The serological response of calves to Leptospira interrogans serovar hardjo vaccines and infection as measured by the microscopic agglutination test and anti-IgM and anti-IgG enzyme-linked immunosorbent assay.

The microscopic agglutination test (MAT) and the anti-IgM and anti-IgG enzyme-linked immunosorbent assays (ELISA) were used to examine sera taken over the course of 16 weeks from 35 calves vaccinated and/or infected with Leptospira interrogans serovar hardjo. The relationship between the IgM and IgG responses to vaccination and infection were determined. The rapid and high rise in IgM levels following challenge made the anti-IgM ELISA a potentially good indicator of recently established infection although some transitory high levels were seen where infection did not become established. The slow IgG response to infection made the anti-IgG ELISA of limited diagnostic use.

Inactivated canine parvovirus vaccines: an alternative method for assessment of potency.

Groups of three-week-old chickens were given graded doses of inactivated canine parvovirus vaccines. Blood samples were taken three weeks later and the sera examined by ELISA for antibodies to canine parvovirus. Reproducible, linear, log-dose serological responses were observed, enabling the potency of the vaccines to be compared. The simultaneous administration of other components of canine multivalent vaccines appeared to reduce the response to the parvovirus component. When its results have been correlated with the degree of protection in dogs this test could be used to assess the potency of inactivated canine parvovirus vaccines.

Canine parvovirus serology: a collaborative assay.

Fifteen laboratories were supplied with coded samples of canine sera for testing for the presence of antibodies against canine parvoviruses. One of these sera had been designated as a potential British standard canine parvovirus antiserum. Most of these laboratories were either providing a canine parvovirus serology service, or represented pharmaceutical companies which manufacture canine parvovirus vaccines for the United Kingdom market. No attempt was made to influence the test methods used. Thirteen of the laboratories used a haemagglutination inhibition test, three an enzyme-linked immunosorbent assay (ELISA), and two performed serum neutralisation tests. Three laboratories used two different techniques. Adequate analysis was possible only with the results of the haemagglutination inhibition tests. The variability of the results between laboratories could be partly controlled by the use of the standard serum. Much of the residual variability was associated with particular laboratories. The results from the vaccine manufacturers tended to be less variable than those from the diagnostic laboratories.

Efficacy of porcine parvovirus vaccines.

Three inactivated porcine parvovirus vaccines were tested for efficacy in 66 susceptible gilts. The gilts were challenged with virulent virus on the 40th day of gestation. All the vaccines provided excellent protection against fetal mortality despite insignificant serological responses to one of them. Good protection was obtained with two of the vaccines even when the dose was substantially reduced. Unvaccinated controls had very few viable fetuses.

Control of manufacture--principles and purposes.

The control of manufacture is centred on the assessment of the operation based on information supplied by the manufacturer and on detailed physical inspection. The purpose of controlling manufacture is to ensure, as far as practicable, that products are manufactured within premises, and by processes and personnel, of such standard that the quality of the final product is assured. The required standards are written in the "Guide to Good Manufacturing Practice for Medicinal Products", and its several supplementary guidelines, so in practical terms the purpose of inspection is to assess compliance with these guidelines. It is usual, however, for manufacturers' premises and practices not to comply with the guidelines in all respects. There is therefore a need to make judgements on the significance of, and risks associated with, these discrepancies. It is necessary to consider potential problems in the context of the overall manufacturing process, bearing in mind the nature of the products involved. A decision as to what remedial actions are required, and over what time-scale, is then made.

Serology-based potency test for inactivated Newcastle disease vaccines.

Twenty-seven inactivated oil-emulsion Newcastle disease vaccines were tested for potency in chickens. Serum samples from groups given 1/50 dose of vaccine were examined by the haemagglutination inhibition (HI) test and the indirect enzyme-linked immunosorbent assay (ELISA). Good correlations were observed between potency and HI titres and between potency and ELISA absorbance. It is recommended that a serology-based potency test replaces the challenge test, reserving challenge only for those batches of vaccines where a clear pass is not indicated.