Calibration and use of an in-house anti-measles IgG standard serum

For the purpose of research a large quantity of anti-measles IgG working reference serum was needed. A pool of sera from five teenagers was prepared and named Alexandre Herculano (AH). In order to calibrate the AH serum, 18 EIA assays were performed testing in parallel AH and the 2nd International Standard 1990, Anti-Measles Antibody, 66/202 (IS) in a range of dilutions (from 1/50 to 1/25600). A method which compared parallel lines resulting from the graphic representation of the results of laboratory tests was used to estimate the power of AH relative to IS. A computer programme written by one of the authors was used to analyze the data and make potency estimates. Another method of analysis was used, comparing logistic curves relating serum concentrations with optical density by EIA. For that purpose an existing computer programme (WRANL) was used. The potency of AH relative to IS, by either method, was estimated to be 2.4. As IS has 5000 milli international units (mIU) of anti-measles IgG per millilitre (ml), we concluded that AH has 12000 mIU/ml.

Comparison of a commercial enzyme immunoassay with plaque reduction neutralization for maternal and infant measles antibody measurement

A tecnica de doseamento imunoenzimatico (ELISA) de IgG anti-sarampo (IgG-AS) e a mais pratica e conveniente para estudos com muitos soros. A tecnica de referencia e a reducao de neutralizacao em placa (RNP). Para avaliar a concordancia dos resultados obtidos por ELISA e pela tecnica padrao RNP, comparamos os resultados de doseamentos efetuados pelas duas tecnicas em 43 pares de soros de puerperas e respectivos recem-nascidos (cordao umbilical), e ainda nos soros dessas criancas em amostras colhidas entre os 11 e os 14 meses de idade. Nos soros maternos e do cordao umbilical, as diferencas medias das concentracoes de IgG-AS medidas por ELISA ou RNP nao eram estatisticamente significativas. No entanto, a nivel individual as diferencas eram por vezes grandes. A concordancia nao era tao boa no caso dos soros infantis, nos quais os niveis de anticorpos residuais eram muito baixos...