Production of class switched antibody secreting cells and antibody is inversely correlated with expression of the adaptor protein HSH2 (IRM8P.712)

Control and HSH2 transgenic (HSH2-Tg) mice were compared to mice that express approximately 1/6th the normal level of HSH2 (HSH2-Lo) to determine if there is an inverse relationship between HSH2 expression and class switched antibody (Ab) production. In contrast to HSH2-Tg mice, HSH2-Lo mice have normal serum Ig titers for IgG1 and IgG2b and elevated titers of IgG3. HSH2-Lo mice also exhibit enhanced production of IgG1, and IgG2b, or IgG3 in response to challenge with either TD or TI Ag, respectively. Stimulation of B cells isolated from HSH2-Lo mice with anti-CD40 and IL-4 results in the production of significantly more antibody secreting cells (ASC) that produce IgG1 and IgE versus control B cells, whereas HSH2-Tg B cells produce significantly fewer class switched ASCs. Although HSH2 expression is associated with a modest effect on class switch recombination, changes in class switched ASC production are most closely linked to alterations in terminal differentiation of GC B cells into plasma cells. Terminal differentiation of class switched B cells from HSH2-Lo mice is significantly increased following in vitro stimulation, resulting in enhanced production of class switched ASCs compared to control B cells. Conversely, class switched B cells generated from HSH2-Tg mice exhibit a significant decrease in differentiation into ASCs in vitro. Thus, differential expression of HSH2 in the B lineage regulates multiple steps associated with the generation of class switched ASCs.

Regulation of HSH2 adaptor protein turnover via a novel NF-κB-dependent mechanism is involved in determining the nature of the class switched antibody response (IRM8P.715)

The Hematopoietic Src Homology 2 (HSH2) adaptor protein is differentially expressed in mature, peripheral B cell subpopulations; exhibiting high-level expression in B1 and marginal zone B cells versus low-level expression in germinal center B cells, independent of gene transcription. HSH2 plays an important role in regulating the production of class switched antibodies through its effect on B cell class switching and terminal differentiation. Mouse models revealed that over expression of HSH2 in the B cell lineage attenuates the class switched antibody response, whereas reduced expression accelerates the class switched response. Thus, it is of significant interest to delineate the molecular mechanisms by which expression of HSH2 is controlled. Upregulation of HSH2 expression in response to TNF receptor family and TLR agonists occurs in an NF-κB-dependent manner, yet does not involve increased transcription of the HSH2 locus based on analysis of HSH2 mRNA levels. Additionally, maintenance of HSH2 expression is dependent on NF-κB signaling. Inhibition of NF-κB results in the rapid down regulation of HSH2 with a half-life of 1 hour, which is in contrast to the results obtained following treatment with cycloheximide or actinomycin D demonstrating that mRNA for HSH2 is stable and the protein itself has a half-life greater than 12 hours. These data support the conclusion that HSH2 protein stability is regulated post-transcriptionally via a novel NF-κB-dependent mechanism.

CD19 cytoplasmic tyrosines 482 and 513 mediating binding to PI3K are sufficient to reconstitute the T-dependent humoral immune response (IRM8P.713)

CD19 is a co-stimulatory receptor on B cells that has been shown to play a critical role in regulating B cell differentiation and the humoral immune response. In mice lacking CD19 expression, B1 and marginal zone (MZ) B cell subpopulations are absent and the T-dependent humoral response is severely impaired in association with defective GC B cell generation and GC responses resulting in loss of class switching, affinity maturation and ultimately the failure to generate Ag-specific memory B cells and Ab secreting cells (ASC) that produce class switched, high affinity Abs. Previous studies have demonstrated the selective mutation of tyrosines 482 and 513 (4/5F mice) in the cytoplasmic domain of CD19 is sufficient to recapitulate the phenotype associated with complete loss of CD19 expression. In the present study, mice were generated in which CD19 is expressed containing only Y482 and Y513 in the absence of the other seven cytoplasmic tyrosine residues (4/5Y mice). Analysis of 4/5Y mice revealed that these residues alone are sufficient to restore B1 and MZ B cell development as well as the T-dependent humoral immune response. Studies to examine mice expressing CD19 with a selective mutation to either tyrosine 482 or 513 revealed a preferential requirement for tyrosine 482 to promote a normal humoral response. These data support the conclusion that CD19 predominantly contributes to normal B cell development and the T-dependent humoral response through its recruitment of PI3K.

Evaluation of antimicrobial resistance profiles of Salmonella isolates from broiler chickens at slaughter in Alberta, Canada

Antimicrobial-resistant Salmonella species are threatening to become a serious public health problem. Therefore, surveillance and prudent use of antimicrobials is needed in both the agricultural and human health sectors. The aim of this study was to describe the antimicrobial susceptibility profiles of Salmonella isolates recovered from healthy broiler chickens at slaughter from November 2004 to April 2005. Salmonella isolates recovered from 36 broiler flocks in Alberta, Canada, were serotyped and tested for antimicrobial susceptibility against 15 antimicrobials. Of 272 Salmonella isolates tested, 64.0% were resistant to one or more antimicrobials, 10.0% were resistant to three or more antimicrobials, and 1.8% were resistant to five antimicrobials. All isolates were susceptible to amikacin, amoxicillin-clavulanic acid, ceftiofur, cefoxitin, ceftriaxone, ciprofloxacin, and nalidixic acid. The highest prevalence of resistance was to tetracycline (54.8%), followed by streptomycin (24.2%) and sulfisoxazole (8.4%). The most common multiantimicrobial resistance patterns were to streptomycin-tetracycline (24.3%), streptomycin-sulfisoxazole-tetracycline (6.6%), and ampicillin-streptomycin-sulfisoxazole-tetracycline (3.7%). The strongest associations were observed between resistance to kanamycin and tetracycline (odds ratio = 65.7, P = 0.001) and to ampicillin and sulfisoxazole (odds ratio = 62.9, P = 0.001). Salmonella Hadar and Salmonella Heidelberg were the two most common serovars accounting for 40.4 and 13.6% of the total isolates, respectively. Eighty-one percent and 12.7% of Salmonella Hadar isolates and 62.0 and 8.1% of Salmonella Heidelberg isolates were resistant to 1 or more and three or more antimicrobials, respectively. The flock level prevalence of resistance ranged from 5.6% for trimethoprim-sulfamethoxazole to 83.3% for tetracycline. This study provides baseline information on antimicrobial susceptibility of Salmonella isolates of broiler chickens at slaughter in Alberta that can serve as a benchmark for future research.

Effects of grain, fructose, and histidine feeding on endotoxin and oxidative stress measures in dairy heifers

Ruminal endotoxin and plasma oxidative stress biomarker concentrations were studied in dairy heifers challenged with grain, fructose, and histidine in a partial factorial study. Holstein-Friesian heifers [n=30; average body weight (BW) of 359.3±47.3 kg] were randomly allocated to 5 treatment groups: (1) control (no grain); (2) grain [crushed triticale at 1.2% of BW dry matter intake (DMI)]; (3) grain (0.8% of BW DMI) + fructose (0.4% of BW DMI); (4) grain (1.2% of BW DMI) + histidine (6g/head); and (5) grain (0.8% of BW DMI) + fructose (0.4% of BW DMI) + histidine (6 g/head). Rumen samples were collected by stomach tube 5, 65, 115, 165, and 215 min after diet consumption and blood samples at 5 and 215 min after consumption. Rumen fluid was analyzed for endotoxin concentrations. Plasma was analyzed for concentrations of the following oxidative stress biomarkers: reactive oxygen metabolites (dROM), biological antioxidant potential (BAP), advanced oxidation protein products, and ceruloplasmin, and activity of glutathione peroxidase. Dietary treatment had no effect on concentrations of endotoxin or oxidative stress biomarkers. We observed no interactions of treatment by time. Ruminal concentrations of endotoxin decreased during the sampling period from 1.12×10(5) ± 0.06 to 0.92×10(5) endotoxin units/mL ± 0.05 (5 and 215 min after diet consumption, respectively). Concentrations of dROM and the oxidative stress index (dROM/BAP × 100) increased over the sampling period, from 108.7 to 123.5 Carratelli units (Carr U), and from 4.1 to 4.8, respectively. Ceruloplasmin concentrations markedly declined 5 min after the consumption of diets, from 190 to 90 mg/L over the 215-min sampling period. Overall, a single feeding challenge for dairy cattle with grain, fructose, and histidine, and combinations thereof, may not be sufficient to induce marked changes in endotoxin or oxidative stress biomarker concentrations.

Sarcoidosis, alveolar β-actin and pulmonary fibrosis

BACKGROUND

Sarcoidosis is a multisystem granulomatous disease of unknown aetiology. Proteins present within the alveolar space early in sarcoidosis disease may provide an insight into novel mechanisms for the development of fibrotic disease and in particular pulmonary fibrosis.

METHODS

A modified two-dimensional difference gel electrophoresis protocol was applied to the human bronchoalveolar lavage fluid (hBALF) of four patients with non-persistent pulmonary interstitial disease at 4-year follow-up (defined as mild disease) and four patients who developed pulmonary interstitial disease at 4-year follow-up (defined as severe disease). The protein β-actin was identified by LC-MS/MS from a preparative gel and found to be significantly elevated in early lavages from the severe disease group. To look at the potential pro-fibrotic effects of this protein, primary human pulmonary fibroblasts (CCD-19Lu) were treated with recombinant β-actin following which qPCR and ELISA assays were used to measure any effects.

RESULTS

We found that β-actin levels were significantly elevated in early hBALF samples in patients who subsequently developed severe disease when compared to the mild group. Treating primary human pulmonary fibroblasts with recombinant β-actin led to enhanced gene expression of the pro-fibrotic markers alpha smooth muscle actin and collagen 1 as well as the increased secretion of interleukin-13 and metalloproteinases 3 and 9.

CONCLUSION

Free β-actin within the lungs of sarcoidosis patients potentially may contribute to disease pathogenesis particularly in the context of abnormal remodelling and the development of pulmonary fibrosis.

The adaptor protein HSH2 regulates the terminal differentiation of B cells resulting in qualitative and quantitative differences in the humoral response (P1120)

Endogenous expression of the adaptor protein HSH2 is regulated in a dynamic manner during B cell maturation and differentiation. Developing B cells lack detectable HSH2, whereas T1 and T2 B cells in the periphery exhibit increasing levels of expression. Mature follicular B cells exhibit decreased expression of HSH2 compared to T2 cells and expression is further downregulated in germinal center B cells. In contrast, marginal zone B cells and B1a/b B cells exhibit high-level HSH2 expression. Regulation of HSH2 expression plays a critical role in determining the outcome of the humoral immune response as demonstrated using HSH2 transgenic (Tg) and HSH2 hypomorph (HSH2-Lo) mice. Constitutive expression of HSH2 in B cells results in decreased serum Ig titers for all subclasses with the exception of IgA. HSH2-Tg mice immunized with T-dependent or T-independent antigens exhibit a moderate decrease in the production of antigen-specific IgM, whereas class switched isotypes are significantly decreased compared to control mice. In contrast, HSH2-Lo mice exhibit accelerated and enhanced class switching in response to challenge with antigen. Analysis of HSH2 Tg versus HSH2-Lo B cell activation in vitro demonstrated that altered HSH2 expression does not affect class switching, but it does lead to altered expression of the transcriptional regulatory proteins Bach2 and Blimp-1. Thus, HSH2 appears to play an important role in regulating terminal differentiation of B cells.

In vivo indices for predicting acidosis risk of grains in cattle: Comparison with in vitro methods

Our objective was to evaluate a near-infrared reflectance spectroscopy (NIRS) used in the feed industry to estimate the potential for grains to increase the risk of ruminal acidosis. The existing NIRS calibration was developed from in sacco and in vitro measures in cattle and grain chemical composition measurements. To evaluate the existing model, 20 cultivars of 5 grain types were fed to 40 Holstein heifers using a grain challenge protocol and changes in rumen VFA, ammonia, lactic acids, and pH that are associated with acidosis were measured. A method development study was performed to determine a grain feeding rate sufficient to induce non-life threatening but substantial ruminal changes during grain challenge. Feeding grain at a rate of 1.2% of BW met these criteria, lowering rumen pH (P = 0.01) and increasing valerate (P < 0.01) and propionate concentrations (P = 0.01). Valerate was the most discriminatory measure indicating ruminal change during challenge. Heifers were assigned using a row by column design in an in vivo study to 1 of 20 grain cultivars and were reassigned after a 9 d period (n = 4 cattle/treatment). The test grains were dry rolled oats (n = 3), wheat (n = 6), barley (n = 4), triticale (n = 4), and sorghum (n = 3) cultivars. Cattle were adapted to the test grain and had ad libitum access to grass silage 11 d before the challenge. Feed was withheld for 14 h before challenge feeding with 0.3 kg DM of silage followed by the respective test grain fed at 1.2% of BW. A rumen sample was taken by stomach tube 5, 65, 110, 155, and 200 min after grain consumption. The rumen is not homogenous and samples of rumen fluid obtained by stomach tube will differ from those gained by other methods. Rumen pH was measured immediately; individual VFA, ammonia, and D- and L-lactate concentrations were analyzed later. Rumen pH (P = 0.002) and all concentrations of fermentation products differed among grains (P = 0.001). A previously defined discriminant score calculated at 200 min after challenge was used to rank grains for acidosis risk. A significant correlation between the discriminant score and the NIRS ranking (r = 0.731, P = 0.003) demonstrated the potential for using NIRS calibrations for predicting acidosis risk of grains in cattle. The overall rankings of grains for acidosis risk were wheat > triticale > barley > oats > sorghum.

Does a medicinal dose of kava impair driving? A randomized, placebo-controlled, double-blind study

OVERVIEW

Increasing concerns over the potentially impairing effects of prescriptive sedative drugs such as benzodiazepines on driving have been raised. However, other alternatives such as natural medicines may also carry similar risks with respect to driving safety. Kava (Piper methysticum) is a psychotropic plant commonly used both recreationally and medicinally in the United States, Australia, and the South Pacific to elicit a physically tranquilizing effect. To date no controlled study has tested a medicinal dose of kava versus placebo and a standard sedative drug on driving ability and driving safety.

OBJECTIVE

Due to the need to establish the safety of kava in operating a motor vehicle, we compared the acute effects of the plant extract versus the benzodiazepine oxazepam and placebo using a driving simulator.

METHODS

A driving simulator (AusEd) was used by 22 adults aged between 18 and 65 years after being randomly administered an acute medicinal dose of kava (180 mg of kavalactones), oxazepam (30 mg), or placebo one week apart in a crossover design trial.

RESULTS

No impairing effects on driving outcomes were found after kava administration compared to placebo. Results on specific driving outcome domains revealed that the oxazepam condition had significantly slower braking reaction time compared to the placebo condition (p =.002) and the kava condition (p =.003). The kava condition had significantly fewer lapses of concentration compared to the oxazepam condition (p =.033). No significant differences were found between conditions for steering deviation, speed deviation, and number of crashes. Results were not modified by driving experience. On the Bond-Lader visual analogue sub-scale of alertness, a significant Treatment × Time interaction (p =.032) was found, with a significant reduction over time for oxazepam decreasing alertness (p <.001), whereas no significant reduction was found in the kava or placebo conditions.

CONCLUSION

The results indicate that a medicinal dose of kava containing 180 mg of kavalactones does not impair driving ability, whereas 30 mg of oxazepam shows some impairment. Research assessing larger recreational doses of kava on driving ability should now be conducted.

Effects of grain, fructose, and histidine on ruminal pH and fermentation products during an induced subacute acidosis protocol

The effects of grain, fructose, and histidine on ruminal pH and fermentation products were studied in dairy cattle during an induced subacute acidosis protocol. Thirty Holstein heifers were randomly allocated to 5 treatment groups: (1) control (no grain); (2) grain [fed at a crushed triticale dry matter intake (DMI) of 1.2% of body weight (BW)]; (3) grain (0.8% of BW DMI)+fructose (0.4% of BW DMI); (4) grain (1.2% of BW DMI)+histidine (6 g/head); and (5) grain (0.8% of BW DMI)+fructose (0.4% of BW DMI)+histidine (6 g/head) in a partial factorial arrangement. Heifers were fed 1 kg of grain daily with ad libitum access to ryegrass silage and alfalfa hay for 10 d. Feed was withheld for 14 h before challenge day, on which heifers were fed 200 g of alfalfa hay and then the treatment diets immediately thereafter. Rumen samples were collected 5 min after diet ingestion, 60 min later, and at 3 subsequent 50-min intervals. Grain decreased ruminal pH and increased ammonia, total volatile fatty acid (VFA), acetate, butyrate, propionate, and valerate concentrations compared with controls. The addition of grain had no effect on ruminal D- and L-lactate concentrations. Fructose markedly decreased ruminal pH and markedly increased D- and L-lactate concentrations. Fructose increased total VFA and butyrate and decreased valerate concentrations. Although histidine did not have a marked effect on ruminal fermentation, increased concentrations of histamine were observed following feeding. This study demonstrates that the substitution of some grain for fructose can lower ruminal pH and increase VFA and lactate concentrations, warranting further investigation into the role of sugars on the risk of acidosis in dairy cattle.