Human plasmacytoid dendritic cells support Th17 cell effector function in response to TLR7 ligation

Signals involved in the commitment of Th17 differentiation are of substantial interest for our understanding of antimicrobial defense mechanisms and autoimmune disorders. Various ways in which myeloid dendritic cells modulate Th17 differentiation have been identified. However, although plasmacytoid dendritic cells (PDCs) are regarded as important players in antiviral/antimicrobial host defense and autoimmune diseases, a putative modulatory role of PDCs in Th17 differentiation has not yet been elucidated in detail. We demonstrated that PDCs are capable of promoting Th17 differentiation in response to TLR7 stimulation. Further, both the differentiation of Th17 cells from naive T cells and the amplification of Th17 effector functions of memory T cells are promoted by PDCs after TLR7 activation. Our data are of strong clinical relevance because TLR7 activation in PDCs might represent one of the missing links between innate and adaptive immune mechanisms and contribute to the amplification of Th17-driven autoimmune disorders as well as viral host defense.

HBsAg inhibits TLR9-mediated activation and IFN-alpha production in plasmacytoid dendritic cells

Plasmacytoid dendritic cells (pDCs), the professional producers of type I interferons (IFN-alpha/beta), play a pivotal role in innate and adaptive immune responses against viral infections. Although functional impairment of circulating pDCs in chronic hepatitis B (CHB) patients has been reported previously, the mechanism responsible for these defects remains unclear. We hypothesize that HBsAg circulating in high amounts during HBV infection may interact with pDC and contribute to pDC dysfunction. In support of this hypothesis we show that pDCs treated with HBsAg secreted much less IFN-alpha than control pDCs. Furthermore, suppression is specific for TLR9, with no effects upon TLR7-mediated IFN-alpha secretion. HBsAg inhibited TLR9-mediated IRF-7 expression and nuclear translocation, which are important for induction of IFN-alpha gene transcription. HBsAg upregulated the SOCS-1 expression and bound to BDCA-2 receptors on the plasma membrane of pDCs, resulting in the inhibition of the IFN-alpha production. In conclusion, the above data suggested that HBsAg may directly interfere with the function of pDC through HBsAg-mediated upregulation of SOCS-1 expression and BDCA-2 ligation, which could partially explain how HBV evades the immune system to establish a persistent infection.

Patients with chronic hepatitis B infection display deficiency of plasmacytoid dendritic cells with reduced expression of TLR9

Chronic hepatitis B virus (HBV) infection is a complex interaction between replicating noncytopathic virus and dysregulatory host antiviral immunity. Plasmacytoid dendritic cells (pDCs) contribute to innate antiviral immunity via secreting type I interferons. Toll-like receptor (TLR) 9 is involved in major pattern recognition receptors expressed in pDCs. The frequency of pDCs and TLR9 expression in peripheral blood mononuclear cells (PBMC) was determined, using flow cytometry. IFN-alpha production by PBMC was evaluated in vitro in the presence of cytidine phosphate guanosine (CpG) with/without pDCs. The correlation between TLR9, pDCs frequency and viral load was also evaluated. TLR9 expression in pDCs in chronic HBV patients was significantly ( approximately 50%) reduced, supported by approximately 70% reduction of TLR9 mRNA, in comparison to healthy controls, correlating with the impairment of IFN-alpha production in vitro. Furthermore, pDCs frequency in these patients was substantially reduced ( approximately 30%), inversely correlating with serum ALT levels and HBV viral load. HBsAg and HBcAg were detected by immunohistochemistry in pDCs in chronic HBV patients. We conclude that HBV infection results in reduced frequency of circulating pDCs and their functional impairment via inhibiting the expression of TLR9. These data may provide useful information in both basic research and clinical treatment of chronic HBV infection.

Relationship between HBV DNA load in monocyte-derived dendritic cells and dendritic cell function in patients with chronic hepatitis B

AIM: To investigate the HBV DNA load in monocyte-derived dendritic cells (DCs) from patients with chronic hepatitis B, and to explore the reason for decrease of DC function.

METHODS: Twenty patients with chronic hepatitis B and 10 healthy controls were included in this study. We incubated and induced DC subsets differentiated from peripheral blood mononuclear cells (PBMCs). The expression levels of HLA-DR, CD-1α, CD80 and CD86 were detected by flow cytometry, and the levels of interleukin-12 (IL-12) in supernatants were measured by enzyme-linked immunosorbent assay (ELISA). The stimulatory ability of DCs for proliferation of allogeneic T cells was evaluated with mixed lymphocyte reaction (MLR). HBV DNA load in DCs was detected by fluorescent quantitative real-time PCR.

RESULTS: HBV DNA was detected in the DCs of 13 patients. The expression levels of HLA-DR, CD-1α, CD80, CD86, IL-12, and the stimulatory ability of DCs for allogeneic T cell proliferation were much lower in patients than those in healthy controls (P < 0.01 or 0.05); moreover, the above indicator levels were lower in patients with DC HBV DNA positive than those in patients with DC HBV DNA negative (correspondingly: 39.17 ± 6.02 vs 60.11 ± 7.92; 46.03 ± 5.52 vs 58.77 ± 4.12, 20.95 ± 6.32 vs35.24 ± 7.41, 25.16 ± 6.05 vs 45.30 ± 8.01, 19.67 ± 7.32 vs 30.74 ± 8.39, 0.32 ± 0.08 vs 0.59 ± 0.11; P < 0.01 or 0.05 ). The expression levels of HLA-DR, CD-1α, CD80 and CD86 on DCs, as well as the secretion of IL-12 and the stimulatory ability of DCs for allogeneic T cell proliferation, were significantly correlated with DC HBV load (r = -0.713, -0.713, -0.623, -0.702, -0.525, -0.841; P < 0.001).

CONCLUSION: The monocyte-derived DCs can be infected by HBV DNA. There is a significantly negative correlation between DC function and HBV DNA load, and the function of DCs is good when the load of HBV DNA is lower.

Association of suboptimal prescribing and change in lower extremity physical function over time

BACKGROUND

Previous studies have found inconsistent links between suboptimal prescribing and negative patient outcomes. While suboptimal prescribing consists of multiple components, e.g. drugs to avoid in the elderly (DAE), potential drug interactions (PDI) and polypharmacy, most research has focused on the impact of drugs to avoid. This study explores the relationship between suboptimal prescribing, comorbid disease, and change in lower extremity functional limitation (LEFL).

METHODS

This prospective cohort study used data from the Hispanic Established Population for the Epidemiologic Study of the Elderly. Baseline data collection occurred between 1993 and 1994 with three additional waves of data collected approximately every 2 years. Based on the disablement process model, the dependent variable was change in LEFL over the 7-year study period. Independent variables included suboptimal prescribing: DAE, PDI and polypharmacy. Measures of pathology included comorbid diseases (stroke, cancer, hypertension, cardiovascular disease, arthritis, and diabetes). Age, gender, education, smoking, cognitive status, depression, body mass index, marital status, and self-reported health were controlled in analyses.

RESULTS

Diabetes, stroke, and arthritis were associated with a decline in LEFL. Polypharmacy mediated the relationship between diabetes and LEFL, and polypharmacy was also significantly associated with decrements in LEFL.

CONCLUSION

The effect of suboptimal prescribing on change in LEFL was limited to both direct and mediational effects of polypharmacy. Additional research exploring the association between suboptimal prescribing and a variety of quality measures using a diverse set of outcomes would improve our understanding of the impact of suboptimal prescribing more broadly defined.

New concepts in the immunopathogenesis of chronic hepatitis B: the importance of the innate immune response

Acute and chronic infection with hepatitis B virus (HBV) is associated with an increased risk of developing liver disease including cirrhosis, decompensated liver disease, and hepatocellular carcinoma. The clinical presentation and natural history of HBV infection is mediated through complex interactions between the virus and the host immune response. HBV is not directly cytopathic to heptocytes; however, the interaction between the virus and the host immune response plays a central role in the pathogenesis of necroinflammation and liver fibrosis. Emerging data from immunopathogenesis studies in animal models and in vitro studies of liver biopsies from patients with chronic hepatitis B demonstrate a potentially important interaction between hepatitis B e antigen, HBV, and components of the innate immune response including Toll-like receptors, Kupffer cells, natural killer T-cells, and dendritic cells. These findings suggest that the innate immune response has an important role in influencing the outcome of acute and chronic HBV infection. The current knowledge regarding the interaction between HBV and components of the innate immune response during acute and chronic HBV infection is reviewed.

Role of viral factors in the natural course and therapy of chronic hepatitis B

Hepatitis B virus (HBV) infection is a global health problem that causes a wide spectrum of liver disease, including acute or fulminant hepatitis, inactive carrier state, chronic hepatitis, cirrhosis, and hepatocellular carcinoma (HCC). The pathogenesis of hepatocyte damage associated with HBV is mainly through immune-mediated mechanisms. On the basis of the virus and host interactions, the natural history of HBV carriers who are infected in early life can be divided into four dynamic phases. The frequency, extent, and severity of hepatitis flares or acute exacerbation in the second immune clearance and/or fourth reactivation phase predict liver disease progression in HBV carriers. In the past decade, hepatitis B viral factors including serum HBV DNA level, genotype, and naturally occurring mutants predictive of clinical outcomes have been identified. The higher the serum HBV DNA level after the immune clearance phase, the higher the incidence of adverse outcomes over time. In addition, high viral load, genotype C, basal core promoter mutation, and pre-S deletion correlate with increased risk of cirrhosis and HCC development. As to the treatment of chronic hepatitis B, patients with high HBV DNA level and genotype C or D infection are shown to have a worse response to interferon therapy. In conclusion, serum HBV DNA level, genotype, and naturally occurring mutants are identified to influence liver disease progression and therapy of chronic hepatitis B. More investigations are needed to clarify the molecular mechanisms of the viral factors involved in the pathogenesis of each stage of liver disease and the response to antiviral treatments.