Elsevier

Biologicals

Volume 44, Issue 5, September 2016, Pages 448-455
Biologicals

Establishment of replacement International Standard 13/132 for human antibodies to Toxoplasma gondii

https://doi.org/10.1016/j.biologicals.2016.04.006Get rights and content
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Abstract

Sixteen laboratories carried out a collaborative study to validate 13/132 as a replacement International Standard (IS) for TOXM (3rd IS for anti-Toxoplasma Serum, Human, 1000 IU). 13/132 is a freeze dried preparation of pooled human plasma from six donors who experienced a recent Toxoplasma gondii infection. The potency of 13/132 was compared to TOXM and 01/600 (1st IS for anti-Toxoplasma IgG, Human, 20 IU). Samples were tested for IgA, IgG, IgG avidity and IgM in agglutination assays; enzyme linked immunosorbent assays (ELISA), enzyme linked fluorescent assays, immunoblots, immunofluorescence assays and the Sabin–Feldman dye test for Ig. 13/132 was strongly positive for Ig, IgA, IgG and IgM and the reproducibility was very good. 13/132 contains high levels of anti-Toxoplasma Ig, IgG and IgM and its potency falls between TOXM and 01/600. The avidity of IgG was found to be low, similar to the avidity of IgG from TOXM. 13/132 was established by the Expert Committee on Biological Standardization as the 4th IS for Antibodies, Human, to T. gondii with an assigned unitage of 160 IU per ampoule for Ig by dye test and 263 U per ampoule for IgG by ELISA.

Keywords

Toxoplasmosis
Ig
Immunoassays
Dye test
Standardisation

Abbreviations

CV
coefficient of variation
ECBS
Expert Committee on Biological Standardization
ELFA
enzyme linked fluorescent assay
ELISA
enzyme linked immunosorbent assay
GCV
geometric coefficients of variation
GM
geometric mean
HSDA
high sensitivity direct agglutination assay
IFA
immunofluorescence assay
IS
International Standard
ISAGA
imunosorbent agglutination assay
kD
kilo Dalton
NIBSC
National Institute for Biological Standards and Control

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See acknowledgements for representatives and affiliations of the Toxoplasma study group.