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Biomedical subjects

Graham R Foster

Publications and source records attributed to Graham R Foster.

18 recordsLinked to original sources
PubMed2006

Chronic exposure to Helicobacter pylori impairs dendritic cell function and inhibits Th1 development.

Helicobacter pylori causes chronic gastric infection that affects the majority of the world's population. Despite generating an inflammatory response, the immune system usually fails to clear the infection. Since dendritic cells (DCs) play a pivotal role in shaping the immune response, we investigated the effects of H. pylori on DC function. We have demonstrated that H. pylori increased the expression of activation markers on DCs while upregulating the inhibitory B7 family molecule, PD-L1. Functionally, H. pylori-treated DCs resulted in the production of interleukin-10 (IL-10) and IL-23 but not of alpha interferon (IFN-alpha). While very little or no IL-12 was produced to H. pylori alone, simultaneous ligation of CD40 on DCs induced IL-12 release. We also demonstrated that DCs treated with H. pylori-induced IFN-gamma production by allogeneic naive T cells. However, stimulation of DCs with H. pylori for an extended period of time impaired their ability to produce cytokines after CD40 ligation and limited their ability to promote IFN-gamma release, suggesting that the DCs had become exhausted by the prolonged stimulation. The effect of chronic infection with H. pylori on DC function was further investigated by focusing on DC development. Demonstrating that monocytes differentiated into DCs in the presence of H. pylori exhibited an exhausted phenotype with an impaired ability to produce IL-12 and a downregulation of CD1a. Our results raise the possibility that in chronic H. pylori infection DCs become exhausted after prolonged antigen exposure leading to suboptimal Th1 development. This effect may contribute to persistence of H. pylori infection.

Antigens, CD↗
PubMed2006

Health-related quality of life before, during and after combination therapy with interferon and ribavirin in unselected Swedish patients with chronic hepatitis C.

OBJECTIVE: To study the relationship between health-related quality of life (HRQOL) and mode of acquisition, treatment discontinuations, drop in haemoglobin levels and treatment outcome in patients with chronic hepatitis C (CHC). MATERIAL AND METHODS: Consecutive unselected Swedish patients with CHC completed the SF-36 questionnaire before, during and after treatment with interferon and ribavirin. Results. At baseline, HRQOL was reduced in all SF-36 subscales in our patients (n=147) as compared with the general Swedish population. Former intravenous drug users (IVDUs) scored significantly lower in social function (p=0.03) and mental health (p=0.03) than patients who had acquired their infection from blood transfusions (PTH). A decline of >40 points in HRQOL from baseline to week 12 was noticed in the role limitations-physical (RP) score for the IVDU and PTH groups (p<0.0001 and 0.001, respectively). Patients with a >or=20% fall in haemoglobin levels at treatment week 12 had a significantly poorer RP (p=0.006) and role limitations-emotional score (p<0.02) than patients with a <10% fall. Early treatment dropouts had significantly lower HRQOL scores at baseline than adherent patients. At follow-up, sustained viral responders had significantly higher scores than non-responders. CONCLUSIONS: Swedish outpatients with CHC have a marked reduction in their HRQOL as compared to the general population. Therapy reduces HRQOL most substantially in those with a marked reduction in haemoglobin. Early dropouts from therapy have significantly lower HRQOL scores at baseline than adherent patients, and sustained viral responders improve their HRQOL significantly more than non-responders.

Adult↗
PubMed2005

Type I interferons and the innate immune response--more than just antiviral cytokines.

The role of type I interferon (referred to as IFN in this review) in early antiviral immunity is well known. More recently IFN has been shown to be a potent regulator of adaptive immunity. It is now becoming clear that a broad range of viruses, bacteria and even parasites express ligands capable of stimulating a growing number of signalling pathways that results in, often subtype specific, induction of IFN. Of particular interest are the signalling pathways associated with the Toll-like receptors. This family of receptors, each able to induce signals in response to a variety of ligands, initiates the pro-inflammatory response. They also contain members that have the capacity to induce IFN, making use of, and perhaps promoting the evolution of its pleiotropic responses. Greater knowledge of the events that result in induction of IFN is necessary in understanding the specificity of expression of an increasingly complex and important aspect of our immune system. This may reveal to us further therapeutic opportunities, either in the use of IFN or in the manipulation of their expression. This review details the established knowledge and recent advances made in understanding how and under what circumstances the IFNs are expressed, starting with brief overviews of IFN and Toll-like receptors before following the molecular processes from induction of IFN, activation of the JAK-STAT pathway and finally the expression of interferon stimulated genes and their functions.

Animals↗
PubMed2005

Prevalence of hepatitis C-related cirrhosis in elderly Asian patients infected in childhood.

BACKGROUND & AIMS: Approximately 20% of hepatitis C virus (HCV) patients develop cirrhosis from infection after about 20 years. The proportion of patients developing cirrhosis for longer than 30 years after infection is unknown. Our objectives were to determine the prevalence of HCV-related cirrhosis in a population of Asian patients who were infected in childhood 20 to 80 years ago and compare this with the prevalence of cirrhosis in Caucasian patients referred to the same hospitals. METHODS: Retrospective analyses were performed of all patients who had detectable HCV-RNA levels and who attended local hospitals in northeast London between 1992 and 2003. Factors implicated in the development of cirrhosis were examined by multivariable analysis. RESULTS: A total of 143 adult Asian patients who had been infected with HCV for many decades were compared with 239 Caucasian patients. The prevalence of cirrhosis increased with age. Of Asian patients aged 61-80 years (n = 55) 78% had cirrhosis, whereas 25% of Caucasian patients aged 61-80 years (n = 55) had cirrhosis. Multivariable linear analysis revealed that fibrosis progression and age were similar in both groups and the difference in the prevalence of cirrhosis was not explained by any unique Asian characteristic other than prolonged infection. CONCLUSIONS: The prevalence of cirrhosis in patients with chronic HCV increases with increasing duration of infection. In Asian patients infected at birth, infection for over 60 years causes cirrhosis in 71% of infected individuals. Because relationship between the severity of fibrosis and age in Asian patients is similar to that seen in Caucasian patients it is likely that similar rates of cirrhosis will be seen in other patients who are infected for more than 60 years.

Adult↗
PubMed2005

Qualitatively distinct patterns of cytokines are released by human dendritic cells in response to different pathogens.

Dendritic cells produce cytokines that regulate the class of the adaptive immune response. Microbial recognition is mediated, at least in part, by pattern recognition receptors such as Toll-like receptors, which influence dendritic cell maturation. In humans it is not yet clear how intact pathogens modulate the developing immune response. To address the effects of intact pathogens on the maturation and effector functions of human dendritic cells, we investigated their responses to a number of microbial pathogens. We studied a range of micro-organisms including Gram-negative bacteria (Escherichia coli and Salmonella enterica sv. typhimurium), Gram-positive cocci (Staphylococcus aureus) and atypical bacteria (Mycobacterium tuberculosis and Mycoplasma hominis) as well as the human protozoal parasite Trichomonas vaginalis. The micro-organisms were fixed in formaldehyde to prevent replication whilst preserving surface morphology. All the pathogens induced similar up-regulation of dendritic cell activation-associated cell surface markers but there was a profound difference in the patterns of cytokines produced by the stimulated dendritic cells. Some pathogens (E. coli, Salmonella enterica sv. typhimurium and S. aureus) induced interleukin-12 (IL-12), IL-10 and interferon-alpha whereas others (M. tuberculosis, Mycoplasma hominis and T. vaginalis) induced only IL-10. This differential effect was not altered by costimulation of the dendritic cells through CD40. These results support the notion that human dendritic cells are plastic in their response to microbial stimuli and that the nature of the pathogen dictates the response of the dendritic cell.

Animals↗
PubMed2005

Dengue virus inhibits alpha interferon signaling by reducing STAT2 expression.

Alpha/beta interferon (IFN-alpha/beta) is a key mediator of innate antiviral responses but has little effect on the established replication of dengue viruses, which are mosquito-borne flaviviruses of immense global health importance. Understanding how the IFN system is inhibited in dengue virus-infected cells would provide critical insights into disease pathogenesis. In a recent study analyzing the ability of individual dengue virus-encoded proteins to antagonize the IFN response, nonstructural (NS) protein 4B and possibly NS2A and NS4A were identified as candidate IFN antagonists. In monkey cells, NS4B appeared to inhibit both the IFN-alpha/beta and IFN-gamma signal transduction pathways, which are distinct but overlapping (J. L. Munoz-Jordan, G. G. Sanchez-Burgos, M. Laurent-Rolle, and A. Garcia-Sastre, Proc. Natl. Acad. Sci. USA 100:14333-14338, 2003). For this study, we examined the effects of dengue virus on the human IFN system, using cell lines that were stably transfected with self-replicating subgenomic dengue virus RNA (replicons) and that expressed all of the dengue virus nonstructural proteins together. We show here that in replicon-containing cells dengue virus RNA replication and the replication of encephalomyocarditis virus, an IFN-sensitive virus, are resistant to the antiviral effects of IFN-alpha. The presence of dengue virus replicons reduces global IFN-alpha-stimulated gene expression and specifically inhibits IFN-alpha but not IFN-gamma signal transduction. In cells containing replicons or infected with dengue virus, we found reduced levels of signal transducer and activator of transcription 2 (STAT2), which is a key component of IFN-alpha but not IFN-gamma signaling. Collectively, these data show that dengue virus is capable of subverting the human IFN response by down-regulating STAT2 expression.

Cell Line↗
PubMed2004

IFN-alpha subtypes differentially affect human T cell motility.

The type I IFN family includes 14 closely related antiviral cytokines that are produced in response to viral infections. They bind to a common receptor, and have qualitatively similar biological activities. The physiological relevance of this redundancy is still unclear. In this study, we analyzed and compared the effects of two potent antiviral type I IFNs, IFN-alpha 2 and IFN-alpha 8, on the motility of various populations of human T lymphocytes in vitro. In this study, we show that IFN-alpha 2 induces chemokinesis of both CD4(+) and CD8(+) T cells at various stages of differentiation, and induces functional changes that result in enhanced T cell motility, including up-regulation of the integrins LFA-1 and VLA-4, and subsequently, increased ICAM-1- and fibronectin-dependent migration. In contrast, IFN-alpha 8 did not affect T cell motility, despite having similar antiviral properties and similar effects on the induction of the antiviral protein MxA. However, transcription of other IFN-stimulated genes showed that transcription of these genes is selectively activated by IFN-alpha 2, but not IFN-alpha 8, in T cells. Finally, while the antiviral activity of the two subtypes is inhibited by Abs against the two subunits of the IFN-alpha receptor, the chemokinetic effect of IFN-alpha 2 is selectively blocked by Abs against the A1 receptor subunit. These observations are consistent with the possibility that subtype-specific intracellular signaling pathways are activated by type I IFNs in T lymphocytes.

Antibodies, Monoclonal↗
PubMed2004

Telomere erosion in memory T cells induced by telomerase inhibition at the site of antigenic challenge in vivo.

The extent of human memory T cell proliferation, differentiation, and telomere erosion that occurs after a single episode of immune challenge in vivo is unclear. To investigate this, we injected tuberculin purified protein derivative (PPD) into the skin of immune individuals and isolated responsive T cells from the site of antigenic challenge at different times. PPD-specific CD4+ T cells proliferated and differentiated extensively in the skin during this secondary response. Furthermore, significant telomere erosion occurred in specific T cells that respond in the skin, but not in those that are found in the blood from the same individuals. Tissue fluid obtained from the site of PPD challenge in the skin inhibited the induction of the enzyme telomerase in T cells in vitro. Antibody inhibition studies indicated that type I interferon (IFN), which was identified at high levels in the tissue fluid and by immunohistology, was responsible in part for the telomerase inhibition. Furthermore, the addition of IFN-alpha to PPD-stimulated CD4+ T cells directly inhibited telomerase activity in vitro. Therefore, these results suggest that the rate of telomere erosion in proliferating, antigen-specific CD4+ T cells may be accelerated by type I IFN during a secondary response in vivo.

BCG Vaccine↗
PubMed2004

Combination therapy with amantadine and interferon in naïve patients with chronic hepatitis C: meta-analysis of individual patient data from six clinical trials.

BACKGROUND/AIMS: In chronic hepatitis C, clinical trials evaluating the efficacy of amantadine (AMA) and interferon (INF) compared to INF monotherapy, have produced conflicting results. We performed a meta-analysis of the individual patient's data from previous studies. METHODS: Nine hundred and seventy-two patients from six European centres were evaluated by means of individual patient meta-analysis, using mixed models with centres and the centre-treatment interaction fitted as random variables. RESULTS: At the end of therapy, virological responses were 38.5% (95% CI 34.1-42.8) after INF and AMA, and 29.5% (95% CI 25.5-33.6) after INF alone (P = 0.003). Sustained response occurred in 111 (23.1%; 95% CI 19.3-20.2) and 85 patients (17.3%; 95% CI 14.0-20.7), respectively (P = 0.03). Even accounting for the centre effect, therapy with AMA and INF was more effective than IFN alone (P = 0.029). When genotypes and viraemia levels were combined, the response rate after combination therapy doubled that observed with IFN alone in all subgroups, except those with low viraemia and genotypes 2 or 3. CONCLUSIONS: In chronic hepatitis C, therapy with AMA and INF is effective and may be an alternative to INF and ribavirin in patients who cannot tolerate ribavirin.

Adult↗
PubMed2004

Past, present, and future hepatitis C treatments.

Conventional interferon (IFN) alfa has been used for many years in the treatment of chronic hepatitis C. However, few patients achieve sustained virological responses with IFN. Combining IFN with ribavirin improves efficacy considerably, but at the expense of diminished tolerability attributable to ribavirin. Pegylated interferons have improved pharmacokinetic profiles, may be administered once weekly, and are more effective than IFN is alone or in combination with ribavirin. In addition to enhanced efficacy, pegylated interferon alfa-2a (40 kD) also improves health-related quality of life during therapy compared with IFN-based therapy. New adjuvant agents have the potential to further improve sustained response rates and tolerability; however, pegylated interferons will likely remain the backbone of therapy in the foreseeable future. Therapies under development and evaluation for patients with HCV infection include adjunctive use of the antiviral agent amantadine and the immunomodulatory agent thymalfasin. Novel small molecules include the ribavirin analogues, viramidine and levovirin, and BILN 2061, an inhibitor of HCV serine protease. Other therapeutic strategies that have reached the clinic include antisense oligonucleotides (ISIS 14803), nuclease-resistant ribozymes targeting HCV RNA (Heptazyme), human monoclonal antibodie, and human antibody fragments directed at HCV helicase.

Antibodies, Monoclonal↗
PubMed2003

High yield expression, refolding, and characterization of recombinant interferon alpha2/alpha8 hybrids in Escherichia coli.

Interferons (IFNs) are a family of pleiotropic cytokines used for the treatment of various viral infections and cancers. The low-cost production of IFNs with high biological value and the discovery of IFNs with improved properties are important for the treatment of these diseases as well as for understanding the physiological functions of these compounds. We describe a protein expression system for the production of IFNs alpha2, alpha8, and their hybrids in insoluble form in Escherichia coli, coupled to an efficient two-step optimized refolding and histidine-tag purification protocol. The expressed IFNs were of high biological value, as shown in antiviral and antiproliferative assays and some had specific activities higher than those of the commercially available interferon preparations and exhibited novel properties. This time-efficient, optimized protein expression method allows for the production of not just a single interferon subtype but several native and hybrid IFNs with relatively high yield and low cost that can be used in functional and potentially clinical assays.

Amino Acid Sequence↗
PubMed2003

Activity of hybrid type I interferons in cells lacking Tyk2: a common region of IFN-alpha 8 induces a response, but IFN-alpha2/8 hybrids can behave like IFN-beta.

Type I interferons (IFNs) are a family of pleiotropic cytokines with antiviral, antiproliferative, and immunomodulatory properties. The type I IFN family consists of 12 IFN-alpha subtypes, IFN-beta, and IFN-omega. Cells lacking the receptor-associated protein kinase Tyk2 (U1A) are responsive only to IFN-beta and partially to IFN-alpha8. We constructed a series of IFN-alpha2/alpha8 hybrids and mutants and identified the region within IFN-alpha8 responsible for its activity in Tyk2-deficient cells. The same domain mediates the interactions between IFN and IFN-alpha receptor (IFNAR) in Tyk2-complemented and Tyk2-deficient cells (U1A). The presence or absence of Tyk2 altered the inhibitory effects of anti-IFNAR antibodies, suggesting that the IFN-alpha binding domain on IFNAR is altered by the presence of Tyk2. The activity of IFN-beta was not significantly affected by the deletion of Tyk2, and, surprisingly, one of our IFN-alpha2/alpha8 hybrids (IFN-alpha288) behaved like IFN-beta in a number of assays that distinguish IFN-alphas from IFN-beta. This suggests that this hybrid mimics the interactions of IFN-beta with the receptor and also suggests the existence of a distinct binding site(s) on IFNAR for IFN-beta and some hybrid IFN-alphas.

Amino Acid Sequence↗
PubMed2003

Pegylated interferon with ribavirin therapy for chronic infection with the hepatitis C virus.

Chronic infection with the hepatitis C virus is common. In the past, therapy involved a combination of thrice-weekly interferon (IFN) injections combined with oral ribavirin. This therapy was expensive, poorly tolerated and poorly effective, only curing approximately 40% of treated patients. Long-acting IFNs have recently been developed by linking IFN to polyethylene glycol and these 'pegylated' IFNs are now the standard of care for patients with chronic hepatitis C (CHC). Two pegylated (PEG) IFNs are available; 40 kDa PEG-IFNalpha(2a) (Pegasys, Hoffmann-La Roche) and the 12 kDa PEG-IFN-alpha(2b) (Peg-Intron, Schering-Plough). They have different physicochemical, pharmacokinetic and pharmacodynamic properties. The 40 kDa PEG-IFN-alpha(2a) is dispensed as a solution and used at a fixed dose whereas the 12 kDa PEG-IFN-alpha(2b) is a dry powder, which is reconstituted prior to administration, and the dose is dependent upon body weight. Both PEG-IFNs are given by a once-weekly injection and as monotherapy, they are more effective than standard IFN-alpha. The 40 kDa PEGIFN-alpha(2a) cures 36 - 39% of patients and the 12 kDa pegylated-IFN-alpha(2b) cures 23 - 25%. When combined with ribavirin, the two PEG-IFNs have acceptable safety profiles and cure > 50% of treated patients (56 and 54% for the 40 kDa PEG-IFN-alpha(2a) and 12 kDa PEG-IFN-alpha(2b), respectively). For the 40 kDa PEG-IFN-alpha(2a) it is possible to predict the outcome of therapy after 12 weeks of treatment. The new PEG-IFNs are a significant advance in the therapy of CHC infection. Their ease of administration, coupled with their improved efficacy, is likely to lead to an increase in the proportion of infected patients who wish to receive treatment.

Antiviral Agents↗
PubMed2002

Different activities of type I interferons on hepatitis B virus core promoter regulated transcription.

The type I interferons (IFNs) are a group of closely related cytokines which have different signal transduction pathways and different biological activities. Using transient transfection of human hepatoma cells with reporter plasmids containing the firefly/renilla luciferase genes under the control of the HBV-Enhancer (Enh) I, Enh II and core promoter we have investigated the biological activities of 10 recombinant (r) type I IFNs on transcription. Low concentrations of IFN (0.025 ng/ml) had a significant and specific inhibitory effect but the potencies of the different recombinant type I IFNs differed markedly with IFNalpha8 and IFNbeta being six-fold more potent than the least effective subtype (IFNalpha1). However, the addition of IFNalpha5-the subtype produced predominantly in the human liver-did not cause any synergistic effects.The non-natural consensus IFN displayed a more pronounced inhibition of HBV-regulated transcription than IFNalpha8 or IFNalpha2 but not IFNbeta. The INF-induced inhibitory effect was not dependent on the presence of the HBV-Enh1 and in particular of an interferon stimulated response element (ISRE)-like sequence. The characterization of different effects among type I interferons on HBV-regulatory elements may implicate an IFN-subtype-specific role for the pathogenesis and treatment of HBV-infection.

Cell Line↗
PubMed2002

Hepatitis C and cognitive impairment in a cohort of patients with mild liver disease.

Patients with chronic hepatitis C virus (HCV) infection frequently report fatigue, lassitude, depression, and a perceived inability to function effectively. Several studies have shown that patients exhibit low quality-of-life scores that are independent of disease severity. We therefore considered whether HCV infection has a direct effect on the central nervous system, resulting in cognitive and cerebral metabolite abnormalities. Twenty-seven viremic patients with biopsy-proven mild hepatitis due to HCV and 16 patients with cleared HCV were tested with a computer-based cognitive assessment battery and also completed depression, fatigue, and quality-of-life questionnaires. The HCV-infected patients were impaired on more cognitive tasks than the HCV-cleared group (mean [SD]: HCV-infected, 2.15 [1.56]; HCV-cleared, 1.06 [1.24]; P =.02). A factor analysis showed impairments in power of concentration and speed of working memory, independent of a history of intravenous drug usage (IVDU), depression, fatigue, or symptom severity. A subgroup of 17 HCV-infected patients also underwent cerebral proton magnetic resonance spectroscopy (1H MRS). The choline/creatine ratio was elevated in the basal ganglia and white matter in this group. Patients who were impaired on 2 or more tasks in the battery had a higher mean choline/creatine ratio compared with the unimpaired patients. In conclusion, these preliminary results demonstrate cognitive impairment that is unaccounted for by depression, fatigue, or a history of IVDU in patients with histologically mild HCV infection. The findings on MRS suggest that a biological cause underlies this abnormality.

Adult↗