A prospective study of Toxoplasma-positive pregnant women in southern Brazil: a health alert

We evaluated anti-Toxoplasma gondii IgM-reactive pregnant women seen at a high-risk pregnancy outpatient clinic. From March 2005 to January 2008 in Paraná, Brazil, pregnant women seen by the Brazilian Public Health System, in any gestational period, who were anti-T. gondii IgM-positive, were followed. Clinical symptoms were noted, and tests performed including IgA, IgG avidity, ultrasonogram, and amniocentesis (PCR/inoculation in mice). Of 75 patients, 8 showed low, 3 intermediate and 31 high IgG avidity. Of those who underwent the avidity test, 31 (70.5%) were in the second trimester of pregnancy. Thirty-two (42.7%) pregnant women received specific treatment. Six received triple combination treatment; in three, tachyzoites were isolated, although only one was PCR-positive, showing changes in the cerebral sonogram, borderline IgA, and the Sabin tetrad. One fetus died, and one non-reactive IgM pregnant woman showed ocular recurrence. The municipality of residence, contact with cats during adulthood, and ingestion of unpasteurized milk were shown to be important risk factors. Congenital toxoplasmosis was observed in a pregnancy referred late for treatment. Follow-up of children born to mothers with diagnosed or suspected acute toxoplasmosis is crucial in the management of the changes that toxoplasmosis may cause.     

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.     

Seroprevalence and incidence of Toxoplasma gondii infection in the Legnano area of Italy.

The decreasing prevalence of anti-Toxoplasma antibodies in Europe has re-opened the question of the appropriateness of serological screening during pregnancy. A study of 3426 pregnant women, resident in the Legnano area of Italy, revealed that the IgG seroprevalence according to ELISA was 21.5%, and that of IgM according to ELISA and enzyme-linked fluorescent assay was 1.2% and 0.9%, respectively. The incidence of infection, estimated on the basis of IgG avidity, was 0.9%. These results confirm a decrease in the prevalence of IgG, but indicate a high incidence of infection, thus suggesting that screening for anti-Toxoplasma antibodies during pregnancy should be maintained.     

2004年海珠区特殊人群弓形虫血清学调查分析

目的了解和掌握广州市海珠区屠宰和肉类销售人员、肉类检疫员和家庭宠物饲养者三类特殊人群的弓形虫病血清学IgG抗体水平状况及流行特点．为制订防治策略提供科学依据。方法选择不同职业的人群作为调查对象，采用弓形虫IgG抗体酶免检测试剂盒进行抗体检测。结果共检测232人，阳性21人，感染率为9．05％。上述三类特殊人群感染率无显著性差异，但感染率随着接触动物时间的延长而增高。结论特殊人群弓形虫感染率较高，接触动物年限与弓形虫感染有正相关，提示应加强对特殊人群的重视．尤其是加强对有长期接触动物史人群的健康教育、个人防护及其弓形虫抗体的检测。     

Antibody responses to Toxoplasma gondii antigen in human peripheral blood lymphocyte-reconstituted severe-combined immunodeficient mice reproduce the immunological status of the lymphocyte donor

These studies describe the production of specific antibodies in human peripheral blood lymphocyte-reconstituted severe-combined immunodeficient (PBL-SCID) mice following vaccination with antigen from the protozoan parasite Toxoplasma gondii. To determine the effect of previous exposure of the lymphocyte donor to antigen, human-PBL-SCID animals were created by transferring peripheral blood lymphocytes from either a single T. gondii-seronegative or a single seropositive donor. These reconstituted animals were subsequently inoculated with T. gondii soluble tachyzoite antigen (STAg) entrapped within non-ionic surfactant vesicles as an immunological adjuvant. Animals were bled at pre-determined time points post-vaccination and the expression of human anti-STAg antibodies in the plasma determined by enzyme-linked immunosorbent assay. Human antibodies specific for STAg were readily inducible in both groups of reconstituted animals, although the pattern of isotype production differed markedly between groups. The response in animals reconstituted with lymphocytes from the T. gondii-seronegative donor consisted primarily of IgM and subsequently of IgG (predominantly IgG1). In animals reconstituted with lymphocytes from the seropositive donor, no parasite-specific IgM could be demonstrated. The detectable response to STAg consisted entirely of human antibodies of the IgG isotype (IgG1), indicative of a memory-type response. These results mimicked exactly the antibody responses that would be expected had the lymphocyte donors been directly challenged with either the antigen or the live infectious agent, demonstrating that the immune system within these animals is functional and reproducible with regard to both the primary and secondary responses of the human donors.     

Influence of maternal infections with viral agents or Toxoplasma gondii during pregnancy on fetal IgE production

The importance of maternal infections with Toxoplasma gondii , cytomegalovirus (CMV), Parvovirus B19, respiratory syncytial virus (RSV), and influenza A and B on fetal IgE synthesis was studied in 153 pregnant women. No case of specific IgM activity or viral DNA in cord blood, indicating a congenital infection, was found. From gestational week 15 to delivery, maternal IgG-Ab seroconversion to Parvovirus B19, RSV, influenza A, or influenza B occurred in 47 women. At delivery, serologic signs of past infection with T. gondii were observed in 29 (19%) women, and the corresponding figure for CMV was 117 (77%). The number of women with positive IgG seroconversion during pregnancy or positive IgG-Ab activity toward the studied infectious agents at delivery did not differ significantly among infants with an increased (≥1.3 kU/1; n =51) or with an undetectable (<0.1 kU/l; n =102) cord-blood IgE level. These results show that genetic and other environmental factors probably have a greater influence on fetal IgE synthesis than do maternal infections during pregnancy.     

弓形虫分离株表膜脂肪酸的色质谱分析

本文采用有机质谱法（ＧＣ／ＭＳ）对弓形虫不同分离株，虫体表膜脂肪酸的种类和含量进行观察分析，实验结果表明弓形虫速殖子细胞膜含有６种主要脂肪酸，范围在Ｃ１４－Ｃ１８之间，分别为肉豆寇酸、棕榈油酸、软脂酸、硬脂酸、油酸和亚油酸，而油酸和软脂酸约占总脂肪酸含量的７０％（５２－８４％）。本室自畸胎儿分离获得的ＳＨ多个虫株的脂肪酸含量及组分与国际标准人源ＲＨ株相一致，而ＳＨ４，ＳＨ（１０）与ＰＰ株，ＲＴ株相似，与平行观察的人和哺乳动物细胞膜的脂肪酸在含量与组分上均有明显差异，为鉴定分离的弓形虫株提供了实验依据。     

Isolation of a Toxoplasma gondii cyclin by yeast two-hybrid interactive screen

GAL4-based yeast two-hybrid cDNA libraries from Toxoplasma gondii RH strain were constructed and screened for interactors of a putative T. gondii cdc2-related kinase, TgCRK2. A screen of 3.2 million transformants yielded a single yeast clone that harbored a protein fusion capable of specifically interacting with TgCRK2. Sequencing revealed the cDNA insert (TgCYC1) had homology to the cyclin class of proteins. The TgCYC1 cDNA fragment was used to probe a conventional T. gondii cDNA library and a 2.65 kb cDNA coding for a predicted protein of 582 amino acids was obtained. Based on comparison with a 5'-RACE product from tachyzoite mRNA, the 2.65 kb cDNA for TgCYC1 appeared to be complete. TgCYC1 had the highest similarity to Plasmodium falciparum CYC1 and displayed sequence characteristics that place it in the cyclin H class of eukaryotic cyclins. In synchronous tachyzoite populations the level of TgCYC1 mRNA was unchanged indicating it is not cell cycle regulated at the mRNA level. TgCYC1 rescues the G(1)/S cyclin cell cycle defect in S. cerevisiae strain DL1 demonstrating that this apicomplexan cyclin can function in an established heterologous model system.     

弓形虫主要表膜P30抗原的免疫保护作用研究

目的 研究弓形虫主要表膜P30抗原免疫小鼠所诱导的免疫性保护作用及免疫保护机制。方法 将单克隆抗体免疫亲和层析分离纯化的P30抗原免疫C57BL／6纯系小鼠,然后用弓形虫RH株速殖子和Fukaya株包衰攻击感染,观察P30抗原免疫对急性弓形虫感染鼠死亡时间及慢性感染鼠脑内包囊形成的影响,同时对感染后不同时间鼠血清特异性抗体水平、IL－2及IFN－r细胞因子水平和脾T淋巴细胞亚群动态变化进行了测试分析。结果 显示P30抗原免疫可在一定程度上延长感染小鼠的存活时间,减少脑内包囊的形成数量,增强小鼠抵抗急慢性弓形虫感染的能力。在感染后不同时期免疫鼠血清中特异性抗休还清瘃IFN－r、IL－2水平均高于同期对照鼠,而且免疫鼠脾CD4^ t CD8^ T淋纠细胞尤其是CD8^ 细胞的数量在感染早期升高较快,至感染后4周达高峰,两者的比值随感染时间的延长而逐渐下降。结论 P30抗原免疫对感染小鼠具有明显的保护作用,是细胞免疫和体液免疫共同作用的结果,尤其是细胞免疫可能发挥着更为重要的作用。