In October 2018 a large number of international experts with complementary expertise came together in Taormina to participate in a workshop on occult hepatitis B virus infection (OBI). The objectives of the workshop were to review the existing knowledge on OBI, to identify issues that require further investigation, to highlight both existing controversies and newly emerging perspectives, and ultimately to update the statements previously agreed in 2008. This paper represents the output from the workshop.

Sequence heterogeneity is a feature of hepatitis B virus (HBV), the prototype member of the family Hepadnaviridae. Based on an intergroup divergence of greater than 7.5% across the complete genome, HBV has been classified phylogenetically into 9 genotypes, A-I, with a putative 10th genotype ‘J', isolated from a single individual. With between approximately 4 and 8% intergroup nucleotide divergence across the complete genome and good bootstrap support, genotypes A-D, F, H, and I are classified further into subgenotypes. There is a broad and highly statistically significant correlation between serological subtypes and genotypes, and in some cases, serological subtypes can be used to differentiate subgenotypes. The genotypes, and certain subgenotypes, have distinct geographical distributions and are important in both the clinical manifestation of infection and response to antiviral therapy. HBV genotypes/subgenotypes and genetic variability of HBV are useful in epidemiological and transmission studies, tracing human migrations, and in predicting the risk for the development of severe liver disease and response to antiviral therapy. Moreover, knowledge of the genotype/subgenotype is important in implementing preventative strategies. Thus, it is crucial that new strains are correctly assigned to their respective genotype/subgenotype and consistent, unambiguous, and generally accepted nomenclature is utilized.

Of approximately 360 million people in the world chronically infected with hepatitis B virus (HBV), 65 million reside in Africa. Thus, Africa, with 12% of the world's population, carries approximately 18% of the global burden of HBV infection, with hepatocellular carcinoma and cirrhosis accounting for 2% of the continent's annual deaths. Despite HBV being endemic or hyperendemic in Africa, there is a paucity of data on the genotypes and their distribution. Genotype A is found mainly in southern, eastern and central Africa. Most African genotype A strains belong to subgenotype A1, with subgenotype A3 found in western Africa. Genotype D prevails in northern countries and genotype E in western and central Africa. Ithas become increasingly evident that heterogeneity in the global distribution of HBV genotypes may be responsible for differences in the clinical outcomes of HBV infections and the response to antiviral treatment and vaccination. A limited number of studies have been published relating genotypes to clinical outcomes in African countries. Because observations from other regions of the world can not be extrapolated from one locale to another, the HBV strains circulating in Africa should be studied and related to clinical outcomes.

No abstract

Chronic hepatitis B virus (HBV) infection is a global public health challenge on the same scale as tuberculosis, HIV, and malaria. The International Coalition to Eliminate HBV (ICE-HBV) is a coalition of experts dedicated to accelerating the discovery of a cure for chronic hepatitis B. Following extensive consultation with more than 50 scientists from across the globe, as well as key stakeholders including people affected by HBV, we have identified gaps in our current knowledge and new strategies and tools that are required to achieve HBV cure. We believe that research must focus on the discovery of interventional strategies that will permanently reduce the number of productively infected cells or permanently silence the covalently closed circular DNA in those cells, and that will stimulate HBV-specific host immune responses which mimic spontaneous resolution of HBV infection. There is also a pressing need for the establishment of repositories of standardised HBV reagents and protocols that can be accessed by all HBV researchers throughout the world. The HBV cure research agenda outlined in this position paper will contribute markedly to the goal of eliminating HBV infection worldwide.

Various genotypes of the hepatitis B virus (HBV) induce liver disease of distinct severity, but the underlying virological differences are not well defined. Huh7 cells were transfected with plasmids carrying 1.24-fold the HBV genome of different genotypes/subgenotypes (2 strains each for Aa/A1, Ae/A2, Ba/B2 and D; 3 each for Bj/B1 and C). HBV DNA levels in cell lysates, determined by Southern hybridization, were the highest for C followed by Bj/Ba and D/Ae (P < .01), and the lowest for Aa (P < .01), whereas in culture media, they were the highest for Bj, distantly followed by Ba/C/D and further by Ae/Aa (P < .01). The intracellular expression of core protein was more than 3-fold lower for Ae/Aa than the others. Hepatitis B e antigen (HBeAg) was excreted in a trend similar to that of HBV DNA with smaller differences. Secretion of hepatitis B surface antigen (HBsAg) was most abundant for Ae followed by Aa, Ba, Bj/C and remotely by D, which was consistent with mRNA levels. Cellular stress determined by the reporter assay for Grp78 promoter was higher for C and Ba than the other genotypes/subgenotypes (P < .01). Severe combined immunodeficiency mice transgenic for urokinase-type plasminogen activator (uPA/SCID), with the liver replaced for human hepatocytes, were inoculated with virions passed in mouse and recovered from culture supernatants. HBV DNA levels in their sera were higher for C than Ae by 2 logs during 4-7 weeks after inoculation. In conclusion, virological differences among HBV genotypes were demonstrated both in vitro and in vivo.

The purpose of this study was to identify mutations in the basic core promoter and enhancer II region of the hepatitis B virus (HBV) that might cause the HBV e antigen (HBeAg)-negative phenotype and contribute to hepatocarcinogenesis in black African carriers of the virus. The basic core promoter/enhancer II overlaps with the X gene. HBV DNA from serum of 47 asymptomatic carriers and 50 patients with hepatocellular carcinoma and from 28 tumor and 10 nontumor liver tissues was amplified and sequenced directly. That part of the enhancer II region not overlapping the basic core promoter was completely conserved in all samples. Missense mutations at nucleotides 1809 and 1812 in the basic core promoter were found in 80% of all sequences and may represent wild-type sequence in Southern African isolates. Nucleotide and amino acid divergences were higher in the basic core promoter of hepatocellular carcinoma patients when compared with asymptomatic carriers (P F .0001). This applied particularly to the paired 1762 adenine to thymine (1762 T ) and 1764 guanine to adenine (1764 A ) missense mutations, the prevalence of which was 66% in patients with hepatocellular carcinoma compared with 11% in asymptomatic carriers (P F .0001). Black Africans who are symptomless carriers of the hepatitis B virus (HBV) usually seroconvert from HBV e antigen (HBeAg) positivity to negativity after a relatively short time. 1 The carrier state is established in the first few years of life, 2 and by early adulthood between 1% and 14% only of black carriers remain HBeAg positive compared with 40% or more among ethnic Chinese, another population in which the virus is endemic. 1-4 Why black African carriers seroconvert earlier is not known. Nucleotide sequencing of the precore region of HBV isolates from a number of countries has shown the 1896 stop codon mutation to be a frequent cause of the HBeAgnegative phenotype, 5,6 with other nonsense or frame-shift mutations accounting for a small proportion (reviewed in Miyakawa et al. 7 ). However, these mutations are seldom present in black African carriers in Southern Africa 8,9 and our focus has shifted to the X open reading frame.The X open reading frame encodes the X protein that has transactivating activity (reviewed in Koike and Takada 10 ) and contains the basic core promoter (BCP)/enhancer II complex. The BCP, mapping between nucleotides 1742 and 1849, controls the transcription of both precore messenger RNA (mRNA), which codes for the protein that is the precursor of the e antigen, and pregenomic RNA (pgRNA), which controls HBV replication. 11 A pair of mutations in the BCP that is associated with a reduced level of HBeAg expression was first described in Japanese patients [12][13][14] : an adenine (A) to thymine (T) transversion at position 1762 together with a guanine (G) to A transition at 1764 in the second AT-rich region of the BCP are often present in patients with chronic hepatitis B [15][16][17][18][19][20] and fulminant hepatitis B, [14][15][16][21][22][23] and less often in asymptoma...

Using phylogenetic analysis and pairwise comparison of 670 complete hepatitis B virus (HBV) genomes, we demonstrated that nucleotide divergence greater than 7.5% can be used to separate strains into genotypes A–H. Strains can be separated into subgenotypes when two criteria are met: nucleotide divergence of about 4% but less than 7.5% and good bootstrap support. There is a highly statistically significant association between serological subtypes and genotypes (χ2‐test for association, P < 0.0001): adw is associated with genotypes A, B, F, G, and H, adr with C and ayw with D and E. The logistic regression method showed that 1802–1803CG are characteristic of genotypes A, D, and E whereas 1802–1803TT are characteristic of genotypes B, C, and F. 1858C is positively associated with genotypes A, F, and H and 1858T with genotypes B, D, and E. Subgenotypes C2, F1/F4 can be differentiated from subgenotypes C1, F2/F3, respectively, because the latter have 1858C as opposed to 1858T in the former. 1888A was positively associated with subgenotype A1 and TAA at 1817 with genotype G. The Haploplot method revealed high linkage between loci 1858 and 1896 but strong evidence of recombination between loci 1862 and 1896. Loci 1809–1812, 1862, and 1888 may have co‐evolved. Using a computer program, we showed that serological subtype deduced from the S region (position 155–835) and mutations/variations within the basic core promoter/precore region (1653–1900), allowed genotyping of HBV with 97% sensitivity and 99% specificity. Certain subgenotypes or subgenotype groups could also be differentiated. J. Med. Virol. 80:27–46, 2008. © 2007 Wiley‐Liss, Inc.