Detection of False-Positive Sera in Contagious Agalactia with a Multiantigen ELISA and their Elimination with a Protein G Conjugate

In serology, lack of specificity can generally be attributed to cross-reactions between different pathogens with antigens bearing similar epitopes. During seroepidemiologic surveys of contagious agalactia of sheep caused by Mycoplasma agalactiae infection, numerous sera were analyzed by enzyme-linked immunosorbent assay (ELISA). A few sera reacted with various antigens coated on plates, including the well with no antigen. This reactivity was not due to cross-reactions as initially suspected, and these multipositive sera were designated false-positive sera. Elimination of this false positivity was not possible by using covalent ELISA plates or different rabbit anti-sheep IgG conjugates. Only conjugates using monoclonal antibodies or protein G were efficient in elimination of false positivities without reducing the true specific positive titers. No false-positive sera have been observed since the implementation of protein G conjugates in the serologic diagnosis of contagious agalactia by ELISA for the past 2 years.

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Unreliable Measurement of Basophil Maximum Leukotriene Release with the Bühlmann CAST 2000 Enzyme-Linked Immunosorbent Assay Kit

Clinical and Vaccine Immunology ◽

10.1128/cvi.13.3.420-422.2006 ◽

2006 ◽

Vol 13 (3) ◽

pp. 420-422 ◽

Cited By ~ 6

Author(s):

S. E. Burastero ◽

C. Paolucci ◽

D. Breda ◽

G. Monasterolo ◽

R. E. Rossi ◽

...

Keyword(s):

Monoclonal Antibody ◽

Monoclonal Antibodies ◽

Immunosorbent Assay ◽

False Positive ◽

Positive Control ◽

Enzyme Linked Immunosorbent Assay ◽

Positive Results

ABSTRACT The Bühlmann CAST 2000 enzyme-linked immunosorbent assay is a potentially useful assay for measuring sulfidoleukotrienes released in vitro by allergen-challenged basophils. However, we observed that the positive-control reagent yielded positive signals in cell-free systems. These false-positive results depended on using a mouse anti-FcεRI monoclonal antibody and were prevented by degranulation-inducing reagents other than mouse monoclonal antibodies.

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Development of an Enzyme-Linked Immunosorbent Assay for Serotyping Ureaplasma urealyticum Strains Using Monoclonal Antibodies

Clinical and Diagnostic Laboratory Immunology ◽

10.1128/cdli.8.1.52-57.2001 ◽

2001 ◽

Vol 8 (1) ◽

pp. 52-57 ◽

Cited By ~ 11

Author(s):

Fedoua Echahidi ◽

Gaëtan Muyldermans ◽

Sabine Lauwers ◽

Anne Naessens

Keyword(s):

Monoclonal Antibodies ◽

Immunosorbent Assay ◽

Ureaplasma Urealyticum ◽

Polyclonal Antibodies ◽

Enzyme Linked Immunosorbent Assay ◽

Elisa Method ◽

Cross Reactions ◽

Antigenic Preparation ◽

Negative Controls ◽

Reference Strains

ABSTRACT Ureaplasma urealyticum comprises 14 serotypes. The existing serotyping methods all use polyclonal antibodies. These methods are time-consuming and labor-intensive, and they cannot always be performed on primary isolates; in addition, the results are difficult to interpret. We developed a new enzyme-linked immunosorbent assay (ELISA) method using serotype-specific monoclonal antibodies (MAbs) to enable the serotyping of U. urealyticum isolates from primary broth cultures. Each of the 14 serotype reference strains was tested against 14 selected MAbs. Homologous reactions were very strong, while heterologous reactions were negligible. Three cross-reactions were observed: MAb 5 cross-reacted with serotype 2, MAb 14 cross-reacted with serotype 3, and MAb 8 cross-reacted with serotype 13. Despite the cross-reactions observed, all the serotype reference strains ofU. urealyticum could be identified and differentiated using a combination of MAbs. Reproducibility was analyzed with a fractionated antigenic preparation and with several freshly prepared antigens of the same strain. No significant interrun variation was found with the fractionated antigen, but significant variations in optical density (OD) values were found when freshly prepared antigens were tested. However, the variation in OD values did not influence the overall interpretation of the ELISA: reactions with homologous MAbs were always prominent compared to those of the negative controls. This newly developed ELISA using MAbs seems promising for serotyping of U. urealyticum clinical isolates.

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Trichinella strain, pig race and other parasitic infections as factors in the reliability of ELISA for the detection of swine trichinellosis

Parasitology ◽

10.1017/s0031182000073753 ◽

1992 ◽

Vol 105 (1) ◽

pp. 111-115 ◽

Cited By ~ 9

Author(s):

F. Serrano ◽

E. Pérez ◽

D. Reina ◽

I. Navarrete

Keyword(s):

Antibody Response ◽

Immunosorbent Assay ◽

Post Infection ◽

False Positive ◽

Maximum Sensitivity ◽

Enzyme Linked Immunosorbent Assay ◽

Parasitic Infections ◽

Low Grade ◽

High Background ◽

Cross Reactions

An enzyme-linked immunosorbent assay (ELISA) using crude worm extracts (CWE) and mixtures of these as antigens of five Spanish isolates (P, C, B1, B2 and W) was developed for detecting homologous and heterologous experimental infections with these isolates between – 14 and 82 days post-infection (p.i.) in white and Iberian pigs. A total of 243 pigs (Ilberian or cross-bred with this race) with numerous parasitic infections were also screened for the presence of antibodies to a mixture of CWE of C, B1 and B2 isolate. The test showed a specificity of 93·1–98·9% depending on the cut-off values and a maximum sensitivity of 92·8–100% between days 34 and 82 p.i. A low grade of infectivity was shown in the T3 isolates compared to the T1 isolates (P, C, B1 and B2) but high cross-reactions were observed between all the isolates with minor differences between P and W isolates. The highest antibody response was found in P infections and the lowest in pigs infected with the W isolate. A clear association between the presence of several parasitic infections and false positive reactions was not found, but an important relation was shown between high background levels and the Iberian race in experimentally and conventionally raised pigs

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