Quantitation of bovine TNF-alpha mRNA by reverse transcription and competitive polymerase chain reaction amplification

Long-term impacts of late-gestation maternal heat stress on growth performance, blood hormones and metabolites of newborn calves independent of maternal reduced feed intake

The objective of this study was to evaluate the effects of heat stress in late gestation independent of maternal reduced feed intake on performance, blood hormones and metabolites, and immune responses of dairy calves from birth through weaning. A total of 30 multiparous Holstein cows at 45 d before expected calving were randomly assigned to one of 3 groups: (1) thermal neutral (CL, n = 10) conditions with ad libitum feed intake (10% of refusals on an as-fed basis); (2) pair-fed thermal neutral (CLPF, n = 10) conditions to reduce feed intake to levels similar to the heat stress (HS) group while reared under thermoneutral conditions (80% of the CL group); or (3) heat stress (HS, n = 10) conditions with ad libitum feed intake. Pair-feeding was conducted to quantify the confounding effects of dissimilar feed intake. Calves (10/group) born to cows that were exposed to cooling (IU-CL), pair-feeding (IU-CLPF), or heat stress (IU-HS) were used from birth through weaning. After birth, all the calves were managed under identical conditions. IU-HS calves had lower birth weight, and hip height at birth and 14 d of age. Compared with IU-CL and IU-CLPF calves, IU-HS calves had lower serum concentration of IgG and apparent efficiency of IgG absorption but higher serum insulin concentrations. Cortisol concentration in serum was higher in IU-HS and IU-CLPF calves compared to IU-CL calves. The neutrophil percentage was lower in IU-CL calves than in IU-HS and IU-CLPF calves. Neutrophil-lymphocyte ratio was higher in IU-HS calves compared to IU-CLPF and IU-CL calves. The mRNA expression of TNFα of IU-HS calves was downregulated compared with IU-CL and IU-CLPF calves. In summary, maternal HS during late gestation reduces calf birth weight and dramatically alters blood hormones and metabolites, but its effect on immune system function was not independent of maternal reduced feed intake.

Acute brief heat stress in late gestation alters neonatal calf innate immune functions

Heat stress, as one of the environmental stressors affecting the dairy industry, compromises the cow milk production, immune function, and reproductive system. However, few studies have looked at how prenatal heat stress (HS) affects the offspring. The objective of this study was to evaluate the effect of HS during late gestation on calf immunity. Calves were born to cows exposed to evaporative cooling (CT) or HS (cyclic 23-35°C) for 1 wk at 3 wk before calving. Both bull and heifer calves (CT, n=10; HS, n=10) were housed in similar environmental temperatures after birth. Both CT and HS calves received 3.78 L of pooled colostrum within 12 h after birth and were fed the same diet throughout the study. In addition to tumor necrosis factor α, IL-1β, IL-1 receptor antagonist (IL-1RA), and toll-like receptor (TLR)2, and TLR4 mRNA expression, the expression of CD14(+) and CD18(+) cells, and DEC205(+) dendritic cells were determined in whole blood samples at d 0, 3, 7, 14, 21, and 28. The neutrophil to lymphocyte ratio, differential cell counts, and the hematocrit were also determined. During late gestation, the HS cows had greater respiration rates, rectal temperatures, and tended to spend more time standing compared with the CT cows. The HS calves had less expression of tumor necrosis factor-α and TLR2 and greater levels of IL-1β, IL-1RA, and TLR4 compared with CT calves. The HS calves also had a greater percentage of CD18(+) cells compared with the CT calves. Additionally, a greater percentage of neutrophils and lesser percentage of lymphocytes were in the HS calves compared with the CT calves. The results indicate that biomarkers of calves' immunity are affected in the first several weeks after birth by HS in the dam during late gestation.

Acute phase cytokines, TAC1, and toll-like receptor4 mRNA expression and health associated with group size in veal calves

Chronic stressors are a major health and well-being issue in animals. Immune status of animals under chronic stress is compromised, thus reducing disease resistance and compromising well-being of the animal. The objective of this study was to determine the influence of group size of veal calves on immune status and leukocyte mRNA expression of acute phase cytokines, toll-like receptor 4 (TLR4) and tachykinin 1 (TAC1) over a five-month finishing period. Holstein bull calves (n=168), 44±3 days of age were assigned to one of three treatments; 2, 4, or 8 calves/pen (pen space allowance of 1.82m(2)/calf). Jugular blood samples were collected at the day of grouping and then monthly for 4 months. The differential leukocyte counts were determined and mRNA was extracted from the leukocytes. Reverse transcription-qPCR was used to measure the gene expression of interleukin-1 (IL-1β), IL-1 receptor antagonist (IL-1Ra), tumor necrosis factor (TNF-α), TLR4, and TAC1 in leukocytes. Health was evaluated before grouping and monthly for 4 months. On the 1st month after grouping, veal calves that were housed in groups of 8 have greater expression of IL-1β mRNA than calves housed in groups of 4 or 2 (treatment×month, P=0.04). Also at 1 month, groups of 8 had greater TAC1 expression (P<0.05) than calves housed in groups of 4 or 2. However, the expression of IL-1Ra, TNF-α, and TLR4 were not influenced by group size. In the first month of the trial, calves in groups of 8 coughed more (P<0.05) than calves in groups of 2 and coughed more than calves in groups of 4 and 2 during the 2nd month (treatment×month, P=0.03). Calves housed in groups of 8 tended to have greater neutrophil percentage (P=0.09), neutrophil to lymphocyte ratio (P=0.06), and had lower lymphocyte percentage (P=0.06) than those housed in groups of 4 or 2. In conclusion, the number of veal calves in a group, given the same space during the finishing period did not alter IL-1Ra, TNF-α, and TLR4 mRNA expression. However, housing of calves in groups of 8 was associated with greater expression of IL-1β and TAC1 mRNA in peripheral blood leukocytes, and coughing during the first 2 months after grouping. Therefore, housing of veal calves in larger groups may lead to greater susceptibility to respiratory disease and stress.

Differential innate immune responses of bovine peripheral blood leukocytes to Salmonella enterica serovars Dublin, Typhimurium, and Enteritidis

The majority of Salmonella serovars cause no clinical disease in cattle, while some are associated with severe disease. The objective of the current study was to determine the innate immune responses of bovine peripheral blood leukocytes exposed to Salmonella enterica serovar Dublin (bovine-specific), Salmonella typhimurium (murine adapted, but zoonotic), and Salmonella enteritidis (poultry host-adapted) in 3-week-old calves. All Salmonella exposures increased cell surface CD14 and CD18 regardless of serovar. The greatest CD14 marker mean fluorescence was in monocytes and the greatest mean fluorescent of the marker mean was in neutrophils. Phagocytosis increased with all serovars, but was not different among them. Neutrophils had the greatest marker mean fluorescence for phagocytosis, with all serovars being equal. Oxidative burst increased in all serovars compared to control cells, but were not different among the serovars. Neutrophils and monocytes were similar in the oxidative burst, with limited oxidative burst detected in the primarily lymphocyte population. mRNA expression of TNF-α, IL-8, and IL-12, increased above the control cells whereas none of these serovars affected mRNA expression of TLR4. TNF-α was greatest in S. enterica and S. typhimurium, compared to Salmonella dublin. In contrast, IL-8 was expressed more in S. dublin than S. typhiurium, with S. Enteriditus intermediary. These results show while cell surface markers, phagocytosis, and oxidative burst were largely unaffected by serovar, cytokine and chemokine expression differed among the Salmonella serovars. It appears that internal responses of the cells differ, rather than cell recognition, creating pathogenicity differences among of the serovars, even in the neonate with developing immunity.

Toll-like receptors 2 and 4, and acute phase cytokine gene expression in dexamethasone and growth hormone treated dairy calves

Cattle are exposed to growth hormone stimulants and to stressors that cause cortisol release. Both of these hormones affect immune responses which may reduce disease resistance. Toll-like receptors are the pattern recognition molecules of pathogens that are on immune cells. They then orchestrate the induction of the appropriate acute phase cytokines of the early innate response. The objective of this study was to determine changes in toll-like receptors and acute phase cytokines following treatment with a synthetic glucocorticoid (dexamethasone) and growth hormone (GH). Twenty-eight calves were given the control (Cnt), dexamethasone (DEX), GH, or dexamethasone and GH (Both) treatments from 3 until 56 days of age. Blood was collected by jugular venipuncture on days 14, 28, 42, and 56. On day 56, a lung lavage was performed and spleen and thymus tissues collected. Total RNA was extracted from blood leukocytes, lung lavage cells, spleen and thymus cells. Real-time reverse transcriptase-polymerase chain reaction (RT-PCR) was used to quantify interleukin-1 (IL-1), IL-1 receptor antagonist (IL-1Ra), tumor necrosis factor (TNF)-alpha, toll-like receptor 2 (TLR2), and toll-like receptor 4 (TLR4). Blood leukocytes had a time effect for IL-1Ra (P < 0.01), with a trend for a treatment effect (P = 0.07) and had a treatment by time interaction (P < 0.05). IL-1, TNF, and TLR2 and TLR4 were greatest (P < 0.05) for Cnt only at day 14. IL-1 expression of lung lavage cells was greatest (P < 0.05) for calves on the Both treatment compared to the other three treatments. However, IL-1Ra was not different among the treatments. Toll-like receptor 2 expression was enhanced with Both compared to either DEX (P < 0.05) or GH (P < 0.05) and tended to be greater than Cnt expression (P = 0.07). Expression of TLR4 tended to be reduced by Both compared to Cnt (P = 0.06). Tumor necrosis factor-alpha was greatly enhanced by Both compared to the other three treatments (P < 0.05). Spleen cell tended to have different IL-1 expression between GH and Both (P < 0.10). Interleukin-1 receptor antagonist and TLR2 and TLR4 were not different among treatments. However, TNF-alpha expression was enhanced by the DEX treatment alone compared to the GH treatment (P < 0.05), and tended (P < 0.10) to be greater than Cnt expression. None of the gene expressions were different among treatments for thymus cells. Lung lavage cell expression appears to be most susceptible to these hormones while blood leukocyte expression was only slightly affected, and thymus cells were not affected at all. These data demonstrate that TLR2 and TLR4 and acute phase cytokine expression can be altered by stress and growth hormones, which may decrease resistance of those animals to disease.

T cell populations and cytokine expression in milk derived from normal and bacteria-infected bovine mammary glands

This study investigated the effect of naturally acquired bacterial infection of the bovine mammary gland on subpopulations of T lymphocytes and cytokine expression in milk. Twenty-nine lactating cows with mastitis were compared to 12 normal animals. CD4+ lymphocytes represented a significantly greater percentage of the milk-derived lymphocytes in infected mammary glands compared to normal controls. Cytokine mRNA expression by cells derived from milk was investigated using reverse transcriptase-polymerase chain reaction (RT-PCR). No IL-2 or IL-4 mRNA was detected in any samples, while IFN-gamma mRNA was detected in all milk samples. IL-10 mRNA was detected in cells from the milk of 2 mastitic cows and 1 normal cow, and IL-12 mRNA was detected in 2 cows with mastitis. While TNF-alpha mRNA was not detected in this study, IL-6 mRNA was identified in cells from the milk of all animals, with levels being greater in mastitic animals.

Antigen-induced interferon-gamma and interleukin-2 responses of cattle inoculated with Mycobacterium bovis

Bovine purified protein derivative (PPD)-induced interferon-gamma (IFN-gamma) and interleukin-2 (IL-2) mRNA expression was measured in peripheral blood lymphocyte cultures of cattle inoculated with Mycobacterium bovis and compared to cytokine protein levels as measured by IFN-gamma enzyme-linked immunosorbent assay and IL-2 bioassay. For individual animals, positive correlations were observed between mRNA and protein levels of bovine PPD-induced IFN-gamma and IL-2, although the correlations were stronger for IFN-gamma. Expression of these two cytokines also correlated with responses from a comparative intradermal test and a M. bovis antibody test. At 7 and 20 weeks after inoculation, bovine PPD-induced IFN-gamma and IL-2 mRNA expression was detected in all animals with tuberculous lesions and in a proportion of the M. bovis-inoculated animals with no lesions. Correlation of antigen-induced IFN-gamma and IL-2 with other immune parameters suggests that these two cytokines play an important role in the immune response to bovine tuberculosis.

Modulatory effect of mycobacterium cell wall extract (Regressin) on lymphocyte blastogenic activity and macrophage cytokine gene transcription in swine

Mycobacterium cell wall extract (MCWE) (Regressin) contains trehalose dimycolate and muramyl dipeptide, both of which have immunomodulatory properties. The goal of this study was to evaluate the effect of MCWE on the in vitro peripheral blood lymphocyte blastogenic activities to mitogens phytohemagglutinin (PHA) and concanavalin A (ConA) in 6- to 8-week-old piglets. The effect of MCWE on alveolar macrophage tumor necrosis factor alpha (TNF-alpha) and interleukin-1beta (IL-1beta) gene transcription, as determined by a reverse transcription-PCR assay standardized with the endogenous glyceraldehyde-3-phosphate dehydrogenase gene, was also investigated. The results show enhanced blastogenic lymphocyte activities to mitogens PHA and ConA in MCWE-exposed cell cultures compared to those of control cell cultures. The enhanced blastogenic activity effect of MCWE was dose dependent. The cell background activity (spontaneous [3H]thymidine incorporation) of lymphocyte cultures was also significantly increased in the presence of MCWE, thereby demonstrating a lymphocyte mitogenic effect of MCWE. Cytokine gene transcription analysis showed that the TNF-alpha transcript levels in alveolar macrophage cell cultures stimulated with MCWE for 6 or 16 h were enhanced compared with those in control cell cultures. An enhancement of IL-1beta mRNA levels in cell cultures stimulated for 16 h with MCWE, compared with those in control cell cultures, was also observed. The overall results demonstrate that MCWE can stimulate lymphocyte functional activity and cytokine mRNA expression in swine, thereby indicating its potential use as a clinical immunotherapeutic agent.