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C J Howard

Publications and source records attributed to C J Howard.

At least 19 recordsLinked to original sources
PubMed1998

Influence of IL-12 on interferon-gamma production by bovine leucocyte subsets in response to bovine respiratory syncytial virus.

The cytokine IL-12 is a key molecule in the regulation of CD4+ T cell development and specifically potentiates the development of T helper 1 responses in mouse and man. However the biological effects mediated by bovine IL-12 have not been defined in cattle. To produce the expression of the two mature proteins a polyprotein approach was used. This system is employed by positive strand viruses and encodes both products from a single open reading frame (ORF). The 2A region of foot-and-mouth disease virus (FMDV) encodes a site that appears to undergo auto-cleavage. Here the 2A was flanked by sequences encoding the p35 and p40 polypeptides of the heterodimeric cytokine to mediate their cleavage. Formation of the correct heterodimeric structure is an absolute requirement for IL-12 biologic activity. Using bovine respiratory syncytial virus (BRSV) and ovalbumin (OVA) we studied the effects of IL-12 on the responses of peripheral blood mononuclear cells (PBMC) to these antigens, in vitro. The presence of IL-12 markedly influenced the level of IFNg secreted by these cells, and although IL-12 induced IFNg production in the absence of antigenic stimulation, IFNg production was accelerated and augmented in response to IL-12 and antigen. Analysis of the T cell subsets by flow cytometry showed that CD4+ T cells comprised the largest contributors to IFNg production. The WC1 + gd T cells did not appear to contribute to the production of IFNg.

Animals↗
PubMed1998

Analysis of the phenotype and phagocytic activity of monocytes/macrophages from cattle infected with the bovine leukaemia virus.

The bovine leukaemia virus (BLV) is a retrovirus that infects mainly B lymphocytes of cattle, but proviral DNA can also be isolated from monocytes/macrophages. This study investigated the effect of BLV infection on surface antigens on freshly isolated peripheral blood monocytes and cultured monocyte-derived macrophages, with and without lipopolysaccharide (LPS) stimulation. The effect of BLV infection on phagocytic activity of CD14+ monocytes was also assessed. The percentage of monocytes expressing the surface antigens CD11b, CD32 (FcgammaRII), MHC class II and the surface antigen recognised by mAb DH59B were increased in BLV-positive cattle. In contrast, expression intensity of all markers was low in samples from BLV-positive cattle. CD14+ monocytes from BLV-positive cattle showed less Fcgamma-receptor-mediated phagocytosis compared to monocytes from BLV-negative cattle. After 7 days in culture, there was evidence for shedding/downregulation of surface antigens on monocyte-derived macrophages, in particular on cells from BLV-positive cattle. LPS stimulation decreased the percentage of cells expressing the measured markers in monocyte-derived macrophages taken from BLV-negative cattle, but not in cultures derived from BLV-positive cattle. The results provide further evidence for an altered function of monocytes and macrophages in BLV-infected cattle.

Animals↗
PubMed1998

Cloning of two members of the SIRP alpha family of protein tyrosine phosphatase binding proteins in cattle that are expressed on monocytes and a subpopulation of dendritic cells and which mediate binding to CD4 T cells.

Recent experimental studies have greatly clarified the function of cell surface molecules in the induction and modulation of T cell responses by antigen-presenting cells (APC). However, the differences in ability to stimulate T cells evident for different types and subpopulations of the same APC, such as dendritic cell subsets, is less well understood. This report details an investigation of an antigen expressed on monocytes that is also expressed on a subset of cattle afferent lymph veiled cells (ALVC). A cDNA library derived from cattle monocytes was screened with monoclonal antibodies (mAb) for expression in COS-7 cells. Using separate mAb for screening, two cDNA were cloned, the sequences of which showed a single long open reading frame encoding a predicted type I glycoprotein of 506 amino acids that contained three immunoglobulin superfamily domains and a long 112-amino acid cytoplasmic tail. We have termed this antigen MyD-1, reflecting its myeloid and dendritic cell distribution. Analysis of the EMBL database revealed that the molecule is a member of the recently described family of signal regulatory proteins (SIRP). The outeremost Ig domain was of the adhesion/receptor I-type, suggesting that MyD-1 might bind to a ligand on another cell. Evidence for this was subsequently obtained by demonstrating that COS-7 cells transfected with MyD-1 cDNA bound CD4 T cells and this binding was blocked by specific mAb. The potential importance of this interaction was supported by the finding that the proliferation of resting memory CD4 T cells to ovalbumin-pulsed monocytes was significantly reduced in the presence of mAb to MyD-1. A role for the molecule in the modulation of the monocyte/dendritic APC response is also predicted from the existence of multiple potential tyrosine phosphorylation sites in the cytoplasmic domain, including the presence of an immunoreceptor tyrosine-based inhibitory motif (ITIM) and the observation that the SIRP alpha family members have been shown to bind to SHP-1 and SHP-2. Together these data indicate a possible functional importance for MyD-1 in the regulation of monocyte and dendritic cell function.

Amino Acid Sequence↗
PubMed1998

Gammadelta T cells present antigen to CD4+ alphabeta T cells.

Gammadelta and alphabeta TCR+ T cells share many properties and their interactions are likely to be coordinated and regulated. We provide evidence that cattle gammadelta T cells are able to present antigen to CD4+ T cells. To help elucidate their function gammadelta T cell lines were propagated for extensive characterization. Cells expressed high levels of MHC class II and production of co-stimulatory molecules as evidenced by the binding of a CTLA-4 fusion protein and synthesis of CD80 transcripts. These properties and the presence of a well-developed endosomal compartment indicated the cells might function as antigen-presenting cells. Resting CD4+ T cells from calves immunized with ovalbumin or respiratory syncytial virus-antigen proliferated in response to gammadelta T cells pulsed with antigen that appeared to be endocytosed via clathrin-coated pits or specific receptors.

Abatacept↗
PubMed1998

Immune responses in calves immunised orally or subcutaneously with a live Salmonella typhimurium aro vaccine.

Salmonella aro vaccines are able to confer solid protection against homologous virulent challenge in several animal species. Calves were protected against virulent S. typhimurium challenge following administration of a single oral dose of live BRD562 vaccine. Immune responses elicited by the S. typhimurium aro vaccine strain BRD562 were studied following administration to calves by either the oral or subcutaneous route. Serum antibodies to Salmonella polypeptides, following oral or subcutaneous vaccination, were detected by immunoblotting and the route of inoculation found to affect both the antibody isotype and the antigens detected. Oral, but not subcutaneous, immunisation induced bovine serum IgA antibodies against Salmonella antigens of 30 kDa and 65 kDa and bovine IgG2 antibodies against a 35 kDa antigen. Subcutaneous vaccination triggered responses against antigens of 52 kDa, 54 kDa and 57 kDa which were not detected by immune plasma of animals immunised orally. Antibody responses to LPS were poor in animals inoculated by either route. Subcutaneous vaccination elicited T-cell responses against Salmonella antigens as measured by in vitro peripheral blood cell thymidine incorporation. These studies show that the S. typhimurium vaccine strain BRD562 is capable of inducing both humoral and cellular immune responses. Further studies are necessary to identify the nature of the antigens responsible for protection. Oral or subcutaneous inoculation of BRD562(pTETnir15) failed to induce serum antibodies against the fragment C of tetanus toxin (TetC) but was effective in mice. Oral vaccination with this recombinant vaccine induced mucosal IgA against TetC. This is the first time that Salmonella recombinant vaccines have been shown to successfully elicit antibodies against a guest antigen in cattle after one single oral inoculation.

Administration, Oral↗
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

Cellular requirements for the activation and proliferation of ruminant gammadelta T cells.

Requirements for the activation and proliferation of gammadelta T cells were investigated. Maximum numbers of gammadelta T cells expressed the IL-2R alpha-chain after 6-h Con A stimulation in peripheral blood, efferent lymph, and afferent lymph. In comparison, IL-2R alpha-chain expression on CD4 T cells only reached maximum levels in response to Con A stimulation in peripheral blood and afferent lymph populations. Analysis of enriched gammadelta T cells demonstrated that Con A-induced expression of the IL-2R alpha-chain was independent of APC. Together, these data suggest that the requirements for gammadelta T cell activation are less stringent than those for alphabeta T cell activation. Unfractionated peripheral blood, efferent lymph, and afferent lymph cell populations proliferated in response to Con A alone. In contrast, enriched gammadelta T cells (CD4/CD8 depleted) from efferent lymph did not proliferate in response to Con A alone, but required the addition of IL-2. This requirement for exogenous IL-2 could be overcome by the addition of dendritic cells purified from afferent lymph. These results suggested that gammadelta T cells required costimulatory signals provided by APC to ensure the production of sufficient IL-2 to drive proliferation. CD28 and CTLA-4 mRNA were detected in efferent lymph and afferent lymph populations containing CD4 and CD8 T cells stimulated with Con A and IL-2 or with Con A alone, respectively. In contrast, negligible levels of these mRNA species were detected in efferent and afferent lymph populations devoid of CD4 and CD8 T cells. These results suggest that ovine gammadelta T cells may use alternative costimulatory pathways.

Animals↗
PubMed1997

Mapping of bovine FcgammaR (FCGR) genes by sperm typing allows extended use of human map information.

Polymorphic sites within the bovine FcgammaRI (FCGR1), FcgammaRII (FCGR2), and FcgammaRIII (FCGR3) genes were used for proximal mapping of these genes to bovine Chromosome (Chr) 3 (BTA3) with paternal half-sib families from Norwegian Cattle. A fine-structure genetic map of the region was obtained by the analysis of 288 sperm cells from three bulls that were heterozygous for the loci included in the study. No recombinants were observed between FCGR2 and FCGR3 (242 sperm cells). Considering FCGR2 and FCGR3 as a single locus, a three-point linkage analysis for [FCGR2/FCGR3], FCGR1, and INRA003 was carried out. The best-supported order of the loci was found to be INRA003-FCGR1-[FCGR2/FCGR3]. Map distances in a two-point linkage analysis were 10.3 cM between [FCGR2/FCGR3] and FCGR1, and 25.5 cM between FCGR1 and INRA003, respectively. This linkage mapping of the bovine FCGR gene family resembles the human situation where all FCGR genes are located at Chr 1 (HSA1), at position q21-q24. Moreover, the results locate the evolutionary breakpoint between HSA1q and BTA3 within the human 1q24 region.

Alleles↗
PubMed1997

Cross-reactivity of monoclonal antibodies to defined human leucocyte differentiation antigens with bovine cells.

Thirty-seven subpanels of monoclonal antibodies (mAbs) included within the Vth International Workshop on Human Leucocyte Differentiation Antigens (Vth Workshop) were assayed for reactivity with bovine peripheral blood leucocytes. Sixty-five of the 772 mAbs (8.4%) stained bovine cells. mAbs from each of the 27 different CD groups that contained a mAb reacting with cattle were further investigated to compare the cellular expression of the antigen in cattle with that reported for the different CD antigens in humans. Two-colour immunofluorescence staining of the Vth Workshop mAbs against characterized bovine leucocyte subpopulation markers that identified monocytes, B cells, CD4, CD8 and WC1 +T cells were used for these analyses. Eighteen of the mAbs to different human CD antigens (CD11a, CD14, CD18, CD21, CD27, CD29, CD49a, CD49b, CD49d, CD49e, CD51, CD61, CD62L, CD62P, CD63, CDw78, CD98, CD100) stained bovine antigens with an almost identical cellular distribution to that reported in humans. This implies that these mAb react with the homologous cattle molecules. Nine mAbs (CD35, CD37, CD49c, CD50, CD54, CD66, CD81, CD88, CD102) stained bovine cells but the cellular distribution of the bovine antigen was different to that reported in humans implying either a different cellular distribution for these antigens in cattle or a reaction with a different molecule. The investigation has allowed the identification of several bovine homologues of human CD antigens that have not been previously defined in cattle and the cross-reacting mAbs will be valuable reagents for future investigations of bovine immunology.

Animals↗
PubMed1997

A polymerase chain reaction assay for the detection of Leptospira spp. in bovine semen.

A rapid and specific method for the detection of pathogenic Leptospira spp. in bovine semen using the polymerase chain reaction (PCR) is described. The primers used were derived from an EcoR1/BamH1 fragment that hybridized strongly to chromosomal DNA from the hardjobovis serovar. Three different extraction methods were evaluated in this study: phenol-chloroform extraction method, proteinase K (PK) in 1% SDS, followed by phenol-chloroform, and phenol-chloroform followed by 1% cetyltrimethylammonium bromide (CTAB). A PCR product of approximately 500 base pairs (bp) in length was obtained when DNA from pure Leptospira culture was used as a template for PCR, regardless of the DNA extraction method used. The product was consistent with that predicted from the gene sequence. However, in semen seeded in vitro, as well as in semen from infected bulls, a PCR product was obtained only when the leptospiral DNA was extracted from the specimen using the CTAB method. In contrast, other methods used for DNA extraction did not generate suitable templates for the PCR procedure. This is the first PCR protocol developed to detect Leptospira in bovine semen. The PCR protocol provided a direct and unequivocal demonstration that Leptospira can be detected in semen of infected animals. The CTAB method was also used successfully in detecting Leptospira in the urine of infected animals. The PCR procedure was shown to be more sensitive than either the fluorescent antibody test (FAT) or culture for detecting the organism in urine.

Animals↗
PubMed1996

Ruminant cluster CD62L.

Within the Third Workshop, four monoclonal antibodies (mAbs) were considered to belong to this cluster: IAH-CC32 (3W-360), BAQ92 (3W-485), Buf44 (3W-452) and IVA94 (3W-563). IAH-CC32 was the workshop control and has previously been identified as a CD62L-specific mAb (Howard, C.J., Sopp, P. and Parsons, K.R., 1992. L-selectin expression differentiates T cells isolated from different lymphoid tissues in cattle but does not correlate with memory. Immunol., 77:228-234) by showing that human L-selectin mAb LAM1.4 (Spertini, O., Kansas, G.S., Reimann, K.A., Mackay, C.R. and Tedder, T.F., 1991. Functional and evolutional characteristics of distinct epitopes on the leukocyte adhesion molecule-1 (TQ-1, Leu-8) that regulate leukocyte migration. J. Immunol., 147:942) cross-reacts with bovine cells and blocks binding of IAH-CC32. The mAb DREG-56 to human CD62L (Bosworth, 1993. Bovine L-selectin: a peripheral lymphocyte homing receptor. Vet., Immunol., Immunopathol, 37:201-215) also stains cattle cells. Buf44 blocked binding of IVA94 and IAH-CC32, indicating that all three bind to the same or closely related epitope on the L-selectin molecule (Naessens, 1996. Biochemical analysis of preliminary clusters in the non-lineage panel. Vet. Immunol. Immunopathol., 52: 347-356).

Animals↗
PubMed1996

Ruminant cluster WC14.

Two monoclonal antibodies (mAbs) belong to this cluster: IL-A155 (3W-380) and BT3/8.12 (3W-302). These two mAbs inhibited the binding of each other to granulocytes, indicating that they bound to the same or closely related epitopes on the same molecule (Naessens et al., 1996; Naessens, J., Nthale, J.M. and Muiya, P., 1996. Biochemical analysis of preliminary clusters in the non-lineage panel. Vet. Immunol. Immunopathol., 52: 347-356).

Animals↗
PubMed1996

Ruminant cluster WC15.

A new cluster is described, WC15, comprised of five monoclonal antibodies which recognise an antigen expressed on erythrocytes.

Animals↗