Vitamin D levels vary during antiviral treatment but are unable to predict treatment outcome in HCV genotype 1 infected patients.

BACKGROUND: Different parameters have been determined for prediction of treatment outcome in hepatitis c virus genotype 1 infected patients undergoing pegylated interferon, ribavirin combination therapy. Results on the importance of vitamin D levels are conflicting. In the present study, a comprehensive analysis of vitamin D levels before and during therapy together with single nucleotide polymorphisms involved in vitamin D metabolism in the context of other known treatment predictors has been performed. METHODS: In a well characterized prospective cohort of 398 genotype 1 infected patients treated with pegylated interferon-α and ribavirin for 24-72 weeks (INDIV-2 study) 25-OH-vitamin D levels and different single nucleotide polymorphisms were analyzed together with known biochemical parameters for a correlation with virologic treatment outcome. RESULTS: Fluctuations of more than 5 (10) ng/ml in 25-OH-vitamin D-levels have been observed in 66 (39) % of patients during the course of antiviral therapy and neither pretreatment nor under treatment 25-OH-vitamin D-levels were associated with treatment outcome. The DHCR7-TT-polymorphism within the 7-dehydrocholesterol-reductase showed a significant association (P = 0.031) to sustained viral response in univariate analysis. Among numerous further parameters analyzed we found that age (OR = 1.028, CI = 1.002-1.056, P = 0.035), cholesterol (OR = 0.983, CI = 0.975-0.991, P<0.001), ferritin (OR = 1.002, CI = 1.000-1.004, P = 0.033), gGT (OR = 1.467, CI = 1.073-2.006, P = 0.016) and IL28B-genotype (OR = 2.442, CI = 1.271-4.695, P = 0.007) constituted the strongest predictors of treatment response. CONCLUSIONS: While 25-OH-vitamin D-levels levels show considerable variations during the long-lasting course of antiviral therapy they do not show any significant association to treatment outcome in genotype 1 infected patients.

Improved responses to pegylated interferon alfa-2b and ribavirin by individualizing treatment for 24-72 weeks.

BACKGROUND & AIMS: Guidelines recommend that patients with chronic hepatitis C virus (HCV) infection be treated with pegylated interferon and ribavirin for 24, 48, or 72 weeks, based on their virologic response to treatment. We investigated the effects of treating patients for individualized durations. METHODS: We treated 398 treatment-naïve patients who had HCV genotype 1 infections with pegylated interferon alfa-2b and ribavirin for 24, 30, 36, 42, 48, 60, or 72 weeks (mean of 39 weeks, termed individualized therapy); the duration of therapy was determined based on baseline viral load and the time point at which HCV RNA levels became undetectable (measured at weeks 4, 6, 8, 12, 24, and 30). Results were compared with those of 225 patients who received standard treatment for 48 weeks (mean of 38 weeks). RESULTS: Rates of sustained virologic response (SVR) were 55% among patients who received individualized treatment and 48% among those who received standard treatment (P < .0001 for noninferiority). SVR rates, according to the time point at which HCV RNA levels became undetectable, did not differ significantly between groups. Patients with a rapid virologic response (undetectable levels of HCV RNA at week 4) who were treated for 24 to 30 weeks achieved high rates of SVR (86%-88%). Rates of SVR increased among slow responders who first tested negative for HCV RNA at week 24 and were treated for 60 to 72 weeks compared with those treated for 48 weeks (60%-68% vs 43%-44%). The CC polymorphism at IL28B rs129797860 was associated with an increased rate of SVR compared with the CT/TT polymorphism (P < .0001) at baseline but not among patients who had undetectable levels of HCV RNA following treatment. CONCLUSIONS: Individualizing treatment of patients with chronic HCV genotype 1 infections for 24 to 72 weeks results in high rates of SVR among rapid responders and increases SVR among slow responders.

Toll-like receptor-dependent activation of antigen-presenting cells affects adaptive immunity to Helicobacter pylori.

BACKGROUND & AIMS: Recognition of infection leads to induction of adaptive immunity through activation of antigen-presenting cells (APCs). Among APCs, dendritic cells (DCs) have the unique capacity to deliver antigens from the periphery to T cells in secondary lymphoid organs. METHODS: We analyzed molecular mechanisms of the Helicobacter pylori-induced APC activation in vitro and investigated the influence of Myd88 signaling on the phenotype of adaptive immunity to H pylori in a murine infection model. RESULTS: The adaptor protein Myd88 mediates Toll-like receptor (TLR), interleukin (IL)-1, and IL-18 signaling. DCs from wild-type, IL-1R(-/-), and IL-18(-/-) mice responded to H pylori with secretion of proinflammatory cytokines and up-regulation of major histocompatibility complex II and costimulatory molecules. In Myd88(-/-) DCs these processes were impaired profoundly, showing that TLR-dependent H pylori-sensing affects DC activation. Analysis of the H pylori-specific DC transcriptome revealed that large parts of the bacteria-induced transcriptional changes depended on Myd88 signaling, comprising numerous genes involved in crucial steps of immune regulation, such as DC maturation/differentiation, antigen uptake/presentation, and effector cell recruitment/activation. The impaired ability of Myd88(-/-) DCs, B cells, and macrophages to mount a proinflammatory response to H pylori in vitro was reflected in vivo by reduced gastric inflammation and increased bacterial colonization in Myd88-deficient mice. Furthermore, Helicobacter-specific IgG2c/IgG1 ratios were reduced in Myd88(-/-) animals, suggesting the involvement of the Myd88-dependent pathway in the instruction of adaptive immunity toward a T helper cell type 1 phenotype. CONCLUSIONS: A principal pathway by which DCs sense H pylori and become activated is the TLR-dependent signaling cascade. In vivo, Myd88 signaling affects adaptive immunity to the bacterium.

H pylori and gastric cancer: shifting the global burden.

Infection with H pylori leads to a persistent chronic inflammation of the gastric mucosa, thereby increasing the risk of distal gastric adenocarcinoma. Numerous studies have determined a clear correlation between H pylori infection and the risk of gastric cancer; however, general eradication is not recommended as cancer prophylaxis and time points for treatment remain controversial in different areas of the world. Prevalence rates in Western countries are decreasing, especially in younger people (< 10%); and a decline in distal gastric adenocarcinoma has been observed. Risk groups in Western countries still show considerably higher risk of developing cancer, especially in patients infected with cagA+ strains and in persons harboring genetic polymorphism of the IL-1B promoter (-511T/T) and the corresponding IL-1 receptor antagonist (IL-1RN*2). Thus, general eradication of all infected persons in Western countries not recommended and is limited to risk groups in order to achieve a risk reduction. In contrast, infection rates and cancer prevalence are still high in East Asian countries. A prevention strategy to treat infected persons may avoid the development of gastric cancer to a large extent and with enormous clinical importance. However, studies in China and Japan indicate that prevention of gastric cancer is effective only in those patients that do not display severe histological changes such as atrophy and intestinal metaplasia. Thus, prophylactic strategies to prevent gastric cancer in high risk populations such as China should therefore especially aim at individuals now at younger age when the histological alterations caused by the bacterial infection was still reversible. In countries with a low prevalence of gastric cancer, risk groups carrying cagA+ strains and IL-1 genetic polymorphisms should be identified and treated.

CD25+/Foxp3+ T cells regulate gastric inflammation and Helicobacter pylori colonization in vivo.

BACKGROUND & AIMS: Helicobacter pylori infects more than half of the world's population. In contrast to most other pathogens, the microbe persists for the virtual life of its host. It is unclear why the immune system is unable to eliminate the infection, but recent studies suggested that CD4+/CD25+/Foxp3+ regulatory T cells may be involved in this process. METHODS: By using a mouse model of infection and gastric biopsies from 108 patients, we performed a detailed descriptive and functional characterization of the Helicobacter-induced CD25+/Foxp3+ T-cell response. RESULTS: In C57BL/6 mice, H pylori induced a marked gastric Foxp3+ T-cell response, which increased over several months together with the severity of inflammation, until a stable homeostatic situation became established. Accordingly, in Helicobacter-infected patients, but not in uninfected individuals, large numbers of gastric Foxp3+ T cells were detected immunohistochemically. To define the functional in vivo relevance of this response, CD25+ cells were depleted systemically in mice by using an anti-CD25 monoclonal antibody (PC61). Already 4 weeks after infection, PC61-treated mice, but not untreated animals, developed a severe gastritis with heightened cytokine expression and increased numbers of mucosal T cells, B cells, and macrophages. This was accompanied by increased titers of H pylori-specific IgG1 and IgG2c antibodies in the sera of PC61-treated mice. This increased gastric inflammatory response in CD25-depleted mice was associated with reduced bacterial loads. CONCLUSIONS: CD25+/Foxp3+ T cells actively participate in the immune response to H pylori. In vivo depletion of these cells in infected mice leads to increased gastric inflammation and reduced bacterial colonization.

VacA-associated inhibition of T-cell function: reviewed and reconsidered.

Chronic Helicobacter pylori infection is characterized by dense infiltration of the mucosa with neutrophilic granulocytes, lymphocytes, and monocytes/macrophages. Among these different cell types, T-lymphocytes are the most intriguing and crucial cells for the elimination of the bacteria. Previous studies have elucidated possible mechanisms on how bacteria could interfere with the human immune response and claimed that especially the secreted vacuolating toxin VacA may be responsible for the chronic persistence of the bacteria. Some of these results have to be interpreted with caution and may just describe in vitro phenomena; others may reveal promising facts.

Human dendritic cells respond to Helicobacter pylori, promoting NK cell and Th1-effector responses in vitro.

Helicobacter pylori infection leads to chronic gastric inflammation. The current study determined the response of human APCs, NK cells, and T cells toward the bacteria in vitro. Human monocyte-derived dendritic cells (DC) were incubated with bacteria for 48 h. Intact H. pylori at a multitude of infection 5 stimulated the expression of MHC class II (4- to 7-fold), CD80, and CD86 B7 molecules (10- to 12-fold) and the CD83 costimulatory molecule (>30-fold) as well as IL-12 secretion (>50-fold) in DCs, and thereby, strongly induced their maturation and activation. CD56(+)/CD4(-) NK cells, as well as CD4(+)/CD45RA(+) naive T cells, were isolated and incubated with DCs pulsed with intact bacteria or different cellular fractions. Coculture of H. pylori-pulsed DCs with NK cells strongly potentiated the secretion of TNF-alpha and IFN-gamma. Coculture of naive T cells with H. pylori-pulsed DCs significantly enhanced TNF-alpha, IFN-gamma, and IL-2 secretion as well as T-bet mRNA levels, while GATA-3 mRNA was lowered. However, the effect appeared attenuated compared with coculture with Escherichia coli. A greater stimulation was seen with naive T cells and DCs pulsed with H. pylori membrane preparations. Intact H. pylori potently induced the maturation and activation of human monocyte-derived DC and thereby promote NK and Th1 effector responses. The strong activation of NK cells may be important for the innate immune response. Th1-polarized T cells were induced especially by incubation with membrane preparations of H. pylori, suggesting that membrane proteins may account for the specific adaptive immune response.