Molecular epidemiology of hepatitis B virus in Spain: identification of viral genotypes and prediction of antigenic subtypes by limited sequencing

The unexpected high prevalence of HBV subgenotype D4 in patients with chronic hepatitis B in Galicia, a northwestern Spanish region, reflects strong links with Latin America

BACKGROUND

Hepatitis B virus (HBV) comprises 9 genotypes and multiple subgenotypes that depict differences in geographic distribution, clinical outcome and response to antiviral therapy. However, the molecular epidemiology of HBV geno/subgenotypes is globally scarce. In Spain, HBV genotype D seems to be more prevalent in the northwestern regions compared to the rest of the country for unclear reasons.

METHODS

HBV genotyping was performed using geno2pheno on a S gene fragment amplified from plasma collected from all chronic hepatitis B individuals attended at one reference hospital in Santiago de Compostela, the Galicia's capital town. Phylogenetic and phylogeographic analyses using a fragment of 345 bp were performed in all viremic specimens. To avoid misleading allocation as consequence of short fragment analysis, several bioinformatic controls were used.

RESULTS

A total of 320 individuals with persistent serum HBsAg+ and detectable HBV-DNA were seen between 2000 and 2016 (male 68.4%; median age, 52 years-old; native Spaniards 83.8%). HBV genotype distribution was as follows: A 15.3%; B 1.6%; C 2.5%; D 71.6%; E 3.1%; F 2.2%; G 3.1%; and H 0.6%. HBV genotype D was mostly represented by D4 and D2 subgenotypes (33.4% and 15% of total, respectively). Compared to chronic hepatitis B patients with genotypes B, C, E and G, HBV-D4 carriers tended to be older (54.2% had >50 years-old) and HBeAg-negative (85%). Moreover, 43% were female, 4.7% had cirrhosis, 10.2% hepatitis C and 6.4% HIV coinfection. Phylogenetic analyses could be performed on 82 HBV-D4 specimens; and 79 were confirmed as HBV-D4 using PhyML. Phylogeography using FasTree suggested at least two distinct introductions of HBV-D4 in Galicia, one from the Caribbean and South America, and another from India.

CONCLUSIONS

HBV subgenotype D4 is the most prevalent HBV variant in chronic hepatitis B patients living in the northwest of Spain, representing 33.4% (107/320) of all chronic hepatitis B infections. This rate of HBV-D4 is among the highest reported worldwide. Epidemiological and phylogenetic analyses suggest a strong association with historical migrant exchanges with Latin America, and especially with the Caribbean basin.

Genotype characteristic and phylogenetic analysis of hepatitis B virus in northeast-Iran

Viral hepatitis is considered as a worldwide health problem and hepatitis B virus (HBV) infection is one of the major health concerns which are annually responsible for more than one million deaths. HBV can be classified into at least eight genotypes, A-H and four major subtypes. Predominant HBV genotype in Mediterranean and Middle East countries is genotype D, but there is a few studies have been performed on the HBV genotype in Iran. The genotype characteristic and phylogenetic analyses were determined in chronic HBV patients in the northeast of Iran. First, seventy-eight patients with chronic HBV infection were enrolled. Demographic features were reviewed and sera samples were collected. HBV genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method, and results were confirmed by sequencing. Finally, a phylogenetic tree was obtained using Geneious software. Sixty-two (79.48%) of patients were males (mean age: 36.82 years). Twelve out of 78 patients (15.4%) were hepatitis B envelope antigen (HBeAg)-reactive. There were no significant differences between the clinical and HBeAg-positive serological data and HBeAb positive individuals. RFLP DNA sequencing and phylogenetic analysis showed that genotype D was the only genotype which observed in Mashhad, northeast of Iran. This is the first report of HBV genotyping in Mashhad. The results revealed that genotype D was the only genotype detected in this area which was consistence with previous studies in the Middle East, Mediterranean countries, southwest and center of Iran.

Genetic Diversity of the Hepatitis B Virus Strains in Cuba: Absence of West-African Genotypes despite the Transatlantic Slave Trade

Cuba is an HBsAg low-prevalence country with a high coverage of anti-hepatitis B vaccine. Its population is essentially the result of the population mix of Spanish descendants and former African slaves. Information about genetic characteristics of hepatitis B virus (HBV) strains circulating in the country is scarce. The HBV genotypes/subgenotypes, serotypes, mixed infections, and S gene mutations of 172 Cuban HBsAg and HBV-DNA positive patients were determined by direct sequencing and phylogenetic analysis. Phylogenetic analysis of HBV S gene sequences showed a predominance of genotype A (92.4%), subgenotype A2 (84.9%) and A1 (7.6%). Genotype D (7.0%) and subgenotype C1 (0.6%) were also detected but typical (sub)genotypes of contemporary West-Africa (E, A3) were conspicuously absent. All genotype A, D, and C strains exhibited sequence characteristics of the adw2, ayw2, and adrq serotypes, respectively. Thirty-three (19.1%) patients showed single, double, or multiple point mutations inside the Major Hydrophilic domain associated with vaccine escape; eighteen (10.5%) patients had mutations in the T-cell epitope (amino acids 28-51), and there were another 111 point mutations downstream of the S gene. One patient had an HBV A1/A2 mixed infection. This first genetic study of Cuban HBV viruses revealed only strains that were interspersed with strains from particularly Europe, America, and Asia. The absence of genotype E supports previous hypotheses about an only recent introduction of this genotype into the general population in Africa. The presence of well-known vaccine escape (3.5%) and viral resistance mutants (2.9%) warrants strain surveillance to guide vaccination and treatment strategies.

HBV genotypic variability in Cuba

The genetic diversity of HBV in human population is often a reflection of its genetic admixture. The aim of this study was to explore the genotypic diversity of HBV in Cuba. The S genomic region of Cuban HBV isolates was sequenced and for selected isolates the complete genome or precore-core sequence was analyzed. The most frequent genotype was A (167/250, 67%), mainly A2 (149, 60%) but also A1 and one A4. A total of 77 isolates were classified as genotype D (31%), with co-circulation of several subgenotypes (56 D4, 2 D1, 5 D2, 7 D3/6 and 7 D7). Three isolates belonged to genotype E, two to H and one to B3. Complete genome sequence analysis of selected isolates confirmed the phylogenetic analysis performed with the S region. Mutations or polymorphisms in precore region were more common among genotype D compared to genotype A isolates. The HBV genotypic distribution in this Caribbean island correlates with the Y lineage genetic background of the population, where a European and African origin prevails. HBV genotypes E, B3 and H isolates might represent more recent introductions.

Imported transmissible diseases in minors coming to Spain from low-income areas

We prospectively studied the prevalence of imported transmissible diseases in 373 immigrant children and adolescents coming from Sub-Saharan Africa, North Africa and Latin America to Salamanca, Spain. The most frequent transmissible diseases in this group were latent tuberculosis (12.7%), chronic hepatitis B virus infection (4.2%), hepatitis C virus infection (2.3%), syphilis (1.5%) and human T-lymphotropic virus type 1 or 2 infections (1.4%). A total of 24.2% of patients had serologic profiles suggesting past hepatitis B virus infection. Anti-human immunodeficiency virus antibodies were not detected in any subject. Largely asymptomatic immigrant children show a high prevalence of communicable diseases. Thus, infectious disease screenings are highly advisable in immigrant children coming from low-income countries.

Molecular characterization of hepatitis B virus (HBV) strains circulating in the northern coast of the Persian Gulf and its comparison with worldwide distribution of HBV subgenotype D1

Iran is a large country that covers the northern coast of the Persian Gulf. Iranian residents of this coastal region interact closely with people from neighboring countries because of historical and cultural relationships, as well as economic activities. In addition, the inhabitants of this border region have experienced several wars, which have affected public health infrastructures. This study characterized for the first time, the evolution of the full-length genome of HBV strains in asymptomatic carrier patients living in this particular region. In addition, this study was compared and complemented by a comprehensive evolutionary analysis of the worldwide geographical distribution of HBV subgenotype D1. Evolutionary analysis demonstrates that patients living in the northern coast of the Persian Gulf are mainly infected with HBV subgenotype D1, subtype ayw2. Specific mutations related to advanced liver disease were found more frequently in these strains compared to other strains isolated from asymptomatic carriers from other regions of Iran. This global comprehensive analysis showed that HBV subgenotype D1 strains have a worldwide distribution and that human mobility and immigration had a large impact on dispersal of HBV subgenotype D1, subtype ayw2 in Middle Eastern countries such as Iran, Syria, and Turkey. In addition to association of subtype ayw2 with subgenotype D1, it was demonstrated that other HBV subtypes like adw2, ayw1, and ayw3 are associated with HBV subgenotype D1 in different regions of the world. This study also revealed a remarkable distribution of subgenotype D1, subtype ayw4 although this particular subtype is associated with subgenotype D4 of HBV in European countries.

Lamivudine resistance mutations in patients infected with hepatitis B virus genotype D

AIM: To determine the distribution of viral genotypes for primary or acquired lamivudine resistance.

METHODS: A total of 283 patients with chronic hepatitis B virus (HBV) infection (245 patients with chronic hepatitis B and 38 inactive hepatitis B surface antigen carriers) were included in the study. The HBV genotype was determined by using quantitative real-time polymerase chain reaction and sequence analysis, and tyrosine-methionine-aspartate-aspartate (YMDD) motif mutations were determined using the reverse transcriptase hybridization method.

RESULTS: Lamivudine resistance was determined in a total of 25 (10.7%) chronic hepatitis B patients. Eight subjects (4%) had primary resistance to lamivudine, and 17 (53.1%) had secondary resistance to lamivudine. Genotype D, which was isolated from 267 of the patients with chronic HBV infection, was the dominant genotype in Turkey.

CONCLUSION: Identification of YMDD motif mutations should have a positive impact on the selection of proper antiviral medication for patients, even for those who are nucleoside naïve.

Reconstruction of the epidemic history of hepatitis B virus genotype D in Albania

Despite a recent decrease in the prevalence of HBsAg in the general population, Albania is still highly endemic for HBV infection. Genotype D is the most prevalent HBV strain in the Mediterranean area. We studied the prevalence and distribution of HBV genotypes and subgenotypes in a total of 73 HBsAg-positive patients living in Albania, and reconstructed the epidemiological history of the most prevalent HBV D subgenotype using a "phylodynamic" framework. A time-scaled genealogy of the Albanian patients' and reference P gene sequences with known sampling dates was reconstructed using an MCMC Bayesian approach that allows population growth to be estimated on the basis of coalescent theory. All of the Albanian subjects were infected with the HBV D genotype, and a percentage varying from 44.4% to 100% (depending on the ethnic or risk group) were infected with subgenotype D2, the most prevalent in the study population (72.4%). The other subgenotypes present in a minority of subjects were D1 (13.8%) and D3 (13.8%). The Bayesian skyline plot population dynamics analysis showed that genotype D2 entered the Albanian population in the late 1960s, and that the effective number of infections grew gradually until the second half of the 1980s and more rapidly until the mid-1990s, when it reached a plateau that still persists today. Our data suggest that political and socio-economic factors played an important role in determining the rapid spread of HBV infection in Albania.

High levels of serum hepatitis B virus DNA in patients with 'anti-HBc alone': role of HBsAg mutants

It remains unclear how the detection of hepatitis B core antibody (anti-HBc) in the absence of hepatitis B surface antigen (HBsAg) and antibody (anti-HBs) should be interpreted and whether all patients with this pattern need to be tested for hepatitis B virus (HBV)-DNA. This study aimed at reassessing the significance of 'anti-HBc alone' in unselected sera referred to the clinical laboratory and determining whether significant HBV viraemia can be found in this setting. Of the 6431 patients tested for HBsAg, total anti-HBc and anti-HBs in a Paris hospital over a 1-year period, 362 (5.6%) had 'anti-HBc alone' (24.8% of anti-HBc-positive patients). Only 11 of the 362 sera (3.0%) were found to be false positive. One patient was in the resolving phase of acute hepatitis B. HBV-DNA was detected in 10 of 362 (2.8%) patients, using a commercial standardized assay (threshold: 350 IU/mL). Viral loads exceeded 10(4) copies/mL in 6 of 10 patients. Mutations in the HBsAg immunodominant region were identified in seven of the viraemic patients. HBsAg was detected in only two cases when retested by one of the latest, multivalent assays. Neither human immunodeficiency virus nor hepatitis C virus serostatus distinguished between patients with and without HBV-DNA. In conclusion, 'anti-HBc alone' should be considered a risk marker for a so-called 'false occult' HBV infection with significant viraemia. Indeed, results in this hospital population indicate that a small proportion of patients with 'anti-HBc alone' have high viral loads, revealing the occurrence of infection with HBV mutants that escape detection even by multivalent HBsAg assays.

Prevalence of Genotype D and Precore/Core Promoter Mutations in Hepatitis B Virus-infected Population of North India

Hepatitis B virus (HBV) isolates (21) from Punjab (North India) were studied for genotype distribution and precore/core promoter mutations. Assays of alanine aminotransaminase (ALT) and HBeAg were performed in all isolates. Genotypes were determined in all the samples by restriction fragment length polymorphism and the precore/core promoter mutations were studied by amplification and by direct sequencing of precore/core promoter region. Sixty-two percent of the isolates had higher ALT levels and 57% of the isolates were HBeAg negative. It was observed that 90% of the isolates were HBV D genotype (subgenotype D1 and D2) and 10% of the isolates were HBV A genotype (subgenotype A1). Amplification and sequencing of the precore/core promoter region showed 1762(A-T) and 1764(G-A) mutations in 29% and 19% of the isolates, respectively. 1809(C/T) mutation was observed in 71% of the isolates under study. Novel precore and core promoter mutations like 1690(A), 1695(A/T/G), 1700(A/C), 1703(c), 1850(A) and 1915(A/G) were observed in HBV-infected population of the state of Punjab (North India). Deletion and insertional mutations were also observed in some patients. (J CLIN EXP HEPATOL 2011;1:73-76).

Clinical, epidemiological characteristics and indications for liver biopsy and treatment in immigrants with chronic hepatitis B at a referral hospital in Madrid

The increase in immigration from less developed countries to Europe has led to an increase in the incidence of hepatitis B infection. The objective of this study was to describe the clinical, epidemiological characteristics and indications for treatment of chronic hepatitis B in a cohort of immigrants, given the relative lack of current evidence. We performed a noninterventional retrospective chart review; different characteristics depending on geographical origin were compared. A case-control study was also performed to describe factors potentially associated with chronic or past hepatitis B virus (HBV) infection. We selected a random sample of 436 patients out of the 2989 immigrants attending during the study period (1989-2008). Hepatitis B serology was performed in 74% (322/436): 10.6% had chronic HBV infection (95% CI: 7.4-13.7%), and 46.9% had evidence of past infection (95% CI: 41.7-52.0%). The average age was 31 years, 60% were men, and 70% were sub-Saharan Africans. Chronic infection was related to being men (OR 2.03; 95%CI: 1.29-3.18), younger (OR 0.98; 0.96-0.99) and sub-Saharan African (OR 5.41; 2.71-10.83). Past or current infection was related to male sex (OR 2.80; 1.81-4.30), longer time elapsed until first seen at the unit (OR 0.998; 0.997-1.000), HIV infection (OR 4.99; 1.15-21.60) and being sub-Saharan African (OR 15.46; 8.97-27.18). These associations were not confirmed after adjustment for geographical origin. In 27% and 29.5% of patients, liver biopsy and treatment, respectively, would have been indicated. Prevalence of chronic HBV infection amongst immigrants is high, especially in sub-Saharan Africans. Almost a third could be considered for liver biopsy or antiviral therapy.

Detection of hepatitis B virus genotype A3 and primary drug resistance mutations in African immigrants with chronic hepatitis B in Spain

BACKGROUND

Universal vaccination and antiviral therapy have reduced chronic hepatitis B virus (HBV) in natives in the Western world. However, immigration from high HBV endemic areas continues to maintain a relatively stable prevalence of chronic hepatitis B in most developed countries.

METHODS

All foreigners attending a referral infectious diseases department in Madrid, Spain, from January 2007 to December 2008, were evaluated for serum HBV surface antigen (HBsAg). Positive cases underwent further virological characterization.

RESULTS

A total of 1718 foreigners were examined, of whom 1322 (77%) were sub-Saharan Africans. Serum HBsAg was positive in 121 (7%), HIV in 135 (7.9%) and hepatitis C virus antibodies in 212 (12.3%). HBV subgenotype A3, which so far had only been reported in people originating from Cameroon, was found in nearly half (14/29) of the tested specimens with detectable serum HBV-DNA. Interestingly, the lamivudine resistance mutation rtM204V was found in two Africans (6.9%), one infected with HBV-A3 and the other with HBV-E. Lack of prior exposure to antiviral therapy in these two patients was confirmed retrospectively.

CONCLUSIONS

Circulation of uncommon HBV variants, including strains with primary drug resistance, may follow large immigrant flows from HBV endemic regions to Western countries. Close surveillance of this population is warranted, as early diagnosis and early antiviral therapy may reduce transmission and prevent clinical complications.

Molecular characterization of the Hepatitis B virus genotypes in Colombia: a Bayesian inference on the genotype F

Hepatitis B is a worldwide health problem affecting about 2 billion people and more than 350 million are chronic carriers of the virus. Nine HBV genotypes (A to I) have been described. The geographical distribution of HBV genotypes is not completely understood due to the limited number of samples from some parts of the world. One such example is Colombia, in which few studies have described the HBV genotypes. In this study, we characterized HBV genotypes in 143 HBsAg-positive volunteer blood donors from Colombia. A fragment of 1306 bp partially comprising HBsAg and the DNA polymerase coding regions (S/POL) was amplified and sequenced. Bayesian phylogenetic analyses were conducted using the Markov Chain Monte Carlo (MCMC) approach to obtain the maximum clade credibility (MCC) tree using BEAST v.1.5.3. Of all samples, 68 were positive and 52 were successfully sequenced. Genotype F was the most prevalent in this population (77%) - subgenotypes F3 (75%) and F1b (2%). Genotype G (7.7%) and subgenotype A2 (15.3%) were also found. Genotype G sequence analysis suggests distinct introductions of this genotype in the country. Furthermore, we estimated the time of the most recent common ancestor (TMRCA) for each HBV/F subgenotype and also for Colombian F3 sequences using two different datasets: (i) 77 sequences comprising 1306 bp of S/POL region and (ii) 283 sequences comprising 681 bp of S/POL region. We also used two other previously estimated evolutionary rates: (i) 2.60 × 10(-4)s/s/y and (ii) 1.5 × 10(-5)s/s/y. Here we report the HBV genotypes circulating in Colombia and estimated the TMRCA for the four different subgenotypes of genotype F.

A novel nucleotide insertion in S gene of hepatitis B virus in a chronic carrier

Hepatitis B virus DNA was extracted from serum of a chronic carrier and polymerase chain reaction was performed on S gene. Direct sequencing showed a variant HBsAg with additional 4-amino acid insertion, and clone sequencing confirmed the mixture of variant HBsAg and wildtype HBsAg. Of 16 clones with 12-nucleotide insertion, 15 clones had identical AGAACAACACAA insertion between nucleotide 494 and nucleotide 495, and one clone had GGAACAACTCAA insertion in the same position plus 3-nucleotide deletion from nucleotide 491 to nucleotide 493. S114T, C121Y, T126S/A, Q129K, G130R, T131N, M133T, G145R, N146D substitution and premature stop codon were also found in those clones. However, the origin of HBV with 4-amino acid insertion in HBsAg was unclear.

Epidemiological and Clinical Features of Hepatitis B Virus Genotypes among Immigrants in Southern Italy

Background/aims. This study aims to determine the distribution and clinical features of HBV-genotypes in a population of immigrants affected by HBV-infection. Methods. Between 01/2003 and 03/2009, 1623 immigrants were tested for HBV-infection. Biochemical and virological activities were determined in HBsAg-positive patients; HBV-genotypes were determined, by the INNO-LiPA HBV Genotyping, in the subjects with HBV DNA detectable. In every patient we evaluated the stage and classified the infection as inactive carrier, mild or moderate/severe chronic hepatitis, cirrhosis, and/or HCC. Results. Among the tested subjects, 191 (11.7%) resulted HBsAg-positive, and in 144/191 (75.4%) serum HBV-DNA was detectable. The genotype distribution was as follows: 45,13% genotype E, 18,1% genotype D, 15,3% genotype B, 13,2% genotype C, 4,9% genotype A, 3,5% mixed genotypes (A-D). The evaluation of liver disease degree showed that 24.6% patients were inactive carriers of HBV infection, 19.4% presented a immunotolerance phase, 34.5% had mild chronic hepatitis, 13.6% had a moderate/severe chronic hepatitis, 6.3% had cirrhosis, and 1.6% presented HCC. Conclusions. Our study evidences a high prevalence of HBV-infection in immigrants, and the potentiality of migratory flow in the introduction of genotype non-D hepatitis B virus. The Hepatitis B virus genotypes presented significant differences in epidemiological and clinical characteristics.

Molecular evolutionary analysis and mutational pattern of full-length genomes of hepatitis B virus isolated from Belgian patients with different clinical manifestations

Molecular evolutionary patterns of 62 HBV full-length genomes obtained from Belgian patients were characterized. Phylogenetic analysis revealed diverse HBV subgenotypes including A2 and A6 (46.8%), D1-D4 (38.8%), E (9.7%), C1 (1.6%), and B2 (1.6%). The study population consisted of patients with different ethnic origin (Caucasian, Turkish, Asian, Arab, and African). One HBV D/C recombinant isolate was identified, which encoded subtype adw2. An HBV subgenotype D4 with an aberrant subtype ayw4 was detected. Although none of the genotypes was associated with a specific disease outcome, several nucleotide substitutions, deletions and insertions were observed within the HBV preS1/S and X genes, particularly among patients with active chronic hepatitis B infection and patients with cirrhosis. Within the immunological domain of the HBsAg gene, the most frequent substitutions were sT125M and sT118A. High rates of precore and basal core promoter mutations were detected in patients infected with genotype D of HBV. Almost half of the patients who received lamivudine therapy for at least 1 year had HBV variants associated with lamivudine drug resistance. In conclusion, the most common HBV genotypes in West Europe (A and D) also prevail in Belgium. The highest degree of genetic diversity was detected in HBV genotype D. In addition, this study reveals the circulation of exotic HBV genotypes B, C, and E in Belgium. J. Med. Virol. 82:379-389, 2010. (c) 2010 Wiley-Liss, Inc.

Ongoing transmission of a single hepatitis B virus strain among men having sex with men in Amsterdam

For the past decade, a specific hepatitis B virus (HBV) genotype A strain has been prevalent among men having sex with men (MSM) in Amsterdam, the Netherlands. At what point in time this strain was introduced in the MSM population, and why only this specific strain continues to be transmitted, remains unclear. Between 1984 and 2003, sera of 1862 MSM were retrospectively screened for anti-HBc in the context of the Amsterdam Cohort studies. After 2003, most MSM participating in this study were vaccinated, making further testing less useful. HBV DNA from anti-HBc seroconverters was amplified and sequenced. Poisson regression was used to test for temporal trends in HBV and HIV incidence. Of the 1042 MSM who were negative for anti-HBc at entry, 64 had seroconverted during follow-up at a median age of 32. At the point of seroconversion, 31 MSM were HIV positive. HBV incidence declined dramatically in the first years and then remained stable throughout the study period. The HBV and HIV incidence ran almost in parallel. With the exception of three MSM, all were infected with genotype A. Fifteen of these (41%) were infected with an identical genotype A strain. For the past two decades, an identical genotype A strain has been circulating among MSM in the Netherlands. Although HBV is generally considered more infectious than HIV, this study shows that the trend and magnitude in HBV and HIV incidence among MSM are similar.

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.

Efficacy of hepatitis B virus (HBV) DNA screening and characterization of acute and occult HBV infections among blood donors from Madrid, Spain

BACKGROUND

Screening of blood units for hepatitis B virus (HBV) DNA identifies donations collected during the window period (WP) of the acute infection and may improve viral safety of the blood supply. It also leads to the detection of occult hepatitis B infection (OBI).

STUDY DESIGN AND METHODS

From January 2005 to December 2006, a total of 383,267 blood units were screened for hepatitis B surface antigen (HBsAg) and HBV DNA in two transfusion centers in Madrid, using either individual-donation nucleic acid testing (ID-NAT) or minipool (MP-NAT) of eight donations (MP8). Samples positive for HBV DNA and negative for HBsAg were confirmed by a second molecular test, the viral DNA was quantified, and a genome fragment including the region encoding the major hydrophilic region (MHR) of HBsAg was sequenced.

RESULTS

The overall yield of HBV DNA-positive, HBsAg-negative units was 1 in 21,282 (18 cases), higher when using ID-NAT than MP8-NAT (1:9862 vs. 1:51,011; p < 0.01). Four donations (1/95,817) were collected during the infectious pre-HBsAg WP, one during an early recovery stage, and the remaining 13 (1/29,482) were OBIs, six of whom had no detectable antibody to HBsAg. Low-level Genotype D HBV DNA was detected in all OBI cases; the frequencies of this genotype and MHR amino acid substitutions were significantly higher than reported from unselected Spanish HBsAg carriers. Donors with OBI had normal aminotransferase levels and were significantly older than donors carrying HBsAg.

CONCLUSIONS

Blood donors in the WP and with OBI are not uncommon in Madrid and are detected at a higher frequency with ID-NAT than MP-NAT.

[Seroprevalence study of hepatitis B among orienteers]

BACKGROUND AND OBJECTIVE

Our objectives were to detect asymptomatic cases involved in an outbreak of hepatitis B, to assess the seroprevalence of hepatitis B (HB) in orienteers and to establish recommendations.

PATIENTS AND METHOD

One hundred sixteen orienteers who had competed in the categories involved in the previous outbreak as well as a stratified random sample of 166 of the remaining orienteers in other competition categories were included in a cross-sectional serological prevalence study. HB surface antigen (anti-HBs); total antibody to HB core antigen (total anti-HBc); HB surface antigen (Ag HBs); and antibody IgM to HB core antigen (anti-HBcIgM) along with the history of vaccination for hepatitis B were analyzed. The results were weighted.

RESULTS

The seroprevalence of HB (total anti-HBc positive) was 6.7% (n=12, 95% CI 0.6-12.9). No case of acute HB or chronic infection was observed. All the serological markers were negative for 61.1% (n=64, 95% CI 46.3-75.6), and 31.5% (n=29, 95% CI 18.2-46.4) had markers of immunity due to vaccination. Among individuals under 25 years of age, 28.4% were unvaccinated, although they were covered by vaccination programs.

CONCLUSION

Our results suggest that the seroprevalence of HB among orienteers is not different from the general population in Spain. However, it is necessary to reinforce the vaccination among adolescents and young adults. General recommendations for the prevention of HB were made to orienteering federations.

[Hepatitis B virus genetic diversity and mutant]

Hepatitis B virus (HBV) is a partially double stranded DNA virus with genetic diversity represented by eight genotypes (A to H). Natural course and response to treatment could be affected by HBV genotypes. HBV shows high rates of turn over in the absence of proof-reading ability. As a result, large amounts of quasispecies are produced naturally or antiviral-associated. HBV consists of four open reading frames, namely preS/S gene, precore/core gene, polymerase gene, and X gene. Mutations on preS gene can result in undetectable HBsAg even in case that HBV is replicating. Surface gene mutation leads to decreased binding affinity to anti-HBs, which is associated with a vaccine escape mutant. Precore mutation abolishes HBeAg whereas mutations on basal core promoter gene down-regulate the HBeAg production. Mutations on basal core promoter are associated with increased HBV replication and high incidence of progressive liver diseases such as liver cirrhosis and hepatocellular carcinoma. Mutations on polymerase genes are often induced by antiviral therapy. Emergence of antiviral-resistant mutation is the major cause of treatment failure. Furthermore, existence of prior antiviral-resistant mutations limits the options of subsequent antiviral agents. Therefore, judicious use of antivirals and selection of the most potent drug with the lowest resistance rate are of the utmost importance for the prevention of antiviral-associated mutants. Detailed knowledge and understanding of HBV genetic diversity and mutant would be critical to establish strategies for the diagnosis and management of HBV infection.

DNA-guided hepatitis B treatment, viral load is essential, but not sufficient

Hepatitis B virus (HBV) infection is a global public health problem that concerns 350 million people worldwide. Individuals with chronic hepatitis B (CHB) are at increased risk of developing liver cirrhosis, hepatic de-compensation and hepatocellular carcinoma. To maintain undetectable viral load reduces chronic infection complications. There is no treatment that eradicates HBV infection. Current drugs are expensive, are associated with adverse events, and are of limited efficacy. Current guidelines try to standardize the clinical practice. Nevertheless, controversy remains about management of asymptomatic patients with CHB who are hepatitis B e antigen (HBeAg)-positive with normal alanine aminotransferase, and what is the cut-off value of viral load to distinguish HBeAg-negative CHB patients and inactive carriers. We discuss in detail why DNA level alone is not sufficient to begin treatment of CHB.

Genotype D amongst injection drug users with acute hepatitis B virus infection in British Columbia

The eight genotypes of hepatitis B virus (HBV) exhibit distinct geographical distributions. This study identified HBV genotypes and transmission modes associated with acute infection in British Columbia (BC), Canada, from 2001 to 2005. Seventy cases of acute HBV in BC were identified from laboratory reports using a standardized case definition. Interviews for risk factors and hepatitis history were conducted for each case. HBV genotypes were determined by BLAST comparison analysis of the surface (S) or preS gene sequence. To illustrate the distribution of genotypes identified amongst acute cases in BC, an annotated map was produced showing the global occurrence of HBV genotypes. The majority of acute HBV cases occurred in Caucasian, Canadian-born males, with 30% of cases reporting injection drug use (IDU) and 21% reporting incarceration. The most common genotype observed was genotype D (62.9%), followed by genotypes A (18.6%), C (11.4%), B (4.3%), and E (1.4%). A significant association was observed between Genotype D and IDU (P = 0.0025) and previous incarceration (P = 0.0067). Phylogenetic analysis of the S gene sequence demonstrated identical or high genetic relatedness amongst genotype D viral strains (86% sub-genotype D3), thus verifying transmission clustering amongst BC injection drug users. The association between acute HBV genotype and reported transmission modes has not been previously described in North America. Tracking of genotypes can help identify disease transmission patterns and target at-risk populations for preventive immunization.

Analysis of hepatitis B genotype changes in chronic hepatitis B infection: Influence of antiviral therapy

BACKGROUND/AIMS

The frequency of mixed hepatitis B virus (HBV) genotypes in chronic HBV (CHB) and genotype changes during natural disease evolution and as a result of antiviral therapy were investigated.

METHODS

Serum samples from 103 CHB patients were included in a cross-sectional study. Longitudinal study of HBV genotypes was performed in 22 patients, 17 of them under antiviral therapy (lamivudine and/or adefovir). HBV genotyping was done by the INNO-LiPA HBV assay.

RESULTS

Genotypes observed in the cross-sectional study: A 32% of cases, D 42%, C 2%, F 2%, and mixed genotypes 22% (mainly A/D, followed by A/G). Genotype G was found in 7% of patients, always combined with other genotypes. In the longitudinal study, genotype changes were observed only in treated patients (9 cases). Genotype A strains were positively selected in 6 of them, mainly as mixed A/D. In 6 patients, selection coincided with a decrease in HBV-DNA levels.

CONCLUSIONS

A high frequency of mixed HBV genotypes was observed in our setting. Selection of genotype A strains during treatment is likely an indication that sensitivity to therapy differs between genotypes A and D. The absence of changes in untreated patients suggests that HBV genotype is stable without external factors.

Improved detection of natural hepatitis B virus surface antigen (HBsAg) mutants by a new version of the VITROS HBsAg assay

The sensitivity of immunoassays for hepatitis B virus (HBV) surface antigen (HBsAg) detection may be hampered by the presence of mutants involving the major antigenic determinant of the protein. The performance of the VITROS HBsAg Assay has been shown to be affected by mutations comprising amino acid changes at residues 143, 144, and 145 of the HBsAg molecule. Sixty-seven serum samples from HBV carriers containing major populations of natural HBsAg mutants assayed previously by that assay were tested by the new VITROS HBsAg ES Assay. Samples displayed either single or multiple amino acid substitutions between positions 112 and 145 of the HBsAg, including changes in relevant residues such as 118-120, 125-127, and 143-145. Testing of undiluted samples by the current assay gave rise to false negative results in two samples displaying the single substitutions 145A and 145R, and in one additional sample displaying a dual mutation 118A + 145A. Unusually weak reactivity (<25 S/CO units) was, in addition, recorded in samples containing mutants 143L (2 samples) and 115N + 120Q + 131K + 144A (1 sample). Testing samples at the 1/40 dilution by the modified assay did not produce, in contrast, false negative results, and reactivity below 25 S/CO units was recorded only in three cases. These results confirm that the capability of immunoassays to detect the presence of natural HBsAg mutants in clinical samples may be improved significantly by introducing changes in their design, and show that such improvement has been achieved successfully with the new VITROS HBsAg ES Assay.

Multicenter study of a new fully automated HBsAg screening assay with enhanced sensitivity for the detection of HBV mutants

In a multicenter study a new, fully automated Roche Diagnostics Elecsys HBsAg II screening assay with improved sensitivity to HBsAg mutant detection was compared to well-established HBsAg tests: AxSYM HBsAg V2 (Abbott), Architect HBsAg (Abbott), Advia Centaur HBsAg (Bayer) Enzygnost HBsAg 5.0 (Dade-Behring), and Vitros Eci HBsAg (Ortho). A total of 16 seroconversion panels, samples of 60 HBsAg native mutants, and 31 HBsAg recombinant mutants, dilution series of NIBSC and PEI standards, 156 HBV positive samples comprising genotypes A to G, 686 preselected HBsAg positive samples from different stages of infection, 3,593 samples from daily routine, and 6,360 unselected blood donations were tested to evaluate the analytical and clinical sensitivity, the detection of mutants, and the specificity of the new assay. Elecsys HBsAg II showed a statistically significant better sensitivity in seroconversion panels to the compared tests. Fifty-seven out of 60 native mutants and all recombinant mutants were found positive. Among 156 HBV samples with different genotypes and 696 preselected HBsAg positive samples Elecsys HBsAg II achieved a sensitivity of 100%. The lower detection limit for NIBSC standard was calculated to be 0.025 IU/ml and for the PEI standards ad and ay it was <0.001 and <0.005 U/ml, respectively. Within 2,724 daily routine specimens and 6.360 unselected blood donations Elecsys HBsAg II showed a specificity of 99.97 and 99.88%, respectively. In conclusion the new Elecsys HBsAg II shows a high sensitivity for the detection of all stages of HBV infection and HBsAg mutants paired together with a high specificity in blood donors, daily routine samples, and potentially interfering sera.

Distribution of HBV genotypes, subgenotypes and HBsAg subtypes among chronically infected patients in Serbia

Hepatitis B virus (HBV) has been classified into eight genotypes (some of them further divided into two or more subgenotypes) and nine HBsAg subtypes, distinctly distributed geographically. The aim of this study was to gain insight into the distribution of HBV genotypes, subgenotypes and HBsAg subtypes among HBV chronically infected patients in Serbia, since there were no previously published data on this subject. Eighty-nine plasma samples that gave a positive result in a nested PCR were included for genotype identification. Genotyping was performed by direct sequencing of the part of the S/pol gene, and the HBsAg subtype was deduced from the HBsAg sequence. Two HBV genotypes, A and D, were encountered in Serbia, with genotype D (D - 82%, A - 18%) and subgenotype D3 (47.9%) being prevalent. Genotype D isolates had three assigned subtypes (ayw2, ayw3, ayw4), with ayw2 found to be the most prevalent (ayw2 - 53.4%, ayw3 - 43.8%, ayw4 - 1.4%). Genotype A isolates belonged to the A2 subgenotype and the HBsAg subtype adw2, as expected for samples from European population. The results correspond to country's geographical position, being in close proximity to the Mediterranean basin and on the main route between the Middle East and Central Europe.

Hepatitis B virus genotypes in Europe

There are eight genotypes of hepatitis B virus (HBV). Most genotypes can be further divided into subgenotypes. HBV genotypes influence the course of disease and treatment, and show geographic preferences. In Europe, A and D are the main genotypes found. Genotype A is more prevalent in northern Europe, where genotype D is mainly found in countries surrounding the Mediterranean Sea and in Eastern Europe. Subgenotype A2 is the dominant subgenotype in Europe, but the geographic prevalence of the four subgenotypes found in genotype D is not yet clear. On treatment with interferon HBV, genotype A, compared to genotype D, showsbetter virological response and in a large proportion of patients, even development of anti-HBs. However, in the first year of treatment with lamivudine, higher rates of emergence of YMDD variants are observed in genotype A. This work summarizes the current knowledge on HBV genotypes in countries with low and intermediate HBV carriership from Europe.

Epidemiology of hepatitis B virus in Africa, its genotypes and clinical associations of genotypes

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.

Hepatitis B virus genotype E surface antigen detection with different immunoassays and diagnostic impact of mutations in the preS/S gene

The major neutralizing epitope, the "a" determinant of the hepatitis B virus (HBV) genotype E surface antigen (HBsAg) is most divergent from that of genotype A, which is used for preparing monoclonal antibodies used in commercially available HBV reagents. To evaluate the performance of the latest generation of HBsAg detection assays with respect to genotype E HBsAg. Three commercial assays were evaluated using sera from 200 Nigerian patients compared to the preS/S sequence of DNA positive samples. Out of 200 samples, 61 and 103 gave concordant positive and negative results between the three HBsAg assays. Of 36 samples with discordant results, 35 were confirmed negative by neutralisation. One of the three assays showed significantly high rate of false positives (29 of 35). DNA positive samples with no detectable HBsAg or reduced HBsAg detection signals (<75% of mean signal obtained with HBsAg positive samples) revealed several mutations (V14A, F46S, N48T, L49R, I49T, D51G, A53V, P54L, Q82P, F83C, L127P, A184V, T189I, S204N, V224A), mostly outside the a-determinant. Several of these mutations are found as wild type nucleotides normally in genotype A and only exceptionally in genotype E. All three assays showed comparable sensitivities for genotype E HBsAg detection (98.4-100%) but differed considerably in specificity (84-99%). Failure to detect HBsAg antigen and differences in signal intensity were mainly associated with mutations in the preS/S gene outside the "a" determinant.

Variability of the PreS1/PreS2/S regions of hepatitis B virus in Hungary

Infection with the hepatitis B virus can occur perinatally, parenterally, or sexually, and it can cause acute or chronic liver diseases. Phylogenetic analysis of the virus has led to its classification into eight genotypes (A-H), which show a characteristic worldwide distribution. The aim of this study was to reveal the HBV genotypes present in Hungary and to investigate a nosocomial and an intrafamilial outbreak. The collected samples were tested by nested PCR, and a 650-nucleotide-long segment of the preS1/preS2/S region was sequenced. As no previous genotype data were available from Hungary, sera of 24 HBsAg-positive patients were collected from different regions of the country. They also served as control samples for the molecular epidemiologic study. Nineteen of them carried genotype D of hepatitis B virus, and five of them carried genotype A. Twenty-nine patients from a haemato-oncology unit were affected in a nosocomial outbreak. The patients had haematological and/or oncological diseases, most of them were immunosuppressed. In twenty-eight cases, based on phylogenetic analysis of the viruses, there was presumably a common source of infection, and an epidemiological investigation showed that the infections seemed to be hospital-acquired. In the intrafamilial outbreak, two asymptomatic carrier children infected their foster mother. The three sequences were totally identical.

Molecular analysis of hepatitis B virus isolates in Mexico: Predominant circulation of hepatitis B virus genotype H

AIM: To determine the genotypes in Mexican hepatitis B virus (HBV) isolates and characterize their precore and core promoter mutations.

METHODS: Forty-nine HBV isolates of Mexico obtained from sera of 15 hepatitis patients, 6 hemodialysis patients, 20 men seeking HIV testing, and 8 AIDS patients were analyzed. HBV isolates were amplified by PCR, and genotyped by line probe assay (INNO-LiPA HBV Genotyping; INNOGENETICS N V, Ghent, Belgium). HBV genotype confirmation was performed by DNA sequencing part of the sAg region. Precore and core promoter mutation characterization was performed by line probe assay (INNO-LiPA HBV PreCore; INNOGENETICS N V, Ghent, Belgium).

RESULTS: Overall, HBV genotype H was found in 37 (75.5%) out of the 49 isolates studied. HBV genotypes G, A, and D were found in 5 (10.2%), 4 (8.2%), and 3 (6.1%) isolates, respectively. HBV genotype H was predominant in isolates from hemodialysis patients (100%), hepatitis patients (80%), and men seeking HIV testing (75%), and accounted for half of infections in AIDS patients (50%). Six (12.2%) out of the 49 HBV isolates showed both wild type and mutant populations at precore codon 28. These mixed wild type and precore mutant populations were observed in one HBV genotype A isolate and in all HBV genotype G isolates. A dual variant core promoter mutation was observed in 1 (2%) of the isolates, which was genotype H.

CONCLUSION: HBV genotype H is highly predominant in HBV isolates of Mexico followed by genotypes G, A and D. A low frequency of precore and core promoter mutations is observed in HBV Mexican isolates.

Evaluation of 17 CE-marked HBsAg assays with respect to clinical sensitivity, analytical sensitivity, and hepatitis B virus mutant detection

Seventeen HBsAg assays, in use in the European market (CE-marked), were assessed for their diagnostic sensitivity using 38 commercially available seroconversion panels, and for their analytical sensitivity with the HBsAg ad and ay standards of the Paul-Ehrlich-Institut (PEI). In addition, the ability to detect HBsAg mutants was investigated by means of 21 recombinant HBsAg mutant samples and 5 natural mutants. Analysis of seroconversion data revealed that there were marked differences in the sensitivity among the CE-marked HBsAg assays. Differences in the window period between the most and the least sensitive assays were up to 2 weeks. Analytical sensitivities of the investigated assays ranged from 0.009 to 0.05 PEI-U/ml for HBsAg ad standard (relating to approximately 0.018 to 0.100 IU/ml of the 2nd WHO HBsAg standard) and 0.012 to 0.11 PEI-U/ml for the ay standard. Clinical and analytical sensitivities were basically correlated. The capacity to detect mutant HBsAg forms was influenced by the assay format and the properties of the monoclonal antibodies used for coating of the solid phase or in the conjugate. While some assays detected all mutants others exhibited weaknesses especially in recognising HBsAg mutations affecting loop 2 of the HBsAg a-determinant. The results obtained with the recombinant mutants were largely confirmed by the investigation of clinical samples. The study gives a broad overview of the current state of the art of about 70% of the HBsAg assays currently available in Europe. The overall sensitivity has not been improved further since 1995 when the most sensitive assay was introduced into the market. In addition, detection of HBsAg mutants seems problematic with several assays. It is concluded that there is potential to improve clinical sensitivity and mutant recognition of HBsAg assays.

Acute hepatitis B virus window-period blood donations detected by individual-donation nucleic acid testing: a report on the first two cases found and interdicted in Spain

BACKGROUND

Mathematical models predict that, in Spain, a significant number of blood units will be obtained during the window period of the hepatitis B virus (HBV) infection. Routine nucleic acid testing (NAT) on individual blood units may provide experimental data to evaluate such a theoretical risk.

STUDY DESIGN AND METHODS

Between February and July 2005, a total of 34,631 individual units were screened for HBV DNA by a multiplex transcription-mediated amplification (TMA) test. Units that repeatedly reacted in the test, but did not react for HBV surface antigen (HBsAg), were submitted to additional testing by both molecular and conventional assays, and the donors were recalled for follow-up studies and the collection of clinical and epidemiologic data.

RESULTS

Confirmatory testing and follow-up studies identified 2 blood units donated during the HBV infection window period (1/17,316 units studied). Sequencing of amplification products obtained by nested polymerase chain reaction (n-PCR) revealed two HBV strains from genotypes D/ayw3 and F/adw4q-, but did not identify HBsAg mutants. The HBV DNA concentration in the index donations was estimated to be below the n-PCR detection level (180 IU/mL), in both cases. One donor developed acute hepatitis 2 months after donating blood, but the other remained asymptomatic and displayed normal alanine aminotransferase levels at follow-up.

CONCLUSIONS

The HBV infection window period is a real issue in the setting of Spanish blood transfusions. NAT of individual units by TMA would make a significant contribution to improving the safety of the blood supply in Spain. Additional studies involving a larger number of units and longer periods of time are required, however, to ascertain the true incidence of the problem in this country.

[Microbiological diagnosis of viral hepatitis]

Hepatitis of viral aetiology caused by hepatotropic virus (A, E, B, D and C) represents an important work load for the clinical virology laboratory. Most of the diagnostic is based upon detection in serum and plasma samples of different serological and virological markers, which correlates with different infection stages. In chronic infection by HBV and HCV is necessary to perform diagnostic by molecular methods as well as antigen detection in sequential samples along the course of the disease taking into account that a reliable storage must be provided for stability of structural components of the virus. Recent knowledge about mutations variants in some of the virus may alter the validity of particular markers.

Frequency of hepatitis B virus 'a' determinant variants in unselected Spanish chronic carriers

The prevalence in the population of hepatitis B virus (HBV) surface antigen (HBsAg) variants that may impair diagnosis, or allow the virus to escape vaccine-induced immunity or passive immunoglobulin therapy is unknown. A genome fragment encoding HBsAg amino acids 112-212 was amplified and sequenced from the sera of 272 unselected DNA-positive, HBV-chronic carriers from Spain. The genotype and the HBsAg subtype were predicted from the sequences. Analysis of amino-acid positions 112-157 revealed single or multiple substitutions in 39% of the carriers studied. Mutations were not detected for residues 121, 135, 137, 139, 140, 141, 142, 146, 147, 148, 149, 151, 152, 153, 155, 156, and 157. Substitutions reported previously to be in association with failures of diagnostic tests or with vaccine or immunoglobulin therapy escape were found in 12.5%, 6.6%, and 9.2% of carriers, respectively. Met133Thr (2.2%); Gln129His, Met133Ile, Phe/Tyr134Asn (1.8%); Phe/Tyr134Leu, Gly145Ala (1.5%), and Pro120Thr (1.1%) were the most frequent. Other substitutions, including Gly145Arg (0.4%), were found at a frequency of less than 1%. Samples containing HBV mutants were tested with three commercial assays for HBsAg screening. Almost all the mutants reacted to the upper cut-off values of the assays, but six samples with weak reactivity with one or more of the methods were also found. Thus, HBV mutants with a potential impact on clinical and public health issues are moderately frequent among chronic carriers from Spain, although their influence on the performance of diagnostic tests seems to be slight.

Molecular epidemiology and evolution in an outbreak of fulminant hepatitis B virus

In order to establish the transmission pathway for two outbreak patients affected by fulminant hepatitis B (FHB) following a shared period of hospitalization, we sequenced the complete genomes of the hepatitis B viruses (HBV) isolated from them as well as from the suspected common source and 11 additional controls. Phylogenetic and statistical analyses of these sequences revealed that the two FHB patients were indeed infected by a common source and that the fatal development of the disease did not appear to be associated with any mutation previously reported to be related to FHB. These data have also allowed us to estimate the extent and distribution of genetic variability along the genomes of HBV genotype D samples from the same source population. As a result of these analyses, we provide an improved statistical method to individualize the assignment of each suspected patient and the source of an outbreak and information on which genome region to analyze in the molecular epidemiological assessment of hepatitis B virus transmission cases.

[Etiology and pathogenesis of viral hepatitis]

In the strictest sense, the term "viral hepatitis" includes a series of clinical conditions of infectious origin caused by five phylogenetically unrelated human viruses that have developed specific tropism to hepatocytes. In a broader sense, it also includes acute liver diseases due to infection by other viruses that do not display specific liver tropism, but may produce liver disease as a complication of the infection. Hepatitis B and C viruses have, in addition, developed strategies that allow them to establish long-lasting, chronic infections in some patients. Chronic viral hepatitis, liver cirrhosis and primary liver cancer are the main clinical outcomes of these phenomena of viral persistence, which respond to two main mechanisms: induction of immune tolerance in the host, and emergence and selection of viral mutants that are able to escape the immune response.

Hepatitis B virus genotyping, core promoter, and precore/core mutations among Afghan patients infected with hepatitis B: A preliminary report

In spite of hepatitis B virus (HBV) vaccination, HBV infection remains an important public health problem worldwide. Although the HBV genotype distribution has been determined in some parts of South Central Asia, no survey has been conducted to determine the HBV genotype in Afghanistan. Twelve Afghan patients infected with HBV living in Afghanistan were enrolled in this study. Partial HBsAg and basic core promoter, precore, and core (BCP/preC/C) regions were amplified and subjected for direct sequencing. In parallel, precore G1896A mutation was also determined by an amplification-created restriction site method. Results revealed HBV genotype D (95% bootstrap value), sub-genotype D1 (98% bootstrap value), and subtype ayw2 in all Afghan isolates. Afghan isolates clustered in a separate branch in the D1 sub-genotype called D1', while supported by 82% bootstrap value. The percentage of intra-genotypic distance among Afghan isolates was 1.05% and inter-genotypic distance with the other genotype D was 2.87% and with other genotypes was 7.50%-11.1%. The wild-type, mixed infection, and precore mutant were found in six, two, and four HBV isolates, respectively. The A1762T/G1764A BCP dual mutation was found in one isolate. Three isolates presented single mutation in the BCP dual mutation region, whereas two showed a novel G1764T mutation. In conclusion, this preliminary study revealed HBV genotype D, sub-genotype D1, and subtype ayw2 of HBV among hepatitis B infected patients from Afghanistan. Further investigation should be carried out.

Hepatitis B virus genetic diversity

Hepatitis B virus (HBV) is a human DNA virus, which replicates through an RNA intermediate because of the reverse-transcriptase (RT) activity of its DNA polymerase. As a result, the mutation rate for HBV is higher than the rate observed for most DNA viruses. HBVs are classified into genotypes based on genomic sequencing, and antigenic subtypes based on the antigenic properties of its major surface glycoprotein, the HBV surface antigen (HBsAg). Subgenotypes have been identified within most of the HBV genotypes. The HBV groups defined by the different genotype-HBsAg subtype associations found over the world display characteristic geographical distributions, reflecting the movements of human populations and other epidemiologically significant events. Such HBV groups constitute genetically stable viral populations sharing a common evolutionary history, but additional stable changes, originating from mutation and mutant selection, are observed within all of them. These viral sub-populations are known as the HBV variants, and some of which have medical and public health relevance. Pre-core (pre-C) defective variants have been shown to make HBV infection much less susceptible to interferon treatment, and treatment failures with other antiviral drugs have been associated with selection of resistant variants that display specific mutations in the genome region encoding the viral RT activity. Since the RT region of the genome overlaps the sequence encoding the HBsAg molecule, selection of drug resistant variants involves, in some cases, the indirect selection of HBsAg variants. Viral variants displaying changes in HBsAg seem to be very common among chronic HBV carriers; and some of these variants may emerge under the pressure of the neutralizing antibody response, leading to vaccine resistance and resistance to immunotherapy. Mutations conferring resistance to immunotherapy are noted often among liver transplant recipients and among babies born to HBV-carrier mothers. In addition, some of these HBsAg variants have been associated with lack of detection by HBsAg tests used for the diagnosis of HBV infection, for the identification of chronic carriers, for screening of blood donations for transfusion, and in the manufacture of therapeutic blood products.

Hepatitis B virus genotypes, core promoter variants, and precore stop codon variants in patients infected chronically in North-Eastern Italy

The hepatitis B virus (HBV) genotypes distribution and the core promoter (CP)/precore (PC) variability were evaluated by a line probe assay in 272 patients infected chronically enrolled consecutively in an area of the North-Eastern Italy. Seven out of the eight genotypes were detected. Italian subjects (83% of the sample) were infected mainly by genotype D (73%) and A (26%); genotype F, and genotype H, were detected only in one subject. In foreigners, the genotype distribution reflected the distribution described for the areas of origin, that is, in Asia genotypes B, C, and D; in Africa genotypes A and E. CP and PC variants prevalence rates were 51% and 60%, respectively, and were significantly higher in Italian patients, probably in relation to their older age. In the analysis restricted to genotypes A and D, PC wild type was linked strongly to genotype A (OR = 4.08, 95% CI = 3.07-5.43, P < 0.0001). In genotype A-infected patients, only e seroconversion was associated significantly with CP variants. In genotype D-infected subjects, CP variants were linked significantly to older age and to a higher e seroconversion rate, while PC variants also showed a strong relationship with an ALT lower activity and a lower viral load. In multivariate analysis, HBeAg positivity was associated strongly and independently with younger age, genotype A and CP wild type. Independent determinants of higher viral loads were recognized by increasing age, in male gender and concomitant presence of HBeAg and the CP wild type virus.