RESUMO
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 1/25,600). 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 12,000 mIU/ml.
Assuntos
Anticorpos Antivirais/sangue , Imunoglobulina G/sangue , Vírus do Sarampo/imunologia , Sarampo/sangue , Adolescente , Calibragem , Ensaio de Imunoadsorção Enzimática , Humanos , Sarampo/diagnóstico , Padrões de ReferênciaRESUMO
The most practicable assay for measurement of measles IgG (mIgG) in large numbers of sera is an enzyme immunoassay (EIA). To assess how EIA results would agree with those by the gold standard method of plaque reduction neutralization (PRN) we compared the results from the two methods in 43 pairs of maternal and umbilical cord sera, and sera from the corresponding infants when aged 11-14 months. In maternal-cord sera, the differences between mean antibody levels by EIA or PRN were not statistically significant, though in individual sera, differences could be large. However, agreement was less good for infants sera, in which levels of mIgG were very low. The conclusions of a study of transplacental transport of mIgG would not be affected by the use of either technique. When studying waning immunity in infants, PRN should be the method of choice, while results from studies using EIA should be interpreted with caution.
Assuntos
Anticorpos Antivirais/sangue , Anticorpos Antivirais/imunologia , Imunidade Materno-Adquirida/imunologia , Técnicas Imunoenzimáticas , Vírus do Sarampo/imunologia , Sarampo/imunologia , Testes de Neutralização , Ensaio de Imunoadsorção Enzimática , Reações Falso-Negativas , Reações Falso-Positivas , Feminino , Sangue Fetal , Humanos , Imunoglobulina G/sangue , Lactente , Sarampo/prevenção & controle , Vacina contra Sarampo/imunologiaRESUMO
A considerable number of field trials have been published over the last 30 years, showing measles vaccines to be highly effective. Due to inconsistencies in methodology, comparisons between these studies have often been difficult with regard to the potencies used and the sero-response of vaccinated children. This article reviews key studies which have measured the response of children to different potencies of vaccine. The review concludes that increasing the titre of vaccine above log10 3.0 does not appear to improve vaccine efficacy. It is recommended that standard titre measles vaccine should be administered with a minimum potency of log10 3.0 TCID50 or PFU per dose at 9 months of age or later. This recommendation is endorsed by the Global Advisory Group and the Research and Development Group of the Expanded Programme on Immunization.