Hepatitis C: public health strategies

Global epidemiology of hepatitis C virus infection: An up-date of the distribution and circulation of hepatitis C virus genotypes

AIM

To review Hepatitis C virus (HCV) prevalence and genotypes distribution worldwide.

METHODS

We conducted a systematic study which represents one of the most comprehensive effort to quantify global HCV epidemiology, using the best available published data between 2000 and 2015 from 138 countries (about 90% of the global population), grouped in 20 geographical areas (with the exclusion of Oceania), as defined by the Global Burden of Diseases project (GBD). Countries for which we were unable to obtain HCV genotype prevalence data were excluded from calculations of regional proportions, although their populations were included in the total population size of each region when generating regional genotype prevalence estimates.

RESULTS

Total global HCV prevalence is estimated at 2.5% (177.5 million of HCV infected adults), ranging from 2.9% in Africa and 1.3% in Americas, with a global viraemic rate of 67% (118.9 million of HCV RNA positive cases), varying from 64.4% in Asia to 74.8% in Australasia. HCV genotype 1 is the most prevalent worldwide (49.1%), followed by genotype 3 (17.9%), 4 (16.8%) and 2 (11.0%). Genotypes 5 and 6 are responsible for the remaining < 5%. While genotypes 1 and 3 are common worldwide, the largest proportion of genotypes 4 and 5 is in lower-income countries. Although HCV genotypes 1 and 3 infections are the most prevalent globally (67.0% if considered together), other genotypes are found more commonly in lower-income countries where still account for a significant proportion of HCV cases.

CONCLUSION

A more precise knowledge of HCV genotype distribution will be helpful to best inform national healthcare models to improve access to new treatments.

Hepatitis C Is Poorly Associated With Drug Use in Cambodian Americans in Lowell, Massachusetts

Background. Hepatitis C (HCV) is the most common chronic blood-borne infection in the United States and affects Asian and non-Asian Americans comparably. Injection drug use, the most common national transmission risk, is not as prevalent in Asian-Americans, but prior studies do not include many Cambodian Americans. Lowell, Massachusetts has the second largest population of Cambodian Americans, allowing a direct comparison of HCV-infected Cambodian and non-Cambodian Americans not previously done. Improving our understanding of HCV risks in this unique community may improve their linkage to care.

Methods. In this cross-sectional study, medical data were collected regarding HCV risk factors for HCV-infected Cambodian and non-Cambodian Americans seen at Lowell Community Health Center from 2009 to 2012.

Results. Cambodian Americans (n = 128) were older (mean age 53 vs 43 years old) and less likely to be male (41% vs 67%, P < .001) compared with non-Cambodians (n = 541). Cambodians had lower rates of injection drug use (1.6% vs 33.6%, P < .001) and any drug use (2.3% vs 82.1%, P < .001). More Cambodians were born between 1945 and 1965 (66.4% vs 44.5%). Within this birth cohort, more Cambodians had no other risk factor (82% vs 69%, P = .02). Fewer Cambodians had chronic HCV (53% vs 74%, P < .001).

Conclusions. Birth between 1945 and 1965 was the major HCV risk factor for Cambodian Americans. Cambodians had lower rates of injection drug use or any drug use history. Risk behavior screening fails to describe HCV transmission for Cambodian Americans and creates a barrier to their linkage to care.

Global epidemiology and genotype distribution of the hepatitis C virus infection

The treatment of chronic hepatitis C virus (HCV) infection has the potential to change significantly over the next few years as therapeutic regimens are rapidly evolving. However, the burden of chronic infection has not been quantified at the global level using the most recent data. Updated estimates of HCV prevalence, viremia and genotypes are critical for developing strategies to manage or eliminate HCV infection. To achieve this, a comprehensive literature search was conducted for anti-HCV prevalence, viraemic prevalence and genotypes for all countries. Studies were included based on how well they could be extrapolated to the general population, sample size and the age of the study. Available country estimates were used to develop regional and global estimates. Eighty-seven countries reported anti-HCV prevalence, while HCV viraemic rates were available for fifty-four countries. Total global viraemic HCV infections were estimated at 80 (64-103) million infections. Genotype distribution was available for ninety-eight countries. Globally, genotype 1 (G1) was the most common (46%), followed by G3 (22%), G2 (13%), and G4 (13%). In conclusion, the total number of HCV infections reported here are lower than previous estimates. The exclusion of data from earlier studies conducted at the peak of the HCV epidemic, along with adjustments for reduced prevalence among children, are likely contributors. The results highlight the need for more robust surveillance studies to quantify the HCV disease burden more accurately.

Prevalence and risk factors for hepatitis C virus infection among young Thai men

Epidemiologic studies of hepatitis C virus (HCV) infection are unusual in developing countries, especially Thailand. We evaluated the prevalence and risk factors for HCV among military conscripts, including a sample of 5,246 men (1:30 sample), and human immunodeficiency virus (HIV)-1 positive men (N = 500) between 2005 and 2008. The HCV prevalence was 2.2% in the sampled group and 8.4% in HIV-1 sero-positives. Among the sampled group, HIV-1 infection, injection drug use (IDU) history, and unsafe injections were associated with HCV infection; adjusted prevalence rate ratios [RRs; 95% confidence intervals (CIs)] were 3.7 (1.04-12.77), 1.9 (1.04-3.54), and 1.8 (1.02-3.11), respectively. Among HIV-1 sero-positives, an IDU history and residence in southern Thailand were associated with HCV prevalence; adjusted RRs (95% CIs) were 3.5 (1.71-7.24) and 2.6 (1.18-5.61), respectively. Public health measures to prevent HCV in Thailand should focus on reducing injection drug use and other exposures to unsafe injections among young Thai men.

HCV genetic variability: from quasispecies evolution to genotype classification

HCV is a ssRNA virus belonging to the Flaviviruses and is found worldwide worldwide in humans. Following primary infection, persistent infection develops in more than 85% of cases, which in up to 30% of cases, may progress to liver disease, cirrhosis and hepatocellular carcinoma. The virus presents a high degree of genetic variability owing to the combination of a lack of proofreading by the RNA-dependent RNA polymerase and a high level of viral replication. This genetic variability allows the classification of genotypes, subtypes, isolates and quasispecies to which epidemiological and pathogenetic significance may be associated. The features and biological implications of HCV variability and of quasispecies dynamics in infection transmission, mechanisms of chronicity and resistance to antiviral therapy are discussed.

Domain 2 of nonstructural protein 5A (NS5A) of hepatitis C virus is natively unfolded

Nonstructural protein 5A protein (NS5A) of hepatitis C virus (HCV) plays an important role in the regulation of viral replication, interferon resistance, and apoptosis. HCV NS5A comprises three domains. Recently the structure of domain 1 has been determined, revealing a structural scaffold with a novel zinc-binding motif and a disulfide bond. At present, the structures of domains 2 and 3 remain undefined. Domain 2 of HCV NS5A (NS5A-D2) is important for functions of NS5A and involved in molecular interactions with its own NS5B and PKR, a cellular interferon-inducible serine/threonine specific protein kinase. In this study we performed structural analysis of domain 2 by multinuclear nuclear magnetic resonance (NMR) spectroscopy. The analysis of the backbone 1H, 13C, and 15N resonances, 3JHNalpha coupling constants ,and 3D NOE data indicates that NS5A-D2 lacks secondary structural elements and reveals characteristics of unfolded proteins. NMR relaxation parameters confirmed the lack of rigid structure in the domain. The absence of an ordered conformation and the observation of a highly dynamic behavior of NS5A-D2 may provide an underlying molecular basis on its physiological function to allow NS5A-D2 to interact with a variety of biological partners.

Spring-loaded mechanism of DNA unwinding by hepatitis C virus NS3 helicase

NS3, an essential helicase for replication of hepatitis C virus, is a model enzyme for investigating helicase function. Using single-molecule fluorescence analysis, we showed that NS3 unwinds DNA in discrete steps of about three base pairs (bp). Dwell time analysis indicated that about three hidden steps are required before a 3-bp step is taken. Taking into account the available structural data, we propose a spring-loaded mechanism in which several steps of one nucleotide per adenosine triphosphate molecule accumulate tension on the protein-DNA complex, which is relieved periodically via a burst of 3-bp unwinding. NS3 appears to shelter the displaced strand during unwinding, and, upon encountering a barrier or after unwinding >18 bp, it snaps or slips backward rapidly and repeats unwinding many times in succession. Such repetitive unwinding behavior over a short stretch of duplex may help to keep secondary structures resolved during viral genome replication.

Association of genetic polymorphism of low-density lipoprotein receptor with chronic viral hepatitis C infection in Han Chinese

To study the association between the Ava II polymorphism at the low-density lipoprotein receptor (LDL-R) gene exon 13 locus and chronic hepatitis C virus (HCV) infection in the Han Chinese, 84 chronic HCV-infected patients without anti-viral treatment, and 72 healthy blood donors were studied. Polymerase chain reaction combined with restriction fragment length polymorphism (PCR-RFLP) was used to detect the Ava II polymorphism at the LDL-R gene exon 13 locus. The comparisons of genotype distribution and allele frequency between chronic HCV-infected patients and healthy controls showed statistically significant differences (P = 0.045 and P = 0.036, respectively). Additionally, the minor allele frequency (MAF) C in the healthy controls was higher than that in the chronic HCV-infected patients group. There was no significant difference (P = 0.130) when the genotype distribution was compared between chronic HCV-infected patients with HCV viremia and those without HCV viremia. However, the comparisons of allele frequency between the two groups showed a statistically significant difference (P = 0.047), and the MAF C in HCV RNA negative group was significantly higher than that in HCV RNA positive group. There were no significant differences in genotype distribution and allele frequency of the Ava II restriction site at the LDL-R gene exon 13 locus between patients with chronic HCV infection and those with HCV-associated cirrhosis as well as between patients with normal serum alanine aminotransferase (ALT) and those with abnormal ALT levels. These results suggest that the Han Chinese have Ava II polymorphism at the LDL-R gene exon 13 locus. The Ava II polymorphism at the LDL-R gene exon 13 locus showed a statistically significant difference between chronic HCV-infected patients and healthy controls, indicating a significant contribution of the Ava II polymorphism in susceptibility to HCV infection in these patients. The MAF C in HCV RNA negative group was higher than that in HCV RNA positive group, suggesting that the Ava II polymorphism might also be associated with viremia in patients with HCV infection.

A review of the evidence for the effectiveness of primary prevention interventions for hepatitis C among injecting drug users

BACKGROUND

Hepatitis C (HCV) prevalence is most common amongst injecting drug users where up to 98% of the population can be infected despite a low prevalence of HIV. This review considers the evidence for the effectiveness of primary prevention interventions to reduce incidence or prevalence of hepatitis C.

METHODS

Systematic review of the major electronic medical databases: Medline, EMBASE, PsycINFO, CINAHL and the Cochrane Library (Evidence Based Health). Either intervention or observational studies were included if they described an intervention targeting injecting drug using populations with the outcome to reduce either the prevalence or incidence of hepatitis C infection.

RESULTS

18 papers were included in the final review from 1007 abstracts. Needle exchange programmes reduce the prevalence of HCV though prevalence remains high. Similarly the effectiveness of methadone maintenance treatment is only marginally effective at reducing HCV incidence. There is limited evidence evaluating either the effectiveness of behavioural interventions, bleach disinfectants, or drug consumption rooms.

CONCLUSION

Primary prevention interventions have led to a reduction in HIV incidence, have been less effective at reducing HCV incidence. Global prevalence of HCV remains disturbingly high in injecting drug users. A robust response to the global health problem of HCV will require provision of new interventions. Behavioural interventions; distribution of bleach disinfectant; other injecting paraphernalia alongside sterile needle distribution; and evaluation of drug consumption rooms merit further expansion internationally and research activity to contribute to the emerging evidence base. Whilst the prevalence of HCV remains high, nevertheless many current interventions aimed at primary HCV prevention have been shown to be cost-effective due to their significant positive impact upon prevalence of HIV.

Preventing hepatitis C: 'common sense', 'the bug' and other perspectives from the risk narratives of people who inject drugs

There is little published research about how people who inject drugs are responding to the hepatitis C epidemic. This study seeks to address the prevention of hepatitis C using qualitative interviews with people who inject drugs in London. We explored narratives about risk reduction and hepatitis C in the social and historical context of other risks such as HIV, vein damage and overdose. Themes of the narratives included: the importance of autonomy in the acquisition of safer injecting skills; that safer injection was regarded as 'common sense', normalised and predicated on the risk of HIV; that hepatitis C risk was relativised with HIV risk and thereby seen as less important; and that hepatitis C infection was also seen as unavoidable. These narrative forms represent significant challenges for the management of the hepatitis C epidemic, both in terms of the existing risk reduction efforts designed for HIV and in terms of the articulation of risk reduction for injectors with general public health policy.

High prevalence of the hepatitis C virus infection among the inpatients of schizophrenia and psychoactive substance abuse in Japan

Prevalence of anti-HCV antibody in 1193 hospitalized patients (848 males and 345 females) in psychiatric department was investigated. Overall prevalence ratio was 9.1%, indicating significantly higher than that of healthy blood donors. In the classification of ICD-10, the prevalence of the inpatients diagnosed in schizophrenia group and psychoactive substance use group accounted for 6.2% and 13.8%, respectively. However, adequate reasons such as sanitary issues were not found to account for the high prevalence. Only the age of the patients could account for the high prevalence in the schizophrenic group. In the psychoactive substance abuse group, the sanitary issues might be a major cause of the very high prevalence of anti-HCV antibody, while other factors such as dysfunction of the immune system might be considered to account for it.

What surgeons should know about viral hepatitis and hepatocellular carcinoma

Most patients with hepatocellular carcinoma (HCC) have viral hepatitis, either hepatitis C (HCV) or hepatitis B (HBV). HCV is an RNA virus that does not integrate into the host genome but likely induces HCC through viral protein: for example, host protein interactions or via the inflammatory response to the virus. Eradication of HCV with interferon plus riboviron therapy may help prevent cancer recurrence in selected patients. In contrast to HCV, HBV is an DNA virus that integrates into the host genome, and this integration is believed, in part, to be carcinogenic. HBV is usually classified as replicative (DNA-positive in the serum) or nonreplicative (DNA-negative in the serum). Treatment with nucleoside analogs is indicated in most patients with cirrhotic-stage replicating HBV. Nonreplicative stages of this virus do not merit therapy with these agents.

Liver targeting of human interferon-beta with pullulan based on metal coordination

Although interferon (IFN)-beta is widely used for the elimination of hepatitis C virus in patients with chronic liver disease, its clinical efficacy is unsatisfactory. Targeting IFN-beta to the liver might enhance its efficacy without increasing its side effects. The objective of the present study was to target IFN-beta to the liver to enhance its biological activity and reduce its side effects. A chelating residue, diethylenetriaminepentaacetic acid (DTPA), was introduced to pullulan, a water-soluble polysaccharide with a high affinity to the liver (DTPA-pullulan) and natural human IFN-beta was coordinately conjugated with the DTPA-pullulan by mixing in an aqueous solution containing zinc ions (Zn(2+)). Intravenous injection of the IFN-beta-DTPA-pullulan conjugate with Zn(2+) coordination into mice enhanced induction of an antiviral enzyme, 2',5'-oligoadenylate synthetase (2-5AS), specifically in the liver to a significantly greater extent than free natural IFN-beta. The enhanced 2-5AS level in the liver depended on the molar mixing ratio of IFN-beta, DTPA residue of the DTPA-pullulan, and Zn(2+). Moreover, the duration of the liver 2-5AS induction by the IFN-beta-DTPA-pullulan conjugate was longer than that by free natural IFN-beta. Thus, human IFN-beta-DTPA-pullulan conjugate appears to be applicable for clinical use, which is promising for treatment of patients with chronic hepatitis C.

Secondary structure of the 3' terminus of hepatitis C virus minus-strand RNA

The 3'-terminal ends of both the positive and negative strands of the hepatitis C virus (HCV) RNA, the latter being the replicative intermediate, are most likely the initiation sites for replication by the viral RNA-dependent RNA polymerase, NS5B. The structural features of the very conserved 3' plus [(+)] strand untranslated region [3' (+) UTR] are well established (K. J. Blight and C. M. Rice, J. Virol. 71:7345-7352, 1997). However, little information is available concerning the 3' end of the minus [(-)] strand RNA. In the present work, we used chemical and enzymatic probing to investigate the conformation of that region, which is complementary to the 5' (+) UTR and the first 74 nucleotides of the HCV polyprotein coding sequence. By combining our experimental data with computer predictions, we have derived a secondary-structure model of this region. In our model, the last 220 nucleotides, where initiation of the (+) strand RNA synthesis presumably takes place, fold into five stable stem-loops, forming domain I. Domain I is linked to an overall less stable structure, named domain II, containing the sequences complementary to the pseudoknot of the internal ribosomal entry site in the 5' (+) UTR. Our results show that, even though the (-) strand 3'-terminal region has the antisense sequence of the 5' (+) UTR, it does not fold into its mirror image. Interestingly, comparison of the replication initiation sites on both strands reveals common structural features that may play key functions in the replication process.

A nationwide survey of hepatitis C services provided by drug treatment programs

Drug treatment programs are a site of opportunity for the delivery of primary and secondary hepatitis C (HCV) prevention services to drug users, a population at great risk for contracting and transmitting the virus. Using data collected from a random nationwide sample (N = 439) of drug treatment programs in the United States, this study examines the extent to which various types of HCV services are provided to their patients. Findings indicate that the majority of drug treatment programs educate at least some of their patients about HCV, and provide some type of support for patients who are infected with the virus. Only 29 of the programs in the sample test all of their patients for HCV, however, and 99 programs test none of them. For the most part, residential treatment programs offer more HCV related services than outpatient drug-free programs.

The B-cell receptor of a hepatitis C virus (HCV)-associated non-Hodgkin lymphoma binds the viral E2 envelope protein, implicating HCV in lymphomagenesis

Hepatitis C virus (HCV) infection is associated with extrahepatic B-cell lymphoproliferative disorders. To determine whether a viral antigen drives this B-cell expansion, the B-cell receptors were cloned from HCV-associated lymphomas and were expressed as soluble immunoglobulins. The rescued immunoglobulins were then tested for their ability to bind the HCV-E2 envelope glycoprotein, an antigen that was previously implicated in the pathogenesis of HCV-associated B-cell diseases. One of 2 lymphoma immunoglobulin test cases bound the E2 protein in a manner identical to a bona fide human anti-E2 antibody. Moreover, it bound E2 from multiple viral genotypes, suggesting reactivity with a conserved E2 epitope. These findings support the hypothesis that some HCV-associated lymphomas originate from B cells that were initially activated by the HCV-E2 protein and might explain the association between HCV infection and some B-cell lymphoproliferative disorders.

Transmission of HCV to a chimpanzee using virus particles produced in an RNA-transfected HepG2 cell culture

It was demonstrated previously that HepG2 cells produce negative strand RNA and virus-like particles after transfection with RNA transcribed from a full-length hepatitis C virus (HCV) cDNA clone [Dash et al. (1997) American Journal of Pathology, 151:363-373]. To determine in vivo infectivity of these in vitro synthesized viral particles, a chimpanzee was inoculated intravenously with HCV derived from HepG2 cells. The infected chimpanzee was examined serially for elevation of liver enzymes, for the presence of HCV RNA in the serum by reverse transcription nested polymerase chain reaction (RT-PCR), anti-HCV antibodies in the serum, and inflammation in the liver. The chimpanzee developed elevated levels of liver enzymes after the second week, but the levels fluctuated over a 10-week period. HCV RNA was detected in the serum of the chimpanzee at the second, seventh and ninth weeks after inoculation, and remained positive up to 25 weeks. Liver biopsies at Weeks 18 and 19 revealed of mild inflammation. Nucleotide sequence analysis of HCV recovered from the infected chimpanzee at the second and ninth weeks showed 100% sequence homology with the clone used for transfection studies. Serum anti-HCV antibodies were not detected by EIA during the 25 weeks follow-up period. These results suggest that intravenous administration of the virus-like particles derived from RNA-transfected HepG2 cells are infectious, and therefore, the pMO9.6-T7 clone is an infectious clone. These results provide new information that in vitro synthesized HCV particles produced from full-length HCV clone can cause infection in a chimpanzee. This study will facilitate the use of innovative approaches to the study of assembly of HCV particles and mechanisms of virus infectivity in cell culture.