Botucatu, estado de São Paulo, Brasil

Os Autores analisaram soros de 47 Cannis familiaris, de 9 Felis cattus, de 64 Didelphis marsupialis aurita, de 9 Dasypus novemcinctus, de 4 Cabassous tatouay e de 29 Rattus rattus, através da reação de imunofluorescência indireta, para pesquisar a presença de anticorpos anti Toxoplasma gondii. Estes foram encontrados apenas em C. familiaris (63,8%) e em D. m. aurita (4,7%). Frente aos resultados obtidos, os Autores sugerem que novas pesquisas nesta área sejam realizadas, para que se conheça melhor a importância epidemiológica de várias espécies animais na disseminação da toxoplasmose.

Regional variation in toxoplasmosis seronegativity in the São Paulo metropolitan region

Toxoplasmosis is a highly prevalent zoonotic human infection caused by the Apicomplexa protozoon Toxoplasma gondii. The acute disease is usually mild or asymptomatic, except for foetal infection transmitted by acutely infected pregnant women, which courses as a devastating disease. In order to determine possible regional variations in risk factors, we studied the frequency of seronegativity in areas of the São Paulo Metropolitan Region, comparing liters and age groups. The prevalence of seronegativity was determined retrospectively in 1286 pregnant women receiving prenatal care at public health services in four selected areas of the São Paulo Metropolitan Region of similar socioeconomic background. The São Paulo City area had the higher frequency of seronegativity (41.1%), followed by the Northwest (31.5%) and Southwest (29.9%) areas, with similar intermediate levels, and by the Northeast (22.5%) area with the lowest frequency (p<0.001). A rough estimate disclosed about 280 infected infants/year in the São Paulo Metropolitan Region. Serological titers analyzed by age group suggested a decline in antibody levels with age, as shown by a lower frequency of higher titers in older groups. Our study emphasizes the importance of determining the regional prevalence of toxoplasmosis for proper planning of public health prenatal care.

Prevalencia de infección toxoplásmica en gestantes de la Provincia la Habana

Se realizó un estudio seroepidemiológico de Toxoplasma gondii en cuatro Municípios de la Provincia La Habana en el periodo comprendido entre el mes de Octubre de 1990 y Abril de 1991, utilizando una técnica de ultramicro ELISA de 10 µL. Se examinaron un total de 362 muestras de mujeres embarazadas y se obtuvo una prevalencia de infección de 71,0%. La infección toxoplásmica fue más frecuente en las embarazadas que residían en zona rural y convivian con gatos. Se estudió la relación entre la infección toxoplásmica y el antecedente de abortos espontáneos sin encontrar diferencias estadísticamente significativas.

IgM and IgA Antibody Responses in 12 Cases of Human Acquired Toxoplasmosis

The persistence, in some subjects, of specific IgM antibodies to Toxoplasma gondii for several months after the acute phase of infection has complicated the interpretation of serological test results for toxoplasmosis. Several reports have emphasized the value of the detection of Toxoplasma-specific IgA antibodies for the diagnosis of acute toxoplasmosis. In this article, we report the follow-up profiles of Toxoplasma-specific IgM and IgA antibodies in serum samples obtained from 12 patients at various intervals after the onset of the clinical manifestations of infection. IgM antibodies were detected by the indirect immunofluorescence (IIF) test, antibody capture enzyme-linked immunosorbent assay (cELISA) and enzyme-mediated chemilluminescent technique (CmL). IgA antibodies were quantified by the direct ELISA (dELISA) and cELISA procedures. As defined by the manufacturer of the cELISA test for IgA used, most patients with acute toxoplasmosis have antibody levels > 40 arbritary units per ml (AU/ml). At values > 40 AU/ml, the cELISA for IgA detected significant antibody levels for a shorter time than the other techniques used for IgM and IgA detection. However, IgA levels £ 40 AU/ml do not exclude the possibility of acute toxoplasmosis since such levels can be reached very soon after infection with T. gondii. The results obtained in the present study show that the serological diagnosis of acute toxoplasmosis may not be such an easy task. Our data suggest that use of the IgA-cELISA concomitantly with IgM antibody screening could permit, in some circumstances, a more efficient diagnosis of acute acquired toxoplasmosis

Seroprevalence of toxoplasmosis in Fortaleza, Ceará, Brazil

A serological survey of Toxoplasma gondii infection in population groups in Fortaleza, Brazil, was conducted, in order to identify seroprevalence rates according to age and risk factors associated with acquired infection. A Toxoplasma IgG-antibody enzyme immunoassay (Sanofi Pasteur Diagnostics, Marnes la Coquette, France) was employed to assess the immunity. Public day-care centers and schools were randomly selected, while three large antenatal clinics and maternity units were choosen by its importance. Population groups and results of 997 blood tests were: 227 children (mean age 3.8 years), 22.8% seropositives; 584 students (mean 11.4 years), 58.4%, and pregnant and postpartum women (mean 24 years), 71.5% seropositives (p < 0.001). Of 256 participants reporting close contact with cats, 59.8% were seropositive, in contrast with 51% seropositives without contact (relative risk 1.17; 95% confidence interval 1.04-1.33; p = 0.01). Having three or more siblings at home was related to higher seroprevalence in children and students (relative risk 1.39; 95% confidence interval 1.21-1.60; p < 0.01). In conclusion, toxoplasmosis seroprevalence showed a rapid increase during the first ten years of life, in association with close contact with cats and larger households, probably related to inappropriate hygiene and child-care practices.

Incidence of congenital toxoplasmosis in southern Brazil: a prospective study

The study aimed to determine the incidence of congenital infection by Toxoplasma gondii and to describe neonatal and maternal characteristics regarding newborn infants treated at a teaching hospital in the town of Passo Fundo, State of Rio Grande do Sul, Brazil. Cord blood samples collected from 1,250 live newborns were analyzed. The laboratory diagnosis was established by the detection of Toxoplasma gondii IgM using an enzyme linked fluorescent assay. Gestational age, intrauterine growth, anthropometric measures, and prenatal characteristics were assessed. The incidence of congenital toxoplasmosis at birth was 8/10,000 (95%CI 0.2-44.5). Mean birthweight was 3,080 ± 215.56 grams and mean gestational age was 38.43 ± 1.88 weeks. With regard to prenatal care, 58% of the pregnant patients visited their doctors five times or more and 38.9% were serologically tested for toxoplasmosis in the first trimester of pregnancy. The incidence of congenital toxoplasmosis was similar to that found in most studies conducted in our country and abroad. Our study sample is representative of the town of Passo Fundo and therefore it is possible to consider the frequency observed as the prevalence of the disease in this town during the study period.

Oligodendroglioma in a patient with AIDS: case report and review of the literature

In the last years, new techniques of neuroimages and histopathological methods have been added to the management of cerebral mass lesions in patients with AIDS. Stereotactic biopsy is necessary when after 14 days of empirical treatment for Toxoplasma gondii encephalitis there is no clinical or neuroradiologic improvement. We report a woman with AIDS who developed a single focal brain lesion on the right frontal lobe. She presented a long history of headache and seizures. After two weeks of empirical treatment for toxoplasma encephalitis without response, a magnetic resonance image with spectroscopy was performed and showed a tumoral pattern with a choline peak, diminished of N-acetyl-aspartate and presence of lactate. A stereotactic biopsy was performed. Histopathological diagnosis was a diffuse oligodendroglioma type A. A microsurgical resection of the tumor was carried out and antiretroviral treatment was started. To date she is in good clinical condition, with undetectable plasma viral load and CD4 T cell count > 200 cell/uL.

Seroprevalence of toxoplasmosis in a low-income community in the São Paulo municipality, SP, Brazil

Toxoplasmosis is one of the most common zoonoses worldwide. The seroprevalence for T. gondii in human population from Brazil might range from 40 to 80%. The aim of this paper was to study the seroprevalence of T. gondii infection in children from age one to 15 living in a low socioeconomic community, named community of Jardim São Remo in the year of 2002. The community is located in the West area of São Paulo municipality, São Paulo State, Brazil. Antibodies to T. gondii were found in 110 (32.4%, CI 95%: 27.5 - 37.7) of the 339 children tested with indirect immunofluorescent antibody test. The titration of the samples revealed 29 children with serum titer equal to 16, 14 children with 32, 18 children with 64, 21 children with 128, 20 children with 256 and eight children with serum titer > 512. The age dependence of the prevalence of T. gondii infection and the association between seroprevalence for T. gondii and seroprevalence for T. canis suggest that the infection is chiefly postnatal. Seroconversion in infant population of community Jardim São Remo occurs in children as young as two years old, earlier than in the children attended at health centers of São Paulo city. The seroprevalence of T. gondii in children from Jardim São Remo was compared to the prevalence in children from other urban centers of Brazil.

Disseminated toxoplasmosis presenting as sepsis in two AIDS patients

This report describes two patients who presented acute disseminated and severe toxoplasmosis as the first opportunistic disease related to acquired immunodeficiency syndrome. At admission, clinical and laboratory findings were similar to sepsis or septic shock and a fast evolutive course to death occurred in both cases. At necropsy, an inflammatory reaction and presence of a great number of Toxoplasma gondii cysts and tachyzoites were observed in most organs examined.

Serology using rROP2 antigen in the diagnostic of toxoplasmosis in pregnant women

Toxoplasma gondii causes severe fetal disease during acute infection in pregnant women, thus demanding early diagnosis for effective treatment and fetus preservation. Fetal tests are inefficient and risky, and diagnosis is based on maternal IgM serology, which had weak screening ability due to increased sensitivity, with alternative IgG avidity tests. Here, we performed ELISA and avidity assays using a recombinant T. gondii antigen, rROP2, in samples from 160 pregnant women screened from a large public hospital who were referred due to positive IgM assays. IgG serology and avidity assays were compared using whole T. gondii extract or rROP2. ELISA IgG detection with rROP2 showed good agreement with assays performed with T. gondii extract, but rROP2 IgG avidity assays were unrelated to whole extract antigen IgG avidity, regardless of the chaotrope used. These data show that avidity maturation is specific to individual antigen prevalence and immune response during infection. ELISA rROP2 IgG assays may be an alternative serological test for the diagnosis of toxoplasmosis during pregnancy, although our data do not support their use in avidity assays.

Nephrotic syndrome associated with toxoplasmosis: report of seven cases

The concomitance of nephrotic syndrome and acute infection by Toxoplasma gondii is a rare occurrence in humans. In this paper seven cases of children, ranging from 11 months to 7 year-old, with concomitant nephrotic syndrome and asymptomatic acute T. gondii infection are reported. In one of those patients only the administration of anti-Toxoplasma therapy was enough to control the clinical and laboratory manifestations of the disease. In the other patients it was necessary to introduce corticosteroids or other immunosuppressant drugs. Three patients had complete clinical and laboratory improvement and the remaining showed only a partial response.