Mutational modifications of hepatitis A virus proteins 2B and 2C described for cell culture-adapted and attenuated virus are present in wild-type virus populations.

Studies have identified certain mutations in the 2B and 2C proteins of hepatitis A virus (HAV) as being essential for efficient growth in cultured cells, and it is assumed that these mutations contribute to the attenuated phenotype. We found that mutations supporting cell culture growth already exist in wild-type HAV populations. This suggests that these variants are not entirely generated de novo but are selected from the wild-type population.

NF-κB activation induced by hepatitis A virus and Newcastle disease virus occurs by different pathways depending on the structural pattern of viral nucleic acids.

NF-κB is activated by hepatitis B virus and hepatitis C virus and is assumed to contribute to viral persistence, leading to the development of hepatocellular cancer by inhibition of apoptosis mediated by cytotoxic T cells. Whether hepatitis A virus (HAV), which does not cause chronic infection, activates NF-κB is a topic of controversy. Here, we confirm that HAV activates NF-κB and show that HAV enhances the activation of NF-κB by poly(I-C), but it inhibits the activation of NF-κB by Newcastle disease virus (NDV), a paramyxovirus.

The role of immunoglobulin A in prolonged and relapsing hepatitis A virus infections.

Hepatitis A virus (HAV) infections result in different courses of the disease, varying between normal, prolonged and relapsing. However, the reason for these heterogeneous clinical appearances is not understood. As HAV-anti-HAV IgA immunocomplexes (HAV-IgA) infect hepatocytes, IgA was postulated as a carrier supporting hepatotropic transport of HAV, and it was speculated that this carrier mechanism contributes to the various clinical outcomes.

Hepatitis A virus protein 2B suppresses beta interferon (IFN) gene transcription by interfering with IFN regulatory factor 3 activation.

Hepatitis A virus (HAV) antagonizes the innate immune response by inhibition of retinoic acid-inducible gene I-mediated and melanoma differentiation-associated gene 5-mediated beta interferon (IFN-beta) gene expression. This study showed that this is due to an interaction of HAV with mitochondrial antiviral signalling protein (MAVS)-dependent signalling, in which the viral non-structural protein 2B and the protein intermediate 3ABC recently suggested in this context seem to be involved, cooperatively affecting the activities of MAVS and the kinases TANK-binding kinase 1 (TBK1) and the inhibitor of NF-kappaB kinase epsilon (IKKepsilon). In consequence, interferon regulatory factor 3 (IRF-3) is not activated.

IgA-coated particles of Hepatitis A virus are translocalized antivectorially from the apical to the basolateral site of polarized epithelial cells via the polymeric immunoglobulin receptor.

Although Hepatitis A virus (HAV) is transmitted by the faecal-oral route, its target for replication is the liver. Little is known of its interactions with cells of the gastrointestinal tract, and it is not known by which mechanisms HAV crosses the intestinal epithelium. In this study, it is shown that HAV associated with IgA is translocated from the apical to the basolateral compartment of polarized epithelial cells via the polymeric immunoglobulin receptor by IgA-mediated reverse transcytosis.

Hepatitis A virus suppresses RIG-I-mediated IRF-3 activation to block induction of beta interferon.

Hepatitis A virus (HAV) antagonizes the innate immune response by inhibition of double-stranded RNA (dsRNA)-induced beta interferon (IFN-beta) gene expression. In this report, we show that this is due to an interaction of HAV with the intracellular dsRNA-induced retinoic acid-inducible gene I (RIG-I)-mediated signaling pathway upstream of the kinases responsible for interferon regulatory factor 3 (IRF-3) phosphorylation (TBK1 and IKKepsilon). In consequence, IRF-3 is not activated for nuclear translocation and gene induction.

Time course of hepatitis A viremia and viral load in the blood of human hepatitis A patients.

The hepatitis A virus (HAV) is the most common etiological cause of acute hepatitis infections in humans in industrialized countries. Investigations into the viral load during HAV viremia, however, are rare. Therefore, correlation studies between viral load, biochemical, and specific serological markers have been undertaken.

Hepatitis A virus inhibits cellular antiviral defense mechanisms induced by double-stranded RNA.

The consequences of a hepatitis A virus (HAV) infection on cell-based antiviral responses and the interactions between virus and host cells resulting in persistent infections are poorly understood. In this report, we show that HAV does inhibit double-stranded (dsRNA)-induced beta interferon (IFN-beta) gene expression by influencing the IFN-beta enhanceosome, as well as dsRNA-induced apoptosis, which suggests that both effects may be connected by shared viral and/or cellular factors. This ability of HAV, which preserves the sites of virus production for a longer time, may allow the virus to establish an infection and may be the presupposition for setting up persistent infections.

Hepatitis A virus suppresses monocyte-to-macrophage maturation in vitro.

To analyze the pathogenetic mechanism of hematopoietic dysregulation associated with hepatitis A virus (HAV) infections, we studied the influence of HAV on monocyte (MO)-to-macrophage (MAC) maturation in vitro. Exposure of peripheral blood-derived mononuclear cells (MNC) to HAV led to diminished adherence of MO to plastic. Furthermore, HAV inhibited the ability of peripheral blood MO to differentiate toward MAC.

Hepatitis A virus-specific immunoglobulin A mediates infection of hepatocytes with hepatitis A virus via the asialoglycoprotein receptor.

The mechanisms underlying the hepatotropism of hepatitis A virus (HAV) and the relapsing courses of HAV infections are unknown. In this report, we show for a mouse hepatocyte model that HAV-specific immunoglobulin A (IgA) mediates infection of hepatocytes with HAV via the asialoglycoprotein receptor, which binds and internalizes IgA molecules. Proof of HAV infection was obtained by detection of HAV minus-strand RNA, which is indicative for virus replication, and quantification of infectious virions.

A cytopathogenic, apoptosis-inducing variant of hepatitis A virus.

A cytopathogenic variant of hepatitis A virus (HAV(cyt/HB1.1)) was isolated from persistently infected BS-C-1 cells by serial passages in FRhK-4 cells. This virus shows a rapid replication pattern and high final titers are obtained, which are main characteristics of cytopathogenic HAVs.

The proposed gene for VP1 of HAV encodes for a larger protein than that observed in HAV-infected cells and virions.

The termini of hepatitis A virus (HAV) mature proteins have been assigned mainly by their homology to other picornaviruses and their apparent electrophoretic mobility; the proposed coding sequence for VP1 is supposed to encompass 900 nucleotides from position 2208 to 3107 of the HAV genome. In order to further characterize this protein, we analyzed the in vitro-and in vivo-synthesized translation products of the putative VP1 gene. cDNA coding for full-length VP1 was cloned under the control of a T7 promoter in pTF7-5; the resulting plasmid (pTF7-5/VP1) was used for both synthesis of RNA to program rabbit reticulocyte lysates and construction of a recombinant vaccinia virus (rvv/T7-VP1).

Lymphocytopenia as an unfavorable prognostic factor in patients with cytomegalovirus infection after bone marrow transplantation.

Sixty-three recipients of an allogeneic marrow transplant were screened for the occurrence of cytomegalovirus (CMV) infection and clinical parameters possibly predicting the development of CMV disease in a retrospective study. Blood and urine samples obtained from these patients were screened weekly after bone marrow transplantation (BMT) for the presence of CMV by polymerase chain reaction (PCR) and virus culture technique. Forty-six of the 63 patients studied were found to be CMV-positive by PCR technique in blood and urine samples at a median of 29 days after BMT.

Disseminated BK type polyomavirus infection in an AIDS patient associated with central nervous system disease.

A 27-year-old man with hemophilia type A and acquired immunodeficiency syndrome developed a subacute meningoencephalitis, associated with a normotensive internal hydrocephalus, 14 weeks before his death. From cerebrospinal fluid and brain autopsy material, a virus could be isolated and was classified by Southern blot analysis and restriction endonuclease reactions as the human polyomavirus BK. The postmortem findings of polyomavirus antigen and BK virus DNA in various cell types of the kidneys, lungs, and central nervous system strongly suggest that BK virus was the causative agent of a tubulointerstitial nephropathy, an interstitial desquamative pneumonitis, and a subacute meningoencephalitis with accentuation of the ventricular and meningeal surfaces of the brain.

Hepatitis A: hepatotropism and influence on myelopoiesis.

Immunopathologic mechanisms leading to liver tissue injury in hepatitis caused by hepatitis A virus (HAV) were studied in an autologous in vitro model. Data show virus-specific killing by liver-infiltrating T lymphocytes in man and support the hypothesis that hepatocellular damage as well as efficient elimination of virus-infected hepatocytes is mediated by HLA-restricted, HAV-specific CD8+ T lymphocytes. Furthermore, experimental results demonstrate that human interferon-gamma produced by HAV-specific T cells may act as a key factor in T-cell-promoted clearance of HAV-infected hepatocytes.

Myelopoiesis in vitro is suppressed by hepatitis A virus.

Perturbations of hematopoietic regulation ranging from transient granulocytopenia to rare cases of bone marrow failure are associated with infections due to hepatitis A virus (HAV). In an attempt to elucidate the pathogenetic mechanisms we had previously established that HAV has a direct suppressive effect on human bone marrow progenitors (CFU-GM, -GEMM, BFU-E). These studies were extended to long-term bone marrow cultures (LTBMC): Inoculation of bone marrow mononuclear cells with HAV did not interfere with the establishment of an adherent stromal layer, nor did the inoculation of already established layers cause any morphologically recognizable changes to the stroma.

Immune pathogenesis of hepatitis A.

In an effort to elucidate the mechanism of liver damage resulting from Hepatitis A virus (HAV) infection, we have studied infected skin fibroblasts and autologous lymphocytes from HAV patients. We report here that HLA-restricted virus-specific T cells play an essential role in HAV-related hepatocellular injury.

Polymerase chain reaction to evaluate antiviral therapy for cytomegalovirus disease.

A sensitive and specific method to monitor suppression of cytomegalovirus (CMV) replication is essential in patients treated with ganciclovir after allogeneic bone-marrow transplantation. In this study, antiviral therapy of eighteen episodes of symptomatic CMV infection in 15 such patients were followed up clinically and by virus culture and polymerase chain reaction (PCR). Clinical improvement, culture, and PCR were assessed for their ability to predict the efficacy of ganciclovir therapy in each patient.

Interferon-gamma secretion by in vivo activated cytotoxic T lymphocytes from the blood and cerebrospinal fluid during mumps meningitis.

Functional studies of cerebrospinal fluid T lymphocytes during acute viral infections of the nervous system are rare. Recently, we had the opportunity to investigate the requirements for interferon-gamma (IFN-gamma) production of human in vivo activated (primary) cytotoxic T lymphocytes (CTL) generated during acute viral meningitis. Two HLA-B7-restricted, CD4-, CD8+ CTL clones from cerebrospinal fluid of one patient with mumps meningitis were studied.

Demonstration of virus-specific cytotoxic T lymphocytes in liver tissue in hepatitis A--a model for immunopathological reactions.

The pathogenetic mechanism leading to liver tissue injury in hepatitis caused by hepatitis A virus is unclear. We have randomly established T cell clones from liver biopsies from 4 patients with hepatitis A. A total of 578 clones was phenotypically analyzed.

Early occurrence of human cytomegalovirus infection after bone marrow transplantation as demonstrated by the polymerase chain reaction technique.

Twenty-eight patients undergoing bone marrow transplantation (BMT) were followed-up at weekly intervals from day -10 to discharge from hospital after BMT for human cytomegalovirus (HCMV) infection using polymerase chain reaction (PCR), slot-blot hybridization, and conventional virus culture. High specificity of the PCR assay applied could be shown by failure to amplify DNA extracted from a wide range of other viruses frequently infecting marrow transplant recipients. The PCR technique allowed us to diagnose viremia and viruria in 20 (83%) of 24 seropositive patients after BMT, whereas culture assays showed 16 (67%) of 24 of these patients to be viruric and 9 (37%) of 24 cases to be viremic.

Comparison of different techniques for detection of cytomegalovirus infection following bone marrow transplantation.

A total of 317 different clinical samples obtained from patients following bone marrow transplantation and 56 blood and urine samples from seronegative control persons were screened for the presence of human cytomegalovirus (CMV) using virus culture and slot-blot hybridization. Immunohistochemical techniques using monoclonal antibodies to various viral antigens and in situ hybridization techniques were also utilised for detection of CMV in tissue samples. In cell suspensions of blood, bone marrow and effusions, and in liver biopsies, CMV DNA could be demonstrated more often by slot-blot and in situ hybridization techniques than by virus culture or immunostaining of viral antigens.

Clonal analysis of infiltrating T lymphocytes in liver tissue in viral hepatitis A.

The pathogenic mechanism leading to liver tissue injury in hepatitis caused by hepatitis A virus is unclear. We have randomly established T-cell clones from liver biopsies from four patients with hepatitis A. A total of 578 clones was phenotypically analysed.

Hybridization techniques provide improved sensitivity for HCMV detection and allow quantitation of the virus in clinical samples.

Hybridization techniques (slot-blot and in-situ hybridization assays) and immunostaining using murine monoclonal antibodies directed against different proteins of the human cytomegalovirus (HCMV) were compared for their sensitivity and specificity for detection of HCMV. A model system with HCMV infected human embryonic lung fibroblasts and lung biopsy specimens obtained from patients with culture positive HCMV interstitial pneumonia were used for evaluation of these techniques. The hybridization techniques were found to provide an improved sensitivity compared to immunostaining.