Search PubMed⌕ Search

Biomedical subjects

Peter Karayiannis

Publications and source records attributed to Peter Karayiannis.

17 recordsLinked to original sources
PubMed2006

Detection of a hepatitis B surface antigen variant emerging in a patient with chronic lymphocytic leukaemia treated with fludarabine.

Fludarabine is used widely for the treatment of chronic lymphocytic leukaemia, but not as yet implicated in the emergence of hepatitis B surface antigen (HBsAg) variants following hepatitis B virus (HBV) reactivation. Such a variant was detected in a 78-year-old female who was HBsAg(-)/anti-HBc(+)/anti-HBs(+)/anti-HBe(+), and with normal ALT levels, who developed HBV reactivation after fludarabine treatment. She had high HBV-DNA levels, and became positive for HBeAg, in the absence of detectable HBsAg. HBV-DNA was extracted from serum and the HBsAg encoding region of the genome was amplified by PCR, followed by cloning and sequencing. The HBV strain appeared to be subtype adw, but had higher nucleotide homology with ayw than adw isolates, supported further by phylogenetic tree analysis. Amino-acid sequence comparisons over the alpha determinant region revealed the following substitutions: C124N, G130R, and N146S. There were also unique substitutions outside the alpha determinant. All these mutations appeared to have a profound effect on the antigenicity of this region, which resulted in failure to detect HBsAg by commercially available diagnostic assays. It is concluded that a surface variant emerged in an HBsAg(-)/anti-HBs(+) patient with chronic lymphocytic leukaemia following fludarabine treatment, with an unprecedented number of amino-acid substitutions in the alpha determinant region of HBsAg, including a subtype switch.

Aged↗
PubMed2006

Established and emerging therapies for the treatment of viral hepatitis.

Patients who are chronically infected with either hepatitis B or C viruses run the risk of developing cirrhosis and hepatocellular carcinoma in later life. Antiviral treatment offers the only means of interrupting this progression. To date, recombinant interferon alpha and the nucleos(t)ide analogues lamivudine and adefovir dipivoxil are the only licensed drugs for the treatment of chronic hepatitis B, whilst recombinant or pegylated interferons in combination with ribavirin are the ones used for chronic hepatitis C virus infections. The efficacy of these treatments, reasons for treatment failure, drug resistance and future options are discussed in the present review.

Antiviral Agents↗
PubMed2005

Heart transplantation in patients with chronic hepatitis B: clinical evolution, molecular analysis, and effect of treatment.

We evaluated clinical evolution and hepatitis B virus (HBV) molecular changes in heart recipients with chronic HBV infection before transplantation, and studied the effects of lamivudine treatment in patients who experienced HBV reactivation. Nine patients with chronic HBV infection who underwent heart transplantation were investigated. HBV surface/core-promoter/precore/core regions were sequenced. Prior to transplantation, all nine patients had consistently normal ALT and low HBV-DNA levels. Seven experienced HBV reactivation after transplantation (ALT elevated, HBV-DNA>200.000 cps/ml). Lamivudine treatment was initially effective in all patients; three patients during the second year of treatment developed lamivudine resistance-associated mutations (rt-L180M, rt-M204V) with severe disease reactivation, remitted after switch to adefovir treatment. No other significant HBV mutations were identified in the genomic regions studied. Immune suppression is crucial in the reactivation of previous inactive HBV infection and in the liver disease progression in heart recipients. Preemptive lamivudine treatment could be useful in the early management of these patients.

Adenine↗
PubMed2004

Hepatitis B surface antigen variant with multiple mutations in the a determinant in an agammaglobulinemic patient.

A patient with agammaglobulinemia developed acute hepatitis that progressed to chronic liver disease with high levels of hepatitis B virus (HBV) DNA in the absence of detectable HBsAg. Sequencing of the a determinant region of HBsAg revealed multiple amino acid substitutions that, unusually, also included a substitution at position 122 that defines subtype specificity. All of these mutations had a profound effect on the antigenicity of this region, which led to the complete failure of variant detection by commercially available routine diagnostic assays or laboratory-based monoclonal antibody assays.

Agammaglobulinemia↗
PubMed2004

Identification of unique hepatitis C virus quasispecies in the central nervous system and comparative analysis of internal translational efficiency of brain, liver, and serum variants.

Reports of cerebral dysfunction in chronic hepatitis C virus (HCV) infection have led to the suggestion that HCV may infect the central nervous system (CNS). We used reverse transcription-PCR, cloning, and sequencing to define quasispecies for the HCV internal ribosomal entry site (IRES) and hypervariable region 1 (HVR1) in autopsy-derived brain, liver, lymph node, and serum samples. There was evidence of tissue compartmentalization of sequences in the brain in two patients, with between 24 and 55% of brain-derived IRES sequences absent from the serum, and significant phylogenetic and phenetic clustering of the brain and lymph node HVR1 sequences. The IRES initiates cap-independent translation of the viral polyprotein. Two unique brain-derived IRES mutations (C(204)-->A and G(243)-->A), which have previously been associated with lymphoid replication and altered translational efficiency in cell culture, were found in one patient. We used a dicistronic reporter vector to test whether brain-derived variants showed altered IRES-mediated translational efficiency, which might favor CNS infection. The translational efficiencies of the brain-derived IRES sequences were generally reduced compared to those of the master serum and liver sequences in rabbit reticulocyte cell lysates and two human cell lines, HuH7 (liver) and CHME3 (microglial). The C(204)-->A and G(243)-->A mutations showed preserved translational efficiency in HuH7 cells but reduced efficiency in CHME3 cells. Our data provide evidence that the CNS is a site of HCV replication, consistent with the recent demonstration of negative-strand HCV RNA in brain, and suggest that IRES polymorphisms may be important as a viral strategy of reduced translation to favor latency in the CNS.

Base Sequence↗
PubMed2004

Current therapies for chronic hepatitis B virus infection.

Patients who are chronically infected with the hepatitis B virus are at an increased risk of developing cirrhosis, hepatic decompensation and hepatocellular carcinoma. Therapeutic intervention offers the only means of interrupting this progression. Currently there are three licensed agents for the treatment of chronic hepatitis B virus infection. These are interferon-alpha, an immunomodulator, and two synthetic nucleos(t)ide analogs, namely lamivudine (Epivir, GlaxoSmithKline) and adefovir dipivoxil (Hepsera, Gilead Sciences). This review aims to summarize current experience with these drugs in the treatment and management of patients with chronic hepatitis B virus infection, their efficacy, and current problems of drug resistance. An outline of future treatment perspectives is also included.

Adenine↗
PubMed2003

Hepatitis B virus: old, new and future approaches to antiviral treatment.

Patients chronically infected with hepatitis B virus (HBV) run the risk of developing cirrhosis and hepatocellular carcinoma in later life. Antiviral treatment offers the only means of preventing such an undesirable outcome. To date, interferon-alpha (IFN-alpha), an immunomodulator, and two synthetic nucleoside analogues, lamivudine and adefovir dipivoxil, are the only licensed antiviral agents for the treatment of chronic HBV infection. However, the standard treatment endpoints of loss of HBeAg with or without seroconversion to anti-HBe, normalization of serum transaminase levels, loss of HBV-DNA and improvement in liver histology following monotherapy with either types of agent are only achievable in approximately 20-30% of those treated. Long-term treatment with lamivudine is effective in suppressing viral replication, but drug-resistant mutants arise with increased length of treatment. Nevertheless, such mutants appear to be susceptible to adefovir and other nucleoside analogues that are undergoing Phase II/III clinical trials at the moment. Therapeutic vaccination and other molecular approaches such as antisense oligonucleotides, ribozymes, DNA vaccines, dominant-negative proteins and aptamers are possible future antiviral therapies, which will supplement our armamentarium against chronic HBV infection. It seems certain that combination therapies involving two or more nucleoside analogues, immunomodulators or gene therapies will be the future treatment regimens for chronic HBV infection.

Antiviral Agents↗
PubMed2003

An outbreak of HBV and HCV infection in a paediatric oncology ward: epidemiological investigations and prevention of further spread.

Hospital-acquired hepatitis B (HBV) and C virus (HCV) infections continue to occur despite increased awareness of this problem among the medical community. One hundred six patients were infected in a haematology oncology ward for children, over the time period 1996 to 2000. Serum samples from 45 such patients and 3 from infected medical personnel were used for nucleic acid amplification. HBV core, as well as HCV core and hypervariable region 1 (HVR1) nucleotide sequences, were analysed by phylogenetic tree analysis, in order to characterise the epidemiological pattern of viral transmission on the ward. Samples from 32 patients were positive for HBV-DNA or HCV-RNA by PCR. Ten patients were positive for both markers. Seventeen out of twenty-three HCV core gene sequences were found to be evolutionarily related and clustered separately from other local sequences in the phylogenetic tree, indicating nosocomial transmission. This was confirmed by analysis of HVR1 gene sequences. One nurse and one physician from the ward were HCV RNA positive, but their HCV sequences were not related evolutionarily to those of the patient cluster. Fifteen out of nineteen HBV core gene sequences were also clustered together and were positioned separately in the relevant tree. Epidemiological investigation excluded a common source infection and indicated that spread of infection was most likely due to inappropriate infection control measures on the ward. No obvious risk factors for transmission were identified during the retrospective survey in patients with related sequences, except use of multidose vials for saline and poor staff compliance with routine hand hygiene procedures. The preventive measures that were introduced reduced the incidence of infection significantly. No new cases of HBV infection and only three anti-HCV seroconversions occurred over a period of 19 months. The introduction and maintenance of strict prevention measures over a 2 year period, combined with HBV vaccination, reduced significantly the incidence of new HCV and HBV infections.

Adolescent↗
PubMed2003

Changes in hypervariable region 1 of the envelope 2 glycoprotein of hepatitis C virus in children and adults with humoral immune defects.

The N-terminal end of the hepatitis C virus (HCV) envelope glycoprotein E2 contains a stretch of 27 amino acids that exhibit increased variability. This hypervariable region 1 (HVR-1), as it is normally referred to, is thought to contain epitopes that come under humoral immune attack. In the present study, 10 patients (5 children and 5 adults) with humoral immune defects and chronic HCV infection were investigated, to see how HVR-1 sequences behave over time in these patients who are unable to produce antibodies. Amplicons of this region showed little or no variation at all over time, indicating that quasispecies variation in this region is driven by the host's humoral immune response.

Adolescent↗
PubMed2003

Hepatitis C virus E2 and NS5A region variability during sequential treatment with two interferon-alpha preparations.

To determine the pattern and significance of the HCV genetic heterogeneity before and during treatment with recombinant-2b or lymphoblastoid alpha-interferon, hypervariable region 1 (HVR-1) and NS5A quasispecies were characterised by cloning and sequencing in 12 HCV-1b-infected subjects. Patients were either responder-relapsers or non-responders to treatment. Extensive amino acid sequence analysis was applied to reveal the significance of HCV variation at key sites within HVR-1 and NS5A regions. Genetic complexity, genetic diversity, and the non-synonymous to synonymous substitution ratios of HVR-1 quasispecies decreased during treatment in responder-relapser patients only, and more markedly so following lymphoblastoid alpha-interferon. In non-responders, the HVR-1 quasispecies broadened. Amino acids G406 and Q409, which represent a major viral epitope, were highly conserved throughout treatment. Responder-relapser patients had a higher mutation frequency in NS5A than non-responders. Lymphoblastoid alpha-interferon promoted the selection of intermediate Interferon Sensitivity Determining Region (ISDR) sequences, whereas recombinant-2b alpha-interferon favoured maintenance or selection of conserved ISDR sequences. Variability upstream of the ISDR was associated with treatment response, but the amino acid substitutions conferring higher replicative ability to in vitro HCV replicons were absent in in vivo isolates. In conclusion, the pattern of HVR-1 quasispecies evolution correlates with the clinical response, and the conservation of specific amino acids may be useful for immune targeting in vivo. In responder-relapser patients, the initial HVR-1 evolution resembles that found in sustained responders. Variability within the entire NS5A, as opposed to a single region (ISDR), may have a role in influencing alpha-interferon treatment outcome. A differential effect of different alpha-interferon preparations on HCV quasispecies kinetics may exist.

Amino Acid Sequence↗
PubMed2002

Intra-familial transmission of hepatitis B virus in Italy: phylogenetic sequence analysis and amino-acid variation of the core gene.

BACKGROUND/AIMS: Transmission of hepatitis B virus (HBV) in countries of intermediate endemicity, such as Italy, is thought to be primarily horizontal and, to a lesser extent, vertical. Most chronic carriers therefore become infected in infancy or at a very young age. The index cases in such events have been assumed to come from within the family unit or from sources outside the immediate family, with whom the affected person is in close contact. METHODS: We studied a number of Italian families with multiple members chronically infected with HBV. The precore/core region of the virus was amplified from serum derived HBV-DNA, and the sequences subjected to phylogenetic tree analysis. In addition, the extent of amino-acid variation within the core region was correlated to HLA type, determined by allele-specific PCR. RESULTS: The phylogenetic tree analysis provided strong evidence of intra-familial transmission of the virus. Analysis of amino-acid substitutions in the core region in relation to HLA class II alleles from members of the same family showed that these substitutions were restricted in siblings with concordant, and more diverse in those with discordant HLA haplotypes. CONCLUSIONS: This is consistent with major histocompatibility complex class II mediated selection pressure on the virus.

Adolescent↗
PubMed2002

Detection and significance of a G1862T variant of hepatitis B virus in Chinese patients with fulminant hepatitis.

The prevalence of a G1862T variant of hepatitis B virus (HBV) has been investigated in patients with fulminant hepatitis and chronic liver disease, using primer mismatch amplification, followed by restriction fragment length polymorphism analysis. This variant was five times more common in patients with fulminant hepatitis (13.7%, 7 of 52) than in chronic carriers (2.5%, 2 of 81). The G-->T substitution at position 1862 leads to an amino acid change in codon 17 of the precore protein of the virus, which is part of a signal peptidase recognition motif. Variants with this mutation were only seen in patients infected with genotype B. In vitro translation experiments showed that this variant has greatly reduced capacity to produce hepatitis B e antigen (HBeAg) from its precore protein precursor. Furthermore, 88.5% of patients with fulminant hepatitis had mutations that are known to be associated with abrogated or reduced production of HBeAg. This suggests that, following HBV infection, the absence or reduced amounts of HBeAg may be a contributing factor in fulminant disease.

Adult↗
PubMed2002

Core promoter mutations 3 years after anti-hepatitis B e seroconversion in patients with chronic hepatitis B or hepatitis B and C infection and cancer remission.

OBJECTIVES: In this study, we aimed to evaluate the persistence of hepatitis B virus (HBV) DNA and the role of HBV core promoter and precore region mutations in 28 young cancer survivor patients with HBV or HBV and hepatitis C virus (HCV) infections, and persistently normal ALT levels, after spontaneous or interferon (IFN)-induced anti-hepatitis B e (HBe) seroconversion. METHODS: Sera from 15 patients with HBV and 13 with dual HBV-HCV infection were analyzed for the presence of HBV-DNA and HCV-RNA by polymerase chain reaction 3 yr after anti-HBe seroconversion. A total of 21 patients had seroconverted spontaneously and seven did so after IFN treatment. The core promoter and the precore regions were amplified sequenced directly. RESULTS: Among patients with HBV infection, HBV-DNA was detected in five of nine (55%) with spontaneous anti-HBe and in all six treated patients (p = 0.092). In the coinfected patients, four had cleared both HBV-DNA and HCV-RNA, five were HBV-DNA negative/HCV-RNA positive and four had the reverse viral pattern. Among the 15 patients with persistence of HBV-DNA, a 7-base pair nucleotide deletion in the core promoter (1757-1763) was present in seven of 10 patients with spontaneous and in one of five patients with IFN-induced seroconversion (p = 0.033). The G1896A precore stop codon mutation was never observed. HBV-DNA levels were significantly lower in patients with the core promoter deletion (p = 0.011). The 7-base pair deletion generated a truncated X protein at amino-acid position 132. CONCLUSIONS: A core promoter deletion after anti-HBe seroconversion was associated with low HBV-DNA levels, probably because of downregulation of pregenomic RNA production and truncation of the X protein. HBV-DNA persistence was a frequent event, even in the absence of active liver disease.

Adolescent↗
PubMed1999

The 5' untranslated region of GB virus B shows functional similarity to the internal ribosome entry site of hepatitis C virus.

Since its characterization in 1995, there has been increasing interest in the significance of GB virus B (GBV-B) due to its close phylogenetic relationship to hepatitis C virus (HCV). The genome of GBV-B is similar in length and organization to that of HCV and the two viruses share sequence similarity in their 5' untranslated regions (5'UTR). A secondary structure model of the GBV-B 5'UTR has been proposed by comparative sequence analysis with HCV. The highly conserved secondary structure, present in HCV and the pestiviruses, is also present in the 5'UTR of GBV-B. Translation of the HCV polyprotein initiates via an internal ribosome entry site (IRES) and it is proposed that the GBV-B UTR may function in a similar manner. Dicistronic reporter constructs were made to investigate the function of the GBV-B 5'UTR. Mutational analysis and in vitro translation experiments demonstrate that GBV-B initiates translation via an IRES.

5' Untranslated Regions↗