In vivo relevance of polymorphic Interleukin 8 promoter haplotype for the systemic immune response to LPS in Holstein-Friesian calves

Genetic polymorphisms in immune- and inflammation-associated genes and their association with bovine mastitis resistance/susceptibility

Bovine mastitis, the inflammation of the mammary gland, is a contagious disease characterized by chemical and physical changes in milk and pathological changes in udder tissues. Depressed immunity and higher expression of inflammatory cytokines with an elevated milk somatic cell count can be observed during mastitis in dairy cattle. The use of somatic cell count (SCC) and somatic cell score (SCS) as correlated traits in the indirect selection of animals against mastitis resistance is in progress globally. Traditional breeding for mastitis resistance seems difficult because of the low heritability (0.10-0.16) of SCC/SCS and clinical mastitis. Thus, genetic-marker-selective breeding to improve host genetics has attracted considerable attention worldwide. Moreover, genomic selection has been found to be an effective and fast method of screening for dairy cattle that are genetically resistant and susceptible to mastitis at a very early age. The current review discusses and summarizes the candidate gene approach using polymorphisms in immune- and inflammation-linked genes (CD4, CD14, CD46, TRAPPC9, JAK2, Tf, Lf, TLRs, CXCL8, CXCR1, CXCR2, C4A, C5, MASP2, MBL1, MBL2, LBP, NCF1, NCF4, MASP2, A2M, and CLU, etc.) and their related signaling pathways (Staphylococcus aureus infection signaling, Toll-like receptor signaling, NF-kappa B signaling pathway, Cytokine-cytokine receptor, and Complement and coagulation cascades, etc.) associated with mastitis resistance and susceptibility phenotypic traits (IL-6, interferon-gamma (IFN-γ), IL17, IL8, SCS, and SCC) in dairy cattle.

Combined effects of CXCL8 (IL-8) and CXCR2 (IL-8R) gene polymorphisms on deregressed MACE EBV indexes of milk-related traits in Simmental bulls

CXCL8 (also known as IL-8) is a member of the CXC subfamily of chemokines that binds two of the seven transmembrane G-protein-coupled receptors (GPCRs), CXCR1 and CXCR2, to mediate and regulate leucocyte accumulation and activation at sites of inflammation. They are known to play a critical role in both disease susceptibility and infection outcome. The aim of this study was to investigate the entire sequences of CXCL8 and CXCR2 genes in thirty-one Simmental sires to evaluate the effects of genomic variants on the indexes of the bulls for milk, fat and protein yields, and for somatic cell score (SCS). Five new single nucleotide polymorphisms (SNPs) were found in CXCR2 gene. The analysis of association indicated that one SNP in CXCL8 and two in CXCR2 influenced the considered traits. To evaluate the existence of functional haplotypic effects, combinations among the three genomic variants (SNP 1 in CXCL8, SNP 6 and SNP 7 in CXCR2) were investigated. Four different haplotypic alleles were identified in the experimental population, one of which at a high frequency (61%). Bulls with Hap 4 (G-C-G at SNP 1, SNP 6, and SNP 7 respectively) had more favourable indexes for SCS (P < 0.05). These results suggest that the SNPs in CXCL8 and CXCR2 may be potential genetic markers to improve udder health in the Simmental breed.

Comparison of the uterine inflammatory response to frozen-thawed sperm from high and low fertility bulls

Some bulls with apparently normal semen quality yield unacceptably low pregnancy rates. We hypothesised that a differential uterine immunological response to sperm from high and low fertility bulls may contribute to these differences. The experimental model used was heifer follicular phase uterine explants incubated with frozen-thawed sperm from high and low fertility bulls (3-5 replicates per experiment). Inflammatory gene expression of IL1A, IL1B, IL6, TNFA and CXCL8 were assessed by qPCR and IL1-β and IL-8 were quantified in explant supernatants by ELISA. Neutrophil binding affinity to sperm from high and low fertility bulls was also assessed. There was a significant up-regulation of IL1A, IL1B and TNFA from frozen-thawed sperm, irrespective of fertility status, compared to the unstimulated control. This response was confirmed at the protein level, with an increase of IL-1β and IL-8 protein concentrations by 5 and 2.7 fold, respectively (P < 0.05). Although no significant differences in the inflammatory response at the gene or protein level were evident between high and low fertility bulls, more sperm from low compared to high fertility bulls bound to neutrophils (P < 0.05). Using bulls of unknown fertility, cauda epididymal sperm (CES) plus seminal plasma (SP) upregulated IL6 (P < 0.05) but there was no upregulation of any inflammatory gene expression for CES alone. Overall, this ex vivo study demonstrated an upregulation of inflammatory gene expression in the uterus in response to frozen-thawed bull sperm. While there was no difference between sperm from high and low fertility bulls, there was a greater binding affinity of low fertility sperm by neutrophils.

Effect of IL8 haplotype on immunological traits in periparturient dairy cows

Interleukin 8 (IL8) is a major mediator of the innate immune response. Polymorphisms in this gene are associated with susceptibility to inflammatory disease in humans. Two major promoter polymorphic haplotypes (IL8-h1 and IL8-h2) segregating in cattle populations have shown a significant effect on the immune response profile in calves but their implications for transition cow immunity have not been established. The aims of this study were to assess functional relevance of the IL8 haplotypes on the immunological traits of periparturient cows (n = 32) belonging to three genetic groups: Holstein (HO), Simmental (SI) and their crosses (CR) and to evaluate the frequency of IL8 haplotypes in the HO (dairy) and SI (dual purpose) pure breeds. IL8 haplotypes showed a significant effect on circulating number of both T helper lymphocytes (P = 0.0133) and T cytotoxic lymphocytes (P = 0.0024). Differences in percentage of CD14⁺ monocytes and T lymphocyte subsets were found between haplotype groups at different time points. Plasma concentrations of Serum Amyloid A (SAA) and Haptoglobin (Hp) were enhanced at calving in IL8-h2 (P = 0.0019, P = 0.0029) and IL8-het (P = 0.050 and P = 0.052) respectively, compared with IL8-h1 cows. In contrast, significantly lower levels of reactive oxygen metabolites (d-ROMs) activation were identified in IL8-h2 and IL8-het cows after calving compared with IL8-h1 cows. Furthermore, genotyping results showed that SI cows have a high frequency of the homozygous IL8-h2 haplotype compared to the HO cows (87.5 % vs 40 %) which reflects the different selective pressure between the two pure breeds. In conclusion, our preliminary data suggests that IL8 promoter haplotype is associated with significant and dynamic changes in immunological traits during peripartum and early lactation period. Future work will focus on a more comprehensive assessment of immune changes in additional cows.

The immune response in bovine primary dermal fibroblasts is influenced by Interleukin 8 promoter haplotype and vitamin D

Interleukin-8 (IL-8) is a potent inflammatory chemokine, and two gene promoter haplotypes have been previously reported to segregate in cattle populations. Our earlier work showed how these divergent IL8 genotypes influence IL-8 expression and other immune response parameters at a systemic level. Here we extend that work to characterise the influence of haplotype on the local immune response - in primary bovine dermal fibroblasts. Furthermore, we also investigated how this response is modulated by 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃). Significant induction of IL8 expression was observed in cells from both haplotypes at 3 and 24 h post-stimulation with the TLR1/2 ligand, Pam3CSK4 and with the TLR4 ligand, LPS. IL8 expression was elevated in response to both LPS and Pam3CSK4 in fibroblasts carrying the IL8-h1 haplotype and this result was supported by significantly enhanced IL-8 protein secretion. Gene expression profiles for other known fibroblast immune mediators (SAA3 and CCL20) did not show significant differences between haplotypes but NOS2 gene expression was significantly elevated in response to vitamin D, even above the level detected in response to both TLR ligands. In conclusion, this work has demonstrated that the IL-8 response of dermal fibroblasts is dependent on IL8 haplotype and that the immune response profile in these cells is significantly differentially regulated by 1,25(OH)₂D₃. Fibroblasts have important immune response capacity and their function in driving inflammatory responses (including iNOS) is underappreciated. Understanding the relationship between cattle genotype and immune function is critically important for uncovering sustainable solutions for animal disease.

Effect of IL-8 haplotype on temporal profile in circulating concentrations of interleukin 8 and 25(OH) vitamin D in Holstein-Friesian calves

Interleukin-8 (IL-8) is an inflammatory chemokine released during the primary innate immune response to recruit neutrophils to the site of infection. Two distinct gene promoter haplotypes have been previously reported to segregate in the Holstein-Friesian breed (IL8-h1 and IL8-h2). Our earlier work showed how these divergent IL8 haplotypes influence IL-8 concentration and other immune response parameters at a systemic level. While a close relationship has been established between vitamin D and IL-8 in other species, the role of genetic haplotype on temporal variation in vitamin D concentrations and its impact on immunity remains unexplored in cattle. Therefore this study had two objectives - 1: to establish the temporal variation in IL-8 concentration profile in healthy calves of each IL-8 haplotype (n = 5/6 per group) and 2: to identify the relationship between systemic 25(OH)D concentration and IL8 haplotype in blood at 10 time points across their first year of life. Elevated IL-8 protein concentration profiles were apparent in IL8-h2 calves at multiple time points throughout the year (P < 0.05). In contrast, circulating concentrations of 25(OH) vitamin D were negatively correlated (0.38) with IL-8, with elevated concentrations in calves of the IL8-h1 haplotype. Increased numbers of innate immune cells - specifically monocytes and basophils, were also detected in blood from IL8-h2 calves (P < 0.05). Importantly, circulating concentrations of vitamin D were substantially below recommended concentrations of 30 ng/mL serum for optimal immunity in the first five months of life, indicating a window of potentially heightened disease susceptibility - particularly in calves of the IL8-h1 haplotype. In conclusion, this study has established that IL8 haplotype confers divergent chemokine concentrations and which contrasts with circulating concentrations of vitamin D. Accounting for both IL8 haplotype and vitamin D concentration may be critical to provide dairy calves with optimal immune protection in early life.

Application of the TruCulture® whole blood stimulation system for immune response profiling in cattle

Capturing the phenotypic variation in immune responses holds enormous promise for the development of targeted treatments for disease as well as tailored vaccination schedules. However, accurate detection of true biological variation can be obscured by the lack of standardised immune assays. The TruCulture® whole blood stimulation system has now been extensively used to detect basal and induced immune responses to a range of pathogen-associated molecular patterns (PAMPs) in human peripheral blood. This study demonstrates the optimisation of this commercially available assay for systemic immune phenotyping in cattle. The early immune response in Holstein-Friesian bull calves (n = 10) was assessed by haematology, flow cytometry and cytokine expression profiling after 24 h ex-vivo PAMP (LPS, poly (I:C) and zymosan) stimulation in TruCulture® tubes. A comparative analysis was also performed with a traditional whole blood stimulation assay and cell viability using both systems was also evaluated. Results: Supernatant collected from TruCulture® tubes showed a significant increase in IL-1β and IL-8 expression compared to null stimulated tubes in response to both LPS and zymosan. In contrast, a detectable immune response was not apparent at the standard concentration of poly (I:C). Conventional whole blood cultures yielded similar response profiles, although the magnitude of the response was higher to both LPS and zymosan, which may be attributed to prokaryotic strain-specificity or batch of the stimulant used. Despite being a closed system, HIF1A expression - used as a measure of hypoxia was not increased, suggesting the TruCulture® assay did not negatively affect cell viability. This represents the first reported use of this novel standardised assay in cattle, and indicates that the concentration of poly (I:C) immunogenic in humans is insufficient to induce cytokine responses in cattle. We conclude that the low blood volume and minimally invasive TruCulture® assay system offers a practical and informative technique to assess basal and induced systemic immune responses in cattle.

Effect of bovine genotype on innate immune response of heifers to repeated lipopolysaccharide (LPS) administration

This pilot study provides a preliminary assessment of the impact of genotype on acute innate immune pro-inflammatory, metabolic and endocrine responses to repeated lipopolysaccharide (LPS) administered to growing heifers. Heifers (n = 4/genotype) were from unselected (stable milk yield since 1964, UH) or contemporary (CH) Holstein cows that differed in milk yield (6200 vs 11,100 kg milk/305 d) or from contemporary Black Angus (CA) cows bred to contemporary Red Angus bulls. Heifers were challenged with iv administration of 0.5 μg LPS/kg body weight on day 1 (Challenge 1) and d 5 (Challenge 2) of study to assess endotoxin tolerance. Plasma was collected at -1, -0.5, 0, 1, 2, 3, 4, 6, 8, and 24 h relative to each LPS administration. Rectal body temperature (BT) was measured before each blood sampling and at 5 and 7 h. Data were analyzed by repeated measures with sampling time as the repeated effect. Each genotype had at least one pro-inflammatory response that indicated it might have a more robust response than the other genotypes. The CH heifers had a greater TNF-α response, UH heifers had greater IL-6 and XO responses and CA heifers had greater BT and SAA response to LPS than the other genotypes. There was a genotype by time by interaction as cortisol peaked earlier in CH and UH than in CA heifers. Glucose response was less in CA and insulin response was greater in CH heifers. Endotoxin tolerance to LPS was evident as pro-inflammatory, cortisol, glucose and insulin responses were less during Challenge 2 than during Challenge 1. Differences among genotypes during Challenge 1 were eliminated during Challenge 2 except for the greater SAA response in CA heifers and indicate the potential for differential impacts of genotype on the development of endotoxin tolerance. Specific reasons for these effects of genotype are not clear from these data but the results support the hypothesis for differential innate immune signaling among these bovine genotypes.

Bovine neutrophils in health and disease

Bovine neutrophils have similarities to those of other species with respect to mechanisms of their activation and migration into tissue, modulation of immune responses and the balance between microbial killing and host tissue damage. However, bovine neutrophils have biochemical and functional differences from those of other species, which may yield insights about the comparative biology of neutrophils. Neutrophils play protective and harmful roles in the infectious diseases of cattle that occur at times of transition: respiratory disease in beef calves recently arrived to feedlots and mastitis and other diseases of postparturient dairy cows. An important research focus is the mechanisms by which risk factors for these diseases affect neutrophil function and thereby lead to disease and the prospect of genetic or pharmacologic improvement of disease resistance. Further, in keeping with the One Health paradigm, cattle can be considered a model for studying the role of neutrophils in naturally occurring diseases caused by host-adapted pathogens and are thus an intermediary between studies of mouse models and investigations of human disease. Finally, the study of bovine neutrophils is important for agriculture, to understand the pathogenesis of these production-limiting diseases and to develop novel methods of disease prevention that improve animal health and reduce the reliance on antimicrobial use.