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Biomedical subjects

M C Clarke

Publications and source records attributed to M C Clarke.

At least 19 recordsLinked to original sources
PubMed1992

Immunity to bovine virus diarrhoea virus in calves: the role of different T-cell subpopulations analysed by specific depletion in vivo with monoclonal antibodies.

Gnotobiotic calves were injected intravenously with murine monoclonal antibodies (mAb) directed against the BoCD4, BoCD8 or BoWC1 antigens that define the three major T-lymphocyte subpopulations in cattle. This produced a transient, specific depletion of each cell type in the circulation. Calves were then infected intranasally with a non-cytopathogenic biotype of bovine virus diarrhoea virus and the effect of the specific depletion with the mAb on viraemia and shedding of virus from the nasopharynx determined. Depletion of the cells expressing the BoCD4 antigen resulted in an extension of the duration of viraemia and an increase in the titre of virus in blood. No effect on nasopharyngeal shedding was noted. Depletion of either of the other two T-cell subsets that expressed the BoCD8 antigen or the BoWC1 antigen present on the gamma/delta T-cells had no demonstrable effect. These findings are interpreted as showing that the BoCD4+ cells play a pivotal role in controlling a primary infection with this virus but MHC class I restricted BoCD8+ T-cells are not a major effector mechanism. The BoCD4+ cells may be acting directly or be mediators of T-cell help.

Administration, Intranasal↗
PubMed1990

Bovine virus diarrhoea virus: speculation and observations on current concepts.

This final chapter highlights the advances and some of the unanswered questions concerning bovine virus diarrhoea virus (BVDV) presented in this Review by specialists from around the world. Persistently viraemic cattle play an essential role in the dissemination of BVDV but it is suggested that acute infections with the virus are also important. The role of latency is considered but, as yet, there is no evidence that it plays a part in pathogenesis. It is well established that BVDV, Border disease virus and hog cholera virus infect sheep and pigs. There is also some indication that pestiviruses may be involved in other infections of ruminants, such as syndrome X and hyena disease. They also infect other ruminants, such as deer, and human infections have been reported. It is now known that the pathogenesis of mucosal disease is due to the combined action of the two BVDV biotypes. However, the cause of death remains an enigma. It is suggested that, due to the importance of this syndrome, it may be an appropriate time to reconsider the use of "mucosal disease virus" to replace the ungainly name "BVDV".

Animals↗
PubMed1989

Protection against respiratory infection with bovine virus diarrhoea virus by passively acquired antibody.

Susceptibility to infection with bovine virus diarrhoea virus (BVDV) was compared for calves with varying amounts of specific antibody in their sera passively acquired from the ingestion of colostrum. Challenge consisted of intranasal exposure to a strain of BVDV isolated from an outbreak of respiratory disease. Resistance to infection, as judged by nasopharyngeal shedding of virus, was directly related to the titre of neutralizing antibodies in sera. Besides protecting against infection of the upper respiratory tract, passive antibody, which was mainly IgG1, also protected against viraemia and, to a lesser extent, leukopenia. In the presence of colostral antibody, neutralizing and IgG1 antibody responses were apparently inhibited, but a specific IgG2 response occurred.

Animals↗
PubMed1989

Experimental infection of cattle in early pregnancy with a cytopathic strain of bovine virus diarrhoea virus.

Nine pregnant heifers, in early gestation (63 to 107 days), were infected intranasally or in utero with cytopathic bovine virus diarrhoea virus (BVDV) and each dam seroconverted. All nine calves developed to full term; four were stillborn, of which one had seroconverted but virus was not recovered from their tissues. One of the five liveborn calves appeared to have seroconverted in utero to an adventitious BVDV infection in late pregnancy but the remaining four were not viraemic and showed a normal secondary antibody response to BVDV infection at about six months old. Thus, in contrast to results with noncytopathic virus there was no evidence that infection in utero with cytopathic virus could result in a persistent viraemia or immunotolerance. It is suggested that cells able to support a persistent viraemia with cytopathic virus may not be developed in the young fetus.

Animals↗
PubMed1987

Variation in the intracellular polypeptide profiles from different isolates of bovine virus diarrhoea virus.

Variation of the intracellular polypeptides induced in calf testis cells by 5 cloned isolates of bovine virus diarrhoea virus (BVDV) was examined. Three of the isolates were cytopathic (NADL, C 2415 and Pe 515 c) and two were non-cytopathic (C 1226 and Pe 515 nc) in these cells. The isolates Pe 515 c and Pe 515 nc were both isolated from an animal with clinical signs of mucosal disease. In cells infected with NADL, 8 virus specific proteins (vp 1 to vp 8) with molecular weights ranging from 120,000 (vp 1) to 23,000 (vp 8) were detected. Isolates C 2415 and Pe 515 c gave a similar array of polypeptides to NADL, but the 3 cytopathic isolates could be distinguished by the variation in the molecular weights of some of the proteins. The non-cytopathic isolates could also be distinguished from each other by this type of molecular variation; however, one feature that characterised these strains, when compared to the cytopathic isolates, was the absence of vp 2. Comparison of the polypeptides induced by Pe 515 c and Pe 515 nc showed that apart from the lack of vp 2 in the Pe 515 nc virus profile, the molecular weights of the other viral proteins were similar. This supports serological evidence that for mucosal disease to occur the pair of cytopathic and non-cytopathic viruses must be closely related. Four of the polypeptides induced by Pe 515 c were shown to be glycoproteins.

Animals↗
PubMed1987

Comparison by the neutralisation assay of pairs of non-cytopathogenic and cytopathogenic strains of bovine virus diarrhoea virus isolated from cases of mucosal disease.

Neutralising antibody to non-cytopathogenic and cytopathogenic strains of bovine virus diarrhoea virus (BVDV) was assayed in a microtitre test in which cultures of calf testis cells were stained by the immunoperoxidase method to detect viral replication. Fourteen BVDV strains were compared in cross neutralisation tests with antisera prepared in gnotobiotic calves. Ten of the strains comprised five pairs of non-cytopathogenic and cytopathogenic BVDV. Each pair was isolated from an animal with mucosal disease. All five animals were from five separate outbreaks of the disease. Each pair of strains from the same outbreak was found to be antigenically indistinguishable. In contrast, when the coefficient of antigenic similarity was calculated 11 of 45 comparisons between the pairs and 46 of 91 comparisons between all 14 viruses gave R values that distinguished strains. The observations suggest that an antigenic spectrum within a single related group exists for BVDV strains, rather than distinct serotypes. The findings are also consistent with the suggestion that cytopathogenic strains from natural outbreaks of mucosal disease arise by mutation from non-cytopathogenic virus.

Animals↗
PubMed1987

Pathogenesis and epidemiology of bovine virus diarrhoea virus infection of cattle.

An outline of the clinical diseases that arise following BVDV infection is given. Isolates of BVDV can be separated into two forms non-cytopathic and cytopathic depending on their effect on cell cultures. In utero infection of the foetus with non-cytopathic virus may result in a number of syndromes, such as abortions, stillbirths or weak calves. It may also result in the birth of calves with a persistent viraemia and these animals may later develop mucosal disease as a result of superinfection with a "homologous" cytopathic strain of BVDV. Acute infection of seronegative animals in usually mild and subclinical. A chronic disease also occurs and this can be protracted with progressive wastage and diarrhoea. This condition has not yet been well defined but it is suggested that it may be the result of superinfection of a viraemic animal with a "heterologous" cytopathic strain of virus. The maintenance of non-cytopathic virus within the cattle population can be either by the slow spread following acute infections of seronegative animals or, more importantly, by spread from persistently viraemic cattle. The cytopathic virus is usually found in association with cases of mucosal disease and may be maintained in the population only by continually arising, possibly by mutation, from the non-cytopathic virus. It is recommended that persistently viraemic animals are eliminated from the herd to avoid in utero infections and the possibility of subsequent mucosal disease.

Animals↗
PubMed1986

A comparison of three anti-double stranded DNA antibody assays on sera from SLE and other diseases.

Systemic lupus erythematosus (SLE) is a multisystem disorder accompanied by a diverse spectrum of serum autoantibodies. Antibodies to double stranded DNA (dsDNA) are considered to be the most specific marker for this disease. In this study the results obtained from three different assays for dsDNA are compared: an indirect fluorescence antibody assay (IFA), a radioimmunoassay (RIA) and, an enzyme-linked immunosorbent assay (ELISA), on 57 SLE sera and 28 Sera from other disorders. Correlation of these anti-DNA results are made with C3, C4, and antinuclear antibody (ANA) titers. Our results show the IFA assay is the most sensitive and the least specific of the three tests. The RIA was found to be the most specific and was approximately as sensitive as the ELISA. We also found significant inverse correlations between anti-dsDNA levels and circulating complement levels among SLE sera for all three assays. ANA titers were significantly correlated with all anti-dsDNA assays as well. However, these anti-dsDNA assays show only modest differences explainable by numerous mechanisms. Hence, a clearly superior anti-dsDNA method does not emerge from our study.

Antibodies, Antinuclear↗
PubMed1985

An enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies to bovine viral diarrhoea virus (BVDV) in cattle sera.

A microtitre ELISA has been established for the quantitation of antibodies to bovine viral diarrhoea virus (BVDV). Single dilutions of sera were assayed and units of antibody were calculated from a standard curve. In order to detect the maximum number of responding animals both IgG1 and IgG2 antibody should be assayed, although detection of IgG1 alone was nearly as effective. The ELISA was as sensitive as the virus neutralization test for detection of antibody; comparison of an ELISA that detected IgG1 plus IgG2 antibody to BVDV with the virus neutralization test gave a correlation coefficient (r) of 0.89 (P less than 0.001 for 95 compared sera). Although similar amounts of IgG1 and IgG2 antibodies were present in sera from both experimentally- and naturally-infected cattle, antibody to BVDV in colostrum and in the sera from young calves was predominantly IgG1. The number of adult cows with antibody was 40 out of 41 while 36 of 44 calves reared in a beef unit were found to have produced antibody by the time they were 31.5 weeks old, an indication of the high prevalence of BVDV in the cattle population.

Animals↗
PubMed1978

The scrapie agent: evidence against its dependence for replication on intrinsic nucleic acid.

Exposure of the scrapie agent to u.v. light at various wavelengths has shown that light of 237 nm is 4 to 5 times as effective in inactivating it as 'germicidal' wavelengths (250 to 270 nm); whereas with systems that depend on RNA or DNA for function, inactivation is most effective by wavelengths in the germicidal range and there is a minimum of response in the wavelength region round 240 nm. The action spectrum for the scrapie agent is reminiscent of the absorption spectrum for purified bacterial endotoxin, identified as a lipopolysaccharide complex. Dilute aqueous suspensions of scrapie agent were exposed to ionizing radiations in the presence or absence of oxygen. In dilute suspensions of test systems depending on the integrity of nucleic acid or protein, oxygen is almost invariably protective, but it was extremely sensitizing for inactivation of the scrapie agent, to an extent approached only in the case of membranous systems like lysosomes. Results of these two methods argue against dependence of the scrapie agent on an intrinsic nucleic acid moiety for ability to replicate. They suggest that a lipid fraction is an important component and to that extent provide additional support for the 'membrane hypothesis'.

Animals↗
PubMed1976

The membrane location of scrapie infectivity.

Using 5'-nucleotidase and NADPH: cytochrome c reductase as respective enzyme markers for the plasma membrane and endoplasmic reticulum, a satisfactory separation of these two membrane fractions from a cell line (SMB) derived from a scrapie mouse brain has been achieved. The coincident distribution of scrapie infectivity and 5'-nucleotidase in various fractions isolated from these cells indicates that most of the scrapie infectivity present in this cell line is associated with the plasma membrane.

Animals↗
PubMed1976

The effect of homogenisation on the level of scrapie activity detected in cells from spleens of scrapie affected mice.

Suspensions of cells from the spleens of mice inoculated with scrapie agent were titrated for scrapie activity at two stages, before and after disruption to release activity. Similarity between the titres obtained from the two types of suspension provided evidence to support the suggestion that there is one unit of activity per affected cell and that multiplication of scrapie agent is associated with cell replication.

Animals↗