Control of HBV and HDV infection in an isolated Pacific Island: 1. Pattern of infection

Hepatitis D Review: Challenges for the Resource-Poor Setting

Hepatitis D is the smallest virus known to infect humans, the most aggressive, causing the most severe disease. It is considered a satellite or defective virus requiring the hepatitis B surface antigen (HBsAg) for its replication with approximately 10–70 million persons infected. Elimination of hepatitis D is, therefore, closely tied to hepatitis B elimination. There is a paucity of quality data in many resource-poor areas. Despite its aggressive natural history, treatment options for hepatitis D to date have been limited and, in many places, inaccessible. For decades, Pegylated interferon alpha (Peg IFN α) offered limited response rates (20%) where available. Developments in understanding viral replication pathways has meant that, for the first time in over three decades, specific therapy has been licensed for use in Europe. Bulevirtide (Hepcludex^®) is an entry inhibitor approved for use in patients with confirmed viraemia and compensated disease. It can be combined with Peg IFN α and/or nucleos(t)ide analogue for hepatitis B. Early reports suggest response rates of over 50% with good tolerability profile. Additional agents showing promise include the prenylation inhibitor lonafarnib, inhibitors of viral release (nucleic acid polymers) and better tolerated Peg IFN lambda (λ). These agents remain out of reach for most resource limited areas where access to new therapies are delayed by decades. strategies to facilitate access to care for the most vulnerable should be actively sought by all stakeholders.

Molecular Phylogenetics of Hepatitis D Virus in New Zealand and the Implications for Pacific Island Countries

Hepatitis delta virus (HDV) is considered a satellite virus that requires hepatitis B virus surface antigen for infectivity. HDV is endemic in some Pacific Island (PI) countries, including Kiribati and Nauru, with a unique genotype 1, "Pacific clade." The aims of this study were to determine the HDV genotypes in New Zealand and investigate the link of strains to other PI countries and the rest of the world through phylogenetics. Sequencing and phylogenetic analyses were performed on 16 HDV-positive serum samples from 14 individuals collected between 2009 and 2014 at Auckland Hospital. Thirteen of 14 strains were confirmed as genotype 1 and 1 was genotype 5. Eleven of the 13 genotype 1 strains clustered with the Pacific clade. These were isolated from subjects born in Samoa, Kiribati, Tuvalu, and Niue. Another genotype 1 strain isolated from a Maori health-care worker clustered most closely with a European strain. There was an African genotype 1 and genotype 5 from African-born subjects with HIV coinfection. This study supports the probable transmission of HDV Pacific clade around the PI from Micronesia to Polynesia. The data also confirm the need to screen hepatitis B surface antigen-positive individuals for HDV.

Hepatitis B and D in the Pacific Islands of Kiribati

BACKGROUND

Historical reports indicate that hepatitis B and hepatitis D are highly endemic in the Pacific Island of Kiribati but current levels are unknown.

OBJECTIVES

To determine current prevalence of HBV and HDV in Kiribati, characterize the strains in both mono-infection and co-infection and assess individuals for antiviral therapy.

STUDY DESIGN

Sera obtained from 219 patients were screened for HBsAg, HBeAg, HBV DNA, anti-HD, and HDV RNA. 61 HBV isolates were sequenced for genotype, phylogenetic analysis and detection of pre-core and basal core promoter mutations. 82 HDV isolates were also sequenced.

RESULTS

55.7 % HBsAg positive samples had antibodies to HDV and 73.2 % had detectable HDV RNA, indicating that 40.8 % HBsAg-positive individuals had current HBV/HDV co-infection. There were 42 co-infected males and 40 females; the youngest individual was a 4 year-old boy. HBV isolates were genotype D4, and HDV strains formed a distinct Pacific clade of genotype 1. Undetectable HBV DNA loads were statistically more frequent in the co-infected sub-population (p < 0.0001). Basal core promoter and pre-core mutations were present in both mono and co-infection.

CONCLUSION

Kiribati has one of the highest HBV/HDV co-infection rates in the world. The epidemiology of co-infection in this population was unusual with males and females equally represented and the presence of co-infection in a 4 year old child suggesting neonatal or early horizontal transmission, which is extremely rare. Coinfection with HDV resulted in statistically significant suppression of HBV DNA levels. The HDV strain identified in Kiribati was unique to the Pacific Islands.

Epidemiology and phylogenetic analysis of hepatitis D virus infection in Australia

BACKGROUND

The incidence and trends of the hepatitis D virus (HDV) in Australia have not been recently assessed, and the circulating genotypes have never been determined.

AIM

To characterise the current virology and epidemiology of HDV.

METHODS

Notifiable disease surveillance and laboratory testing data were analysed to assess demographics, risk factors and trends. HDV serology and RNA testing were performed on requested samples from 2010 to 2016. Sequencing of a 500-nucleotide amplicon of the delta antigen and phylogenetic analysis of the strains from 2009 to 2016 were also conducted.

RESULTS

Ninety HDV notifications were reported to the Victorian Department of Health and Human Services between 2010 and 2016. The majority (64.4%) of those diagnosed were born overseas, most commonly in Sudan, Pakistan and Vietnam. Over the same period, 190 patients tested positive for anti-HDV serology and 166 for HDV RNA. Sequencing of isolates from 169 individuals between 2009 and 2016 found that 80.5% strains were genotype 1, 16% genotype 5 and 3.5% genotype 2. Phylogenetic analysis confirmed the relatedness of strains from birth country, demonstrated the presence of the 'Pacific Island' genotype 1 strain in Queensland and supported possible transmission in correctional facilities and within families.

CONCLUSIONS

This study demonstrates the ongoing need for routine HDV screening and engagement in clinical care for people living with HBV in Australia. Epidemiological findings highlight the diversity in those affected and provide insights into local and global geographic distribution and transmission patterns.

Progress towards hepatitis B prevention through vaccination in the Western Pacific, 1990-2014

Hepatitis B infections are responsible for more than 300 thousand deaths per year in the Western Pacific Region. Because of this high burden, the countries and areas of the Region established a goal of reducing hepatitis B chronic infection prevalence among children to less than 1% by 2017. This study was conducted to measure the progress in hepatitis B prevention and assess the status of achievement of the 2017 Regional hepatitis B control goal. A literature review was conducted to identify studies of hepatitis B prevalence in the countries and areas of the region, both before and after vaccine introduction. A mathematical model was applied to assess infections and deaths prevented by hepatitis B vaccination and hepatitis B prevalence in countries without recent empirical data. The majority of countries and areas (22 out of 36) were estimated to have over 8% prevalence of chronic hepatitis B infection among persons born before vaccine introduction. After introduction of hepatitis B vaccine, most countries and areas (24 out of 36) had chronic infection prevalence of less than 1% among children born after vaccine introduction. It was estimated that in the past 25 years immunization programmes in the Western Pacific Region have averted 7,167,128 deaths that would have occurred in the lifetime of children born between 1990 and 2014 if hepatitis B vaccination programmes had not been established. Regional prevalence among children born in 2012 was estimated to be 0.93%, meaning that the Regional hepatitis B control goal was achieved. While additional efforts are needed to further reduce hepatitis B transmission in the region, this study demonstrates the great success of the hepatitis B vaccination efforts in the Western Pacific Region.

Chronic hepatitis B: Virology, natural history, current management and a glimpse at future opportunities

The host immune system plays an important role in chronic hepatitis B (CHB), both in viral clearance and hepatocellular damage. Advances in our understanding of the natural history of the disease have led to redefining the major phases of infection, with the "high replicative, low inflammatory" phase now replacing what was formerly termed the "immune tolerant" phase, and the "nonreplicative phase" replacing what was formerly termed the "inactive carrier" phase. As opposed to the earlier view that HBV establishes chronic infection by exploiting the immaturity of the neonate's immune system, new findings on trained immunity show that the host is already somewhat "matured" following birth, and is actually very capable of responding immunologically, potentially altering future hepatitis B treatment strategies. While existing therapies are effective in reducing viral load and necroinflammation, often restoring the patient to near-normal health, they do not lead to a cure except in very rare cases and, in many patients, viremia rebounds after cessation of treatment. Researchers are now challenged to devise therapies that will eliminate infection, with a particular focus on eliminating the persistence of viral cccDNA in the nuclei of hepatocytes. In the context of chronic hepatitis B, new definitions of 'cure' are emerging, such as 'functional' and 'virological' cure, defined by stable off-therapy suppression of viremia and antigenemia, and the normalization of serum ALT and other liver-related laboratory tests. Continued advances in the understanding of the complex biology of chronic hepatitis B have resulted in the development of new, experimental therapies targeting viral and host factors and pathways previously not accessible to therapy, approaches which may lead to virological cures in the near term and functional cures upon long term follow-up. This article forms part of a symposium in Antiviral Research on "An unfinished story: from the discovery of the Australia antigen to the development of new curative therapies for hepatitis B."

Molecular epidemiology of hepatitis delta virus in the Western Pacific region

BACKGROUND

Hepatitis delta virus (HDV) is a defective RNA virus requiring the presence of the hepatitis B virus (HBV) for the completion of its life cycle. Active replication of HDV can lead to severe hepatitis, and although present worldwide has an irregular geographical distribution, especially in the Asian Pacific region.

OBJECTIVES

The aim of this study was to determine the prevalence and molecular epidemiology of HDV isolates in Oceania following the 1998 evaluation of the hepatitis B vaccine program.

STUDY DESIGN

Sera collected from 184 hepatitis B surface antigen (HBsAg) positive Pacific Islanders living in Micronesia, Polynesia and Melanesia were tested for HDV RNA.

RESULTS

Twenty of 54 patients with chronic hepatitis B (CHB) from Kiribati were positive for serum HDV RNA (37%), whilst sera from patients with CHB from Tonga (59), Fiji (42) and Vanuatu (29) were negative. The mean HDV RNA load for the 20 samples was 7.00log10copies/mL. Phylogenetic analysis revealed that the Kiribati HDV isolates were of genotype 1 and clustered with a previously published isolate from Nauru forming a distinct clade of Pacific HDV. All Micronesian isolates contained a serine at codon 202 of large hepatitis delta antigen (L-HDAg) demonstrating possible relatedness to strains of HDV-1 of African origin.

CONCLUSIONS

This study has confirmed endemic HDV infection in Micronesia and identified Kiribati as having amongst the highest prevalence for HDV viraemia in patients with CHB. Further investigations are ongoing into the origins of this unique HDV Pacific strain, and its inter-relationship with HBV.

Hepatitis D: Scenario in the Asia-Pacific region

Hepatitis D virus (HDV) infection is present worldwide and affects all age groups. Around 18 million people are estimated to be infected with HDV. An important trend in HDV infection is global decline. HDV prevalence has decreased significantly in Europe since the 1970s and 1980s when it was first reported. The Asia-Pacific region now seems to be where HDV is a major health concern. There is a lack of available data from most of the countries from this region; hence, the true status of HDV cannot be determined. In South Asia, most of the countries have conditions that are favorable for the spread of hepatitis B and other related infections. Countries like Pakistan and Iran have shown an increase in HDV prevalence over a period of time. Other countries and region like China, Turkey, Australia, Japan, India and Taiwan, some of which had very high HDV prevalence in the past, have shown a decline in the incidence, but high prevalence persists in some. Intravenous drug abusers, homosexual men and women, prostitutes, and people on hemodialysis are the groups with very high HDV prevalence.

Chronic hepatitis B virus infection in the Asia-Pacific region and Africa: review of disease progression

Countries in the the Asia-Pacific region and Africa tend to have the highest prevalence of hepatitis B infection worldwide. Hepatitis B infection progresses from an asymptomatic persistently infected status to chronic hepatitis B, cirrhosis, decompensated liver disease and/or hepatocellular carcinoma. The aim of this review was to summarize rates and risk factors for progression between disease states in the Asia-Pacific region and Africa. A literature search was conducted employing MEDLINE and EMBASE (1975-2003) using the following key words: hepatitis B, natural history, disease progression, cirrhosis, hepatocellular carcinoma, mortality, Africa and the Asia-Pacific region. Bibliographies of articles reviewed were also searched. Ranges for annual progression rates were: (i) asymptomatic persistent infection to chronic hepatitis B, 0.84-2.7%; (ii) chronic hepatitis B to cirrhosis, 1.0-2.4%; and (iii) cirrhosis to hepatocellular carcinoma, 3.0-6.6%. Patients with asymptomatic persistent infection and chronic hepatitis B had relatively low 5-year mortality rates (<4%); rates (>50%) were much higher in patients with decompensated liver disease and hepatocellular carcinoma. No data were found for progression rates in African populations. Hepatitis B e antigen was a risk factor for chronic hepatitis B, and bridging hepatic necrosis in chronic hepatitis B increased the risk of cirrhosis. Risk factors for hepatocellular carcinoma included cirrhosis, co-infection with hepatitis C virus, and genetic and environmental factors. In this review, wide ranges of disease progression estimates are documented, emphasizing the need for further studies, particularly in Africa, where progression rates are largely not available. Summarizing information on factors associated with disease progression should assist in focusing efforts to arrest the disease process in those at most risk.

Prevalence of HBsAg mutants and impact of hepatitis B infant immunisation in four Pacific Island countries

The prevalence rate of hepatitis B virus (HBV) infection in Pacific Island countries is amongst the highest in the world. Hepatitis B immunisation has been incorporated into national programmes at various times, often with erratic supply and coverage, until a regionally co-ordinated programme, which commenced in 1995 ensured adequate supply. The effectiveness of these programmes was recently evaluated in four countries, Vanuatu and Fiji in Melanesia, Tonga in Polynesia and Kiribati in Micronesia. That evaluation established that the programmes had a substantial beneficial impact in preventing chronic hepatitis B infection [Vaccine 18 (2000) 3059]. Several studies of hepatitis B vaccination programmes in endemic countries have identified the potential significance of surface gene mutants as a cause for failure of immunisation. In the study outlined in this paper, we screened infected children and their mothers for the emergence and prevalence of these variants in specimens collected from the four country evaluation. Although the opportunity for the emergence of HBV vaccine escape mutants in these populations was high due to the presence of a considerable amount of the virus in the population and the selection pressure from vaccine use, there were no "a" determinant vaccine escape mutants found. This suggests that vaccine escape variants are not an important cause for failure to prevent HBV transmission in this setting. Other HBsAg variants were detected, but their functional significance remains to be determined. The failure to provide satisfactory protection during such immunisation programmes reflects the need for achieving and sustaining high vaccine coverage, improving the timeliness of doses as well as improving 'cold-chain' support, rather than the selection of vaccine-escape mutants of HBV.

The effectiveness of the infant hepatitis B immunisation program in Fiji, Kiribati, Tonga and Vanuatu

The aims of this project were: (1) to determine the extent to which infant hepatitis B immunisation is preventing chronic hepatitis B infection in children living in a sample of Pacific Island countries; and (2) to identify factors associated with the successful prevention of hepatitis B infection in these populations. A regional hepatitis B immunisation project which supplied hepatitis B vaccine to 10 Pacific Island countries began in 1995. Seroepidemiological surveys were conducted in Fiji, Kiribati, Tonga and Vanuatu in early 1998. These included immunised pre-school children and their biological mothers, and a historical control group of unimmunised students. Prevalence rates for hepatitis B surface antigen (HBsAg) in the populations of students, mothers and their pre-school children were respectively: Fiji: 6.9, 6.6, 0.7%; Kiribati: 27.4, 15.1, 3.8%; Tonga: 11.1, 18.6, 3.8%; Vanuatu: 16.3, 12.3, 3.0%; and for all four countries: 13.2, 12.5, 2.6%. Compared to the historical control group of students, the pre-school population had a much lower probability of HBsAg positivity (relative risk [RR]=0.19 [95%CI: 0.12-0.31]). Statistically significant differences in risk were apparent for all the countries: Fiji: RR=0.10; Kiribati: RR=0.14; Tonga: RR=0.34; Vanuatu: RR=0.19. This is equivalent to an overall program effectiveness of 81% (95%CI: 69-88%) in reducing chronic carriage. Also, the overall protective effectiveness against vertical hepatitis B transmission resulting in HBsAg positivity among children exposed to HBeAg positive and negative carrier mothers, was estimated to be 70%. By age 6 months, when all children should have had three vaccine doses, completed immunisation rates ranged from 22 (Fiji) to 84% (Vanuatu). Coverage of the first dose being given within 2 days of birth varied from 43% in Kiribati to 92% in Tonga. In conclusion hepatitis B immunisation of infants in these four countries is having a substantial beneficial effect in preventing chronic hepatitis B infection. Nevertheless, there is significant scope for further improving the timeliness of immunisation.

Age-specific prevalence of hepatitis B surface antigenaemia in hospitalized children at Port Moresby, Papua New Guinea (a cross-sectional study with implications for the Hepatitis B Control Programme)

A cross-sectional analysis of the prevalence of hepatitis B surface antigenaemia in cord blood from 50 newborn babies and in blood from 415 children admitted to the children's ward of Port Moresby General Hospital indicates that perinatal vertical transmission is likely to be important and that there is a high rate of horizontal transmission in the 1st few years of life. Thirteen per cent of infants aged 3-5 months and 29-30% of those over 2 years of age were strongly positive for hepatitis B surface antigen. Open sores and poor hygiene are likely to play a significant role in the high level of horizontal transmission of hepatitis B virus (HBV) in our context. Our findings give support and urgency to the current active immunization policy against HBV, beginning as soon as possible after birth.

Chronic delta hepatitis in haemophiliacs

The seroepidemiological profile of HBV and HDV was investigated in 640 male haemophiliacs. Twenty-seven of forty-four HBsAg carriers were anti-HDV-IgG positive, 22 were also anti-HDV-IgM positive. A markedly lower prevalence of HDV infection was found in patients with anti-HBc in the absence of HBsAg and anti-HBs (6/41). Repeated detection of anti-HDV-IgM in 5/41 individuals of this group indicates that circulating HBsAg is not an absolute prerequisite for chronic HDV infection. Overall, chronically active HDV infection was detected more frequently in quiescent than in active chronic HBV infections. Anti-HDV-IgM was not detected in the absence of anti-HDV-IgG antibodies. Anti-HDV-IgG may disappear after resolution of HDV infection, as indicated by the low prevalence (1/42) in such individuals with past HBV infection as well as by loss of anti-HDV-IgG observed in two patients.

The hepatitis B virus

Of all the hepatotropic viruses, HBV is associated with the greatest worldwide morbidity and mortality. This is because of the ease of transmission and the potential for progression to a chronic infective carrier state, with the complications of cirrhosis and hepatocellular carcinoma. The use of PCR has shown that some of the earlier concepts concerning the interpretation of serological data were inaccurate. Many patients with anti-HBe and anti-HBs have viral DNA detectable by PCR, and some hepatocellular carcinoma patients have detectable HBV DNA in their livers in the absence of all serological markers of HBV disease. The clearance of HBV infected cells from the liver is dependent on the interplay between the interferon system and the cellular limb of the host immune response. The importance of the nucleocapsid proteins as targets for sensitized cytotoxic T cells has been established for chronic HBV infection. The importance of pre-S sequences as inducers and targets of the virus-neutralizing humoral immune response is becoming established, but their precise role must await the development of in vitro models of hepadnavirus infection and a greater understanding of the mechanisms of viral uptake. The epidemiology and clinical course of the disease can be modified by immunization, immune stimulation and antiviral chemotherapy. For the developing world, a programme of immunization at birth would be the most effective way of eliminating this disease, but at present the cost is prohibitive. For the developed world, immunization is realistic for the at-risk population, and anti-viral and immunostimulatory therapy available for those already infected. In adult acquired chronic HBV infection alpha-interferon produces HBe antigen clearance in 40-60% of cases and is followed by resolution of the hepatic inflammation. Results in neonatally acquired infection are less impressive and prednisolone priming followed by interferon may be needed. The presence of a mutation in the pre-core region of some virus isolates has recently been described. Hepatocytes infected with this virus cannot produce HBe antigen and the course of the liver disease is fairly rapid. Whether this mutant causes liver damage in the same way as the wild virus or is directly cytopathic remains unclear, and its relationship to fulminant hepatitis is under investigation.

Epidemiology of hepatitis B infection in the Western Pacific and South East Asia

The Western Pacific and South East Asia regions are the largest and most populous of the six World Health Organisation regions and include more than 40 countries. More than 75% of the world's estimated 350 million carriers are located here. The region has therefore provided many insights into the epidemiology, natural history, and control of hepatitis B infection and has been home to the first national control programmes. Hepatitis B is hyperendemic in most countries of the region, with carrier rates ranging from 5-35% except in Australia, New Zealand, and Japan, where the mean carrier rate is less than 2%. Patterns of infection vary considerably from country to country, city to city, and even village to village, and can change with time. Most infections are acquired early in childhood or in early adult life. A variety of control measures are in place and many countries in the region have introduced widespread or universal childhood immunisation policies with significant success. While it is theoretically possible that hepatitis B infection could be eradicated by universal childhood immunisation, there are several biological and practical issues that make this extremely difficult, suggesting that, for the foreseeable future, control may be a more realisable goal.