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Biomedical subjects

D H Thornton

Publications and source records attributed to D H Thornton.

At least 19 recordsLinked to original sources
PubMed1991

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.

Agglutination Tests↗
PubMed1989

An international collaborative study of an anti-infectious bursal disease virus reference serum.

Fourteen laboratories participated in a collaborative study of a freeze-dried preparation of anti-infectious bursal disease virus serum to assess the suitability of the serum as a standard for use in the infectious bursal disease virus neutralization test. Ten laboratories carried out micro-virus neutralization tests and six carried out plaque reduction tests, two laboratories carrying out both tests. When titres were expressed as a proportion of that obtained for a reference preparation there was a marked reduction in variation between results from different laboratories. The use of a reference preparation was therefore of value when comparing results from different laboratories. It is proposed that the reference preparation used in this study be used as a standard to facilitate the comparison of results from different laboratories. The proposed standard contains by definition 10,000 UK units.

Animals↗
PubMed1987

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.

Animals↗
PubMed1987

Sterility testing of immunological products: comparative efficacy of media and effect of preservatives.

A comparison was made of the abilities of various culture media to support the growth of a range of micro-organisms commonly recommended as control strains in tests for the sterility of immunological products. The effects of phenol, cresol, formaldehyde and thiomersal on the growth of these organisms were studied. Attention is drawn to some limitations of the current pharmacopoeial test methods.

Bacteria↗
PubMed1986

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.

Animals↗
PubMed1986

Observations on the ability of avian reovirus vaccination of hens to protect their progeny against the effects of challenge with homologous and heterologous strains.

Avian reovirus vaccines of the S1133 strain, used indirectly in the dams of challenged chicks, were found to confer protection against clinical signs and/or deaths resulting from the use of both homologous and heterologous challenge strains. There was some protection against every strain used, although this did vary in degree. It was difficult to relate this variation in protection to the differences in in vitro neutralization of the strains by S1133 antiserum, though there were some similarities.

Animals↗
PubMed1986

The development of a potency test for Leptospira hardjo vaccines: a comparison of protection in calves and serology in guinea-pigs.

The protective properties of two commercial Leptospira hardjo vaccines in calves were compared with the serological responses induced in guinea-pigs with a view to establishing a potency test based on serology. Groups of calves were given graded doses of the two vaccines and after eight weeks were challenged with virulent L. hardjo. Infection was monitored by microscopy and culture of urine and, eight weeks after challenge, by culture of the kidneys post mortem. Groups of guinea-pigs also were tested by the microscopic agglutination test (MAT). A clear dose response was observed and the response was related to the degree of protection achieved in the calves. The MAT titre in guinea-pigs indicative of an effective vaccine was calculated for the minimum dose of each vaccine that gave full protection in calves. A close correlation was observed. Two further batches of each vaccine were tested in guinea-pigs on two occasions with reproducible results. A potency test based on the MAT response of guinea-pigs is proposed.

Agglutination Tests↗
PubMed1986

A survey of mycoplasma detection in veterinary vaccines.

Nine live virus veterinary vaccines from six sources were found to be contaminated with mycoplasma. The vaccines were for use in canine, feline and avian species, and 53 batches of the products were at fault. The isolates were identified as Mycoplasma hominis, M. arginini, M. orale, M. hyorhinis and M. gallinarum. Investigation of the contamination rate of other batches or other products from the same source in some cases helped to determine the source of infection. Mycoplasma contaminants can be considered important not only because of their role as pathogens but also because they may indicate that insufficient care has been taken during vaccine manufacture or quality control.

Animals↗
PubMed1986

Detection of avian encephalomyelitis virus.

Methods for the detection of two strains of avian encephalomyelitis virus (AEV) in chick embryo brain cell cultures and chickens were compared. It was found that the agar gel precipitin test (AGPT) and the enzyme-linked immunosorbent assay (ELISA) carried out on the serum of inoculated chickens were more sensitive than either the indirect fluorescent antibody test in cell cultures or the detection of clinical signs in chicks. On the basis of results obtained in this experiment the effects were then determined of routes and time of inoculation of chickens on the detection of AEV. It was found that birds infected at two weeks old produced higher antibody titres than one-day-old birds and the AGPT and ELISA detected comparable levels of antibody in them. It was recommended that the tests to detect the presence of AEV as a contaminant of vaccines be replaced by a serological test carried out on chicks inoculated intramuscularly at two weeks old.

Animals↗
PubMed1986

Development of in vitro tests for detection of extraneous agents.

The use of animals in tests to detect extraneous agents is not only undesirable from the ethical viewpoint but also because of the expense and length of time involved in such tests. We have carried out tests on a variety of potential contaminating avian pathogens to determine whether tests in chicks offer any advantage over tests in embryos or cell cultures. In many cases, but not all, in vitro tests were shown to be more sensitive. The use fluorescent antibody or enzyme-linked assays serves to enhance the sensitivity of the tests. In the future it may be possible to adapt techniques such as nucleic acid hybridisation to the detection of extraneous agents.

Animal Testing Alternatives↗
PubMed1986

A comparison of titration methods for live avian encephalomyelitis virus vaccines.

Factors associated with the indirect fluorescent antibody test used for the titration of avian encephalomyelitis virus (AEV) in chick embryo brain cell cultures were examined for their influence on virus replication. It was found that virus should be inoculated onto semi-confluent cell cultures and adsorbed for two hours at room temperature. The cells should then be examined for fluorescence after five days' incubation. Using these conditions, the cell culture assay was compared with the embryo and chick assays for its ability to estimate the virus content of live commercial AEV vaccines. In most cases titres obtained by the chick assay were slightly, but not significantly, higher than those obtained in the cell culture assay, although the reliability of the chick assay was, at times, questionable. In all cases titres obtained in the embryo assay were low. It is recommended that the cell culture assay be adopted as the method of choice for titrating AEV vaccines because it is rapid, reproducible, specific and greatly reduces the requirement for experimental animals.

Animals↗
PubMed1986

Improved potency test for live avian encephalomyelitis vaccines.

Potency tests were carried out on live avian encephalomyelitis virus (AEV) vaccines. Vaccines were titrated in chick embryo brain cell cultures using an indirect fluorescent antibody test just before vaccination. Groups of chickens were inoculated orally with graded doses of each vaccine. After three weeks serum was taken from the chickens and examined for antibodies to AEV by indirect enzyme-linked immunoassay (ELISA). The chickens were then challenged by intracerebral inoculation of virulent AEV and monitored for signs attributable to clinical AE. The results showed a relationship between virus content, protection and antibody development. It is recommended that serological evaluation using ELISA replace the challenge step in potency tests for live AEV vaccines.

Animals↗
PubMed1986

Application of polyacrylamide gel electrophoresis of genome fragments to control of reovirus products.

The reoviridae are notable for their genome consisting of 10 to 12 pieces of double-stranded RNA. The migration pattern of these pieces produced by polyacrylamide gel electrophoresis has been used by other workers as a means of identifying these viruses for epidemiology or classification. This paper reports attempts by the authors to apply this technique to various aspects of control of reovirus products, with a view to supplementing or replacing techniques involving animals. The findings are discussed in relation to those of other workers.

Electrophoresis, Polyacrylamide Gel↗