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

In Vitro Supplementation of Copper Modulates the Functional Th1/Th2 Phenotype of Peripheral Blood Mononuclear Cells in Cattle

Simple Summary

This study investigated the association of copper levels and the appearance of blood monocytes, a white blood cell. One type of monocytes (M1) supports cellular immunity and the M2 monocyte helps the immune system through antibodies. Five samples of cow monocytes (PBMCs) were incubated in different levels of copper; 0, 4, 8 and 16 μM. After stimulation under three different conditions, we stained them for CD14 and CD16 to allow typing of the monocytes (M1 and M2). M1 function was also measured through nitric oxide (NO) production. The results showed a significant reduction in viability of the monocytes with increased copper (p < 0.001). Increasing copper resulted in more M1 type monocytes in cows older than 4 years (p = 0.001). CD14 expression affected both CD16 (M2) expression and NO production. For CD16 expression, there was a further significant negative effect of copper levels in cows older than 4 years, whereas NO was not affected by the varying copper levels. In our small sample, monocytes incubating in a higher copper environment showed a stronger M1 support for better cellular immunity containing intracellular infections more effectively. In the live animal low copper levels could possibly affect progression of a bacterial infection to clinical disease.

Abstract

This study investigated the association of copper levels and monocyte plasticity between M1 (CD14⁺ CD16⁻) and M2 (CD14⁻ CD16⁺⁺) phenotypes. Five samples of female bovine PBMCs were incubated in 0, 4, 8 and 16 μM copper and stimulated (PPD-A, TLR- 2 ligand (Pam₃CSK₄), or media alone) before they were washed and stained for cell surface expression analysis by flow cytometry. M1 function was measured through nitric oxide production using a Griess assay. Flow cytometry analysis showed a significant reduction in viability with increased copper (p < 0.001). Increasing copper had a significant impact on CD14 expression (p = 0.026) and in cows older than 4 years copper levels positively affected CD14 expression (p = 0.001), whereas in animals of four years or younger, Cu did not affect the CD14 expression (p = 0.701 and 0.939, respectively). CD14 expression affected both CD16 expression and NO production. For CD16 expression, there was a further significant negative effect of copper levels in cows older than 4 years, NO was not affected by varying copper levels. In our small sample, monocytes in the presence of a higher copper environment showed a stronger M1 support for better cellular immunity which might contain intracellular infections more effectively. To test this, a randomised clinical trial will be required to determine whether copper supplementation could prevent progression to Johne’s disease in MAP infected cows.

Bovine Derived in vitro Cultures Generate Heterogeneous Populations of Antigen Presenting Cells

Antigen presenting cells (APC) of the mononuclear phagocytic system include dendritic cells (DCs) and macrophages (Macs) which are essential mediators of innate and adaptive immune responses. Many of the biological functions attributed to these cell subsets have been elucidated using models that utilize in vitro-matured cells derived from common progenitors. However, it has recently been shown that monocyte culture systems generate heterogeneous populations of cells, DCs, and Macs. In light of these findings, we analyzed the most commonly used bovine in vitro-derived APC models and compared them to bona fide DCs. Here, we show that bovine monocyte-derived DCs and Macs can be differentiated on the basis of CD11c and MHC class II (MHCII) expression and that in vitro conditions generate a heterologous group of both DCs and Macs with defined and specific biological activities. In addition, skin-migrating macrophages present in the bovine afferent lymph were identified and phenotyped for the first time. RNA sequencing analyses showed that these monophagocytic cells have distinct transcriptomic profiles similar to those described in other species. These results have important implications for the interpretation of data obtained using in vitro systems.

Modulation of the transcription factor NF-κB in antigen-presenting cells by bovine respiratory syncytial virus small hydrophobic protein

Bovine respiratory syncytial virus (BRSV) is an important cause of respiratory disease in young cattle and is closely related to human RSV (HRSV), which causes severe respiratory disease in infants and the elderly. The RSV genome encodes a small hydrophobic (SH) protein with viroporin activity. Previous studies have shown that recombinant BRSV lacking the SH gene (rBRSVΔSH) is attenuated in the lungs, but not in the upper respiratory tract, of calves and mucosal vaccination with rBRSVΔSH induced long-lasting protective immunity. Attenuation of rBRSVΔSH may be due to the ability of this virus to induce an early innate response as rBRSVΔSH induces higher levels of pro-inflammatory cytokines than wild-type (wt) rBRSV. In this study, we investigated the effects of the BRSV SH protein on NF-κB p65 phosphorylation, a master step in the regulation of pro-inflammatory cytokines. Expression of SH resulted in the inhibition of NF-κB p65 phosphorylation in response to BRSV infection and extracellular lipopolysaccharide, and a reduction in the production of pro-inflammatory cytokines. In contrast, rBRSVΔSH does not inhibit NF-κB p65 phosphorylation in bovine antigen-presenting cells, including monocytes, macrophages and dendritic cells, resulting in increased expression of pro-inflammatory cytokines and increased activation of T cells compared to cells infected with wt BRSV. These findings highlight an important role for the BRSV SH protein in immune modulation.

Evaluation of leptin receptor expression on buffalo leukocytes

Experimental evidences support a direct role for leptin in immunity. Besides controlling food intake and energy expenditure, leptin was reported to be involved in the regulation of the immune system in ruminants. The aim of this work was to highlight the expression of leptin receptor (LEPR) on Bubalus bubalis immune cells using a multi-approach assessment: flow cytometry, confocal microscopy and gene expression analysis. Flow cytometric analysis of LEPR expression showed that peripheral blood monocytes were the predominant cells expressing LEPR. This result was corroborated by confocal microscopy and RT-PCR analysis. Moreover, among lymphocytes, LEPR was mainly expressed by B lymphocytes and Natural Killer cells. Evidence of LEPR expression on buffalo blood leukocytes showed to be a good indicator of the responsivity of these cells to leptin, so confirming the involvement of leptin in buffalo immune response.

Bovine γδ T cells are a major regulatory T cell subset

In humans and mice, γδ T cells represent <5% of the total circulating lymphocytes. In contrast, the γδ T cell compartment in ruminants accounts for 15–60% of the total circulating mononuclear lymphocytes. Despite the existence of CD4⁺CD25^high Foxp3⁺ T cells in the bovine system, these are neither anergic nor suppressive. We present evidence showing that bovine γδ T cells are the major regulatory T cell subset in peripheral blood. These γδ T cells spontaneously secrete IL-10 and proliferate in response to IL-10, TGF-β, and contact with APCs. IL-10–expressing γδ T cells inhibit Ag-specific and nonspecific proliferation of CD4⁺ and CD8⁺ T cells in vitro. APC subsets expressing IL-10 and TFG-β regulate proliferation of γδ T cells producing IL-10. We propose that γδ T cells are a major regulatory T cell population in the bovine system.

Recombinant bovine respiratory syncytial virus with deletion of the SH gene induces increased apoptosis and pro-inflammatory cytokines in vitro, and is attenuated and induces protective immunity in calves

Bovine respiratory syncytial virus (BRSV) causes inflammation and obstruction of the small airways, leading to severe respiratory disease in young calves. The virus is closely related to human (H)RSV, a major cause of bronchiolitis and pneumonia in young children. The ability to manipulate the genome of RSV has provided opportunities for the development of stable, live attenuated RSV vaccines. The role of the SH protein in the pathogenesis of BRSV was evaluated in vitro and in vivo using a recombinant (r)BRSV in which the SH gene had been deleted. Infection of bovine epithelial cells and monocytes with rBRSVΔSH, in vitro, resulted in an increase in apoptosis, and higher levels of TNF-α and IL-1β compared with cells infected with parental, wild-type (WT) rBRSV. Although replication of rBRSVΔSH and WT rBRSV, in vitro, were similar, the replication of rBRSVΔSH was moderately reduced in the lower, but not the upper, respiratory tract of experimentally infected calves. Despite the greater ability of rBRSVΔSH to induce pro-inflammatory cytokines, in vitro, the pulmonary inflammatory response in rBRSVΔSH-infected calves was significantly reduced compared with that in calves inoculated with WT rBRSV, 6 days previously. Virus lacking SH appeared to be as immunogenic and effective in inducing resistance to virulent virus challenge, 6 months later, as the parental rBRSV. These findings suggest that rBRSVΔSH may be an ideal live attenuated virus vaccine candidate, combining safety with a high level of immunogenicity.

Identification of immune traits correlated with dairy cow health, reproduction and productivity

Detailed biological analyses (e.g. epidemiological, genetic) of animal health and fitness in the field are limited by the lack of large-scale recording of individual animals. An alternative approach is to identify immune traits that are associated with these important functions and can be subsequently used in more detailed studies. We have used an experimental dairy herd with uniquely dense phenotypic data to identify a range of potentially useful immune traits correlated with enhanced (or depressed) health and fitness. Blood samples from 248 dairy cows were collected at two-monthly intervals over a 10-month period and analysed for a number of immune traits, including levels of serum proteins associated with the innate immune response and circulating leukocyte populations. Immune measures were matched to individual cow records related to productivity, fertility and disease. Correlations between traits were calculated using bivariate analyses based on animal repeatability and random regression models with a Bonferroni correction to account for multiple testing. A number of significant correlations were found between immune traits and other recorded traits including: CD4⁺:CD8⁺ T lymphocyte ratio and subclinical mastitis; % CD8⁺ lymphocytes and fertility; % CD335⁺ natural killer cells and lameness episodes; and serum haptoglobin levels and clinical mastitis. Importantly these traits were not associated with reduced productivity and, in the case of cellular immune traits, were highly repeatable. Moreover these immune traits displayed significant between-animal variation suggesting that they may be altered by genetic selection. This study represents the largest simultaneous analysis of multiple immune traits in dairy cattle to-date and demonstrates that a number of immune traits are associated with health events. These traits represent useful selection markers for future programmes aimed at improving animal health and fitness.

Expression of complement receptors 1 (CR1/CD35) and 2 (CR2/CD21), and co-signaling molecule CD19 in cattle

C3d is a sub-fragment of the C3 component of the complement system. Covalent binding of multiple C3ds to antigen reduces the activation threshold of cognate B lymphocytes by one thousand fold through co-ligation of the B cell antigen receptor (BCR) and complement receptor 2 (CR2/CD21). Reverse transcriptase polymerase chain reaction (RT-PCR) revealed that, in cattle, four distinct complement receptors are produced from the Cr2 gene by alternative splicing. Cattle express two major variants of the Cr2 gene representing homologues of murine CR1 and CR2, each of which is expressed in both a long and a short form. Expression of CR1 and CR2 was detected in IgM(+) cells from both the spleen and peripheral blood. Additionally, the coding sequence of CD19, the CR2 co-signaling molecule, was determined. CD19 was confirmed to be expressed by IgM(+) cells from the spleen and peripheral blood.

Induction of a cross-reactive CD8(+) T cell response following foot-and-mouth disease virus vaccination

Foot-and-mouth disease virus (FMDV) causes a highly contagious infection in cloven-hoofed animals. Current inactivated FMDV vaccines generate short-term, serotype-specific protection, mainly through neutralizing antibody. An improved understanding of the mechanisms of protective immunity would aid design of more effective vaccines. We have previously reported the presence of virus-specific CD8(+) T cells in FMDV-vaccinated and -infected cattle. In the current study, we aimed to identify CD8(+) T cell epitopes in FMDV recognized by cattle vaccinated with inactivated FMDV serotype O. Analysis of gamma interferon (IFN-γ)-producing CD8(+) T cells responding to stimulation with FMDV-derived peptides revealed one putative CD8(+) T cell epitope present within the structural protein P1D, comprising residues 795 to 803 of FMDV serotype O UKG/2001. The restricting major histocompatibility complex (MHC) class I allele was N*02201, expressed by the A31 haplotype. This epitope induced IFN-γ release, proliferation, and target cell killing by αβ CD8(+) T cells, but not CD4(+) T cells. A protein alignment of representative samples from each of the 7 FMDV serotypes showed that the putative epitope is highly conserved. CD8(+) T cells from FMDV serotype O-vaccinated A31(+) cattle recognized antigen-presenting cells (APCs) loaded with peptides derived from all 7 FMDV serotypes, suggesting that CD8(+) T cells recognizing the defined epitope are cross-reactive to equivalent peptides derived from all of the other FMDV serotypes.

Expression of complement receptor 2 (CD21), membrane IgM and the inhibitory receptor CD32 (FcgammaRIIb) in the lymphoid tissues of neonatal calves

Limited active antibody responses in neonates following vaccination have been attributed to immaturity of the immune system and to the suppressive effects of maternal antibodies. The activating receptor CD21 (CR2), when co-ligated with membrane IgM (mIgM) by complement-bound antigen lowers the threshold for activation of B lymphocytes. The inhibitory receptor CD32 (FcgammaRII) when co-ligated with mIgM by antigen-antibody complexes raises the threshold for activation. Expression of these receptors, which potentially play roles in regulation of B cell responses in the presence of maternal antibodies in neonates, has been recently characterized in blood lymphocytes in neonatal calves. Little is known however about expression of these receptors in the lymphoid tissues, where immune responses are initiated. In this study, expression of CD21, mIgM and CD32 receptors by B lymphocytes was studied in a range of lymphoid tissues including spleen, lymph nodes and bone marrow from newborn and 7-week-old calves using flow cytometry. The proportion of naïve B lymphocytes in the lymphocyte gate was significantly lower in blood and spleen of newborn calves compared to 7-week-old calves. Over 90% of B lymphocytes expressed CD21 in the lymphoid tissues. In the lymph nodes and spleen, a lower proportion of mIgM(+) B lymphocytes expressed CD32 compared to blood. In addition, intensity of expression of CD32 on B cells in lymph nodes was significantly lower compared to that in blood, suggesting a lower potential for inhibitory signalling in B cells in the lymphoid microenvironment. Investigation of the CD5(+) B cell population (as an indicator of B1 B cells) suggested an increase in the proportion of IgM(+)CD5(+) cells with age in calves, in both blood and lymphoid tissue, in contrast to the situation in humans and mice. Overall, the majority of naïve B lymphocytes in lymphoid tissues in neonatal calves expressed both activating (CD21, mIgM) and inhibitory (CD32) receptors. These receptors may provide targets for novel adjuvants, to lower the threshold for activation of B cells in neonates, and enhance antibody responses.

Use of flow cytometry to develop and characterize a set of monoclonal antibodies specific for rabbit leukocyte differentiation molecules

Flow cytometry was used to identify and characterize monoclonal antibodies (mAbs) that react with rabbit leukocyte differentiation molecules (LDM). Screening sets of mAbs, developed against LDM in other species, for reactivity with rabbit LDM yielded 11 mAbs that recognize conserved epitopes on rabbit LDM orthologues and multiple mAbs that recognize epitopes expressed on the major histocompatibility class I or class II molecules. Screening of mAbs submitted to the Animal Homologues Section of the Eighth Human Leukocyte Differentiation Workshop yielded 7 additional mAbs. Screening of mAbs generated from mice immunized with leukocytes from rabbit thymus or spleen or concanavalin A activated peripheral blood and/or spleen lymphocytes has yielded 42 mAbs that recognize species restricted epitopes expressed on one or more lineages of leukocytes. Screening of the anti-rabbit mAbs against leukocytes from other species yielded one additional mAb. The studies show that screening of existing sets of mAbs for reactivity with rabbit LDM will not be productive and that a direct approach will be needed to develop mAbs for research in rabbits. The flow cytometric approach we developed to screen for mAbs of interest offers a way for individual laboratories to identify and characterize mAbs to LDM in rabbits and other species. A web-based program we developed provides a source of information that will facilitate analysis. It contains a searchable data base on known CD molecules and a data base on mAbs, known to react with LDM in one or more species of artiodactyla, equidae, carnivora, and or lagomorpha.

An MHC-restricted CD8+ T-cell response is induced in cattle by foot-and-mouth disease virus (FMDV) infection and also following vaccination with inactivated FMDV

Foot-and-mouth disease virus (FMDV) causes a highly contagious disease of cloven-hooved animals that carries enormous economic consequences. CD8(+) cytotoxic T lymphocytes play an important role in protection and disease outcome in viral infections but, to date, the role of the CD8(+) T-cell immune response to FMDV remains unclear. This study aimed to investigate major histocompatibility complex (MHC) class I-restricted CD8(+) T-cell responses to FMDV in vaccinated and in infected cattle. An in vitro assay was used to detect antigen-specific gamma interferon release by CD8(+) T cells in FMDV-infected cattle of known MHC class I genotypes. A significant MHC class I-restricted CD8(+) T-cell response was detected to both FMDV strain O1 BFS and a recombinant fowlpox virus expressing the structural proteins of FMDV. Antigen-specific MHC class I-restricted CD8(+) T-cell responses were also detected in cattle vaccinated with inactivated FMDV. These responses were shown to be directed, at least in part, to epitopes within the structural proteins (P12A region) of the virus. By using mouse cells expressing single cattle MHC class I alleles, it was possible to identify the restriction elements in each case. Identification of these epitopes will facilitate the quantitative and qualitative analysis of FMDV-specific memory CD8(+) T cells in cattle and help to ensure that potential vaccines induce a qualitatively appropriate CD8(+) T-cell response.

Cross-reactivity of mAbs to human CD antigens with sheep leukocytes

A panel of 377 commercially available mAbs was submitted to the animal homologue section of the Eighth International Workshop on Human Leukocyte Differentiation Antigens (HLDA8, Adelaide, Australia) for cross-reactivity studies in a range of vertebrate species. Eight commercial suppliers participated by providing isotype controls and mAbs specific for a total of 144 CD antigens. In this study, we describe the results of flow cytometric testing of the reactivity of these mAbs with leukocyte populations isolated from blood, bronchoalveolar lavage, and ileal Peyer's patches of sheep. A total of 52 mAbs were identified as potentially reacting with sheep blood leukocytes in the first round of screening with blood leukocytes. In the second phase, reactivity of selected mAbs was further analyzed by repeating the screening with blood leukocytes at an independent facility. Screening of selected mAbs for reactivity with myeloid antigens was completed with alveolar macrophages and screening for reactivity with B cell antigens was completed with ileal Peyer's patch B cells. This screening identified mAbs that consistently reacted with both putative myeloid (CD10, CD22, CD23, CD27, CD29, CD32, CD49d, CD81, CD86, CD88, CD163, CD165) and B cell (CD10, CD22, CD23, CD27, CD29, CD32, CD49d, CD81, CD86, CD88, CD165) activation or differentiation antigens. Further studies will be required to determine if each mAb cross-reacts with an orthologous leukocyte antigen.

Summary of the animal homologue section of HLDA8

The development of reagents against leukocyte differentiation antigens in veterinary species is delayed compared to mouse and men and therefore also the number of existing reagents for the characterisation of leukocytes derived from species with importance in veterinary medicine is restricted. Cross-reactive studies with existing well defined monoclonal antibodies directed against leukocyte differentiation antigens derived from other species are an alternative approach to enhance the panel of reagents in veterinary immunology. This study describes the activities of the animal homologue section in frame of human leukocyte differentiation antigen 8-workshop (HLDA8) were 376 monoclonal antibodies, mainly directed against human leukocytes had been tested for their reactivity with 17 different animal species including non-human primates, ruminants, swine, horse, carnivores, rabbit, guinea pig, chicken and fish. In a first round 182 mAb were selected based on there reactivity in FCM analyses with at least one species for further studies, including multi-colour FCM, and molecular analyses of the antigens. Interesting was the species-overlapping reactivity of mAb directed against distinct clusters: 11 out of 17 species reacted with CD9, 11 of 17 with CD11a, CD14 (11/17), CD18 (13/17), CD21 (7/17), CD29 (10/17), CD44 (13/17), CD45 (9/17), CD47 (10/17), CD49d (13/17), CD61 (6/17), CD86 (7/17), CD91 (5/17), and CD172a (10/17), indicating evolutionary highly conserved epitopes on these surface molecules. Our results suggest the suitability of cross-reactive mAb for the animal model studies. Moreover, these findings contribute to our understanding of the evolution of the immune system.

Cross-reactivity of mAbs to human CD antigens with cells from cattle

A panel of 377 commercially available mAbs were submitted to the animal homologue section of the 8th International Workshop on Human Leukocyte Differentiation Antigens (HLDA8, Adelaide, Australia) for cross-reactivity studies on different animal species. In this study we describe the results of testing the mAbs on cattle cells by flow cytometry and Western blot. Eight commercial suppliers participated, providing mAbs to a total of 144 CD antigens plus controls. Fifty-two mAbs were identified as potentially staining cattle cells in the first round screen. In the second phase, 38 mAbs were confirmed as staining cattle cells. This included some that may recognise polymorphic determinants and others with atypical distribution patterns compared to humans. mAb to human CD9, CD11a, CD14, CD18, CD21, CD23, CD29, CD44, CD45R, CD47, CD49d and CD172a cross-reacted with bovine cells and mAb to CD22, CD88, CD119 and CD163 stained CD antigens that have not previously been identified in cattle.

Screening of anti-human leukocyte monoclonal antibodies for reactivity with equine leukocytes

Three hundred and seventy-nine monoclonal antibodies (mAbs) against various human CD molecules supplied to the HLDA8 animal homologues section (including four isotype controls) were analysed for cross-reactivity with equine leukocytes. First, flow cytometric identification of positively reacting mAbs was performed in one laboratory. Thereafter, a second round of flow cytometric evaluation was performed, involving three laboratories participating in the study. The first test-round indicated 17 mAbs as potentially positive. After the second round of flow cytometric analysis, 14 mAbs remained (directed against CD2, CD11a, CD18, CD44, CD45, CD49d, CD91, CD163 and CD172) where cross-reactivity was anticipated based on similarities between the human and equine staining pattern. Additionally, there was 1 mAb with weak likely positive reactivity, 12 mAbs with positive staining, which likely do not reflect valuable data, 5 mAbs with clear alternate expression pattern from that expected from humans, 5 mAbs with a questionable staining pattern itself, i.e. that was variable between the three labs, 32 mAbs with weak-positive expression and alternate staining pattern, and 279 negative mAbs (including the four isotype controls) were detected. In 31 cases, more appropriate target cells, such as thymocytes or stem cells, were not available for the screening. The results underline the value of this "cross-reactivity" approach for equine immunology. However, as only a few mAbs against leukocyte surface antigens reacted positively (approximately 4% of the mAbs submitted), the analysis of further anti-human mAbs and directed efforts to develop species-specific anti-CD mAb are still required.

Leukocyte-platelet aggregates and monocyte tissue factor expression in bovines implanted with ventricular assist devices

Infection and thromboembolism remain significant complications associated with ventricular assist device (VAD) support, including the newer rotary VADs, limiting wider adoption of this promising technology. These complications persist in spite of extensive preclinical testing in large animal models. The amount of biocompatibility information collected during preclinical trials is limited due to a lack of available assays. We thus developed three flow cytometric assays to measure leukocyte-platelet aggregates and monocyte tissue factor expression and applied them to 26 bovines implanted with two types of rotary VADs. All animals displayed low levels of circulating aggregates and monocytes expressing tissue factor prior to device implant. The assay values significantly increased following VAD implant, then usually declined to a lower, yet significantly elevated versus baseline, level indicative of ongoing inflammation. The implementation of more robust biocompatibility assays for the evaluation of cardiovascular device performance and modification might ultimately contribute to the development of safer artificial organs.

The bovine antibody repertoire

Cattle are able to produce a full range of Ig classes including the long-elusive IgD through rearrangement of their germline genes. Several IgL groupings have been reported but as in several other livestock species (e.g. sheep, rabbits, chickens), rearrangement per se fails to generate significant IgH diversity. This is largely because of the modest number of bovine VH segments that participate in rearrangement and their conserved sequences. Perhaps in compensation, bovine Ig heavy chains carry CDR3 sequences of exceptional length. Processes that operate post-rearrangement to generate diversity remain ill defined as are the location, timing and triggers to these events. Reagents are needed to understand better the maturation of B lymphocytes, their responses to antigens and cytokines, and to provide standards for the quantitation of Ig responses in cattle; recombinant methods may help meet this need as Ab engineering technologies become more widely used.

Cytokine gene expression profiles of bovine dendritic cells after interaction with Mycobacterium avium ssp. paratuberculosis (M.a.p.), Escherichia coli (E. coli) or recombinant M.a.p. heat shock protein 70

Mycobacterium avium paratuberculosis (M.a.p.) resides and replicates in macrophages. Many of the of immune mechanisms aiding M.a.p. survival in the host's cells are known. However, little is known about interactions of M.a.p. with dendritic cells (DC). As DC are important for the induction of protective immunity against infectious diseases, we investigated the interaction of M.a.p. with these cells. Quantitative real-time PCR (RT-PCR) was used to analyse differential expression of cytokine genes after 6 h and 24 h of incubation by immature DC that phagocytosed either M.a.p. or Escherichia coli (E. coli). We hypothesized that phagocytosis of E. coli would induce pro-inflammatory cytokines due to abundant presence of lipopolysaccharide (LPS) and that the cytokine expression profile induced by phagocytosis of live M.a.p. would differ. In addition we hypothesized that incubation of immature DC with rHsp70, an immunodominant antigen of M.a.p., would induce a similar profile of cytokine gene expression as phagocytosis of intact M.a.p. However, phagocytosis of both E. coli and M.a.p. resulted in a cytokine gene expression pattern representative of a (pro-)inflammatory reaction, dominated by strong induction of IL-12 gene expression, that was higher after 24 h than after 6 h of incubation, although the response to M.a.p. was less vigorous than to E. coli. Incubation with rHsp70 resulted in a more inhibitory type of cytokine gene expression, with delayed IL-12 gene expression and downregulation of the genes for IL-1beta and IL-6 after 24 h of incubation. We conclude that bovine DC produce an immuno-stimulatory, anti-mycobacterial response to infection with M.a.p., while Hsp70 potentially contributes to pathogen virulence by allowing the bacteria to invade the host cell.

Summary of the animal homologue section of HLDA8

Development of reagents against leukocyte differentiation antigens in veterinary immunology is slower compared to humans and mice. Cross-reactivity studies with monoclonal antibodies (mAb) generated against human molecules represent an excellent approach for the detection of new reagents for the minor characterised species. Three hundred seventy-seven commercially available mAb from different companies were tested for their reactivity with cells from 17 species--including non-human primates, ruminants, swine, horse, carnivores, rabbit, guinea pig, chicken and fish. In a first round of testing by flow cytometry (FCM) 182 mAb showed reactivity with atleast one of the species described above. Most of the cross-reactivity was found against non-human primate leukocytes, but also species in evolutionarily more distant from humans showed in some cases a clear staining pattern in flow cytometry (FCM). In a second round these FCM-results were confirmed by molecular analyses, by immunoprecipitation studies and analyses on transfectants. Interesting was the broad species-overlapping reactivity of mAb directed against CD9 (11 out of 17 species), CD11a (11/17), CD14 (11/17), CD18 (13/17), CD21 (7/17), CD29 (10/17), CD44 (13/17), CD45 (9/17), CD47 (10/17), and CD49d (13/17), CD61 (6/17), CD86 (7/17), CD91 (5/17), and CD172a (10/17), indicating evolutionary highly conserved epitopes on these surface molecules. Our results suggest the suitability of crossreactive mAb for the animal model studies. Moreover, these findings contribute to our understanding of the evolution of the immune system.

Expression of PrPC on cellular components of sheep blood

PrPC, a glycosylphosphatidylinositol-linked glycoprotein, plays a central role in the pathogenesis of transmissible spongiform encephalopathies (TSEs), undergoing a conformational alteration to the disease-associated isoform, commonly designated PrPSc. PrPC is expressed in many tissues other than the nervous system, although its precise function(s) remains unclear. It has previously been demonstrated that TSEs can be transmitted by blood transfusion in sheep. The aim of this work was to identify which components of blood carried the infection. As an initial step, the distribution of PrPC on cellular components of sheep blood was examined to identify potential targets for infection. Cell-surface expression of PrPC was found only on peripheral blood mononuclear cells (PBMCs); however, platelets also contained significant amounts of intracellular PrPC. The level of PrPC expressed on the cell surface of PBMCs was influenced by PrP genotype, with the highest levels found in scrapie-susceptible VRQ/VRQ sheep and the lowest levels in scrapie-resistant ARR/ARR sheep. In susceptible sheep, PrPC was expressed at varying levels on all major subsets of PBMCs, with the highest levels on the CD21+ subset of B cells, and PrP expression was upregulated dramatically on CD21+ B cells in some scrapie-infected sheep.

Mycobacterium avium ssp. paratuberculosis recombinant heat shock protein 70 interaction with different bovine antigen-presenting cells

Abstract Heat shock proteins (Hsp) can deliver antigen into the major histocompatibility complex class I presentation pathway of antigen-presenting cells (APC), a process called cross priming, thus stimulating antigen-specific CD8+ T-cell reactions. Hsp were shown to elicit proinflammatory responses in APC. Both processes require interaction of Hsp with APC via specific receptors. This study describes the interaction of recombinant Hsp70 (rHsp70) of Mycobacterium avium subspecies paratuberculosis with bovine peripheral blood mononuclear cells that was restricted to CD14+ cells. Characterized monocyte-derived macrophages, monocyte-derived dendritic cells (DC) and BoMac, an immortalized bovine macrophage cell line, were used to investigate the interaction of rHsp70 with different bovine APC. Saturation of immature DC with high concentrations of rHsp70 is demonstrated, and it was found that interaction of rHsp70 with DC was related to the maturation stage of the DC. Involvement of CD91 as a cellular receptor for rHsp70 was demonstrated; however, competition studies with immature DC demonstrated that other receptors exist on bovine APC. These data suggest that rHsp70-based vaccines may be useful for the successful immunization of cattle.

Initial interaction of U2OS cells with noncoated and calcium phosphate coated titanium substrates

From previous studies, we know that calcium phosphate (CaP) coated implants stimulate bone formation compared to uncoated implants. Nevertheless, the mechanism by which substrate surface characteristics affect cell function is unclear. In this study, we examined the initial interaction (30 min to 24 h) of U2OS cells with titanium substrates with or without a CaP coating. The effect of substrate roughness was also studied. When cell attachment was studied, we found that cells attached more readily to rough than to smooth surfaces. Also, more cells attached to the uncoated than to the CaP coated surface. After 24 h, cell numbers were similar for all substrate surfaces. Further, cells spread to a larger area on noncoated titanium than on the CaP coated substrates. At 24 h, the sequence of cell size was smooth titanium > rough titanium > CaP coated titanium. Shape measurements showed differences in cell shape between the cells on the different materials only at 7 h, not at different culture times. Cells expressed alpha2, alpha3, alpha5, alpha6, alphav, and beta1 subunits. Expression of alpha1, alpha4, alphavbeta3, beta3, beta4, and beta7 was extremely low or was not found. The beta1 integrin expression was higher on the coated than on the noncoated titanium at 3 h, but not on the other studied times. Expression of alpha2, alpha5, alpha6, and alphav expression was found to be upregulated at 24 h compared to earlier culture times on coated titanium, but not on uncoated titanium substrates. From this we conclude that the surface characteristics of a material (roughness and composition) can affect the initial interaction of cells with the material.

Comparative analysis of normal prion protein expression on human, rodent, and ruminant blood cells by using a panel of prion antibodies

BACKGROUND

It is not known whether variant CJD can be transmitted within the human population by blood transfusion. The expression of normal cellular prion protein (PrPC) by different blood cell types may permit selective uptake and dissemination of infectivity.

STUDY DESIGN AND METHODS

The normal distribution of PrPC on the major blood cell types of species known to be susceptible to natural or experimental transmissible spongiform encephalopathies was studied. Blood from healthy humans, mice, hamsters, cattle, and sheep was examined by flow cytometry by using a large panel of antibodies with different prion protein (PrP) epitope specificities to maximize the detection of PrP variants across species and cell type.

RESULTS

PrP was detected on all major human blood cells types except eosinophils, but was not detected as ubiquitously or uniformly on major blood cell types of different animal species.

CONCLUSION

Different animal species have unique patterns of expression of PrPC on blood cell types, with none equivalent to the human pattern. This needs to be considered when extrapolating from animal models of blood-borne transmissible spongiform encephalopathy infectivity, particularly in regard to the risk assessment of potential variant CJD spread within the human population. The relationship between PrP distribution and infectivity distribution in blood needs further investigation.

Separation of bovine bone marrow into maturation-related myeloid cell fractions

A prerequisite for studies on bovine myeloid cells in relation to maturity is a reliable separation method, in order to obtain enriched and partially purified cell fractions of different maturation stages. Since current techniques for bovine bone marrow cell isolation fall short of this requirement, a technique for fractionating bovine bone marrow using a three-layer discontinuous Percoll gradient was developed. Three maturation-dependent myeloid cell fractions were obtained at specific densities, as maturation of cells is accompanied with a progressive density increase. Early immature myeloid cells, i.e. myeloblasts and promyelocytes, were found at a density of 1.060g/ml. Late immature myeloid cells, i.e. myelocytes and metamyelocytes, were retrieved at 1.080g/ml. Bands and segmented cells, representing the mature fraction, accumulated in the high-density pellet (>1.080g/ml). Myeloid cell populations were identified in each fraction by flow cytometry based on their forward and side scatter pattern. Confirmation was provided by light microscopy of flow cytometrically sorted myeloid populations, using morphological characteristics. The developed method provides a unique tool for studying maturation-dependent functions in bovine bone marrow.

Globotriaosylceramide (Gb(3)/CD77) is synthesized and surface expressed by bovine lymphocytes upon activation in vitro

Neutral glycosphingolipids (GSLs) are considered activation markers on human lymphocytes, which are fundamental for studying the immune system. For cattle, only a limited number of activation markers has yet been identified. We recently showed that Shiga toxin 1, known to use globotriaosylceramide (Gb(3) syn. CD77) as a cellular receptor, depresses proliferation of activated bovine lymphocytes [Infect. Immunol. 67 (1999b) 2209]. In order to confirm the expression of Gb(3)/CD77 on bovine lymphocytes, we flowcytometrically examined a bovine B-lymphoma cell line (BL-3) and bovine peripheral blood mononuclear cells (PBMC) before and after mitogenic stimulation and biochemically characterized neutral GSLs extracted from PBMC. CD77 was detected on the surface of BL-3 cells and cultured PBMC essentially after mitogenic stimulation. Although expressed by all PBMC subpopulations identified, the portion of CD7+ cells was highest for BoCD8+ cells, followed by B-cells and BoCD4+ cells at day 4 of cultivation. Ceramide trihexoside of stimulated PBMC was structurally determined as Gal(alpha1-4)Gal(1-4)Glc(1-1)ceramide (Gb(3)). Biochemically, Gb(3) was also detected within unstimulated PBMC which contained ceramide monohexoside (CMH) and Gb(3) in a ratio of about 4:1. However, stimulation induced an increase of CMH and Gb(3) by a factor of 2.5 and 10, respectively, implicating that bovine lymphocytes regulate surface expression of Gb(3)/CD77 predominantly by quantitative changes in the Gb(3) metabolism. This report presents Gb(3)/CD77 as the first GSL identified on bovine immune cells and highly recommends this activation dependent antigen as a useful tool to investigate lymphocyte activation within the bovine immune system.

Cross-reactivity with bovine cells of monoclonal antibodies submitted to the 6th International Workshop on Human Leukocyte Differentiation Antigens

Twelve subpanels of monoclonal antibodies (MAb) included within the 6th International Workshop on Human Leukocyte Differentiation Antigens (6th HLDA) were assayed for reactivity with bovine peripheral blood leukocytes. Sixty-nine of the 807 MAb (8.6%) stained bovine cells. These MAb represented 30 different human CD groups. Nine of the MAb to different human CD antigens (CD19, CD23, CD39, CD47, CD86, CD117, CD120b, CDw149, CD165) potentially recognized antigens on cattle cells that had not previously been identified. These were investigated further by two-colour immunofluorescence to compare the cellular expression of the antigen on cattle cells with that reported for the different CD antigens in humans. Four of the MAb that belonged to CD23, CD39, CD47, and CDw149 stained bovine cells in a manner that indicated an almost identical cellular distribution of the antigen to that reported in humans. This implied that these MAb reacted with the homologous cattle molecules. Further work would be necessary to confirm specificity of CD19, CD86, CD117, CD120b and CD165 MAb. Other cross-reacting MAb either recognized antigens already defined in cattle or antigens not yet clustered in humans. The study has identified valuable new reagents for studies of cattle and confirmed that most common cross-reactive MAb are to epitopes on integrins.

The anti-human CD21 antibody, BU33, identifies equine B cells

The number of antibodies for identifying equine B cells is small and the number that react with well-defined epitopes even smaller. The monoclonal antibody, BU33, which is directed against human CD21 (Complement Receptor 2; CR2) was shown to identify (1) follicular lymphocytes in the lymph nodes and spleen of three horses, and (2) a mean of 18 +/- 6% (SEM) of peripheral blood lymphocytes from 10 horses. These findings indicate that the antibody identifies equine B cells and possibly equine CR2 or a related molecule. This study adds to the reagents available for equine research and diagnostic pathology.

Lymphocyte function-associated antigen 1 is a receptor for Pasteurella haemolytica leukotoxin in bovine leukocytes

Pasteurella (Mannheimia) haemolytica leukotoxin (Lkt) causes cell type- and species-specific effects in ruminant leukocytes. Recent studies indicate that P. haemolytica Lkt binds to bovine CD18, the common subunit of all beta2 integrins. We designed experiments with the following objectives: to identify which member of the beta2 integrins is a receptor for Lkt; to determine whether Lkt binding to the receptor is target cell (bovine leukocytes) specific; to define the relationships between Lkt binding to the receptor, calcium elevation, and cytolysis; and to determine whether a correlation exists between Lkt receptor expression and the magnitude of target cell cytolysis. We compared Lkt-induced cytolysis in neutrophils from control calves and from calves with bovine leukocyte adhesion deficiency (BLAD), because neutrophils from BLAD-homozygous calves exhibit reduced beta2 integrin expression. The results demonstrate for the first time that Lkt binds to bovine CD11a and CD18 (lymphocyte function-associated antigen 1 [LFA-1]). The binding was abolished by anti-CD11a or anti-CD18 monoclonal antibody (MAb). Lkt-induced calcium elevation in bovine alveolar macrophages (BAMs) was inhibited by anti-CD11a or anti-CD18 MAb (65 to 94% and 37 to 98%, respectively, at 5 and 50 Lkt units per ml; P < 0.05). Lkt-induced cytolysis in neutrophils and BAMs was also inhibited by anti-CD11a or anti-CD18 MAb in a concentration-dependent manner. Lkt bound to porcine LFA-1 but did not induce calcium elevation or cytolysis. In neutrophils from BLAD calves, Lkt-induced cytolysis was decreased by 44% compared to that of neutrophils from control calves (P < 0.05). These results indicate that LFA-1 is a Lkt receptor, Lkt binding to LFA-1 is not target cell specific, Lkt binding to bovine LFA-1 correlates with calcium elevation and cytolysis, and bovine LFA-1 expression correlates with the magnitude of Lkt-induced target cell cytolysis.

Analysis of the immunological cross reactivities of 213 well characterized monoclonal antibodies with specificities against various leucocyte surface antigens of human and 11 animal species

213 Monoclonal antibodies (mAbs) raised against leucocyte surface antigens from human and 11 animal species were analyzed for reactivities against leucocytes from human and 15 different animal species. We found 77 mAbs (36%) to cross-react. Altogether, 217 cross reactions were registered out of 3195 possible combinations (7%). Most of the cross reacting mAbs had integrin or MHC class II specificities. This study defined cross reactions on the following markers: CD1a, 1c, 2, 4, 5, 8, 9, 11a, 11b, 14, 18, 20, 21, 23, 29, 31, 41, 43, 44, 45, 45R, 46, 49, 61, 62L, TCR gamma/delta, BCR, Thy-1, MHC class I and MHC class II, Swine-WC7 and Cattle-WC1. In order to characterize the molecular weight (MW) of the corresponding cross reacting antigens, selected mAbs were used to immunoprecipitate the antigens. The MW's of the analyzed precipitated antigens were in good agreement with the MWs of the homologous antigens. The followed strategy was found to be efficient and economical in defining new leucocyte antigen reactive mAbs.