Simplified Assay for Measuring Toxoplasma gondii Immunoglobulin G Avidity

ABSTRACT A Toxoplasma gondii immunoglobulin G (IgG) avidity enzyme-linked immunosorbent assay (ELISA) was developed that combines the accuracy of assays based on end point titers and the relative ease of assays based on optical density values. Like published procedures, the new assay's avidity index (AI) was based on differential T. gondii-specific IgG reactivity in serum-treated wells washed with urea buffer versus that in wells washed with control buffer; unlike previous assays, however, the IgG reactivity was measured quantitatively using a standard curve. The assay was evaluated using 24 IgG-positive and IgM-positive sera collected within 5 months of the onset of symptoms (recent-infection group) and 25 IgG-positive and IgM-negative sera (past-infection group). All sera in the recent-infection group exhibited AI values of <0.18, whereas all sera in the past-infection group exhibited AI values of >0.27. The AI values of the recent-infection group showed significant correlation with the number of days after the onset of symptoms. A subset of 16 sera (8 recent and 8 past) was tested using a commercially availableT. gondii IgG avidity ELISA based on end point titration; the results of the two assays showed highly significant correlation (R 2 = 0.9125). In addition, we confirmed and extended the findings of other investigators, showing that AI values calculated using optical density values, but not AI values calculated using quantitative IgG values, varied significantly depending on the serum dilution used. This new assay should facilitate the accurate measurement of T. gondii IgG avidity in a reference laboratory setting.

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Use of Dense Granule Antigen GRA6 in an Immunoglobulin G Avidity Test To Exclude Acute Toxoplasma gondii Infection during Pregnancy

Clinical and Vaccine Immunology ◽

10.1128/cvi.00199-10 ◽

2010 ◽

Vol 17 (9) ◽

pp. 1349-1355 ◽

Cited By ~ 17

Author(s):

Hossein Elyasi ◽

Jalal Babaie ◽

Hélène Fricker-Hidalgo ◽

Marie-Pierre Brenier-Pinchart ◽

Mehrak Zare ◽

...

Keyword(s):

Toxoplasma Gondii ◽

Immunoglobulin G ◽

Chronic Infection ◽

Dense Granule ◽

Enzyme Linked Immunosorbent Assay ◽

High Avidity ◽

Igg Antibodies ◽

Serum Samples ◽

Recent Infection ◽

Igg Avidity

ABSTRACT The usefulness of a specific immunoglobulin G (IgG) avidity enzyme-linked immunosorbent assay (ELISA) based on recombinant GRA6 antigen for distinguishing between acute and chronic Toxoplasma infection was investigated. Two sets of serum samples obtained from pregnant women with acute, chronic, or no Toxoplasma infection collected in France and Iran were used. Among the French subjects, 19 of 20 (95%) women who experienced seroconversion during the past 4 months before sampling displayed low-avidity IgG antibodies against GRA6, while all 17 (100%) women with chronic infection had high-avidity antibodies. When the Euroimmun IgG avidity ELISA was used, 15 of 19 (78.9%) recently infected women had low-avidity antibodies, and 20 of 22 (90.9%) women with chronic infection displayed high-avidity antibodies. The results suggested better performance of the GRA6 avidity ELISA than the Euroimmun avidity ELISA for exclusion of a recent infection occurring less than 4 months previously. Similarly, all 35 Iranian women with acute Toxoplasma infection had low-avidity antibodies against GRA6, whereas all 34 women with chronic infection displayed IgG antibodies of high avidity, indicating the value of GRA6 avidity testing for ruling out a recent infection. Avidity tests based on lysed whole-cell Toxoplasma gondii antigen are currently used to exclude recently acquired infections; however, the use of recombinant antigen(s) might improve the diagnostic performance of avidity tests and facilitate the development of more standardized assays.

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Enzyme-Linked Immunosorbent Assays Using the Recombinant Dense Granule Antigens GRA6 and GRA1 of Toxoplasma gondii for Detection of Immunoglobulin G Antibodies

Clinical and Diagnostic Laboratory Immunology ◽

10.1128/cdli.7.4.607-611.2000 ◽

2000 ◽

Vol 7 (4) ◽

pp. 607-611 ◽

Cited By ~ 36

Author(s):

Laurence Lecordier ◽

Marie-Pierre Fourmaux ◽

Corinne Mercier ◽

Eric Dehecq ◽

E. Masy ◽

...

Keyword(s):

Escherichia Coli ◽

Toxoplasma Gondii ◽

Recombinant Protein ◽

Optical Density ◽

Immunoglobulin G ◽

Recombinant Antigen ◽

Dense Granule ◽

Human Sera ◽

Density Values ◽

Immunosorbent Assays

ABSTRACT The potential of the dense granule antigens GRA1 and GRA6 ofToxoplasma gondii to be used as diagnosis reagents in a recombinant form was evaluated. Both proteins were expressed inEscherichia coli as glutathione-S-transferase (GST) fusions. The GST-GRA1 fusion comprises the entire GRA1 sequence devoid of its N-terminal signal peptide. Separate expression of the two N- and C-terminal hydrophilic regions of GRA6 showed that only the N-terminal hydrophilic part of the protein was recognized by a pool of positive human sera in an immunoblot. One hundred T. gondii-positive and 98 negative human sera were tested in two separate immunoglobulin G (IgG)-direct enzyme-linked immunosorbent assays (ELISAs) using either GST-GRA1 or GST-GRA6-Nt recombinant protein. Whereas the sensitivity of the GST-GRA1 IgG ELISA was low (68%), the GST-GRA6-Nt IgG ELISA reached a sensitivity of 96%. The reactivity to GRA6-Nt was shown to be high even with human sera of low IgG titers. In addition, comparison of the optical density values for each serum revealed that GRA1 may complement GRA6-Nt to reach an overall sensitivity of 98%. Therefore, the GST-GRA6-Nt ELISA could be used together with another antigen like GRA1 for the development of a recombinant antigen-based test for serodiagnosis of toxoplasmosis.

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Toxoplasma gondii seroprevalence among pregnant women in Rabat, Morocco

Tropical Medicine and Health ◽

10.1186/s41182-021-00311-5 ◽

2021 ◽

Vol 49 (1) ◽

Author(s):

Majda Laboudi ◽

Zoubida Taghy ◽

Oussama Duieb ◽

François Peyron ◽

Abderrahim Sadak

Keyword(s):

Toxoplasma Gondii ◽

Pregnant Women ◽

Congenital Toxoplasmosis ◽

Immunoglobulin M ◽

Bivariate Analysis ◽

Enzyme Linked Immunosorbent Assay ◽

Seroprevalence Rate ◽

Recent Infection ◽

Igg Avidity ◽

Avidity Test

Abstract Background Toxoplasmosis is an infectious disease caused by a protozoan parasite named Toxoplasma gondii (T.gondii). Pregnant women are considered one of the risk groups. The objective of this retrospective study is to provide an updated estimate of the seroprevalence of anti-T. gondii antibodies among a group of Moroccan pregnant women monitored at the Parasitology Laboratory of the National Institute of Hygiene in Rabat in Morocco. Methods Serum samples were tested for the presence of specific anti-T. gondii immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies using indirect enzyme-linked immunosorbent assay (ELISA). Anti-Toxoplasma IgM- and IgG-positive cases were also evaluated with the anti-Toxoplasma IgG avidity test. All cases were evaluated according to the age, parity, and historical of abortion. Results Among 677 pregnant women, 94.1% (637/677) were serologically screened for the first time and therefore had no knowledge of their serological status, and only 5.9% (40/677) were screened for the second or third time. The overall anti-T. gondii IgG and IgM seropositivity among the 637 pregnant women included in the study analysis was 43% (274/637) and 3.9% (25/637), respectively. The use of the IgG avidity test allowed excluding recent infection among 83% of cases with IgG and IgM positive sera. The mean age was 29.4 ± 6.3 years. The result of the bivariate analysis revealed that the age influenced significantly the seroprevalence rate, while the parity and the existence of previous spontaneous abortion did not have any significant statistical correlation with seropositivity to T. gondii. Conclusion This study shows that 43% of pregnant women were positive and 57% of them had no antibody against the T. gondii infection. However, the pregnancy follow-up and the counseling of pregnant women remain essential for the prevention of congenital toxoplasmosis.

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Evaluation of the TGS TA system for the detection of anti-cytomegalovirus antibodies

Microbiologia Medica ◽

10.4081/mm.2017.6581 ◽

2017 ◽

Vol 32 (2) ◽

Author(s):

Annalisa Cianflone ◽

Maria Teresa Manco ◽

Olivia Arpino ◽

Alessia Paganini ◽

Massimo De Paschale ◽

...

Keyword(s):

Fluorescent Assay ◽

Infection Group ◽

Past Infection ◽

Recent Infection ◽

Igm Antibodies ◽

Igg Avidity ◽

Group 3 ◽

Group 2 ◽

Sera Samples ◽

Group 1

Background and aims: The aim of the present study was to evaluate the new Technogenetics TGS TA system for detecting anti-Cytomegalovirus IgG and IgM antibodies and IgG avidity. The TGS TA system was compared with our routinely used system, LIAISON XL, for the detection of IgG and IgM antibodies. Only in positive IgM samples, TGS TA system was compared to an enzyme linked fluorescent assay (ELFA) test (VIDAS, BioMérieux, Marcy-l’Étoile, France) and with LIAISON XL system for the IgG avidity (if possible). Materials and methods: Three hundred sera samples from pregnant women were examined with the TGS TA system and divided in 3 groups according to IgG and IgM screening LIAISON XL tests: 102 were non-immune women (Group 1), 98 were pregnant with past infection (Group 2) and 100 were pregnant with positive or equivocal IgM (95 with positive IgG and 5 with negative IgG) (Group 3). Results: The overall concordance of the IgG results between LIAISON XL and TGS TA was 98.3%: 97.1% in Group 1, 100% in Group 2 and 98.0% in Group 3. The overall concordance of the IgM results between LIAISON XL and TGS TA was 92.1%: 100% in Group 1, 99.0% in Group 2 and 70.1% in Group 3. In Group 3, the concordance between the results of the IgG avidity with the LIAISON XL and TGS TA tests was 87.4%. Comparing the clinical diagnosis obtained with our protocol and that of the TGS TA system, the overall concordance was 94.3%: 97.1% in Group 1, 99.0% in Group 2 and 87.0% in Group 3. Conclusions: In conclusion, the overall clinical concordance between the LIAISON XL/VIDAS protocol and the TGS TA system is excellent. TGA TA system shows to be a valuable tool able to clearly identify non-specific subjects, those with a non-recent infection and classify as either recent or past infection half of the subjects with undetermined infection with our protocol.

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Evaluation of the TGS TA system for the detection of anti-Toxoplasma antibodies

Microbiologia Medica ◽

10.4081/mm.2017.6583 ◽

2017 ◽

Vol 32 (1) ◽

Author(s):

Olivia Arpino ◽

Annalisa Cianflone ◽

Maria Teresa Manco ◽

Alessia Paganini ◽

Massimo De Paschale ◽

...

Keyword(s):

High Avidity ◽

Past Infection ◽

Recent Infection ◽

Igm Antibodies ◽

Igg Avidity ◽

Avidity Test ◽

Group 3 ◽

Group 2 ◽

Group 1

Background and aims. The aim of the present study was to evaluate the new chemiluminescence TGS TA system of Technogenetics (Milan, Italy) for detecting anti-Toxoplasma IgG and IgM antibodies and IgG avidity. The TGS TA system was compared with our chemiluminescence routinely used system, LIAISON XL, supplied by Diasorin (Saluggia, Italy), for the detection of IgG and IgM antibodies. Only in positive IgM samples (retrospective study) and for the IgG avidity (if existent), TGS TA system was compared to an Enzyme Linked Fluorescent Assay (ELFA) test (VIDAS, BioMérieux, Marcy-l’Étoile, France). Materials and methods. Three hundred and one sera samples, from women who came to our centre for the routine follow up pregnancy, were examined with the TGS TA system and divided in 3 groups according to IgG and IgM screening LIAISON XL tests: 106 were non-immune women (Group 1), 100 were pregnant with past infection (Group 2) and 95 were pregnant with positive or equivocal IgM (82 with positive IgG and 13 with negative IgG) (Group 3). Results. The overall concordance of the IgG results between LIAISON XL and TGS TA was 99.3%: 100% in Group 1, 98% in Group 2 and 100% in Group 3. The overall concordance of the IgM results between LIAISON XL and TGS TA was 93.9%: 100% in Group 1, 94% in Group 2 and 82.8% in Group 3. In Group 3, the concordance between the results of the IgG avidity with the ELFA and TGS TA tests was 81.7%. Comparing the clinical diagnosis obtained with our protocol and that of the TGS TA system, the overall concordance was 92.7%: 100% in Group 1, 92.0% in Group 2 and 78.9% in Group 3. Conclusions. The overall concordance of IgG antibodies is excellent for both protocols while for IgM antibodies is very high in the first group and lower in the third group, due to the presence of non-specific IgM subjects in this group. The TGS TA avidity test seems to predict ealier the maturation of the IgG compared to the ELFA test since many samples with low avidity with the ELFA were seen with moderate avidity with TGS TA and all those with borderline avidity with the ELFA were seen with high avidity with TGS TA. This system shows to be a valuable tool with overall good clinical correlation and able to clearly identify nonspecific subjects, those with a non-recent infection.

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Evaluation of the TGS TA system for the detection of anti-rubella antibodies

Microbiologia Medica ◽

10.4081/mm.2017.6582 ◽

2017 ◽

Vol 32 (2) ◽

Author(s):

Olivia Arpino ◽

Annalisa Cianflone ◽

Maria Teresa Manco ◽

Alessia Paganini ◽

Massimo De Paschale ◽

...

Keyword(s):

Elisa Test ◽

Childbearing Age ◽

Past Infection ◽

Recent Infection ◽

Igm Antibodies ◽

Igg Avidity ◽

Group 3 ◽

Group 2 ◽

Sera Samples ◽

Group 1

Background and aims: The aim of the present study was to evaluate the new Technogenetics TGS TA system for detecting antirubella IgG and IgM antibodies and IgG avidity. TGS TA system was compared with our routinely used system, LIAISON XL, for the detection of IgG and IgM antibodies. Only in positive IgM samples (retrospective study), TGS TA system was compared to an ELFA IgM test and with an ELISA test for the IgG avidity (if existent). Materials and methods: Two hundred and seventy six sera samples from women were examined with TGS TA system and divided in 3 groups according to IgG and IgM screening LIAISON XL tests: 112 were of childbearing age and non-immune women (Group 1), 106 were pregnant with past infection or vaccinated (Group 2) and 49 were pregnant with positive or equivocal IgM (Group 3). Results: The overall concordance of the IgG results between LIAISON XL and TGS TA was 93.3%: 86.6% in Group 1, 97.2% in Group 2 and 100% in Group 3. The overall concordance of the IgM results between LIAISON XL and TGS TA was 89.0%: 100% in Group 1, 100% in Group 2 and 35.6% in Group 3. In Group 3, the concordance between the results of the IgG avidity with the ELISA and TGS TA tests was 85.7%. Comparing the clinical diagnosis obtained with our protocol and that of the TGS TA system, the overall concordance was 97.4%: 86.6% in Group 1, 97.2% in Group 2 and 85.7% in Group 3. Conclusions: TGA TS system shows to be a valuable tool with overall good clinical correlation and able to clearly identify nonspecific subjects, those with a non-recent infection or those who are vaccinated. The TGS TA test also seems to be especially sensitive in indicating vaccinated subjects with low IgG levels as immune.

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Immunoglobulin G Avidity in Diagnosis of Toxoplasmic Lymphadenopathy and Ocular Toxoplasmosis

Clinical and Diagnostic Laboratory Immunology ◽

10.1128/cdli.6.4.514-518.1999 ◽

1999 ◽

Vol 6 (4) ◽

pp. 514-518 ◽

Cited By ~ 27

Author(s):

Malgorzata Paul

Keyword(s):

Pregnant Women ◽

Immunoglobulin G ◽

Large Range ◽

Congenital Toxoplasmosis ◽

Chronic Phase ◽

Ocular Toxoplasmosis ◽

Enzyme Linked Immunosorbent Assay ◽

Ocular Infection ◽

High Avidity ◽

Igg Avidity

ABSTRACT Traditional serological techniques have some limitations in evaluating the duration of Toxoplasma gondii infection in pregnant women, patients with lymphadenopathy, and older children suspected of having congenital toxoplasmosis. In these three groups of patients, two variants of T. gondii immunoglobulin G (IgG) avidity tests were used: an EIA Kit (Labsystems) and a noncommercial enzyme-linked immunosorbent assay specially elaborated in the laboratory. The avidity of specific IgG in sera from 23 patients with a known recently acquired infection (mainly pregnant women) was low (less than 30%), whereas that in sera from 19 patients with toxoplasmic lymphadenopathy of 3 weeks to 6 months in duration (mean, 8.3 weeks) covered a large range (between 0.2 and 57.8%; mean, 25.7%); high avidity results were observed for 10 of 19 patients (52.6%). The large range of IgG avidity in patients with toxoplasmic lymphadenopathy suggests various durations of infection in these patients, with a tendency for a chronic phase of toxoplasmosis. According to the avidity marker, five patients with lymphadenopathy for less than 3 months did not have a recent Toxoplasma infection. In 6 of 19 patients with lymphadenopathy (31.6%), low IgG avidity values persisted until 5 months after the first serological examination. In all four patients with a documented chronic course of Toxoplasma infection (6 months to 8 years after the first positive serology), high IgG avidity values were observed. Among sera from 10 children and young immunocompetent adults suspected of having ocular reactivation of congenital toxoplasmosis, all had high IgG avidity values (over 40%), suggesting congenitally acquired ocular infection rather than noncongenital infection. In conclusion, the avidity of IgG is a valuable marker of recent toxoplasmosis in pregnant women, suggests the duration of invasion in patients with lymphadenopathy, and may be helpful for differentiation between reactivation of congenital infection and recently acquired ocular toxoplasmosis in immunocompetent patients. A low IgG avidity does not always identify a recent case of toxoplasmosis, but a high IgG avidity can exclude primary infections of less than 5 months’ duration.

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Detection of Immunoglobulin G and A Antibodies to Rubella Virus in Urine and Antibody Responses to Vaccine-Induced Infection

Clinical and Diagnostic Laboratory Immunology ◽

10.1128/cdli.5.1.24-27.1998 ◽

1998 ◽

Vol 5 (1) ◽

pp. 24-27 ◽

Cited By ~ 13

Author(s):

Shigeo Takahashi ◽

Fusaichi Machikawa ◽

Atsunari Noda ◽

Tetsuya Oda ◽

Tetsuya Tachikawa

Keyword(s):

Healthy Volunteers ◽

Immunoglobulin G ◽

Rubella Virus ◽

Enzyme Linked Immunosorbent Assay ◽

Serum Samples ◽

Recent Infection ◽

Serum Igg ◽

Assay Methods ◽

Rubella Vaccination ◽

Serum Igg Levels

ABSTRACT Urine and serum samples from 89 healthy volunteers and three healthy individuals who underwent rubella vaccination were tested for immunoglobulin G (IgG), IgA, and IgM to rubella virus (RV) by enzyme-linked immunosorbent assay methods. Subjects with positive (n = 68) or negative (n = 21) results for serum IgG were exactly the same as those with the corresponding results for urinary IgG. Both urinary and serum IgG levels remained elevated from the 3rd or 4th week after vaccination until the end of the study. Both urinary IgA and serum IgM levels tended to increase rapidly between the 3rd and 5th week and then gradually decrease until the end of the study, but the levels of both remained positive except for one sample each at the end (26th week). On the other hand, the ratio of anti-RV IgA titer to anti-RV IgG titer in urine (urinary anti-RV IgA/IgG ratio) increased rapidly between the 3rd and 4th week after vaccination and then rapidly returned to the ratio levels of the subjects positive for serum IgG from among the healthy volunteers. In summary, detection of urinary anti-RV IgG should be useful for screening for previous RV infection, and measurement of urinary anti-RV IgA/IgG ratio might be useful for diagnosing recent infection.

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

Clinical and Vaccine Immunology ◽

10.1128/cvi.00341-08 ◽

2009 ◽

Vol 16 (4) ◽

pp. 510-514 ◽

Cited By ~ 31

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.

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