ABSTRACT
As an alternative to the formalin fixation of cells before staining, microwave irradiation was found a very advantageous fixation procedure in viral vaccine quantitation assays. The use of microwaves allows to avoid dangerous chemicals and thereby reduces time and equipment.
Subject(s)
Fixatives , Microwaves , Viral Vaccines/analysis , Calibration , Cells, Cultured/radiation effects , TemperatureABSTRACT
A statistical analysis was performed on the results obtained in titrations of yellow fever vaccine using a cytopathic end-point microassay in the Vero cell line. The present test system appeared less sensitive than the conventional plaque assay in PS cells but the consistency in titres was satisfactory since both test-to-test and within-test variations were small. In addition, the test is easy to perform, economical and fast.
Subject(s)
Viral Vaccines/standards , Yellow fever virus/immunology , Analysis of Variance , Animals , Antigens, Viral , Vero Cells , Viral Vaccines/toxicityABSTRACT
A trivalent working reference preparation for oral poliovaccine was prepared, and assayed over a period of three years; its stability at different temperatures was investigated. The results show that the batch of cryotubes is homogeneous and stable when stored frozen. The preparation, while containing no stabilizer is similar in composition with the vaccines to be tested and suitable to judge the acceptability of assays. The test system was shown to be accurate and reproducible.
Subject(s)
Drug Stability , Poliovirus Vaccine, Oral/analysis , Humans , Poliovirus Vaccine, Oral/standards , Reference Standards , Temperature , Time FactorsABSTRACT
A simple recursive formula, which yields an estimate for the statistical error resulting from pipetting errors accumulated throughout a dilution procedure, is described. Its influence on the variance of the end-point titre estimate is then inferred.
Subject(s)
Virology/methods , Viruses/isolation & purification , Biometry , Quality ControlABSTRACT
Placental transfer of maternal IgG is known to be an active process resulting in a concentration on the fetal side of the circulation--at the apparent expense of that in the mother--at full term. However, when this apparent decrease in maternal IgG is related to the actual hemodilution occurring in parallel, the total inventory of the mother's IgG appears to be constant throughout pregnancy. Therefore, conclusions regarding the variations in IgG concentrations cannot be drawn without simultaneous information about plasma volume fluctuations.
Subject(s)
Immunity, Maternally-Acquired , Female , Humans , Immunoglobulin G/metabolism , Plasma Volume , Pregnancy , Time FactorsABSTRACT
A simple and accurate plaque assay is described for potency testing of attenuated varicella vaccine. Assays were performed on the African green monkey kidney continuous cell line CV-1, in multidish-plates, under a semi-solid carboxymethylcellulose overlay. The test is economical and yields accurate individual titre estimates, the reliability of which may be assessed by parallel titration of reference preparations.
Subject(s)
Herpesvirus 3, Human/immunology , Viral Vaccines/standards , Animals , Cell Line , Chickenpox Vaccine , Herpesvirus 3, Human/growth & development , Regression Analysis , Viral Plaque Assay/methodsABSTRACT
For routine control purposes, a statistical analysis was performed on the results obtained in titrations of varicella vaccine using a cytopathic effect microassay in a continuous line of monkey kidney cells. Although the results were lower than those obtained by conventional plaque assay, the end-point titres were quite reliable. The within-test variation was very small compared with test-to-test differences and the reference and vaccine titres were highly correlated. Expression of titre in relation to the reference is of value in this microsystem. The microassay has the advantage of economy and less labour. Staining of the microplates ensured convenience and reliability of reading comparable with that of plaque counting.
Subject(s)
Chickenpox/prevention & control , Cytotoxicity Tests, Immunologic/methods , Kidney/immunology , Vaccines/standards , Animals , Chickenpox/immunology , Chlorocebus aethiops , Kidney/cytology , Vaccines/toxicityABSTRACT
The W.H.O.'s titration method for attenuated poliovaccines, using two-fold dilution steps, was assayed concurrently with an alternative method, using four-fold dilution steps. For the two-fold dilution method, the dispersion of the observed proportions of response was very wide, inducing biased estimations for titers and their standard-error by means of simple usual calculation procedures. On the other hand, the use of the four-fold dilution method constantly provides more accurate estimates for the titers and their confidence limits and thus increases the reliability of the titration results. In addition, replicate poliovirus titrations were performed in three cell lines (HEp-2, LLC-MK2 and Vero), applying a restricted experimental design, in order to characterize statistically their sensitivity for poliovaccine titrations, and their consistency for infectivity titers. Means of improving the reliability of live poliovaccine potency estimates are suggested.
Subject(s)
Biological Assay/methods , Poliovirus Vaccine, Inactivated/analysis , Analysis of Variance , Animals , Cell Line , Regression Analysis , Virus ReplicationABSTRACT
A method has been developed, based on the Newton-Raphson iterative procedure, for calculating the concentration of viral suspensions from the dose-response data yielded by the cytopathic effect assays. The computation method provides the maximum likelihood estimate with its 95% approximated confidence limits, and determines the value of chi 2 for testing the goodness of the fit. A program for a Hewlett-Packard 41C calculator is presented which is suitable to most experimental situations.
