Hepatitis: Woltman AM

Boonstra A, Woltman AM, Janssen HL. · Department of Gastroenterology and Hepatology, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands. · Best Pract Res Clin Gastroenterol. · Pubmed #19187866 No free full text.

Abstract: Hepatitis B (HBV) and hepatitis C (HCV) viruses are the two major causes of chronic liver inflammation worldwide. Despite distinct virologic features, both viruses are preferentially hepatotropic, not directly cytopathic, and elicit liver diseases that share several aspects of their natural history. HBV and HCV infections also share some important features of the adaptive antiviral immune response. We describe the innate immune response in the early phase following infection, and how these early events may influence the development of the adaptive immune response in these two important viral infections. The mechanisms by which high levels of viral antigens, liver immunological features, the presence of regulatory T cells and impaired dendritic cell functions may maintain the HBV- and HCV-specific immunological failure, characteristic of chronic hepatitis B and C patients, are also evaluated.

Liu B, Woltman AM, Janssen HL, Boonstra A. · Department of Molecular Cell Biology, Sanquin Research and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. · J Leukoc Biol. · Pubmed #18818373 No free full text.

Abstract: Worldwide, chronic viral infections cause major health problems with severe morbidity and mortality. HIV and hepatitis C virus (HCV) manifest themselves as persistent infections, but they are entirely distinct viruses with distinct replication mechanisms, tropism, and kinetics. Coinfections with HCV among people with HIV are emerging as a growing problem. Cellular immune responses play an important role in viral clearance and disease pathogenesis. However, cellular immunity to HIV and HCV is affected severely in chronic patients. Various hypotheses have been proposed to explain the dysfunctional T cell response, including viral escape mutations, exhaustion of the T cell compartment, and the activity of regulatory T cells. Also, modulation of the function of dendritic cells (DC) has been suggested as one of the mechanisms used by persistent viruses to evade the immune system. In this review, we will focus on DC interactions with one murine persistent virus (lymphocytic choriomeningitis virus clone 13) and two human persistent viruses (HIV-1 and HCV), intending to examine if general strategies are used by persistent viruses to modulate the function of DC to improve our understanding of the mechanisms underlying the development and maintenance of viral persistence.

Stoop JN, Claassen MA, Woltman AM, Binda RS, Kuipers EJ, Janssen HL, van der Molen RG, Boonstra A. · Department of Gastroenterology and Hepatology, Erasmus MC University Medical Center Rotterdam, Rotterdam, The Netherlands. · Clin Immunol. · Pubmed #18823821 No free full text.

Abstract: Peripheral blood CD4+CD25+ regulatory T cells (Treg) prevent the development of strong HBV-specific T cell responses in vitro. In this study, we examined the phenotype of FoxP3+ regulatory T cells in the liver of patients with a chronic HBV infection. We showed that the liver contained a population of CD4+FoxP3+ cells that did not express CD25, while these cells were absent from peripheral blood. Interestingly, intrahepatic CD25-FoxP3+CD4+ T cells demonstrated lower expression of HLA-DR and CTLA-4 as compared to their CD25+ counterparts. Patients with a high viral load have a higher proportion of regulatory T cells in the liver, but not in blood, compared to patients with a low viral load. In conclusion, the intrahepatic Treg are phenotypically distinct from peripheral blood Treg. Our data suggest that the higher proportion of intrahepatic Treg observed in patients with a high viral load may explain the lack of control of viral replication.

Op den Brouw ML, Binda RS, van Roosmalen MH, Protzer U, Janssen HL, van der Molen RG, Woltman AM. · Department of Gastroenterology and Hepatology, Erasmus MC, Rotterdam, The Netherlands. · Immunology. · Pubmed #18624732 No free full text.

Abstract: Chronic hepatitis B virus (HBV) infection is the result of an inadequate immune response towards the virus. Myeloid dendritic cells (mDC) of patients with chronic HBV are impaired in their maturation and function, resulting in more tolerogenic rather than immunogenic responses, which may contribute to viral persistence. The mechanism responsible for altered mDC function remains unclear. The HBV-infected patients display large amounts of HBV particles and viral proteins in their circulation, especially the surface antigen HBsAg, which allows multiple interactions between the virus, its viral proteins and DC. To assess whether HBV directly influences mDC function, the effects of HBV and HBsAg on human mDC maturation and function were investigated in vitro. As already described for internalization of HBV by DC, the present study shows that peripheral blood-derived mDC of healthy controls also actively take up HBsAg in a time-dependent manner. Cytokine-induced maturation in the presence of HBV or HBsAg resulted in a significantly more tolerogenic mDC phenotype as demonstrated by a diminished up-regulation of costimulatory molecules and a decreased T-cell stimulatory capacity, as assessed by T-cell proliferation and interferon-gamma production. In addition, the presence of HBV significantly reduced interleukin-12 production by mDC. These results show that both HBV particles and purified HBsAg have an immune modulatory capacity and may directly contribute to the dysfunction of mDC in patients with chronic HBV. The direct immune regulatory effect of HBV and circulating HBsAg particles on the function of DC can be considered as part of the mechanism by which HBV escapes immunity.

Op den Brouw ML, de Jong MA, Ludwig IS, van der Molen RG, Janssen HL, Geijtenbeek TB, Woltman AM. · Department of Gastroenterology and Hepatology, Erasmus MC, Rotterdam, The Netherlands. · J Viral Hepat. · Pubmed #18482282 No free full text.

Abstract: Hepatitis B virus (HBV) is a DNA virus that infects the liver as primary target. Currently, a high affinity receptor for HBV is still unknown. The dendritic cell specific C-type lectin DC-SIGN is involved in pathogen recognition through mannose and fucose containing carbohydrates leading to the induction of an anti-viral immune response. Many glycosylated viruses subvert this immune surveillance function and exploit DC-SIGN as a port of entry and for trans-infection of target cells. The glycosylation pattern on HBV surface antigens (HBsAg) together with the tissue distribution of HBV would allow interaction between HBV and DC-SIGN and its liver-expressed homologue L-SIGN. Therefore, a detailed study to investigate the binding of HBV to DC-SIGN and L-SIGN was performed. For HCV, both DC-SIGN and L-SIGN are known to bind envelope glycoproteins E1 and E2. Soluble DC-SIGN and L-SIGN specifically bound HCV virus-like particles, but no interaction with either HBsAg or HepG2.2.15-derived HBV was detected. Also, neither DC-SIGN nor L-SIGN transfected Raji cells bound HBsAg. In contrast, highly mannosylated HBV, obtained by treating HBV producing HepG2.2.15 cells with the alpha-mannosidase I inhibitor kifunensine, is recognized by DC-SIGN. The alpha-mannosidase I trimming of N-linked oligosaccharide structures thus prevents recognition by DC-SIGN. On the basis of these findings, it is tempting to speculate that HBV exploits mannose trimming as a way to escape recognition by DC-SIGN and thereby subvert a possible immune activation response.

Stoop JN, Woltman AM, Biesta PJ, Kusters JG, Kuipers EJ, Janssen HL, van der Molen RG. · Department of Gastroenterology and Hepatology, Erasmus MC-Rotterdam, The Netherlands. · Hepatology. · Pubmed #17654744 No free full text.

Abstract: Chronicity of hepatitis B virus (HBV) infection is characterized by a weak immune response to the virus. CD4+CD25+ regulatory T cells (Treg) are present in increased numbers in the peripheral blood of chronic HBV patients, and these Treg are capable of suppressing the HBV-specific immune response. The aim of this study was to abrogate Treg-mediated suppression of the HBV-specific immune response. Therefore, Treg and a Treg-depleted cell fraction were isolated from peripheral blood of chronic HBV patients. Subsequently, the suppressive effect of Treg on the response to HBV core antigen (HBcAg) and tetanus toxin was compared, and the effect of exogenous tumor necrosis factor alpha (TNF-alpha), interleukin-1-beta (IL-1beta), or neutralizing antibodies against interleukin-10 (IL-10) or transforming growth factor beta (TGF-beta) on Treg-mediated suppression was determined. The results show that Treg of chronic HBV patients had a more potent suppressive effect on the response to HBcAg compared with the response to tetanus toxin. Neutralization of IL-10 and TGF-beta or exogenous IL-1beta had no effect on Treg-mediated suppression of the anti-HBcAg response, whereas exogenous TNF-alpha partially abrogated Treg-mediated suppression. Preincubation of Treg with TNF-alpha demonstrated that TNF-alpha had a direct effect on the Treg. No difference was observed in the type II TNF receptor expression by Treg from chronic HBV patients and healthy controls. CONCLUSION: Treg-mediated suppression of the anti-HBV response can be reduced by exogenous TNF-alpha. Because chronic HBV patients are known to produce less TNF-alpha, these data implicate an important role for TNF-alpha in the impaired antiviral response in chronic HBV.