Characterization of hepatitis B surface antigen strains circulating in the Kingdom of Cambodia

A Recent Prevalence of Hepatitis B Virus (HBV) Genotypes and Subtypes in Asia: A Systematic Review and Meta-Analysis

Background and Aim: Despite introducing the hepatitis B virus (HBV) vaccine, the incidence of the Hepatitis B virus globally is still a major health concern. This systematic review and meta-analysis were conducted to provide detailed information on the prevalence of HBV genotypes and subtypes in circulation in Asia. Methods: A systematic search for articles describing the prevalence of HBV genotypes and subtypes in Asia was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines. Results: Our search returned 207 eligible articles involving 49,279 genotypes and 7457 subtypes representing 28 Asian countries. A meta-analysis was performed on our eligible studies using the Random effect Model. The pooled prevalence of HBV genotypes showed that genotype C (30.9%) (95% CI, 27.5–34.5%; I2 = 97.57%; p < 0.001) was the most common HBV genotype in Asia, followed by genotype B (17.8%) (95% CI, 15.5–20.4%; I2 = 97.26%; p < 0.001) and genotype D (15.4%) (95% CI, 11.8–19.8%). Vietnam had the highest prevalence of genotype B, Lebanon had the highest prevalence of genotypes C, and Jordan had the highest prevalence of genotype D. There was variation in genotypic prevalence with respect to the target genes for HBV genotyping. Reverse dot blot hybridization had the highest estimate of genotypes B and C. HBV subtype C2 (40.0%) (95% CI, 33.3–47.0) is the most prevalent HBV subtype. Conclusion: Evidence from this study reveals that HBV genotypes C and B are the most dominant HBV genotypes in Asia, and HBV subtype C2 is more endemic in Asia.

Prevalence and genotype distribution of viral hepatitis B in Cambodia between 1990 and 2020: a systematic review and meta-analysis

Background

Hepatitis B virus (HBV) infection is one of the major public health problems globally as well as in Cambodia. Continuous information on HBV infection burden is required to implement effective disease control strategies. This study aimed to determine the prevalence and genotype distribution of HBV infection in Cambodia through a systematic review with meta-analysis.

Methods

Four databases (PubMed, Web of Science, Scopus, and Google Scholar) were used to search published studies reporting either HBV prevalence or genotype distribution in Cambodia until August 21, 2020. Reviews, modeling studies, and studies conducted among Cambodian permanently living abroad were excluded. The Freeman–Tukey double arcsine transformation was implemented to achieve approximate normality. The DerSimonian and Laird method was used to compute pooled estimates based on the transformed values and their variance. Possible publication bias was assessed by the Egger test and the funnel plot.

Results

A total of 22 studies were included, covering 22,323 people. Ten studies reported HBV prevalence in the general population. The HBV infection prevalence was 4.73% (95%CI: 2.75–7.17%) in the general population and 19.87% (95%CI: 10.95–30.63%) in high-risk/co-infected groups. By sub-group analysis, the prevalence was 6.81% (95% CI: 4.43–9.66) in adults older than 15 years old, 2.37% (95% CI:0.04–7.05) in children 6–15 years old, and 2.47% (95% CI: 0.96–4.59) in children less than five years old. The prevalence of HBV infection decreased over time. Predominant HBV genotypes were genotypes C and B with 82.96% and 16.79%, respectively.

Conclusions

The decrease in HBV infection prevalence in Cambodia demonstrates the effects of national hepatitis B immunization, improved clinical hygiene, and the use of disposable devices. However, the estimated HBV prevalence among the general population indicates an intermediate endemicity level of HBV infection. Therefore, population screening and linkage to care, high vaccination coverage, health promotion, and HBV surveillance are essential to meet the WHO 2030 goal.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13690-022-00880-9.

High possibility of hepatocarcinogenesis in HBV genotype C1 infected Cambodians is indicated by 340 HBV C1 full-genomes analysis from GenBank

Approximately 75% of hepatocellular carcinomas (HCC) occur in Asia; core promoter mutations are associated with HCC in HBV genotype C, the dominant genotype in Cambodia. We analyzed these mutations in Cambodian residents and compared them with HBV full genomes registered in GenBank. We investigated the characteristics of 26 full-length HBV genomes among 35 residents positive for hepatitis B surface antigen in Siem Reap province, Cambodia. Genotype C1 was dominant (92.3%, 24/26), with one case of B2 and B4 each. Multiple mutations were confirmed in 24 Cambodian C1 isolates, especially double mutation at A1762T/G1764A in 18 isolates (75.0%), and combination mutation at C1653T and/or T1753V and A1762T/G1764A in 14 isolates (58.3%). In phylogenetic analysis, 16 of 24 isolates were located in the cluster with Laos, Thailand, and Malaysia. In 340 GenBank-registered C1 strains, 113 (33.2%) had combination mutation amongst which 16.5%, 34.2%, and 95.2% were found in ASC, chronic hepatitis, and liver cirrhosis (LC)/HCC respectively (P < 0. 001). Mutations were abundantly found in 24 Cambodian C1 isolates, and 340 C1 strains from GenBank showed mutation in genotype C1 brings high possibility of LC/HCC occurrence. Therefore, we suggest that Cambodian people infected with HBV genotype C1 have high possibility of hepatocarcinogenesis.

High rate of occult hepatitis B virus infection in hemodialysis units of KwaZulu-Natal, South Africa

Occult hepatitis B virus (HBV) infection (OBI) is defined as the presence of HBV DNA in the liver with or without detectable HBV DNA in the serum of individuals testing HBV surface antigen (HBsAg) negative using currently available assays. The prevalence of OBI among patients receiving hemodialysis (HD) treatment remains poorly characterized in South Africa despite the high prevalence of HBV. We sought to determine the prevalence of OBI in HD units in tertiary hospitals of KwaZulu-Natal and to characterize the HBV S gene mutations potentially responsible for OBI. A cross-sectional descriptive study of residual diagnostic plasma samples from 85 HBsAg-negative patients receiving HD treatment was included. The PreS/S gene was amplified with a nested HBV polymerase chain reaction for downstream next-generation sequencing, to determine the viral genotype and identify S gene mutations associated with OBI. Nine of the 85 samples had OBI, based on detectable HBV DNA. The point prevalence of OBI was 10.6% (95% control interval: 5.5%-19.1%). Phylogenetic analysis of the samples with OBI showed that all belonged to genotype A. Three (~33%) samples had mutations in the major hydrophilic region (MHR) within the S gene, three (~33%) had mutations within the S gene but outside the MHR, whilst the remaining three had no mutations observed. The prevalence of OBI in HBsAg-negative patients undergoing HD was 10.6%, suggesting that OBI is a clinically significant problem in patients with HD in this region. The screening methods for HBV infection need to be revised to include nucleic acid testing.

Genotypes and viral variants in chronic hepatitis B: A review of epidemiology and clinical relevance

The Hepatitis B Virus (HBV) has a worldwide distribution and is endemic in many populations. It is constantly evolving and 10 genotypic strains have been identified with varying prevalences in different geographic regions. Numerous stable mutations in the core gene and in the surface gene of the HBV have also been identified in untreated HBV populations. The genotypes and viral variants have been associated with certain clinical features of HBV related liver disease and Hepatocellular carcinoma. For example Genotype C is associated with later hepatitis B e antigen (HBeAg) seroconversion, and more advanced liver disease. Genotype A is associated with a greater risk of progression to chronicity in adult acquired HBV infections. Genotype D is particularly associated with the precore mutation and HBeAg negative chronic hepatitis B (CHB). The genotypes prevalent in parts of West Africa, Central and South America, E, F and H respectively, are less well studied. Viral variants especially the Basal Core Promotor mutation is associated with increased risk of fibrosis and cancer of the liver. Although not currently part of routine clinical care, evaluation of genotype and viral variants may provide useful adjunctive information in predicting risk about liver related morbidity in patients with CHB.

Hepatitis B virus S gene escape mutants

Hepatitis B virus (HBV) can be classified into nine immunological subtypes or eight genotypes. The most prevalent genotypes in Asia are genotypes B and C. HBV is transmitted parenteraly and can produce either asymptomatic or symptomatic disease. Although the consequences of acute hepatitis B can be severe, serious sequelae are associated with chronic infections. HBV seroprevalence ranges from intermediate (2%-7%) to high (≥8%) levels in Asia. Several strategies for the control and prevention of HBV infection have been found to be efficacious. They include vaccination and the administration of HBIG, interferon-a and nucleoside/nucleotide analogues. However, these procedures also apply selective pressures on HBV in infected individuals leading to the generation and accumulation of mutations in the S gene. Most of these mutations occur in the major hydrophilic region (MHR) of the S gene. These mutations create public health concerns as they can be responsible for reactivation of hepatitis B and occult hepatitis B infection. The inability to detect occult infections means that these individuals may become blood donors. This suggests that new strategies for donor evaluation and selection may need to be developed to protect the blood supply.

Molecular epidemiological study of hepatitis B virus among migrant workers from Cambodia, Laos, and Myanmar to Thailand

Although hepatitis B virus (HBV) infection is endemic in Southeast Asia, molecular epidemiological data on HBV circulating in some countries are limited. The aims of this study were to evaluate the seroprevalence of HBV and its genetic variability among migrant workers from Cambodia, Laos, and Myanmar in Thailand. Sera collected from 1,119 Cambodian, 787 Laotian, and 1,103 Myanmarese workers were tested for HBsAg. HBV DNA was amplified and the pre-S/S region was sequenced for genotyping and genetic mutation analysis. HBsAg was detected in 282 (9.4%). The prevalence of HBsAg among migrant workers from Cambodia, Laos, and Myanmar was 10.8%, 6.9%, and 9.7%, respectively. Of 224 subjects positive for HBV DNA, 86% were classified as genotype C (99% were sub-genotype C1) and 11.6% were genotype B (30.8%, 34.6%, and 30.8% were sub-genotypes B2, B3, and B4, respectively). Various point mutations in the "a" determinant region were detected in approximately 18% of these samples, of which Ile126Ser/Asn was the most frequent variant. Sequencing analysis showed that 19.1% of samples had pre-S mutations, with pre-S2 deletion as the most common mutant (7.7%) followed by pre-S2 start codon mutation (3.8%) and both pre-S2 deletion and start codon mutation (3.3%). High prevalence of HBV infection (approximately 7-11%) was found among migrant workers from Cambodia, Laos, and Myanmar, which may reflect the current seroprevalence in their respective countries. The data also demonstrated that HBV sub-genotype C1 was the predominant strain and various mutations of HBV occurring naturally were not uncommon among these populations.

Geographical and genetic diversity of the human hepatitis B virus

Hepatitis B virus (HBV) is one of the most widely distributed viruses that infect humankind. Distinct clinical and virological characteristics of the HBV-infection have been reported in different geographical parts of the world and are increasingly associated with genetic diversity of the infecting virus. HBV is classified into genotypes and subgenotypes that are associated with ethnicity and geography. The genetic diversity of HBV in its various aspects has been the subject of extensive investigations during the last few decades. Since molecular epidemiology research tools have become widely available, the number of new publications in this field has grown exponentially. This review summarises the recent publications on the geographical distribution of genetic variants of HBV, and proposes updated criteria for the identification of new genotypes and subgenotypes of the virus.

Non-A hepatitis B virus genotypes in antenatal clinics, United Kingdom

In the United Kingdom, the National Screening Programme for identification of hepatitits B virus (HBV) infection in pregnant women uses HBV e antigen (HBeAg) and antibody to HBeAg (anti-HBe) as markers of infectivity to determine use of immunoglobulin for hepatitis B. Serum samples from 114 HBV-infected women were analyzed. Viral loads correlated with HBeAg/anti-HBe status and viral genotypes. Among 95 mothers whose serum contained anti-HBe, viral loads ranged between undetectable and 8.6 x 10(6) IU/mL (median 228 IU/mL). Ten (10.5%) of these mothers had plasma viral loads >10(4) IU/mL; 6 were infected with genotype E and one each with genotypes A, B, C, and D. All viruses had precore stop codon or basal core promoter mutations. Preponderance of genotypes other than A among antenatal mothers in the United Kingdom reflects increasing globalization and trends in immigration. HBeAg serostatus is no longer sufficiently accurate for inferring potential infectivity of pregnant HBV carriers.

Presence of hepatitis B virus core promoter mutations pre-seroconversion predict persistent viral replication after HBeAg loss

BACKGROUND

In patients with chronic hepatitis B virus (HBV) infection DNA levels do not always fall after anti-hepatitis B e (anti-HBe) seroconversion.

OBJECTIVES

To follow longitudinally through HB e antigen (HBeAg) loss HBV DNA levels and core promoter/precore sequences in a cohort of 21 chronic HBV carriers.

STUDY DESIGN

Treatment-naïve HBeAg seropositive HBV carriers were monitored through HBeAg loss for between 2 and 22 years (mean 9.3). Core promoter/precore sequences, genotypes, HBV DNA levels and HBe status were determined.

RESULTS

Patients were grouped into those in whom serum/plasma HBV DNA remained high after HBeAg loss (group 1, n=11; HBV DNA>5log(10)IU/ml) and those in whom HBV DNA declined (group 2, n=10). Re-appearance of HBeAg was seen in seven group 1 patients. Pre-seroconversion mutations in the core promoter region including A1762T and/or G1764A were detected more frequently in group 1 (P=0.031). Overall sequence changes at sites other than 1762/1764 were more common post-seroconversion in group 1 than group 2 patients (P=0.037).

CONCLUSIONS

The presence of core promoter mutations prior to HBeAg loss identified those patients in whom HBV DNA persisted at high levels and was associated with temporary re-emergence of serum HBeAg. These patients may benefit from early anti-viral treatment.

Analysis of hepatitis B surface antigen mutations in Mongolia: molecular epidemiology and implications for mass vaccination

Although the potential significance of hepatitis B surface antigen (HBsAg) mutants for failure of immunization has been studied in some endemic countries, whether the "a" determinant variants are responsible for vaccine failure in Mongolia remains unknown. Fifty-nine HBsAg-positive children (age: 8.8 +/- 0.9 years) who had been observed during the nationwide survey of vaccinated cohorts conducted in 2004 were subjected to molecular analyses of hepatitis B virus (HBV). Partial S gene sequences encoding amino acids (aa) 40-171 of HBsAg were determined in 57 children (96.6%) who had detectable HBV DNA. Phylogenetic analysis of the S gene sequences revealed that genotype D accounted for 93.0% and genotype A for 5.3%. Only one child (1.7%) had HBVs of genotypes A and D. HBsAg mutations were found in 17 (29.8%) children ranging from 1 to 4 aa per subject (mean +/- SD, 1.6 +/- 0.9 aa). Pro127Thr and Thr118Ala were the most common substitutions, which occurred in 6 (10.5%) and 3 (5.3%) subjects, respectively; none had Gly145Arg. There were no significant associations in the prevalence of HBsAg mutations with age, sex, residential area, or vaccination status against hepatitis B. Analysis of the deduced amino acid sequence of the entire preS1/preS2/S gene revealed that eight genotype D isolates and one genotype A isolate were quite similar to previously-reported wild-type isolates, suggesting that they are essentially wild-type, but not vaccine-induced mutants. In conclusion, the results demonstrate that hepatitis B surface gene mutants do not play a significant role in vaccination failure in Mongolia.