scholarly journals Serological diagnosis of Toxoplasma gondii: analysis of false-positive IgG results and implications

Parasite ◽  
2020 ◽  
Vol 27 ◽  
pp. 7 ◽  
Author(s):  
Loïc Simon ◽  
Judith Fillaux ◽  
Aurélie Guigon ◽  
Rose-Anne Lavergne ◽  
Odile Villard ◽  
...  
Keyword(s):  
Toxoplasma Gondii ◽  
False Positive ◽  
Primary Infection ◽  
Preventive Measures ◽  
Neospora Caninum ◽  
Confirmatory Test ◽  
Serological Tests ◽  
Past Infection ◽  
Recombinant Antigens ◽  
False Positivity

Background: Primary infection by Toxoplasma gondii in pregnant women can result in serious outcomes for the foetus. A false-positive IgG result during pregnancy can lead to a misdiagnosis of past infection and to stopping preventive measures. We collected 189 sera with positive Architect® Toxo IgG assay (Abbott Laboratories) and negative IgG results with at least two other serological tests, in order to find an explanation for the suspected false-positive IgG results. We used the recomLine Toxoplasma IgG® immunoblot (Mikrogen Diagnostik) to search for specific antigenic reactivities of the sera, and the LDBio Toxo II IgG® immunoblot (LDBio Diagnostics) as a confirmatory test. Results: The bands GRA8 and/or GRA7 were positive for 148 samples (78.3%). GRA8 was the most frequent band, appearing in 133 patterns (70.4%), whereas GRA7 was present for 49 samples (25.9%). Of the 81 samples tested with LDBio®, 23 (28.4%) turned out to be positive. Of the 58 negative LDBio® tests (71.6%) (real false-positive Architect® IgG), 23 samples (39.6%) did not show either a GRA8 or p30 band by recomLine®. Their false positivity with Architect® remains unexplained since Abbott uses these two recombinant antigens for their assay. Conclusions: The Architect® IgG false positivity for T. gondii seems to be due to reactivity against GRA8 for the majority of the sera and GRA7 to a lesser extent. The hypothesis of past contact with parasites genetically close to T. gondii such as Hammondia hammondi or Neospora caninum seems promising and should be assessed further.

scholarly journals Occurrence of antibodies against Neospora caninum and/or Toxoplasma gondii in dogs with neurological signs

2011 ◽  
Vol 20 (3) ◽  
pp. 202-206 ◽  
Author(s):  
Nicolle Fridlund Plugge ◽  
Fabiano Montiani Ferreira ◽  
Rosária Regina Tesoni de Barros Richartz ◽  
Adriana de Siqueira ◽  
Rosangela Locatelli Dittrich
Keyword(s):  
Toxoplasma Gondii ◽  
Neospora Caninum ◽  
Neurological Diseases ◽  
Fluorescent Antibody ◽  
Antibody Test ◽  
Metropolitan Region ◽  
Serological Tests ◽  
Stray Dogs ◽  
Neurological Signs ◽  
Significant Difference

This study aimed to evaluate occurrences of antibodies against Neospora caninum and Toxoplasma gondii in dogs with neurological signs. Blood samples from 147 dogs were collected: 127 from owned dogs (attended at the Veterinary Teaching Hospital of the Federal University of Paraná (HV-UFPR) and at private veterinary clinics in the city of Curitiba), and 20 from stray dogs found in Curitiba's metropolitan region. The dogs presented one or more of the following neurological signs: seizures, paresis or paralysis, ataxia, behavioral abnormalities, sensory and somatic disorders and chorioretinitis. The samples were analyzed by means of the indirect fluorescent antibody test (IFAT), at a cutoff dilution of 1:50. Out of the 147 samples obtained, 17 (11.56%) were seropositive for N. caninum, 31 (21.08%) for T. gondii and four (2.72%) for both protozoa. Serum titration on the positive animals showed that 54.83% (17/31) and 41.18% (7/17) had titers > 1:200 against T. gondii and N. caninum, respectively. A significant difference in seropositivity for T. gondii (P = 0.021; OR = 2.87; CI = 1.1 > 2.8 > 7.4) was observed between owned dogs (18.11%) and stray dogs (40%). Inclusion of serological tests for neosporosis and toxoplasmosis is recommended in diagnosing neurological diseases in dogs.

A Preliminary Evaluation of a Prototype Western Blot Confirmatory Test Kit for Syphilis

1994 ◽  
Vol 5 (6) ◽  
pp. 409-414 ◽  
Author(s):  
H Young ◽  
P J Walker ◽  
D Merry ◽  
A Mifsud
Keyword(s):  
Western Blot ◽  
False Positive ◽  
High Sensitivity ◽  
High Specificity ◽  
Confirmatory Test ◽  
Preliminary Evaluation ◽  
Serological Tests ◽  
Western Blot Test ◽  
Specificity And Sensitivity ◽  
Test Kit

A prototype Western blot kit was evaluated as a confirmatory test for syphilis using 131 sera characterized by other serological tests for syphilis. There were 114 treponemal sera (including 94 cases of early syphilis, 83 of which were untreated) and 17 non-treponemal problem sera (11 gave false positive reactions on screening with the TmpA recombinant antigen enzyme immunoassay (EIA), 3 gave false positive fluorescent treponemal antibody absorbed (FTA-abs) tests, and 3 false positive Captia Syphilis G EIA results). Based on the manufacturer's criteria of reactivity in multiple bands for designating a positive result the Western blot test gave a sensitivity of 99.1% (113/114) and a specificity of 88.2% (15/17) when indeterminate reactions were scored positive and 98.2% (112/114) and 100% (17/17) when indeterminate reactions were scored negative. Sensitivity was high in both treated and untreated infection. Corresponding sensitivities for the TPHA and FTA-abs when equivocal reactions were scored negative were 97.5% (111/114) and 99.1% (113/114). The high sensitivity of the FTA-abs in this study is probably due to the large number of untreated primary infections. Our results with the Western blot, confirm earlier studies using ‘in-house’ test systems and, support a role for a commercial Western blot test in the confirmatory diagnosis of syphilis. Further studies are required to confirm the high specificity and sensitivity of the kit in a larger series including a wider variety of non-treponemal cases as well as patients with untreated and treated infection.

scholarly journals GRA2 and ROP1 Recombinant Antigens as Potential Markers for Detection of Toxoplasma gondii-Specific Immunoglobulin G in Humans with Acute Toxoplasmosis

2009 ◽  
Vol 16 (4) ◽  
pp. 510-514 ◽  
Author(s):  
Lucyna Holec-Gąsior ◽  
Józef Kur ◽  
Elżbieta Hiszczyńska-Sawicka
Keyword(s):  
Toxoplasma Gondii ◽  
Recombinant Proteins ◽  
Immunoglobulin G ◽  
Expression System ◽  
Chronic Phase ◽  
Chronic Infections ◽  
Serum Samples ◽  
Past Infection ◽  
Recombinant Antigens ◽  
Acute Toxoplasmosis

ABSTRACT A goal of the current study was to evaluate serological applications of Toxoplasma gondii GRA2 and rhoptry protein 1 (ROP1) antigens. Soluble recombinant GRA2 and ROP1 antigens as fusion proteins containing six histidyl residues at the N and C terminals were obtained using an Escherichia coli expression system. Purification by one-step metal affinity chromatography allowed recovery of milligram amounts of pure recombinant proteins per liter of culture. The usefulness of these antigens for diagnosis of human infections was tested on 167 serum samples obtained during routine diagnostic tests. A panel of 37 serum samples from patients with acute toxoplasmosis was compared to a panel of 90 serum samples from individuals with past infection. The results indicated that both GRA2 and ROP1 recombinant antigens detected antibodies more frequently in samples from individuals with acute infections (100% and 94.6%, respectively) than in samples from individuals with chronic infections (22.5% and 15.5%, respectively). These results suggest that immunoglobulin G antibodies against GRA2 and ROP1 antigens are produced during the acute stage of toxoplasmosis but are uncommon in the chronic phase of the infection. Hence, these recombinant proteins can be used as specific molecular markers to differentiate between acute and chronic infections.

scholarly journals Toxoplasma gondii Recombinant Antigens as Tools for Serodiagnosis of Human Toxoplasmosis: Current Status of Studies

2013 ◽  
Vol 20 (9) ◽  
pp. 1343-1351 ◽  
Author(s):  
Lucyna Holec-Gąsior
Keyword(s):  
Toxoplasma Gondii ◽  
Current Status ◽  
Serological Tests ◽  
Alternative Source ◽  
Recombinant Antigens ◽  
Content Type ◽  
Congenital Infections ◽  
Antigenic Proteins ◽  
Serious Disease ◽  
Lysate Antigens

ABSTRACTToxoplasma gondiiis a parasitic protozoan which is the cause of toxoplasmosis. Although human toxoplasmosis in healthy adults is usually asymptomatic, serious disease can occur in the case of congenital infections and immunocompromised individuals. Furthermore, despite the exact recognition of its etiology, it still presents a diagnostic problem. Diagnosis of toxoplasmosis is mainly based on the results of serological tests detecting anti-T. gondii-specific antibodies in the patient's serum sample. The specificities and sensitivities of serology tests depend mostly on the diagnostic antigen(s) used. Most of the commercial serological kits currently available are based onToxoplasmalysate antigens (TLAs). In recent years, many studies showed that recombinant antigenic proteins ofT. gondiimay be an alternative source of antigens which are very useful for the serodiagnosis of toxoplasmosis. This article presents a review of current studies on the application and usefulness of differentT. gondiirecombinant antigens in serological tests for the diagnosis of human toxoplasmosis.

Optimization and validation of an ELISA using recombinant Toxoplasma gondii matrix antigen 1 for serodiagnosis of the infection

2015 ◽  
Vol 15 (2) ◽  
pp. 56-60 ◽  
Author(s):  
Buyannemekh Tumurjav ◽  
Mohamad Alaa Terkawi ◽  
Houshuang Zhang ◽  
Guohong Zhang ◽  
Honglin Jia ◽  
...  
Keyword(s):  
Toxoplasma Gondii ◽  
Enzyme Linked Immunosorbent Assay ◽  
Tissue Cultures ◽  
Chain Reaction ◽  
Serological Tests ◽  
Recombinant Antigens ◽  
Crude Antigen ◽  
Polymerase Chain ◽  
Alternative Sources ◽  
Toxoplasma Gondii Infection

Toxoplasma gondii infection can be diagnosed directly by polymerase chain reaction (PCR), hybridization and isolation of parasites and indirectly with serological methods[4; 5; 18].Although all these tests have shortcomings, serological tests, particularly the enzyme-linked immunosorbent assay (ELISA), seem to be the most practical and economical. The crude antigen prepared from tachyzoites has been traditionally utilized for commercially serological detection kits. However the use of recombinant antigens can be alternative sources of antigens allowing better standardization of the tests and reducing the costs of production requires mass production of the parasite either from the peritoneal fluids of infected mice or from tissue cultures. In spite of the potential advantages of using recombinant antigens in serology tests, their sensitivities have not yet achieved perfect result; therefore, further research on new antigensis extremely desirable [10; 16; 17; 3]. In this context, the Toxoplasma gondii matrix antigen 1 (TgMAG1) known as 65-kDa protein abundantly expressed within the cyst and in the cyst wall surrounding the bradyzoites [15], has documented to be immunogenic during the infection with T. gondii in mouse model and promising reagent for serodiagnosis of toxoplasmosis in humans [15;12; 6]. However, its usefulness has not yet been confirmed in animal toxoplasmosis.In this study, the optimization and validation of E.coli-expressed rTgMAG1as ELISA antigen were describedMongolian Journal of Agricultural Sciences Vol.15(2) 2015; 56-60

scholarly journals Immunoblot Assay Using Recombinant Antigens as a Supplemental Test To Confirm the Presence of Antibodies to Trypanosoma cruzi

2007 ◽  
Vol 14 (4) ◽  
pp. 355-361 ◽  
Author(s):  
Kevin Y. Cheng ◽  
Chi-Deu Chang ◽  
Vince A. Salbilla ◽  
Louis V. Kirchhoff ◽  
David A. Leiby ◽  
...  
Keyword(s):  
Trypanosoma Cruzi ◽  
False Positive ◽  
Test Results ◽  
Serological Tests ◽  
Assay Sensitivity ◽  
Immunoblot Assay ◽  
Recombinant Antigens ◽  
Persistent Problem ◽  
Negative Results ◽  
Positive Results

ABSTRACT The diagnosis of chronic Chagas' disease is generally made by detecting antibodies to Trypanosoma cruzi. Most conventional serological tests are based on lysates of whole parasites or semipurified antigen fractions from T. cruzi epimastigotes grown in culture. The occurrence of inconclusive and false-positive results has been a persistent problem with the conventional assays, and there is no universally accepted gold standard for confirmation of positive test results. We describe here an immunoblot assay for detecting antibodies to T. cruzi in which four chimeric recombinant antigens (rAgs), designated FP3, FP6, FP10, and TcF, are used as target antigens. Each of these rAgs is composed of several antigenically distinct regions and includes repetitive as well as nonrepetitive sequences. Each rAg is coated as a discrete line on a nitrocellulose strip. Assay sensitivity was assessed by testing 345 specimens known to be positive for antibodies to T. cruzi. All 345 of these samples showed two to four reactive test bands in addition to the three on-board control bands that are on each strip. Assay specificity was determined by testing 500 specimens from random U.S. blood donors, all of which gave negative results. Based on the results obtained in this study, we propose the following scheme for interpretation of test results: (i) no bands or a single test band = a negative result; (ii) two or more test bands with at least one band showing intensity of 1+ or higher = a positive result; and (iii) multiple faint test bands (±) = indeterminate result. Based on this scheme, the prototype immunoblot assay showed sensitivity of 100% (n = 345) and specificity of 100% (n = 500). Additionally, all 269 potentially cross-reacting and T. cruzi antibody-negative specimens tested negative in our immunoblot assay. The rAg-based immunoblot assay has potential as a supplemental test for confirming the presence of antibodies to T. cruzi in blood specimens and for identifying false-positive results obtained with other assays.

scholarly journals Toxoplasma gondii and Neospora caninum infections in South American camelids in Switzerland and assessment of serological tests for diagnosis

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Walter Basso ◽  
Elena Sollberger ◽  
Gereon Schares ◽  
Susanne Küker ◽  
Flurin Ardüser ◽  
...  
Keyword(s):  
Toxoplasma Gondii ◽  
Neospora Caninum ◽  
South American ◽  
Serological Tests ◽  
South American Camelids

scholarly journals A brain cyst load-associated antigen is a Toxoplasma gondii biomarker for serodetection of persistent parasites and chronic infection

BMC Biology ◽  
2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Céline Dard ◽  
Christopher Swale ◽  
Marie-Pierre Brenier-Pinchart ◽  
Dayana C. Farhat ◽  
Valeria Bellini ◽  
...  
Keyword(s):  
Toxoplasma Gondii ◽  
Biomarker Discovery ◽  
Serological Test ◽  
Genetically Engineered ◽  
Host Cells ◽  
Elisa Assay ◽  
Recombinant Polypeptide ◽  
Serological Tests ◽  
Past Infection ◽  
Immune Balance

Abstract Background Biomarker discovery remains a major challenge for predictive medicine, in particular, in the context of chronic diseases. This is true for the widespread protozoan Toxoplasma gondii which establishes long-lasting parasitism in metazoans, humans included. This microbe successively unfolds distinct genetic programs that direct the transition from high to low replicative potential inside host cells. As a slow-replicating cell, the T. gondii bradyzoite developmental stage persists enclosed in a cyst compartment within tissues including the nervous system, being held by a sustained immune equilibrium which accounts for the prolonged clinically silent phase of parasitism. Serological surveys indicate that nearly one third of the human population has been exposed to T. gondii and possibly host bradyzoites. Because any disruption of the immune balance drives the reverse transition from bradyzoite to fast replicating tachyzoite and uncontrolled growth of the latter, these people are at risk for life-threatening disease. While serological tests for discriminating recent from past infection are available, there is yet no immunogenic biomarker used in the serological test to allow ascertaining the presence of persistent bradyzoites. Results Capitalizing on genetically engineered parasites induced to produce mature bradyzoites in vitro, we have identified the BCLA/MAG2 protein being restricted to the bradyzoite and the cyst envelope. Using laboratory mice as relevant T. gondii host models, we demonstrated that BCLA/MAG2 drives the generation of antibodies that recognize bradyzoite and the enveloping cyst structure. We have designed an ELISA assay based on a bacterially produced BCLA recombinant polypeptide, which was validated using a large collection of sera from mice of different genetic backgrounds and infected with bcla+ or bcla-null cystogenic and non-cystogenic T. gondii strains. To refine the design of the ELISA assay, we applied high-resolution BCLA epitope mapping and identified a specific combination of peptides and accordingly set up a selective and sensitive ELISA assay which allowed the detection of anti-BCLA/MAG2 antibodies in the sera of human patients with various forms of toxoplasmosis. Conclusions We brought proof of principle that anti-BCLA/MAG2 antibodies serve as specific and sensitive serological markers in the perspective of a combinatorial strategy for detection of persistent T. gondii parasitism.

scholarly journals Evaluation of a Recombinant Multiepitope Peptide for Serodiagnosis of Toxoplasma gondii Infection

2012 ◽  
Vol 19 (3) ◽  
pp. 338-342 ◽  
Author(s):  
Jianfang Dai ◽  
Min Jiang ◽  
Yanyun Wang ◽  
Lili Qu ◽  
Rujun Gong ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Toxoplasma Gondii ◽  
Diagnostic Tests ◽  
Routine Screening ◽  
Serological Tests ◽  
Recombinant Antigens ◽  
Content Type ◽  
Prevention And Treatment ◽  
Immunosorbent Assays ◽  
Toxoplasma Gondii Infection

ABSTRACTDetection ofToxoplasma gondiiinfection with sensitive and specific methods is a key step in the prevention and treatment of toxoplasmosis. Among the available diagnostic tests, serology is commonly used. Although serological tests give satisfactory results, the production of reliable reagents remains laborious and expensive. There is therefore a real need to acquire specific and effective recombinant antigens for the serodiagnosis ofT. gondiiinfection. In this study, a multiepitope peptide was designed and successfully expressed inEscherichia coli, and then IgG and IgM enzyme-linked immunosorbent assays (ELISAs) were developed and evaluated. Our results showed that the new multiepitope antigen is one of the most promising recombinant antigens which could be used in routine screening of human toxoplasmosis.

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