Prevalence of antibodies to Toxoplasma gondii in ostriches (Struthio camelus)

Serum samples from 973 ostriches (Struthio camelus) in Canada were examined for antibodies to Toxoplasma gondii by the modified agglutination test incorporating mercaptoethanol and formalin-fixed whole tachyzoites. Twenty-eight (2.9%) of the 973 birds were found to be seropositive for antibodies to T. gondii at titers of 1:25 in 15 birds, 1:50 in 12 birds, and 1:500 in 1 bird. This is the first record of T. gondii exposure in ostriches, and it supports the hypothesis that all avian species are susceptible to Toxoplasma infection. Nevertheless, the results of this study suggest that the risk of acquiring toxoplasmosis from ostriches as a food source is low.     

False-Positive Anti-Toxoplasma Fluorescent-Antibody Tests in Patients with Antinuclear Antibodies

The indirect fluorescent-antibody (IFA) method for diagnosis of toxoplasmosis is widely used and is considered to be as specific as the Sabin-Feldman dye test. After observing a patient with systemic lupus erythematosus (SLE) who had a positive toxoplasma IFA test but a negative dye test, we studied sera with high titers of antinuclear antibodies from 16 SLE patients and from 2 with rheumatoid arthritis for Toxoplasma antibodies in the immunoglobulin G and M (IgG and IgM) IFA tests and the dye test. Results of these tests were compared with titers of antinuclear antibodies, precipitating antibodies to single-strand deoxyribonucleic acid (DNA), and binding antibodies by use of DNA labeled with (3)H-actinomycin D. Of 18 patients, 11 had IgG and 4 had IgM IFA Toxoplasma antibodies; only 2 had antibodies detectable in the dye test. The immunofluorescence patterns in the Toxoplasma IFA test were indistinguishable from those obtained in patients with toxoplasmosis without antinuclear antibodies. Absorption of SLE sera with DNA did not result in a decrease in Toxoplasma IFA titers. When SLE sera were absorbed with live T. gondii, a marked drop in IgG IFA titer was observed as well as a decrease in titers of antinuclear antibodies and (3)H-DNA binding. Treatment of Toxoplasma cells with deoxyribonuclease and ribonuclease did not decrease their fluorescence. These results suggest that T. gondii nuclear antigens can absorb antinuclear antibodies but do not have exposed substrates for deoxyribonuclease. Tests in which organisms containing "nuclear" antigens for IFA detection of antibodies to these organisms are used may result in "false-positives" with sera containing antinuclear antibodies.     

Seroprevalence of Toxoplasma gondii in wild toque macaques (Macaca sinica) at Polonnaruwa, Sri Lanka

From a natural population that inhabits the dry evergreen forest at Polonnaruwa, serum samples of 170 toque macaques were examined for antibodies to Toxoplasma gondii by the modified agglutination test. Of these, 21 (12%) were found with titers of 1:16 in 9, 1:32 in 9, 1:256 in 1, 1:1,024 in 1, and 1:4,096 in 1. There was no evidence of maternal transmission of antibodies or congenital toxoplasmosis. None of the infected macaques died within 1 yr after sampling. Toxoplasma gondii infection was closely linked to human environments where domestic cats were common. Macaques having frequent contact with human settlements showed a significantly greater (P < 0.0001) prevalence (19% infected) than macaques restricted to forest habitat, none of which was infected. Although infection with T. gondii has been noted in several species of Asian primates, this is the first report of T. gondii antibodies in toque macaques (Macaca sinica) that are endemic to the island of Sri Lanka.     

应用单克隆抗体测定人弓形虫IgM抗体的研究

为了检测人血清弓形虫ＩｇＭ抗体,采用抗人ＩｇＭ单克隆抗体和特异性抗弓形虫单克隆抗体建立捕获ＥＬＩＳＡ法,并与ＰＣＲ方法进行了比较。结果检测１０６５份献血员血清,检出阳性３例,用ＰＣＲ方法检测呈阳性结果;检测２３例类风湿病人血清及２份弓形虫ＩｇＧ抗体阳性血清均为阴性反应。说明该方法不受类风湿因子（ＲＦ）和特异性ＩｇＧ抗体的干扰,同时也表明捕获ＥＬＩＳＡ检测人血清中弓形虫ＩｇＭ抗体特异性,敏感性良好。     

Detection of specific antibodies to morbilliviruses, Toxoplasma, and Brucella species in eared seals in North-West of Pacific Ocean

Presence of antibodies to morbilliviruses, Toxoplasma, and Brucella species in eared seals in North-West of Pacific Ocean was studied. Sera from 189 cubs of eared seals from different rookeries and regions. It has been shown that 10-22% of cubs living on Russian coast have antibodies to such dangerous diseases as morbillivirus infection, brucellosis, and toxoplasmosis. Antibodies to the two pathogens were detected in several animals, and brucellosis was more frequently detected associated infection. These results confirm hypothesis that all 3 pathogens are enzootic in eared seals population.     

Toxoplasma gondii-positive human sera recognise intracellular tachyzoites and bradyzoites with diverse patterns of immunoreactivity

Antibody detection assays have long been the first line test to confirm infection with the zoonotic parasite Toxoplasma gondii. However, challenges exist with serological diagnosis, especially distinguishing between acute, latent and reactivation disease states. The sensitivity and specificity of serological tests might be improved by testing for antibodies against parasite antigens other than those typically found on the parasite surface during the acute stage. To this end, we analysed the reactivity profile of human sera, identified as positive for anti-Toxoplasma gondii IgG in traditional assays, by indirect immunofluorescence reactivity to acute stage intracellular tachyzoites and in vitro-induced latent stage bradyzoites. The majority of anti-Toxoplasma gondii IgG positive sera recognised both intracellularly replicating tachyzoites and in vitro-induced bradyzoites with varying patterns of immune-reactivity. Furthermore, anti-bradyzoite antibodies were not detected in sera that were IgM-positive/IgG-negative. These results demonstrate that anti-Toxoplasma gondii-positive sera may contain antibodies to a variety of antigens in addition to those traditionally used in serological tests, and suggest the need for further investigations into the utility of anti-bradyzoite-specific antibodies to aid in diagnosis of Toxoplasma gondii infection.     

Tazonomy of Toxoplasma.

After reviewing reports of the hosts, structure and life cycle of Toxoplasma, the genus is placed in the apicomplexan family Eimeriidae and the folllowing 7 species are recognized: Toxoplasma gondii (Nicolle & Manceaux) (type species) from about 200 species of mammals and birds, with oocysts in felids; Toxoplasma alencari (Da Costa & Pereira) from the frog Leptodactylus ocellatus; Toxoplasma brumpti Coutelen from the iguana Iguana tuberculata; Toxoplasma colubri Tibaldi from the snakes Coluber melanoleucus and Coluber viridiflavus; Toxoplasma hammondi (Frenkel & Dubey) (a new combination for Hammondia hammondi) from the house mouse with oocysts in the domestic cat; Toxoplasma ranae Levine & Nye from the leopard frog Rana Pipiens; and Toxoplasma serpai Scorza, Dagert & Iturriza Arocha from the toad Bufo marinus.     

Toxoplasmosis I. Studies by the Fluorescein-labelled Antibody Technique

The fluorescein-labelled antibody technique was investigated for the diagnosis of toxoplasmosis. The direct method, the inhibition and indirect modifications are suitable for the demonstration of Toxoplasma gondii in fluid and tissue-impression slides from animals in the acute phase of infection. The method was not applicable with the frozen tissue sections. The fluorescein-labelled antibody inhibition technique detected antibodies in immune sera from various species of animal. However the titres obtained were lower than with the complement-fixation test.     

Serosurvey of roe deer, chamois and domestic sheep in the central Italian Alps

Roe deer (Capreolus capreolus), chamois (Rupicapra rupricapra rupicapra), and domestic sheep in the Orobie Alps, Italy, were serologically tested for antibodies to selected pathogens that may be transmitted across species. Antibodies against Brucella spp. and bovine herpesvirus 1 (roe deer and chamois only) were not detected in any species. In roe deer, antibodies were detected against Toxoplasma gondii (13%) and Neospora caninum (3%). Chamois tested positive for antibodies to T. gondii (5%), N. caninum (21%), bovine respiratory syncytial virus (BRSV) (41%), bovine parainfluenza type-3 virus (17%), pestiviruses (18%), and Mycoplasma conjunctivae (17%). In the sheep, particularly high antibody prevalence rates were found for T. gondii (78%), Chlamydophila spp. (20%), pestiviruses (90%), BRSV (82%), and M. conjunctivae (81%).     

Toxoplasmosis in three species of native and introduced Hawaiian birds

Toxoplasma gondii was found in endemic Hawaiian birds, including 2 nene geese (Nesochen sandvicensis), 1 red-footed booby (Sula sula), and an introduced bird, the Erckels francolin (Francolinus erckelii). All 4 birds died of disseminated toxoplasmosis; the parasite was found in sections of many organs, and the diagnosis was confirmed by immunohistochemical staining with anti-T. gondii-specific polyclonal antibodies. This is the first report of toxoplasmosis in these species of birds.     

Toxoplasma gondii antibodies in free-living African mammals.

Twelve species of free-living African mammals from Kenya, Tanzania, Uganda and Zambia were tested for antibodies to Toxoplasma gondii using the indirect hemagglutination test. Of 157 animals sampled, 20 (13%) were seropositive. T. gondii antibodies were detected in Burchell's zebra, (Equus burchelli), hippopotamus (Hippopotamus amphibius), African elephant (Loxodonta africana), defassa waterbuck (Kobus defassa), lion (Panthera leo), and rock hyrax (Procavia capensis), The highest titers were found in elephants, two having titers of 1:4096 and one of 1:8192. These results are discussed in relation to the maintenance of T. gondii among African wildlife.     

Western Blot analysis of the antigens of Toxoplasma gondii recognized by human IgM and IgG antibodies

Western Blot analysis revealed that both IgM and IgG antibodies present in the sera of humans infected with Toxoplasma gondii recognize three major antigens with apparent m.w. of 32,000, 22,000, and 6000, respectively. In addition, IgG antibodies recognized at least 17 other antigenic components. After subcellular fractionation, enrichment of the three major antigens recognized by IgM and IgG antibodies by the membrane fraction was observed. Solubilization of membrane-enriched preparations with a mixture of sodium dodecyl sulfate and sodium deoxycholate did not reveal any new antigenic structures that reacted with IgM or IgG antibodies. Treatment of Toxoplasma lysate preparations and various fractions obtained after differential centrifugation with NaIO4 diminished the reactivity of the antigens with both IgM and IgG antibodies. Lipase treatment had no effect on the number or nature of antigens recognized by IgM antibody. Treatment with pronase and trypsin eliminated the 32,000 and 22,000 m.w. antigenic components detected by IgM antibodies, whereas such treatment had no effect on the 6000 m.w. component. Periodic acid-Schiff staining of polyacrylamide gels of Toxoplasma sonicates revealed the presence of three components corresponding to m.w. of 62,000, 45,000, and 6000, respectively. At least 15 components, including the 6000 m.w. component, directly bound concanavalin A.     

The incidence of toxoplasmosis among wild vertebrates of Turkmenia (based on serologic data)

985 wild small mammals and birds were serologically investigated for toxoplasmosis from 1981 to 1984 in Turkmenia: antibodies to Toxoplasma gondii in the indirect hemagglutination and immunofluorescent complement fixation reactions according to Goldwasser and Shepard were found in 247 (25.0%), in 11 of 17 investigated species of mammals and in 13 of 22 species of birds. A sharp rise in the toxoplasmosis infection level of wild mammals was found out serologically for the first time (from 1.2% in autumn, 1982 to 72.6% in spring, 1983) followed by its reduction against the reduction in the number of animals. This must have taken place as a result of heavy toxoplasmosis epizootics in the region of investigations which is frequented by wild and domestic cats.     

The prevalence of antibodies against Toxoplasma gondii in some Ontario mammals

A survey of serum samples from mammals trapped in Central Ontario showed that many contained antibodies to Toxoplasma gondii. The prevalence of infection as reflected by positive reactions in the Sabin-Feldman Dye Test appeared to be related to the type of diet of each species examined, and specifically, to the proportion of rodents in the diet. Of the fox blood samples tested, 84% were positive. The percentage of positive samples diminished through, coyote, mink, bear, fisher skunk, raccoon, marten and rabbit. Blood samples from squirrel, deer, hare and groundhog were negative.     

Critical analysis of the topology and rooting of the parabasalian 16S rRNA tree

Between 20% and 60% of the population of most countries are infected with the protozoan Toxoplasma gondii . Subjects with clinically asymptomatic life-long latent toxoplasmosis differ from those who are Toxoplasma free in several behavioral parameters. Case–control studies cannot decide whether these differences already existed before infection or whether they were induced by the presence of Toxoplasma in the brain of infected hosts. Here, we searched for such morphological differences between Toxoxoplasma -infected and Toxoplasma -free subjects that could be induced by the parasite (body weight, body height, body mass index, waist–hip ratio), or could rather correlate with their natural resistance to parasitic infection (fluctuating asymmetry, 2D : 4D ratio). We found Toxoplasma -infected men to be taller and Toxoplasma -infected men and women to have lower 2D : 4D ratios previously reported to be associated with higher prenatal testosterone levels. The 2D : 4D ratio negatively correlated with the level of specific anti- Toxoplasma antibodies in Toxoplasma -free subjects. These results suggest that some of the observed differences between infected and noninfected subjects may have existed before infection and could be caused by the lower natural resistance to Toxoplasma infection in subjects with higher prenatal testosterone levels.     

Selection and identification of dense granule antigen GRA3 by Toxoplasma gondii whole genome phage display

Toxoplasma gondii is a ubiquitous, unicellular, eukaryotic parasite with a complex intracellular life cycle capable of invading and chronically infecting a wide variety of vertebrate host species, including man. Although normally opportunistic in healthy adults, it is a lethal pathogen in immunocompromised humans, particularly in AIDS patients. We present the application of a genomic phage display as a tool for the direct identification of antigens with potential value in diagnosis and/or as subunit vaccine components. Using a polycosmid cloning strategy, we constructed a large phagemid display library (>10(9) independent clones) of mixed short genomic restriction fragments (< or = 500 bp) of T. gondii genomic DNA (80 Mbp genome size) fused to gene III of the filamentous phage M13. Biopanning of the library with monoclonal Toxoplasma antibodies resulted in the isolation and identification of an epitope of GRA3, an antigen located in the dense granules of T. gondii tachyzoites. The reactivity of the phage displaying the GRA3 epitope with the monoclonal antibody was confirmed by an enzyme-linked immunosorbent assay. These results demonstrate the accessibility of midsized eukaryotic genomes to display technology and the feasibility to screen these whole genome display libraries with antibodies for isolating novel antigenic determinants.     

Toxoplasma antibodies among bobcats and other carnivores of norther California.

The prevalence of antibodies to Toxoplasma gondii was investigated among five species of wild carnivores in Norther Ccalifornia. The highest prevalence was among bobcats (Lynx rufus), with 15 of 21 tested being serologically positive. Other results included serological evidence of toxoplasmosis in two of seven raccoons (Procyon lotor), one of three badgers (taxidea taxus) and two of three coyotes (Canis latrans). Two gray foxes (Urocyon cinereoargenteus) were serologically negative. Oone badger with an indirect hemagglutination antibody titer of 1:8192 was found to harbor T. gondii in its brain tissues.     

Prevalence of antibodies to Neospora caninum in wild animals

Antibodies to Neospora caninum were determined in several species of wild animals in the United States by the Neospora agglutination test (NAT). Antibodies (NAT 1:40 or higher) were found in 5 of 249 bison (Bison bison), 5 of 160 caribou (Rangifer tarandus), 4 of 162 moose (Alces alces), 4 of 122 wolves (Canis lupus), and 1 of 224 musk ox (Ovibos moschatus) but not in 197 black bears (Ursus americanus). To our knowledge, this is the first report of antibodies to N. caninum in bison and caribou. The total absence of N. caninum antibodies in black bears indicates that bears are not a host for N. caninum and that there is no cross-reactivity between the NAT and the modified agglutination test (MAT) for Toxoplasma gondii, because more than 80% of black bears in eastern United States have MAT antibodies at a 1:25 serum solution.     

Antibodies to immune response gene products inhibit the IgM and IgG antibody response but not the development of resistance to Toxoplasma gondii

We have examined the effects of a monoclonal antibody directed against immune response gene products on the appearance of antibodies and development of resistance to Toxoplasma gondii. In vivo administration of a single dose of anti-I-Ak antibody to C3H/He (H-2k) and not BALB/c (H-2d) mice suppressed both the IgM and IgG response to two different strains of Toxoplasma. Administration of anti-I-Ak antibody to mice 5 days before and 10 days after infection resulted in complete inhibition of IgM and a more pronounced inhibition of IgG response to Toxoplasma. Under these experimental conditions, development of resistance against a subsequent challenge with a virulent strain of Toxoplasma was not affected. The microbicidal and tumoricidal activities of macrophages obtained from anti-I-Ak-treated, Toxoplasma-infected mice and mice infected with Toxoplasma alone were equivalent. Mice treated with anti-I-Ak antibody demonstrated a decreased proliferative response to lipopolysaccharide, a B-cell mitogen. Enumeration of B-cell numbers in anti-I-Ak-treated mice revealed a pronounced decrease in B-cell counts.     

弓形虫GRA6蛋白和P30蛋白的融合表达、纯化及抗原性分析

利用基因工程技术制备抗原性好的弓形虫GRA6蛋白和P30蛋白的融合蛋白,并用作抗原检测弓形虫抗体。根据弓形虫GRA6蛋白和P30蛋白的氨基酸序列,通过计算机分析,筛选出其中较强的抗原决定簇。用PCR方法分别扩增含抗原决定簇的基因片段。将这两个基因片段克隆至同一质粒pET28a(+)内,表达一个融合蛋白。将重组质粒转化大肠杆菌BL21(DE3),筛选表达该融合蛋白的工程菌。纯化表达的融合蛋白,用已知的6份抗弓形虫IgM阳性血清和大量正常人血清,ELISA法检测纯化融合蛋白的抗原性和特异性。获得了高效表达含弓形虫GRA6蛋白和P30蛋白抗原表位的工程菌,表达的融合蛋白约占菌体蛋白总量的25%。纯化获得了表达的融合蛋白,该蛋白有较好的抗原性和特异性。表达的弓形虫GRA6和P30融合蛋白可用做抗原检测弓形虫抗体,用于临床及孕妇检测,对优生优育有较大意义。