Inhibition of phosphodiesterase 12 results in antiviral activity against several RNA viruses including SARS-CoV-2.

The 2',5'- oligoadenylate synthetase (OAS) - ribonuclease L (RNAseL) - phosphodiesterase 12 (PDE12) pathway is an essential interferon-induced effector mechanism against RNA virus infection. Inhibition of PDE12 leads to selective amplification of RNAseL activity in infected cells. We aimed to investigate PDE12 as a potential pan-RNA virus antiviral drug target and develop PDE12 inhibitors that elicit antiviral activity against a range of viruses. A library of 18 000 small molecules was screened for PDE12 inhibitor activity using a fluorescent probe specific for PDE12. The lead compounds (CO-17 or CO-63) were tested in cell-based antiviral assays using encephalomyocarditis virus (EMCV), hepatitis C virus (HCV), dengue virus (DENV), West Nile virus (WNV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), in vitro. Cross reactivity of PDE12 inhibitors with other PDEs and in vivo toxicity were measured. In EMCV assays, CO-17 potentiated the effect of IFNα by 3 log10. The compounds were selective for PDE12 when tested against a panel of other PDEs and non-toxic at up to 42 mg kg-1 in rats in vivo. Thus, we have identified PDE12 inhibitors (CO-17 and CO-63), and established the principle that inhibitors of PDE12 have antiviral properties. Early studies suggest these PDE12 inhibitors are well tolerated at the therapeutic range, and reduce viral load in studies of DENV, HCV, WNV and SARS-CoV-2 in human cells and WNV in a mouse model.

Development of hepatic pathology in GBV-B-infected red-bellied tamarins (Saguinus labiatus).

GB virus B (GBV-B) is a new world monkey-associated flavivirus used to model acute hepatitis C virus (HCV) infection. Critical for evaluation of antiviral or vaccine approaches is an understanding of the effect of HCV on the liver at different stages of infection. In the absence of longitudinal human tissue samples at defined time points, we have characterized changes in tamarins. As early as 2 weeks post-infection histological changes were noticeable, and these were established in all animals by 6 weeks. Despite high levels of liver-associated viral RNA, there was reversal of hepatic damage on clearance of peripheral virus though fibrosis was demonstrated in four tamarins. Notably, viral RNA burden in the liver dropped to near undetectable or background levels in all animals which underwent a second viral challenge, highlighting the efficacy of the immune response in removing foci of replication in the liver. These data add to the knowledge of GBV-B infection in New World primates which can offer attractive systems for the testing of prophylactic and therapeutic treatments and the evaluation of their utility in preventing or reversing liver pathology.

Determinants Involved in Hepatitis C Virus and GB Virus B Primate Host Restriction.

UNLABELLED: Hepatitis C virus (HCV) only infects humans and chimpanzees, while GB virus B (GBV-B), another hepatotropic hepacivirus, infects small New World primates (tamarins and marmosets). In an effort to develop an immunocompetent small primate model for HCV infection to study HCV pathogenesis and vaccine approaches, we investigated the HCV life cycle step(s) that may be restricted in small primate hepatocytes. First, we found that replication-competent, genome-length chimeric HCV RNAs encoding GBV-B structural proteins in place of equivalent HCV sequences designed to allow entry into simian hepatocytes failed to induce viremia in tamarins following intrahepatic inoculation, nor did they lead to progeny virus in permissive, transfected human Huh7.5 hepatoma cells upon serial passage. This likely reflected the disruption of interactions between distantly related structural and nonstructural proteins that are essential for virion production, whereas such cross talk could be restored in similarly designed HCV intergenotypic recombinants via adaptive mutations in NS3 protease or helicase domains. Next, HCV entry into small primate hepatocytes was examined directly using HCV-pseudotyped retroviral particles (HCV-pp). HCV-pp efficiently infected tamarin hepatic cell lines and primary marmoset hepatocyte cultures through the use of the simian CD81 ortholog as a coreceptor, indicating that HCV entry is not restricted in small New World primate hepatocytes. Furthermore, we observed genomic replication and modest virus secretion following infection of primary marmoset hepatocyte cultures with a highly cell culture-adapted HCV strain. Thus, HCV can successfully complete its life cycle in primary simian hepatocytes, suggesting the possibility of adapting some HCV strains to small primate hosts. IMPORTANCE: Hepatitis C virus (HCV) is an important human pathogen that infects over 150 million individuals worldwide and leads to chronic liver disease. The lack of a small animal model for this infection impedes the development of a preventive vaccine and pathogenesis studies. In seeking to establish a small primate model for HCV, we first attempted to generate recombinants between HCV and GB virus B (GBV-B), a hepacivirus that infects small New World primates (tamarins and marmosets). This approach revealed that the genetic distance between these hepaciviruses likely prevented virus morphogenesis. We next showed that HCV pseudoparticles were able to infect tamarin or marmoset hepatocytes efficiently, demonstrating that there was no restriction in HCV entry into these simian cells. Furthermore, we found that a highly cell culture-adapted HCV strain was able to achieve a complete viral cycle in primary marmoset hepatocyte cultures, providing a promising basis for further HCV adaptation to small primate hosts.

An overview of recent treatment options for primary sclerosing cholangitis.

Primary sclerosing cholangitis (PSC) is a chronic hepatic dysfunction characterized by inflammatory and tissue-degenerative strictures of the biliary tree, leading to cirrhosis and cholangiocarcinoma. The pathophysiological mechanisms involve immune-mediated responses. Numerous treatment modalities targeting the inflammatory aspects have been suggested, but a consensus on the best treatment option is lacking. This study aims to review the most up-to-date treatment options for PSC.

Oral fluid and hepatitis A, B and C: a literature review.

BACKGROUND AND AIMS: Viral hepatitis is a significant global health problem that, depending upon the virus, affects individuals of the developing and/or developed world. In recent years, there has been renewed interest in whether oral fluids can be considered as a source of viral hepatitis transmission and whether oral fluid, in particular, whole saliva, may be a useful source for viral detection as part of the diagnosis and monitoring of viral hepatitis. The aim of this article was to review current data concerning the possible carriage of the hepatitis A, B and C viruses within saliva and gingival crevicular fluid. Such knowledge will indicate if (i) oral fluid is a possible source of infection and (ii) whether oral fluid can be used for diagnosis and monitoring of viral hepatitis. DATA AND SOURCES: A literature search was conducted using PubMed (Medline), EMBASE/Excerpta medica, the Cochrane database and Scopus. The results were limited to published material after 2000. Relevant material was evaluated and reviewed. CONCLUSION: There is some evidence that hepatitis viruses A, B and C are present in oral fluids, particularly whole saliva and gingival crevicular fluid and may thus be possible sources of viral detection in clinical diagnosis and monitoring. However, the data are inconsistent and warrant the need for well-planned longitudinal studies to explore the precise frequency of oral carriage of such viruses and to determine the virological and host factors that may influence the oral presence of hepatitis A, B and C viruses.

Predicting spontaneous clearance of acute hepatitis C virus in a large cohort of HIV-1-infected men.

OBJECTIVE: An epidemic of acute hepatitis C virus (HCV) infection in HIV-positive men-who-have-sex-with-men (MSM) is emerging in Europe, Australia and the USA. The aim of this study was to characterise the natural history of primary HCV in this setting and to assess host and viral factors which predict spontaneous clearance. METHODS: This prospective longitudinal cohort study was carried out in 112 HIV-positive patients who were followed in a single centre (the St Mary's Acute HCV Cohort). Plasma and peripheral blood mononuclear cells (PBMCs) were obtained at monthly intervals for 3 months and at 3-monthly intervals thereafter for a median of 45 months (IQR = 29-69 months). The primary end point was spontaneous clearance of HCV. Cox regression was used to assess the impact of clinical and virological variables on outcome, including liver function, CD4 count, rate of HCV RNA decline, T cell response and clonal sequence evolution within the HCV E2 envelope gene. RESULTS: 15% of patients cleared HCV spontaneously, while 85% progressed towards chronicity. The latter group included a significant proportion of 'fluctuating' progressors (37.5%), in whom a fall followed by a rise (>1 log10) in viraemia was observed. This was associated with superinfection with new HCV strains and partially effective T cell responses. Spontaneous clearance was strongly associated with a 2.2 log10 viral load drop within 100 days of infection (HR = 1.78; p < 0.0001), elevated bilirubin (≥ 40 µmol/l; HR = 5.04; p = 0.006), elevated alanine aminotransferase (ALT; ≥ 1000 IU/ml; HR = 2.62; p = 0.048) and baseline CD4 count ≥ 650 × 106/l (HR = 2.66; p = 0.045), and only occurred in patients with genotype 1 infection. Evolution to spontaneous clearance occurred in patients with low viral diversity in the presence of an early multispecific T cell response. CONCLUSIONS: Spontaneous clearance of acute HCV in HIV-positive men can be predicted by a rapid decline in viral load, high CD4 count, elevated bilirubin and ALT, and is associated with low viral diversity and strong T cell responses.

Re-engineering the Cypriot General Healthcare System for Syndemics.

To date in Cyprus, there is no dedicated "Quality Improvement" body or Public Health authority. The long-awaited general healthcare system (known as GeSy or GHS) has been completed, mid-stream of the COVID-19 pandemic. A recently proposed resilience plan in response to the lessons learnt from the pandemic was put forward by the Government of the Republic of Cyprus to strengthen the capacity of the GHS and support public health defense. The negotiator of GeSy and Health Minister 2015-2018 also provided his view that the health system needs a holistic transformation of service provision. Recognizing failures and thinking from a syndemogenesis perspective how the envisioned patient-centric healthcare delivery can be achieved, we propose that the public health response could also be linked to a politico-economic one in shielding GeSy. We make such case for a syndemic strategy (simultaneous management of COVID-19 and pre-existing epidemics on the island) and the development of the five-district model where each main district hospital is to complement the activities of the GHS through developing: 1. A training Center for training and sharing of best practices for COVID-19 and other public emergencies. 2. A public health body. 3. A quality improvement institute. 4. A commissioning center on planning and streamlining healthcare services. 5. A clinical trial platform. The rationale is based on the management literature and use of existing resources and capabilities for transforming the GeSy and generating value.

Hepatitis B surface antigen: relation to hepatitis B replication parameters in HBeAg-negative chronic hepatitis B.

BACKGROUND & AIMS: Translation of HBsAg depends on transcription of the appropriate mRNAs from cccDNA, but its relation to other hepatitis B virus (HBV) replication parameters is not known, inasmuch as integrated sequences of HBV-DNA may also contribute to its serum levels, especially in HBeAg-negative chronic hepatitis B (CHB) patients. METHODS: We investigated HBsAg serum levels, its hepatocellular expression, and their relationship to HBV replicative- and host-response parameters before treatment in 54 HBeAg-negative CHB patients and in 15 of them after 40.1±33.3months of virological response on oral antiviral (NUC) therapy also. Liver cccDNA and HBV-DNA quantitation, HBsAg- and HBcAg-immunostaining were performed in the same needle biopsy material, while serum HBsAg and HBV-DNA levels were measured in samples drawn on the day of liver biopsy. RESULTS: In untreated patients, serum HBsAg correlated positively with HBsAg-positive hepatocytes/mm(2) (p=0.003) and weakly with serum HBV-DNA, but not with cccDNA, liver HBV-DNA, HBcAg-positive hepatocytes/mm(2), or ALT. cccDNA correlated significantly with liver HBV-DNA (p<0.00001), ALT (p=0.001), and serum HBV-DNA levels (p=0.012) but not with liver HBsAg or HBcAg. Antiviral therapy decreased serum HBsAg levels by 79.6% (p=0.012) and liver HBV-DNA by 84.4% (p=0.026) in paired comparisons and, as expected, significantly decreased serum HBV-DNA and ALT levels, but not cccDNA. CONCLUSIONS: In untreated HBeAg-negative CHB, serum HBsAg levels reflect liver HBsAg, but not cccDNA or liver HBV-DNA, suggesting that they are not solely dependent on the replicative cycle of HBV. Effective NUC therapy for 3.34 years significantly lowers serum HBsAg and liver HBV-DNA, but not cccDNA.

Dynamic coinfection with multiple viral subtypes in acute hepatitis C.

INTRODUCTION: Acute hepatitis C virus (HCV) infection is rarely studied, but virus sequence evolution and host-virus dynamics during this early stage may influence the outcome of infection. Hypervariable region 1 (HVR1) is genetically diverse and under selective pressure from the host immune response. We analyzed HVR1 evolution by frequent sampling of an acutely infected HCV cohort. METHODS: Three or more pretreatment samples were obtained from each of 10 acutely infected subjects. Polymerase chain reaction amplification was performed with multiple primer combinations to identify the full range of sequences present. Positive samples were cloned and sequenced. Phylogenetic analyses were used to assess viral diversity. RESULTS: Eight of the 10 subjects were coinfected with at least 2 HCV subtypes. Multiple subtypes were detected in individual samples, and their relative proportions changed through acute infection. The subjects with the most complex subtype structure also had a dynamic viral load; however, changes in viral load were not directly linked to changes in subtype. CONCLUSIONS: This well-sampled cohort with acute HCV infection was characterized by dynamic coinfection with multiple viral subtypes, representing a highly complex virologic landscape extremely early in infection.

Circulating IgG Levels in SARS-CoV-2 Convalescent Individuals in Cyprus.

Long-term persistence and the heterogeneity of humoral response to SARS-CoV-2 have not yet been thoroughly investigated. The aim of this work is to study the production of circulating immunoglobulin class G (IgG) antibodies against SARS-CoV-2 in individuals with past infection in Cyprus. Individuals of the general population, with or without previous SARS-CoV-2 infection, were invited to visit the Biobank at the Center of Excellence in Biobanking and Biomedical Research of the University of Cyprus. Serum IgG antibodies were measured using the SARS-CoV-2 IgG and the SARS-CoV-2 IgG II Quant assays of Abbott Laboratories. Antibody responses to SARS-CoV-2 were also evaluated against participants' demographic and clinical data. All statistical analyses were conducted in Stata 16. The median levels of receptor binding domain (RBD)-specific IgG in 969 unvaccinated individuals, who were reportedly infected between November 2020 and September 2021, were 432.1 arbitrary units (AI)/mL (interquartile range-IQR: 182.4-1147.3). Higher antibody levels were observed in older participants, males, and those who reportedly developed symptoms or were hospitalized. The RBD-specific IgG levels peaked at three months post symptom onset and subsequently decreased up to month six, with a slower decay thereafter. IgG response to the RBD of SARS-CoV-2 is bi-phasic with considerable titer variability. Levels of IgG are significantly associated with several parameters, including age, gender, and severity of symptoms.

New Approaches to the Treatment of Chronic Hepatitis B.

The currently recommended treatment for chronic hepatitis B virus (HBV) infection achieves only viral suppression whilst on therapy, but rarely hepatitis B surface antigen (HBsAg) loss. The ultimate therapeutic endpoint is the combination of HBsAg loss, inhibition of new hepatocyte infection, elimination of the covalently closed circular DNA (cccDNA) pool, and restoration of immune function in order to achieve virus control. This review concentrates on new antiviral drugs that target different stages of the HBV life cycle (direct acting antivirals) and others that enhance both innate and adaptive immunity against HBV (immunotherapy). Drugs that block HBV hepatocyte entry, compounds that silence or deplete the cccDNA pool, others that affect core assembly, agents that degrade RNase-H, interfering RNA molecules, and nucleic acid polymers are likely interventions in the viral life cycle. In the immunotherapy category, molecules that activate the innate immune response such as Toll-like-receptors, Retinoic acid Inducible Gene-1 (RIG-1) and stimulator of interferon genes (STING) agonists or checkpoint inhibitors, and modulation of the adaptive immunity by therapeutic vaccines, vector-based vaccines, or adoptive transfer of genetically-engineered T cells aim towards the restoration of T cell function. Future therapeutic trends would likely be a combination of one or more of the aforementioned drugs that target the viral life cycle and at least one immunomodulator.

Developing a holistic contingency plan: Challenges and dilemmas for cancer patients during the COVID-19.

During the first quarter of 2020 the world is experiencing a pandemic of Severe Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2), a novel beta coronavirus that is responsible for the 2019 novel coronavirus disease (COVID-19). The COVID-19 pandemic revealed that healthcare systems around the world were not prepared to deal with either the direct effects of the pandemic or with the indirect effects that are imposed on the health of patients with chronic disorders such as cancer patients. Some challenges and dilemmas currently faced during the pandemic include the management of cancer patients during the treatment and follow-up phases, the assessment of the safety of treatments currently used for the management of SARS-CoV-2 for use in cancer patients, the development of psychoeducation and emotional support for cancer patients and the safe conduct of clinical trials involving participation of cancer patients. Evidence from the literature supports the need for the urgent development of a holistic contingency plan which will include clear guidelines for the protection and comprehensive care of cancer patients. The implementation of such a plan is expected to have many beneficial effects by mainly minimizing the increased morbidity and mortality of cancer patients that could result as an adverse consequence of the COVID-19 or future pandemics.

Extensive Testing and Public Health Interventions for the Control of COVID-19 in the Republic of Cyprus between March and May 2020.

Coronavirus disease 2019 (COVID-19) has significantly affected the well-being of individuals worldwide. We herein describe the epidemiology of COVID-19 in the Republic of Cyprus during the first epidemic wave (9 March-3 May 2020). We analyzed surveillance data from laboratory-confirmed cases, including targeted testing and population screening. Statistical analyses included logistic regression. During the surveillance period, 64,136 tests (7322.3 per 100,000) were performed, 873 COVID-19 cases were diagnosed, and 20 deaths were reported (2.3%). Health-care workers (HCWs) represented 21.4% of cases. Overall, 19.1% of cases received hospital care and 3.7% required admission to Intensive Care Units. Male sex (adjusted Odds Ratio (aOR): 3.04; 95% Confidence Interval (CI): 1.97-4.69), increasing age (aOR: 1.56; 95%CI: 1.36-1.79), symptoms at diagnosis (aOR: 6.05; 95%CI: 3.18-11.50), and underlying health conditions (aOR: 2.08; 95%CI: 1.31-3.31) were associated with hospitalization. For recovered cases, the median time from first to last second negative test was 21 days. Overall, 119 primary cases reported 616 close contacts, yielding a pooled secondary attack rate of 12% (95%CI: 9.6-14.8%). Three population-based screening projects, and two projects targeting employees and HCWs, involving 25,496 people, revealed 60 positive individuals (0.2%). Early implementation of interventions with targeted and expanded testing facilitated prompt outbreak control on the island.

Core mutations in patients with acute episodes of chronic HBV infection are associated with the emergence of new immune recognition sites and the development of high IgM anti-HBc index values.

Acute exacerbations in HBeAg negative patients with chronic hepatitis B virus (HBV) infection are invariably associated with concurrent increases in the index of IgM class antibodies against the core protein (anti-HBc) of the virus. This study aimed to investigate whether this was related to the clearance of variants from the quasispecies pool and the appearance of new ones, with aminoacid substitutions in well recognized B-cell epitopes. In this study, 5 HBeAg negative patients (A to E) with 13 sequential serum samples (A1-A2, B1-B2-B3, C1-C2, D1-D2-D3, E1-E2-E3) were investigated after amplification of the entire core encoding region followed by cloning/sequencing studies. The sequences at different time points were compared with those from a single HBeAg positive patient with no apparent acute exacerbations. The results from sequence comparison showed that virus variants emerged in all (A2, B3, C2, D3, E2, and E3) but two (B2 and D2) subsequent sera with amino-acid substitutions affecting B-cell epitopes. It is concluded that the rise in the values of IgM anti-HBc may be attributed to the alteration of the antigenic epitopes leading to new antibody production in the majority of the cases. However, it appears that increases in IgM anti-HBc indexes in a few cases may relate to other possible mechanisms which are discussed.

Long-term outcome of hepatitis B and hepatitis C virus co-infection and single HBV infection acquired in youth.

Co-infection with HBV and HCV seems to be associated with more severe liver disease in retrospective and cross-sectional studies in adults, but no data are available when co-infection is acquired in youth. The long-term outcome of infection acquired in youth was assessed in patients co-infected with HBV and HCV and in patients with HBV infection only. Twenty-seven patients with HBV and HCV co-infection and 27 patients infected with HBV only were enrolled. Seventy-six per cent of the patients were treated with alpha-interferon for 1 year. After a median follow-up of 23 years, the annual progression rate of fibrosis was 0.07 in patients co-infected with HBV and HCV, and in those infected with HBV it was 0.07 and 0.11 (P < 0.004) for HBe and anti-HBe-positive patients, respectively. In co-infected patients, the development of cirrhosis was observed in 2 (7.4%) and of hepatocellular carcinoma (HCC) in 1 (3.7%), while in those with HBV, cirrhosis appeared in one patient (3.7%). Alcohol intake (OR = 9.5 +/- 1.2; 95% CI = 6.6-13.9; P < 0.0001) was independently associated with cirrhosis and HCC. alpha-interferon showed no efficacy during treatment, but the treated group showed higher HCV RNA clearance during post-treatment follow-up. Co-infection with HBV and HCV and single HBV infection acquired in youth showed a low rate of progression to liver fibrosis, no liver failure, and low development of HCC during a median follow-up of 23 years (range 17-40).

Diagnosing acute hepatitis C in HIV-infected patients: nucleic acid testing compared with antibody and antigen-antibody detecting methods.

BACKGROUND: Early diagnosis of hepatitis C virus (HCV) infection in HIV-infected patients has significant implications for patient management. However, the currently recommended serological screening strategy for identifying such patients could be improved. Little is known about the performance of routine antibody-only tests, compared with newer serological antigen-antibody detection assays and nucleic acid testing in this patient group. OBJECTIVES: To compare the performance of antibody and antigen-antibody detecting methods with nucleic acid testing in the diagnosis of acute HCV in HIV-infected individuals. STUDY DESIGN: 123 samples from 25 HIV-infected patients with acute HCV infection were tested retrospectively. The time of infection was estimated. The performance of antibody, antigen-antibody and nucleic acid detecting methods in diagnosing acute HCV infection was assessed and the sensitivity of the assays compared. RESULTS: Only 20% of samples that were positive for HCV RNA were simultaneously positive for HCV antibody. In contrast, 68% of the total number of samples were positive and 32% negative by the antigen-antibody assay. Patients became antibody-positive on average 7 months after HCV RNA was detected. CONCLUSION: In HIV-infected patients nucleic acid testing is the most sensitive means of diagnosing acute HCV C infection. A serological assay offering combined detection of antibody and antigen enhances sensitivity of detection, compared to antibody-only assays.

NICE guidelines and a treatment algorithm for the management of chronic hepatitis B: a review of 12 years experience in west London.

BACKGROUND: Treatment strategies in chronic hepatitis B (CHB) are evolving as more potent oral antivirals become available. However, drug resistance remains a major challenge and policy guidelines on management are limited by the evidence base. This study aims to review the implications of the National Institute for Health and Clinical Excellence (NICE) guidelines in a cohort of unselected CHB patients in the United Kingdom and to evolve a management algorithm for their treatment. METHODS: In total, 783 unselected hepatitis B surface antigen-positive patients, were assessed of whom 212 (27%) underwent liver biopsy. Age, alanine aminotransferase, hepatitis B virus DNA and necroinflammatory score were analysed to determine their value as predictors of fibrosis. Patients with biopsy evidence of fibrosis were offered treatment and followed longitudinally. Six-month on-treatment virologic response was evaluated to determine the validity of this strategy in predicting the early emergence of resistance. RESULTS: Age, gender and necroinflammatory score were predictors of fibrosis in CHB patients, whereas age > 40 years was a predictor of cirrhosis in both hepatitis B e antigen (HBeAg)-positive (P < 0.03) and HBeAg-negative patients (P < 0.003). A total of 81% of HBeAg-positive and 65% of HBeAg-negative CHB patients who required adefovir add-on therapy were identifiable after 6 months of lamivudine monotherapy, by continuing HBV DNA positivity (P < 0.002 and P < 0.0001, respectively). CONCLUSIONS: Advanced liver disease was present in patients falling outside current treatment guidelines, highlighting the importance of liver histology in identifying fibrosis and the need for antiviral therapy. While 6 month on-treatment virologic response as a trigger for instituting add-on therapy may be an improvement on the current recommendations, such a strategy should be integrated into any new treatment algorithm, likely to consist of entecavir and tenofovir.

Restricted quasispecies variation following infection with the GB virus B.

The extent of genetic variability following acute infection of tamarins with GB virus B (GBV-B) is not known. In this study we attempted to define the quasispecies variation of GBV-B 17 days post-infection, by PCR amplification of GBV-B RNA extracted from serum and liver. Cloning followed by sequencing revealed a small number of changes in the three regions studied, namely the 5' untranslated region, E2 and NS3. Moreover, there was no region of high amino acid variability in E2, akin to hypervariable region 1 of hepatitis C virus. This was further confirmed by analysing sequences from two additional animals obtained at a similar time point post-infection. Nevertheless, it was apparent that different variants with one or two amino acid substitutions in the region studied had been selected when comparing the sequences from the three animals. This restricted sequence variation of GBV-B during acute hepatitis may explain the infrequent progression of the infection to a chronic stage.

Quasispecies Changes with Distinctive Point Mutations in the Hepatitis C Virus Internal Ribosome Entry Site (IRES) Derived from PBMCs and Plasma.

The 5' untranslated region (UTR) of the hepatitis C virus (HCV) genome contains the internal ribosome entry site (IRES), a highly conserved RNA structure essential for cap-independent translation of the viral polyprotein. HCV, apart from the liver, is thought to be associated with lymphocyte subpopulations of peripheral blood mononuclear cells (PBMCs), in lymph nodes and brain tissue. In this study, RT-PCR, cloning, and sequence analysis were employed to investigate the quasispecies nature of the 5'UTR following extraction of viral RNA from PBMCs and plasma of HCV infected individuals. The nucleotide variation between IRES-derived sequences from PBMCs and plasma indicated the existence of polymorphic sites within the IRES. HCV isolates had divergent variants with unique mutations particularly at positions 107, 204, and 243 of the IRES. Most of the PBMC-derived sequences contained an A-A-A variant at these positions. The mutations associated with the IRESes suggested the presence of unique quasispecies populations in PBMCs compared with plasma.