Hepatitis B genotypes in Aboriginal and Torres Strait Islander Australians: correlation with clinical course and implications for management.

BACKGROUND: The prevalence of chronic hepatitis B (CHB) in Aboriginal and Torres Strait Islander Australians in Far North Queensland (FNQ) is greater than twice that of the general Australian population. CHB is common in Torres Strait Islanders diagnosed with hepatocellular carcinoma (HCC) - and in Aboriginals with HCC living in the Northern Territory - however, Aboriginals diagnosed with HCC in FNQ very rarely have CHB. The explanation for this apparent disparity is uncertain. AIMS: To determine the HBV genotypes in the FNQ Aboriginal and Torres Strait Islander population and their correlation with clinical phenotype. METHODS: We determined the HBV genotype of Aboriginal and Torres Strait Islander Australians living with CHB in FNQ and correlated this with demographic and clinical findings. RESULTS: 134/197 (68%) enrolled individuals had a sufficient viral load for genotyping. All 40 people with HBV/D genotype had Aboriginal heritage, whereas 85/93 (91%) with HBV/C had Torres Strait Islander heritage (P < 0.0001). Individuals with HBV/D were younger than those with HBV/C (median (interquartile range) age: 43 (39-48) vs 53 (42-66) years, P = 0.0002). However, they were less likely to be HBeAg positive (1/40 (3%) vs 23/93 (25%), P = 0.001). All three HCCs developed in Torres Strait Islanders; two-thirds were infected with HBV/C14; genotyping was not possible in the other individual. All 10 diagnoses of cirrhosis occurred in Torres Strait Islanders, 6/10 were infected with HBV/C14, genotyping was not possible in the other four individuals. CONCLUSIONS: HBV genotypes in Aboriginal and Torres Strait Islander Australians in FNQ differ markedly, which could explain the significant differences in the clinical phenotype in the two populations and might be used to inform cost-effective CHB care in the region.

Molecular epidemiology of hepatitis B among Indigenous Australians in Queensland and the Torres Strait Islands.

BACKGROUND: Chronic hepatitis B virus (HBV) infection is a major health problem for all Indigenous Australians. Post-2000, Hepatitis B surface antigen prevalence has decreased, although remaining four times higher among Indigenous compared with non-Indigenous people. AIMS: This study aimed to characterise the HBV from Indigenous populations in Queensland and the Torres Strait Islands. METHODS: Serum samples were collected, with consent, from people within Queensland Indigenous communities prior to 1990 as part of the Queensland Health vaccination programme. Ethics approval was subsequently obtained to further characterise the HBV from 93 of these stored samples. HBV DNA was extracted and genotype was obtained from 82 samples. HBV full genome sequencing was carried out for a subset of 14 samples. RESULTS: Seventy-eight samples were identified as genotype C (2 × C12, 3 × C13 and 73 × C14), one sample as genotype A (A2) and three samples as genotype D (1 × D2, 1 × D3 and 1 × D4). The HBV/C sequences identified were most closely related to sequences isolated from Papua New Guinea and Indonesia (Papua Province). CONCLUSIONS: The HBV isolated from the Torres Strait Islanders was notably different to the HBV/C4 strain isolated from Indigenous people of mainland northern Australia, with no evidence of recombination. This reflects the differences in culture and origin between Torres Strait Islanders and mainland Indigenous people.

Assessment of the cobas® HBV RNA investigational assay in the setting of nucleoside analog therapy cessation.

HBV RNA is used as a marker of cccDNA transcription and is applicable in the setting of nucleos(t)ide analog (NA) treatment, which suppresses HBV DNA. Traditional assays for quantification of HBV RNA rely on labor-intensive 3'RACE assays targeting the polyA tail. In this study, the high-throughput Roche cobas®HBV RNA investigational assay was assessed on the Roche cobas® 6800 automated platform. Of 969 samples collected for a NA treatment cessation trial, and tested on the cobas assay, 249 were analyzed for sensitivity, reproducibility, sample type applicability, and results were compared to a RACE-based assay. Results of 97 paired serum and plasma samples demonstrated an excellent correlation of 0.98. However, 14.5% of plasma samples yielded detectable (below the limit of quantification) results, when the paired serum was undetectable, and plasma was shown to yield a statistically significant (p < 0.001) greater mean 0.119 log10 copies/ml. Quantification of 152 samples showed good correlation (0.91) between the cobas and RACE assays. The cobas assay demonstrated superior lower limit of quantification, 10 copies/ml, which resulted in detection of 13.2% more samples than the RACE assay. Reproducibility and linear range of the automated assay were also confirmed. The Roche cobas assay for HBV RNA is sensitive and highly recommended.

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.

Effect of the G1896A precore mutation on drug sensitivity and replication yield of lamivudine-resistant HBV in vitro.

Hepatitis B e antigen (HBeAg) negative chronic hepatitis B (CHB) is frequently caused by a mutation (G1896A) in the hepatitis B virus (HBV) precore (PC) reading frame that creates a stop codon, causing premature termination of the PC protein. During lamivudine treatment, drug resistance develops at a similar rate in HBeAg positive and HBeAg negative CHB. Lamivudine-resistant HBV mutants have been shown to replicate inefficiently in vitro in the absence of PC mutations, but it is unknown whether the presence of PC mutations affects replication efficiency or antiviral sensitivity. This study utilized the recombinant HBV baculovirus system to address these issues. HBV baculoviruses encoding the G1896A PC stop codon mutation were generated in wild-type (WT) and lamivudine-resistant (rtM204I and rtL180M + rtM204V) backgrounds, resulting in a panel of 6 related recombinant baculoviruses. In vitro assays were performed to compare the sensitivities of the PC mutant viruses with lamivudine and adefovir and to compare relative replication yields. The PC mutation did not significantly affect sensitivities to either adefovir or lamivudine. WT HBV and PC mutant HBV showed similar replication yields, whereas the replication yields of the lamivudine-resistant mutants were greatly reduced in HBeAg positive HBVs, confirming previous observations. However, the presence of the PC mutation was found to compensate for the replication deficiency in each of the lamivudine-resistant mutants, increasing the replication yields of each virus. In conclusion, the PC stop codon mutation appears to increase the replication efficacy of lamivudine-resistant virus but does not affect in vitro drug sensitivity.

Phenylpropenamide derivatives AT-61 and AT-130 inhibit replication of wild-type and lamivudine-resistant strains of hepatitis B virus in vitro.

The phenylpropenamide derivatives AT-61 and AT-130 are nonnucleoside analogue inhibitors of hepatitis B virus (HBV) replication. They inhibited the replication of wild-type HBV with 50% inhibitory concentrations of 21.2 +/- 9.5 and 2.40 +/- 0.92 micro M, respectively, compared to 0.064 +/- 0.020 micro M lamivudine. There were no significant differences in sensitivity between wild-type and nucleoside analogue-resistant (rtL180M, rtM204I, and rtL180M + rtM204V) HBV.