The international reference preparation of influenza virus haemagglutinin (type A)

This paper describes the international collaborative assay that led to the establishment in 1967 of the International Reference Preparation of Influenza Virus Haemagglutinin (Type A) and the studies completed during the following years on the use of the preparation for evaluating the haemagglutinin content of 46 influenza virus vaccines in terms of international units. The WHO Expert Committee on Biological Standardization (1967) defined the International Unit as 0,09361 mg of the International Reference Preparation.Altogether 14 laboratories in 12 countries took part in one or both studies, using a total of 24 methods (HA titrations and, in a few cases CCA titrations). Major differences in the HA titres were found between laboratories, while the potencies (the haemagglutinin content values) relative to the International Reference Preparation were free from most of these differences. Haemagglutination titres varied over a range factor up to 50, while the corresponding relative "potencies" varied with a factor of only 2. The CCA method used in a few laboratories gave results close to the lowest haemagglutination titres and showed relatively small variations between laboratories. The analyses of variance disclosed differences in the variation within laboratories, but for the majority of the laboratories the variation allowed an overall estimate of a standard error.The calculation of haemagglutinin content (in IU) from relative potencies is described. Advice is given on the selection, preparation, and titration of a local reference vaccine with a view to expressing its haemagglutinin content in international units.The test results with 46 local vaccines are also given. The deviations of the relative potencies from the average per vaccine showed a distribution with eight major discrepancies instead of the expected one. The background for these cases is discussed.

International reference preparation of rheumatoid arthritis serum

The National Institute for Medical Research, London, England, was requested by the WHO Expert Committee on Biological Standardization to arrange a collaborative study of the serum pool they had obtained, to determine its suitability to serve as an international reference preparation of rheumatoid arthritis serum. A batch of this serum was assayed by 11 laboratories in 7 countries against 30 test preparations. On the basis of the results obtained, the serum has been established as the International Reference Preparation of Rheumatoid Arthritis Serum and the International Unit of Rheumatoid Arthritis Serum has been defined as the activity contained in 0.171 mg of the international reference preparation.A description is also given of the British reference preparation of rabbit antibody to sheep red blood cells (amboceptor) and this material was also tested in the collaborative study.

BCG-induced allergy and immunity in guinea-pigs during the first year after vaccination

It has been traditional practice in many countries to let revaccination with BCG depend on the outcome of periodically repeated tuberculin testing. Acquired resistance to tuberculosis and tuberculin skin sensitivity are concomitant results of BCG vaccination, and it is apparently inferred that a waning resistance will be faithfully reflected in a waning tuberculin sensitivity. However, it has been demonstrated in recent years, both in man and in animals, that the waning of tuberculin sensitivity may be prevented merely by a repetition of the tuberculin test, while data presented in this and a following report indicate that tuberculin testing has no such influence on the course of BCG-induced resistance to tuberculosis.

International collaborative assay of the international reference preparation of anti-yellow-fever serum

A yellow fever immune serum was established in 1962 by the WHO Expert Committee on Biological Standardization as the International Reference Preparation of Anti-Yellow-Fever Serum, intended to serve as an immune reference serum in the mouse protection test used in the control of yellow fever vaccines.Before its establishment as the International Reference Preparation, the proposed material was assayed in eleven laboratories in ten countries against a number of other immune and non-immune sera, and was found stable. Neutralization test results were consistent and the relative potency was sufficiently high. This paper not only reports on the collaborative assay, but also discusses errors in the testing method and problems connected with the distribution of mouse deaths during the observation period and with the preparation of dilutions.

International Standard for Antistreptolysin-O

A pool of highly potent freeze-dried sera from three patients with streptococcal infection has been examined by twelve laboratories in eleven countries and has now been established as the International Standard for Antistreptolysin-O by the WHO Expert Committee on Biological Standardization. The main part of this collaborative study consisted in a comparison of the proposed international standard serum with other standard preparations. Samples of serum from eight different patients were titrated by the different laboratories. The laboratories each carried out two series of tests, one using their own streptolysin-O preparations and the other using a particular streptolysin-O preparation supplied to all the participants. There was fairly good agreement between the results from the majority of the laboratories, particularly in the tests with the same preparation of streptolysin-O. Some of the variations could be traced to the use of unsuitable streptolysin reagents. On the basis of the results, the International Unit of Antistreptolysin-O has been defined as the activity contained in 0.0213 mg of the International Standard.

The International Standard for Human Syphilitic Serum

Following the establishment by WHO of International Reference Preparations of Cardiolipin and Egg Lecithin to facilitate reproduction of cardiolipin antigens for use in serological tests for syphilis, a series of studies has been carried out between co-operating laboratories in several parts of the world, aiming at the establishment of an international standard preparation for freeze-dried human syphilitic serum.The WHO Expert Committee on Biological Standardization, in 1957, established the new International Standard for Human Syphilitic Serum which is now available to national laboratories from the International Laboratory for Biological Standards, Statens Serum-institut, Copenhagen. The International Unit of Human Syphilitic Serum is equivalent to 3.617 mg of the freeze-dried International Standard. A solution containing 8 International Units per ml can be obtained by reconstituting the contents of one ampoule of the International Standard in 6.1 ml of 0.6% saline.The new Standard will allow major serological laboratories to calibrate their national reference sera in terms of the International Unit; the comparability of results from different areas will be improved by this procedure.Technical details are given on the investigations preceding the establishment of the Standard. The analysis of the collaborative assay between co-operating laboratories also includes data on titres, reactivity, turbidity and other technical aspects.