Search PubMed⌕ Search

Biomedical subjects

J Brownlie

Publications and source records attributed to J Brownlie.

At least 37 records · Page 2Linked to original sources
PubMed1997

Identification of two distinct populations of dendritic cells in afferent lymph that vary in their ability to stimulate T cells.

Immunofluorescent staining and flow cytometric analysis of dendritic cells from cattle afferent lymph has established that within the afferent lymph veiled cells (ALVC) there are two phenotypically distinct, major populations. One is CD11a+, CD5+, CD21- and expresses the bovine WC10 (workshop cluster 10) molecule and the Ag recognized by mAb CC81 but is not recognized by mAbs CC149 and IL-A24. The second ALVC subpopulation is CD11a-, CD5-, CD21+/-, workshop cluster 10- and is not recognized by mAb CC81 but is recognized by mAb CC149. Thus, the two populations, which can be identified by staining for CD11a, are defined by the differential expression of a number of Ag. The ALVC populations had differing capacities to stimulate T cells. CD11a- ALVC were more effective at stimulating proliferative responses in allogeneic CD4+ T cells and CD8+ T cells. This was not related to binding of CTLA4Ig or CD40L fusion proteins, implying similar levels of expression of their ligands, CD80 and CD86 or CD40. Both subsets were able to present OVA to resting memory CD4+ T cells, indicating that both were able to take up and process soluble native protein. In contrast, the CD11a- ALVC were more effective in presenting respiratory syncytial virus Ag to resting CD4+ T cells. Considering the central role of dendritic cells in the initiation of immune responses in naive animals, the two cell types may have different roles in the induction of primary responses induced following infection or immunization.

Animals↗
PubMed1997

The use of a mass-action model to validate the output from a stochastic simulation model of bovine viral diarrhoea virus spread in a closed dairy herd.

The spread of bovine virus diarrhoea virus (BVDV) in a closed dairy herd maintained under typical management conditions is studied using two approaches. In the first instance a stochastic computer model is used to simulate the month-to-month changes in the infection status of each animal. These results are contrasted with the results of a mass-action model which uses three differential equations. A comparison of the two approaches indicates that the results are in broad agreement. The stochastic approach has the benefit of providing an estimate of the probability of the infection becoming extinct and the herd becoming BVDV-free for different herd sizes.

Animals↗
PubMed1997

A computer simulation of the transmission dynamics and the effects of duration of immunity and survival of persistently infected animals on the spread of bovine viral diarrhoea virus in dairy cattle.

This paper describes a computer model that mimics the spread of bovine viral diarrhoea virus (BVDV) infection through a closed herd. The model is able to simulate the spread of infection when a persistently infected (PI) animal is introduced into an infection-free herd, and it is used to investigate the role of persistently infected animals, seroconverting animals, loss of PI calves and duration of immunity on the level of infection within the herd. Under typical management conditions one persistently infected animal poses a real threat to a herd, and the prospect of the herd becoming infection free in a 10-year period without intervention is remote. Seroconverting animals are found to be an important source of infection in herds with few immune animals. The increased loss of PI calves is likely to restrict the numbers of PI animals in a herd, and loss of immunity is important since it increases the possibility of a PI calf being born.

Animals↗
PubMed1996

Afferent lymph veiled cells stimulate proliferative responses in allogeneic CD4+ and CD8+ T cells but not gamma delta TCR+ T cells.

Dendritic cells were identified in afferent lymph derived by lymphatic cannulation of cattle, stained with monoclonal antibody (mAb) to the bovine workshop cluster 6 (WC6) antigen, which is highly expressed on bovine afferent lymph veiled cells, and sorted with a fluorescence-activated cell sorter. These cells expressed major histocompatibility complex (MHC) class I and II and CD1b but not CD14. They bound human and murine CTLA4-immunoglobulin (CTLA4-Ig) fusion proteins indicating expression of CD80 and or CD86. Dendritic cells induced proliferative responses in allogeneic CD4+ and CD8+ cells sorted from blood but did not induce responses in purified allogeneic WC1+, gamma/delta T cells, which are CD2-, CD4-, CD8- and are the major gamma delta T-cell population in cattle blood, even when interleukin-2 (IL-2) was added to cultures. A WC1-, CD2+ gamma delta T-cell receptor (TCR)+ population predominates in cattle spleens and proliferation of a T-cell line with this phenotype was not induced by allogeneic dendritic cells, with or without added IL-2. The observations imply that the ligand for the gamma delta TCR expressed on the two populations is not present on allogeneic dendritic cells or that the costimulatory molecules expressed on dendritic cells that render them highly effective at stimulating MHC class I- and class II-restricted CD8+ and CD4+ T cells are not recognized by the WC1+ or WC1- gamma/delta T cells. Expression of CD28 by the four cell types was assessed by reverse transcriptase-polymerase chain reaction (RT-PCR). Purified CD4+ and CD8+ cells both produced CD28 transcripts but neither purified WC1+ cells nor the WC1- gamma delta TCR+ cell line did so. The findings indicate that CD80 and or CD86 are involved in the stimulation of CD4+ and CD8+ alpha beta TCR+ T cells but not in the stimulation of either of the two gamma delta TCR+ populations.

Animals↗
PubMed1996

Bovine immunodeficiency virus: facts and questions.

Bovine immunodeficiency virus (BIV) is a lentivirus whose serologic prevalence is worldwide. Little is known about its impact on animal health status, pathogenesis and mode of transmission. Understanding BIV biology implies isolation of new viral strains and long-term studies on experimentally-infected cows and surrogate hosts such as rabbits.

Animals↗
PubMed1995

Protection of the bovine fetus from bovine viral diarrhoea virus by means of a new inactivated vaccine.

A model is described for the validation of vaccines designed to protect the bovine fetus from bovine viral diarrhoea virus (BVDV). The fetopathic nature of the challenge strain of virus was confirmed and the method used to test a commercial vaccine (Bovidec) developed from a Compton prototype. Heifers were vaccinated two or three times about the time of impregnation and challenged when they were between 25 and 80 days of gestation. There was no evidence of a viraemia in the heifers after the challenge, or of infection with BVDV of 13 liveborn calves or two aborted fetuses.

Abortion, Veterinary↗
PubMed1995

A rapid method for mRNA detection in single-cell biopsies from preimplantation-stage bovine embryos.

Major questions concerning the control of development and gene expression at the cellular level are still unanswered. Nowhere is this more evident than during the earliest stages of development and embryogenesis. This study describes the detection of specific gene transcripts in single cells derived from bovine embryos. Following in vitro fertilization (IVF) and in vitro culture (IVC) of bovine embryos, small groups of cells and even single blastomeres from 32 to 64-cell embryos were micromanipulated into individual tubes for analysis of cytoplasmic RNAs. Reverse transcriptase-PCR was applied to cell lysates for the amplification of beta-actin mRNA transcripts. Primers were designed to flank an intron expected to be present within genomic DNA sequences, thus allowing for simple differentiation between DNA- and RNA-derived amplification products. Using a 50-cycle amplification profile, a 260 bp band could be seen as a PCR product derived from a single blastomere following electrophoresis in an ethidium bromide-stained agarose gel. The identity of the band was verified by DNA sequence determination and diagnostic restriction digestion. Lysates derived from single blastomeres in this way have been used for simultaneously phenotyping multiple RNA products. This capability allows the spatial analysis of gene expression and development within embryos from the earliest stages of cellular differentiation.

Journal Article↗
PubMed1995

Detection of bovine viral diarrhoea virus antigen and RNA in oviduct and granulosa cells of persistently infected cattle.

Large-scale in vitro bovine embryo production systems commonly use genital tracts obtained from an abattoir as a source of both cumulus-oocyte complexes and co-culture feeder cells. Tissues derived from this source may be contaminated with non-cytopathogenic bovine viral diarrhoea virus (BVDV) since, in several countries surveyed, approximately 1% of animals tested are persistently infected with this pathogen. Therefore, the use of such material in in vitro fertilization systems presents a potential risk for the transmission of BVDV to bovine embryos and via embryo transfer. This potential was investigated by obtaining oviduct epithelial cells and granulosa cells, which are commonly used as feeder cells, from cattle persistently infected with BVDV and examining them for the presence of BVD viral antigen (p80 non-structural protein and gp53 envelope glycoprotein) by indirect immunofluorescent histochemistry, and also viral RNA (encoding the p80 region) by in situ hybridization. In addition, titres of virus present in oviduct, ovary and blood were assayed by immunodetection on calf testis cell cultures. Luminal epithelial cells from the oviduct and primary cultures of granulosa cells and oviduct epithelial cells from such cattle were shown to contain both viral antigen and RNA. The susceptibility of both cell types to BVDV infection was further established by inoculating primary cell cultures of cells derived from cattle not infected with BVDV with a cloned isolate of non-cytopathogenic BVDV (Pe515). RNA encoding BVDV and the antigen were detected 12 h after inoculation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Systemic vaccination with inactivated bovine virus diarrhoea virus protects against respiratory challenge.

Inactivated bovine virus diarrhoea virus, strain 11249nc, inoculated subcutaneously three times with Quil-A into calves protected against intranasal challenge with the same strain. Virus was isolated from nasopharyngeal swabs taken 4 to 8 days post challenge and blood taken 4 to 6 days post challenge from control calves but not from vaccinated calves. A second strain of virus, Ky1203nc, was selected on the basis of previously established data on its antigenicity and the amount of viral antigen produced by five cell cultures compared using an ELISA. Cultures of one cell line, MDBK, yielded a greater amount of viral antigen than the others. Strain Ky1203nc grown in MDBK cells was inactivated with beta-propiolactone, mixed with adjuvant and used as a vaccine inoculated into calves subcutaneously three times. All of 5 calves were protected against intranasal challenge with a heterologous strain. In contrast virus was isolated from nasopharyngeal swabs taken from 5 control calves and from the blood of 4 controls. All 5 control calves, but none of the vaccinates, had a leukopenia after challenge. We conclude that the selected strain and system of vaccine preparation provide an effective means of protecting calves against respiratory infection and that live vaccines are not required to protect against challenge via the respiratory tract.

Administration, Intranasal↗
PubMed1994

Detection of bovine viral diarrhoea virus p80 protein in subpopulations of bovine leukocytes.

Flow cytometry and two-colour immunofluorescence were used to detect cytoplasmic bovine viral diarrhoea virus (BVDV) antigen in leukocytes from viraemic cattle. Monoclonal antibody to the p80 protein of BVDV, a non-structural viral antigen, was used to identify the subpopulations of leukocytes in which viral protein synthesis had occurred. Viral antigen was detected in 23% of peripheral blood mononuclear cells. Monocytes were found to have the highest frequency of infection (35%). A higher proportion of CD2+ T cells (23%) were infected, compared with B cells (11%) or WC1+ gamma delta T cells (11%). No significant differences in percentages of different leukocyte subpopulations in blood were detected in persistently viraemic animals compared with controls.

Animals↗
PubMed1994

Detection of bovine virus diarrhoea virus RNA by in situ hybridisation with digoxigenin-labelled riboprobes.

A non-isotopic in situ hybridisation (ISH) method has been developed for the detection of bovine virus diarrhoea virus (BVDV) RNA. The technique is highly specific and allows the detection of BVDV in formalin-fixed paraffin-wax-embedded sections. Digoxigenin-labelled riboprobes were generated to the coding region for the p125 non-structural protein and consequently it was possible to locate the virus positive-sense RNA in BVDV-infected tissues. Formalin-fixed tissues are ideal for ISH, combining the possibility of a retrospective analysis of tissues for virus distribution with excellent morphological preservation. In situ hybridisation has facilitated a precise examination, at the cellular level, of viral nucleic acid distribution during pestiviral infections, with an increased sensitivity and wider applicability than immunocytochemistry.

Animals↗
PubMed1993

Characteristics of a retrovirus associated with Jembrana disease in Bali cattle.

A virus causing Jembrana disease in Bali cattle (Bos javanicus) was demonstrated to have characteristics of a retrovirus. Reverse transcriptase activity was detected in virus purified by sucrose gradient centrifugation. Electron microscopic examination of tissue from the affected cattle indicated that the virus matured by C-type budding through the plasma membrane and into intracytoplasmic vacuoles of cells in lymphoid tissue, with the formation of circular enveloped virus particles ranging in diameter from 96 to 124 nm with an eccentric nucleoid. Western immunoblotting using sera from recovered animals demonstrated virus proteins of M(r) 100K, 45K, 42K, 33K, 26K, 16K and 14K. The 26K protein of Jembrana disease virus cross-reacted in Western blots with the 26K capsid protein of bovine immunodeficiency virus (BIV). The apparent morphogenesis, protein structure and antigenic relationship with BIV suggested the virus was a lentivirus.

Animals↗
PubMed1993

Experimental and spontaneous mucosal disease of cattle: a validation of Koch's postulates in the definition of pathogenesis.

The complex etiology of mucosal disease of cattle has been unravelled by experimental reproduction of the fatal syndrome, thereby validating Koch's postulates. The causal virus, bovine virus diarrhea virus (BVDV), has two biotypes, noncytopathogenic and cytopathogenic; the former can infect the early bovine fetus, induce immunotolerance and a lifelong persistent viremia (pv), whereas the latter biotype can superinfect the pv cattle and induce mucosal disease. The cytopathogenic biotype appears able to originate de novo from the persisting virus by molecular rearrangement (e.g. template switching) and has been shown to arise in a case of spontaneous mucosal disease. The animal had been maintained in isolation for an extended period.

Animals↗