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Biomedical subjects

D H Thornton

Publications and source records attributed to D H Thornton.

At least 37 records · Page 2Linked to original sources
PubMed1985

Increased virulence of an infectious bursal disease live virus vaccine after passage in chicks.

A live infectious bursal disease virus vaccine increased in virulence when passaged six times in susceptible birds, as judged by damage to the bursa of Fabricius. It is suggested that the increase in virulence of this vaccine was due to the selection of a virulent subpopulation which had been present in the vaccine since its original isolation from the field and which had not been eliminated during its attenuation by passage in cell culture. The vaccine was then plaque purified and a virus strain was selected which protected against challenge, did not damage the bursa and appeared not to passage in birds.

Animals↗
PubMed1985

Detection of antibodies against infectious bursal disease virus: a comparison of three serological methods.

Four different oil emulsion infectious bursal disease virus (IBDV) vaccines were inoculated into four-week-old specific pathogen-free chickens. At weekly intervals for five weeks, sera were obtained from the vaccinated birds and from uninoculated control birds and examined for antibodies against IBDV by enzyme-linked immunosorbent assay (ELISA), the quantitative agar gel precipitin (QAGP) test and the virus neutralisation (VN) test. There was a highly significant correlation between the mean responses to all tests; the highest correlation (0.818) was between VN and QAGP and the lowest (0.573) between QAGP and ELISA. Generally the ELISA detected positive sera earlier than the VN test which in turn was more sensitive than the QAGP test. The ELISA and QAGP test were less variable, more reproducible and easier to perform than the VN test.

Animals↗
PubMed1984

The use of reference preparations in virus content testing of vaccines.

A series of virus content tests on Newcastle disease, avian infectious bronchitis and Marek's disease vaccines was carried out over a period of several years on commercial products together with a standard preparation of each virus. Analysis of the results of Marek's disease vaccine titrations revealed a good correlation between plaque count and the ratio obtained for the standard vaccine tested in parallel. Expression in relation to a reference preparation is therefore of value to vaccine manufacturers and quality control authorities as a method of reducing variation among assays carried out on different occasions or by different laboratories. For infectious bronchitis vaccines, expression in relation to a standard was of less value and the method was of little help for evaluating Newcastle disease vaccines. However, in each case, the standard preparation was of value in judging the acceptability of assays.

Coronaviridae↗
PubMed1984

Detection of avian leukosis virus: comparison of five techniques.

Five techniques were compared for their ability to detect decreasing dilutions of RAV-I, an avian leukosis sarcoma virus, in serially passaged chick embryo fibroblast cell cultures. The indirect fluorescent antibody test, sandwich enzyme-linked immunosorbent assay (ELISA) and reverse transcriptase assay were equally sensitive in detecting the virus. The indirect immunoperoxidase and complement fixation avian leukosis tests were less sensitive. It is recommended that the sandwich ELISA be used for routine detection of the avian leukosis sarcoma virus group as possible vaccine contaminants because it is rapid and simple to perform and may be carried out on a large number of samples conveniently.

Animals↗
PubMed1984

The hazards of retroviruses associated with monoclonal antibody production.

The majority of mammalian cells contain in their chromosomes genetic information related to retroviruses. Mice, and in particular, the inbred strains used in laboratory studies, have a number of different types of these viruses and murine cell lines frequently express virus. Retrovirus production has been noted in a number of myeloma cell lines and in hybridomas prepared from them. Therefore crude monoclonal antibody preparations may contain large numbers of these viruses. Retroviruses have been shown to be capable of activating or of acquiring oncogenes from cells. They may also recombine with endogenous leucosis virus to produce a recombinant virus with pathogenic properties. Comparison of endogenous cell DNA and retrovirus sequences has shown that retroviruses are capable of crossing genus and even class barriers. Retroviruses that are harmless in one species may be pathogenic in another. Hence care is required in the manufacturing and quality control procedures applied to monoclonal antibodies, particularly with products intended for medical and veterinary use. Widespread inoculation of retroviruses into a range of animal species may result only in trauma for the occasional individual but it is not possible to preclude the formation of a new type of pathogenic agent that can spread throughout the population.

Animals↗
PubMed1983

Comparison of techniques for the detection of avian infectious bronchitis virus as a contaminant of vaccines.

Techniques for detecting various levels of both field and vaccine strains of infectious bronchitis virus in a deliberately contaminated Newcastle disease vaccine were compared using chick embryos, chick kidney cells, chick tracheal organ cultures and chickens with a view to determining the most appropriate method for screening vaccines for freedom from IBV contamination. Techniques examined included detection of abnormalities and deaths in embryos, cytopathic effect in chick kidney cells, ciliostasis in chick tracheal organ cultures and clinical signs and virus isolation in chickens as well as the fluorescent antibody test, negative contrast electron microscopy and serology where appropriate. Results showed that the techniques capable of detecting both strains of infectious bronchitis virus were, in order of sensitivity, the fluorescent antibody test on allantoic cells from infected embryos, ciliostasis and direct electron microscopy of allantoic fluid. One surprising feature was the poor results obtained using chickens. Some detection was achieved with tracheal virus isolation and tracheal organ cultures prepared from inoculated birds and to a lesser extent with histology and clinical signs, but no technique detected the field strain.

Animals↗
PubMed1983

Relative efficiency of techniques for detecting avian reticuloendotheliosis virus as a vaccine contaminant.

Three techniques were compared for sensitivity in detecting reticuloendotheliosis virus (REV) in a deliberately contaminated Marek's disease vaccine. The most sensitive and rapid test was the indirect fluorescent antibody test (FAT). The indirect immunoperoxidase test, although simple to perform and only marginally less sensitive than the FAT, was difficult to interpret at low levels of REV. Using immunoelectron microscopy, virions were seen only after three subcultures and then not to the same level as that detected by the FAT or immunoperoxidase test. Serum raised against the HPRS-1 strain of REV detected other strains of this virus in the FAT.

Animals↗
PubMed1983

Use of inactivated oil emulsion infectious bursal disease vaccines in breeder chickens to prevent immunosuppression in progeny chicks.

Two chicken flocks, vaccinated with different inactivated infectious bursal disease vaccines, and one unvaccinated flock provided chicks with high and low levels of and no maternally derived immunity. Following challenge at three ages with a subclinical strain of infectious bursal disease virus the chicks were assessed for bursal damage and suppression of the immune response to Newcastle disease virus. Both high and low levels of maternally derived antibody prevented immunosuppression but the lower level provided only partial protection against bursal damage.

Animals↗