Hepatitis B virus genetic diversity in Latin America

[Hepatitis B in indigenous people in Latin America: a literature reviewHepatite B em indígenas na América Latina: revisão da literatura]

Objetivo.

Identificar publicaciones realizadas entre los años 2000 y 2020 sobre hepatitis B en indígenas de América Latina, con el fin de conocer avances y vacíos en el tema durante los últimos 20 años.

Métodos.

Revisión exploratoria y síntesis rápida de la evidencia. El proceso de organización documental se realizó con los programas Excel^® y Rayyan^®.

Resultados.

Se seleccionaron 30 de 107 artículos encontrados, 17 corresponden a estudios epidemiológicos, 10 a revisiones documentales, dos estudios clínicos y una carta al editor. Brasil fue el país con más publicaciones (50%), la mayoría con enfoque epidemiológico. La temática más abordada fue la medición de prevalencia de la infección por hepatitis B con 22 publicaciones, le siguieron 11 estudios que informan resultados de estudios moleculares del virus, siete estudios sobre vacunación, cinco estudios sobre factores de riesgo y cuatro publicaciones con temas como la transmisión vertical y estudios sociales.

Conclusión.

En comparación con revisiones previas realizadas por otros autores, se observa una mayor diversidad en los temas y métodos de investigación utilizados; sin embargo, aún prevalecen los enfoques epidemiológicos convencionales centrados en la medición de la prevalencia de marcadores serológicos. Esto hace necesario encarar otro tipo de investigaciones centradas en los determinantes socioculturales.

Hepatitis B virus American genotypes: Pathogenic variants ?

Hepatitis B virus (HBV) chronic infection is responsible for almost 900.000 deaths each year, due to cirrhosis or hepatocellular carcinoma (HCC). Ten HBV genotypes have been described (A-J). HBV genotype F and H circulate in America. HBV genotypes have been further classified in subgenotypes. There is a strong correlation between the genetic admixture of the American continent and the frequency of genotypes F or H: a high frequency of these genotypes is found in countries with a population with a higher ratio of Amerindian to African genetic admixture. The frequency of occult HBV infection in Amerindian communities from Latin America seems to be higher than the one found in other HBV-infected groups, but its association with American genotypes is unknown. There is growing evidence that some genotypes might be associated with a faster evolution to HCC. In particular, HBV genotype F has been implicated in a frequent and rapid progression to HCC. However, HBV genotype H has been associated to a less severe progression of disease. This study reviews the diversity and frequency of autochthonous HBV variants in the Americas and evaluates their association to severe progression of disease. Although no significant differences were found in the methylation pattern between different genotypes and subgenotypes of the American types, basal core promoter mutations might be more frequent in some subgenotypes, such as F1b and F2, than in other American subgenotypes or genotype H. F1b and probably F2 may be associated with a severe presentation of liver disease as opposed to a more benign course for subgenotype F4 and genotype H. Thus, preliminary evidence suggests that not all of the American variants are associated with a rapid progression to HCC.

Phylogenetic analysis and genotype distribution of Hepatitis B Virus (HBV) in Roraima, Brazil

Hepatitis B virus (HBV) infection is a serious global health problem. HBV has a high viral genetic diversity, with 10 genotypes recognized. In Brazil, the Roraima State is the third in the Northern region regarding the number of hepatitis B cases. On the other hand, few data on HBV genotyping and phylogenetic analysis are available. The purpose of this study is to characterize the HBV genotypes circulating in Roraima State. Of the 113 chronic hepatitis B patients enrolled in this study, 40 were HBV-DNA positive. A fragment of 280 bp (S gene) was amplified by PCR and submitted to nucleotide sequencing. A dataset containing the viral sequences obtained in this study, plus 130 obtained from GenBank was used for genotyping by phylogenetic analysis. The HBV subgenotype distribution found was A1 (62.5%), A2 (7.5%), D2, D3, D4 (2.5%), F2a (12.5%), and F3 (10%). We characterized the genotypes and subgenotypes of HBV circulating among patients in the State of Roraima. In addition, our study shows for the first time the HBV/F3 genotype circulating in Brazil. In conclusion, our findings showed a high diversity of HBV genotypes in Roraima, which is also found in other Brazilian geographical regions.

Decreasing prevalence of Hepatitis B and absence of Hepatitis C Virus infection in the Warao indigenous population of Venezuela

Prevalence and molecular epidemiology studies for hepatitis B (HBV) and C (HCV) virus are scarce in Warao Amerindians from Venezuela, where an epidemic of human immunodeficiency virus type 1 (HIV-1) has recently been documented. To carry out a molecular epidemiology analysis of hepatitis B (HBV) and C (HCV) virus in Warao individuals from the Delta Amacuro State of Venezuela. A total of 548 sera were tested for serological and molecular markers for HBV and HCV. The prevalence of active infection (presence of HBV surface antigen, HBsAg), exposure to HBV (presence of Antibody to HBV core antigen, anti-HBc) and anti-HCV, was 1.8%, 13% and 0% respectively. HBV exposure was significantly lower in men below 18 years old and also lower than rates previously reported in other Amerindian communities from Venezuela. Thirty one percent (31%, 25/80) of individuals without evidence of HBV infection exhibited anti-HBs titer ≥ 10U.I / ml, being significantly more frequent in individuals younger than 20 years. A higher HBV exposure was observed among HIV-1 positive individuals (33% vs 11%, p <0.005). A high prevalence of occult HBV infection was also observed (5.6%, 11/195). Phylogenetic analysis of S gene and complete HBV genomes showed that F3 is the only circulating subgenotype, different from the F2 subgenotype found in 1991 in this population. These results suggest a recent introduction of subgenotype F3, with a low divergence among the isolates. These results highlight the importance of molecular epidemiology studies for viral control, and support the effectiveness of vaccination in reducing transmission of HBV.

Characterization of hepatitis B virus in Amerindian children and mothers from Amazonas State, Colombia

BACKGROUND

Hepatitis B Virus (HBV) infection is a worldwide public health problem. In the 1980's a highly effective and safe vaccine against HBV was developed, although breakthrough infection still occasionally occurs because of the emergence of escape mutants. The aim of this study was to identify HBV genotypes and escape mutants in children and their mothers in Amerindian communities of the Amazonas State, Southern Colombia.

METHODS

Blood specimens collected from children and mothers belonging to 37 Amerindian communities in Amazonas state, were screened for HBsAg and anti-HBc using ELISA. The partial region containing the S ORF was amplified by nested PCR, and amplicons were sequenced. The phylogenetic analysis was performed using the MEGA 5.05 software.

RESULTS

Forty-six children (46/1275, 3.6%) and one hundred and seventy-seven mothers (177/572, 30.9%) were tested positive for the anti-HBc serological marker. Among them, 190 samples were tested for viral genome detection; 8.3% (2/31) serum samples obtained from children and 3.1% (5/159) from mothers were positive for the ORF S PCR. The predominant HBV genotype in the study population was F, subgenotype F1b; in addition, subgenotype F1a and genotype A were also characterized. Two HBV escape mutants were identified, G145R, reported worldwide, and W156*; this stop codon was identified in a child with occult HBV infection. Other mutations were found, L109R and G130E, located in critical positions of the HBsAg sequence.

CONCLUSIONS

This study aimed to characterize the HBV genotype F, subgenotypes F1b and F1a, and genotype A in Amerindian communities and for the first time escape mutants in Colombia. Further investigations are necessary to elucidate the frequency and the epidemiological impact of the escape mutants in the country.

Molecular epidemiology of hepatitis B virus in Misiones, Argentina

Hepatitis B virus (HBV) infection is a major public health problem worldwide. The aims of this study were to describe the molecular epidemiology of HBV in the Province of Misiones, Argentina and estimate the phylodynamic of the main groups in a Bayesian coalescent framework. To this end, partial or complete genome sequences were obtained from 52 blood donor candidates. The phylogenetic analysis based on partial sequences of S/P region showed a predominance of genotype D (65.4%), followed by genotype F (30.8%) and genotype A as a minority (3.8%). At subgenotype level, the circulation of subgenotypes D3 (42.3%), D2 (13.5%), F1b (11.5%) and F4 (9.6%) was mainly identified. The Bayesian coalescent analysis of 29 complete genome sequences for the main groups revealed that the subgenotypes D2 and D3 had several introductions to the region, with ancestors dating back from 1921 to 1969 and diversification events until the late '70s. The genotype F in Misiones has a more recent history; subgenotype F4 isolates were intermixed with sequences from Argentina and neighboring countries and only one significant cluster dated back in 1994 was observed. Subgenotype F1b isolates exhibited low genetic distance and formed a closely related monophyletic cluster, suggesting a very recent introduction. In conclusion, the phylogenetic and coalescent analyses showed that the European genotype D has a higher circulation, a longer history of diversification and may be responsible for the largest proportion of chronic HBV infections in the Province of Misiones. Genotype F, especially subgenotype F1b, had a more recent introduction and its diversification in the last 20years might be related to its involvement in new transmission events.

High prevalence of HBV/A1 subgenotype in native south Americans may be explained by recent economic developments in the Amazon

Native American populations present the highest prevalence of Hepatitis B Virus (HBV) infection in the Americas, which may be associated to severe disease outcomes. Ten HBV genotypes (A–J) have been described, displaying a remarkable geographic structure, which most likely reflects historic patterns of human migrations. In this study, we characterize the HBV strains circulating in a historical sample of Native South Americans to characterize the historical viral dynamics in this population. The sample consisted of 1070 individuals belonging to 38 populations collected between 1965 and 1997. Presence of HBV DNA was checked by quantitative real-time PCR, and determination of HBV genotypes and subgenotypes was performed through sequencing and phylogenetic analysis of a fragment including part of HBsAg and Pol coding regions (S/Pol). A Bayesian Skyline Plot analysis was performed to compare the viral population dynamics of HBV/A1 strains found in Native Americans and in the general Brazilian population. A total of 109 individuals were positive for HBV DNA (~ 10%), and 70 samples were successfully sequenced and genotyped. Subgenotype A1 (HBV/A1), related to African populations and the African slave trade, was the most prevalent (66–94%). The Skyline Plot analysis showed a marked population expansion of HBV/A1 in Native Americans occurring more recently (1945–1965) than in the general Brazilian population. Our results suggest that historic processes that contributed to formation of HBV/A1 circulating in Native American are related with more recent migratory waves towards the Amazon basin, which generated a different viral dynamics in this region.

Analysis of hepatitis B virus genotypes by restriction fragment length polymorphism

<p><strong>Introducción.</strong> Se han descrito diez genotipos (A-J) del virus de la hepatitis B (HBV) que están distribuidos en todos los continentes. Una de las técnicas utilizadas para determinar el genotipo viral es el análisis del polimorfismo de longitud de los fragmentos de restricción, un método simple y económico, pero con algunas limitaciones.<br /><strong>Objetivo.</strong> El objetivo inicial del estudio fue identificar el genotipo del HBV mediante RFLP en muestras de suero obtenidas de pacientes y donantes de sangre. Sin embargo, por las discrepancias observadas en los patrones de RFLP fue necesario realizar análisis filogenéticos y un análisis in silico de secuencias del HBV.<br /><strong>Materiales y métodos.</strong> Se obtuvieron 56 muestras de suero. Tras la extracción de ADN, se amplificó un fragmento del ORF S del HBV mediante reacción en cadena de la polimerasa, cuyos productos se analizaron por RFLP con las enzimas <em>AlwI</em>, <em>BsrI</em>, <em>CfrI</em>, <em>HpaII</em> y <em>StyI</em>, y algunos se secuenciaron. Los patrones obtenidos se compararon con los reportados previamente. Se efectuó un análisis<em> in silico</em> de RFLP en consideración de las diferencias entre los patrones esperados y los observados.<br /><strong>Resultados.</strong> Se identificaron los genotipos A y F, subgenotipo F3, en las muestras. Este resultado coincide con lo descrito en estudios previos en los que se ha demostrado que el genotipo F, subgenotipo F3, es prevalente en la población de la región andina del país, en tanto que el genotipo A predomina en el occidente (departamento del Chocó). Con base en el análisis <em>in silico</em> de 229 secuencias virales obtenidas del GenBank y las 11 secuencias de este estudio, se caracterizó un nuevo patrón de RFLP específico para el genotipo F, subgenotipo F3, y se describieron algunas modificaciones en el patrón de RFLP del genotipo A, subgenotipo A1.<br /><strong>Conclusiones.</strong> Se caracterizó el patrón de genotipificación del genotipo F, subgenotipo F3, del HBV mediante RFLP, análisis in silico y secuenciación. Se requieren nuevos análisis in silico con un número mayor de secuencias para validar los patrones de RFLP de los genotipos y subgenotipos del VHB.</p>

Hepatitis B virus burden in developing countries

Hepatitis B virus (HBV) infection has shown an intermediate or high endemicity level in low-income countries over the last five decades. In recent years, however, the incidence of acute hepatitis B and the prevalence of hepatitis B surface antigen chronic carriers have decreased in several countries because of the HBV universal vaccination programs started in the nineties. Some countries, however, are still unable to implement these programs, particularly in their hyperendemic rural areas. The diffusion of HBV infection is still wide in several low-income countries where the prevention, management and treatment of HBV infection are a heavy burden for the governments and healthcare authorities. Of note, the information on the HBV epidemiology is scanty in numerous eastern European and Latin-American countries. The studies on molecular epidemiology performed in some countries provide an important contribution for a more comprehensive knowledge of HBV epidemiology, and phylogenetic studies provide information on the impact of recent and older migratory flows.

Characteristics of an outpatient chronic hepatitis B virus infection cohort

Objective:

To characterize a chronic hepatitis B cohort based on initial and follow-up clinical evaluations.

Methods:

A retrospective and descriptive analysis of clinical and laboratory data from chronic HBsAg adult carriers, without HIV, unexposed to treatment, with at least two outpatient visits, between February 2006 and November 2012. Fisher´s exact test, χ², Wilcoxon, Spearman, multiple comparisons and Kappa tests were applied, the level of significance adopted was 5%, with a 95% confidence interval.

Results:

175 patients with mean age of 42.95±12.53 years were included: 93 (53.1%) were men, 152 (86.9%) were negative for hepatitis B e-antigen (HBeAg), 3 (1.7%) had hepatitis C coinfection, 15 (8.6%) had cirrhosis, and 2 (1.1%) had hepatocellular carcinoma. Genotype A predominated. Sixty-six patients (37.7%) had active hepatitis, 6 (3.4%) presented immune tolerance, and 38 (21.7%) were inactive carriers. Exacerbations and/or viral breakthrough were detected in 16 patients (9.1%). In 32 patients (18.3%), hepatitis B virus DNA remained persistently elevated and alanine aminotransferase levels were normal, whereas in 17 (9.7%), there was low hepatitis B virus DNA and alterated alanine aminotransferase. If only initial alanine aminotransferase and hepatitis B virus DNA values were considered, 15 cases of active hepatitis would not have been detected. Advanced fibrosis was more common in HBeAg-positive patients, and it was significantly associated with transaminases, hepatitis B virus DNA, and age.

Conclusion:

Many patients had active hepatitis, but almost 25%, who were HBeAg non-reactive, were only identified because of combined analyses of the hepatitis B virus DNA and transaminases levels, sometimes associated with histological data, after clinical follow-up.

Genetic variability of hepatitis B virus in Uruguay: D/F, A/F genotype recombinants

Hepatitis B virus (HBV) infection is a serious global health problem. Approximately 2 billion people worldwide have been infected, and approximately 350 million individuals currently suffer from HBV-induced chronic liver infection, which causes 600,000 deaths annually from chronic hepatitis, cirrhosis and hepatocellular carcinoma. HBV is classified in eight genotypes (A-H), and two more have been proposed (I-J). In this paper, complete genome sequences of nine Uruguayan HBV are reported. Five samples belong to genotype F1b and one to genotype A2. Three HBV recombinants were detected: A1/F1b, A2/F1b and D3/F1b. The following mutations were detected: a G1896A substitution, a 33-nucleotide deletion from position 2896 to 2928 in the Pre-S1 region involving Pre-S1 residues 3-13, a 33-nt deletion in the Pre-S1 region involving nt 2913-2945 and Pre-S1 residues 9-19. More F genotypes strains than expected were detected in this study, supporting the hypothesis that there are more people of indigenous origin than declared in our population. Also, one third of the samples analyzed were recombinants. This cannot be explained by the low HBV prevalence in Uruguay, but a high HBV infection rate in drug addicts and dialysis patients could act in favor of multiple-genotype HBV infections that could lead to recombination.

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.

Potential mechanisms of hepatitis B virus induced liver injury

Chronic active hepatitis (CAH) is acknowledged as an imperative risk factor for the development of liver injury and hepatocellular carcinoma. The histological end points of CAH are chronic inflammation, fibrosis and cirrhosis which are coupled with increased DNA synthesis in cirrhotic vs healthy normal livers. The potential mechanism involved in CAH includes a combination of processes leading to liver cell necrosis, inflammation and cytokine production and liver scaring (fibrosis). The severity of liver damage is regulated by Hepatitis B virus genotypes and viral components. The viral and cellular factors that contribute to liver injury are discussed in this article. Liver injury caused by the viral infection affects many cellular processes such as cell signaling, apoptosis, transcription, DNA repair which in turn induce radical effects on cell survival, growth, transformation and maintenance. The consequence of such perturbations is resulted in the alteration of bile secretion, gluconeogenesis, glycolysis, detoxification and metabolism of carbohydrates, proteins, fat and balance of nutrients. The identification and elucidation of the molecular pathways perturbed by the viral proteins are important in order to design effective strategy to minimize and/or restore the hepatocytes injury.

Re-appraisal of old and new diagnostic tools in the current management of chronic hepatitis B

Hepatitis B virus (HBV) is a very complex and intricate DNA structure associated with a particular genomic organization and replication cycle. However, many years of investigations allowed clarification of the real HBV natural history, through a deeper knowledge of the behavior of HBV antigens and viral structures. Several of the old diagnostic tools, such as HBV surface antigen (HBsAg) and HBV e antigen (HBeAg) determinations, gained prominence now, since the variation of both HBsAg and HBeAg plasma levels was shown to predict treatment response. In addition, the availability of more sensitive methods, such as HBV DNA detection by real-time PCR, has improved the current knowledge of the relationships between HBV replication levels and the natural history of the disease. It is now well established that some HBV genotypes are associated with a better response to treatment with pegylated interferon. Despite the widely accepted value of liver biopsy as a staging tool, transient elastography is being increasingly acknowledged as a non-invasive method to assess liver stiffness, chiefly for detection of advanced fibrosis. Current international guidelines for the management of chronic hepatitis B have provided several accurate biochemical and serological criteria for selecting patients for treatment, allowing a higher number of cases to be enrolled into antiviral therapy. This review describes the different serological markers used for the study of HBV and their clinical significance. It also deals with methods used for detection of genotypes and HBV DNA, emphasizing the effectiveness of such determinations for both patient selection and chronic hepatitis B therapy/monitoring.

Enigmatic origin of hepatitis B virus: An ancient travelling companion or a recent encounter?

Hepatitis B virus (HBV) is the leading cause of liver disease and infects an estimated 240 million people worldwide. It is characterised by a high degree of genetic heterogeneity because of the use of a reverse transcriptase during viral replication. The ten genotypes (A-J) that have been described so far further segregate into a number of subgenotypes which have distinct ethno-geographic distribution. Genotypes A and D are ubiquitous and the most prevalent genotypes in Europe (mainly represented by subgenotypes D1-3 and A2); genotypes B and C are restricted to eastern Asia and Oceania; genotype E to central and western Africa; and genotypes H and F (classified into 4 subgenotypes) to Latin America and Alaska. This review summarises the data obtained by studying the global phylodynamics and phylogeography of HBV genotypes, particularly those concerning the origin and dispersion histories of genotypes A, D, E and F and their subgenotypes. The lack of any consensus concerning the HBV substitution rate and the conflicting data obtained using different calibration approaches make the time of origin and divergence of the various genotypes and subgenotypes largely uncertain. It is hypothesised that HBV evolutionary rates are time dependent, and that the changes depend on the main transmission routes of the genotypes and the dynamics of the infected populations.

Hepatitis B virus infection in Latin America: A genomic medicine approach

Hepatitis B virus (HBV) infection is the leading cause of severe chronic liver disease. This article provides a critical view of the importance of genomic medicine for the study of HBV infection and its clinical outcomes in Latin America. Three levels of evolutionary adaptation may correlate with the clinical outcomes of HBV infection. Infections in Latin America are predominantly of genotype H in Mexico and genotype F in Central and South America; these strains have historically circulated among the indigenous population. Both genotypes appear to be linked to a benign course of disease among the native and mestizo Mexicans and native South Americans. In contrast, genotypes F, A and D are common in acute and chronic infections among mestizos with Caucasian ancestry. Hepatocellular carcinoma is rare in Mexicans, but it has been associated with genotype F1b among Argentineans. This observation illustrates the significance of ascertaining the genetic and environmental factors involved in the development of HBV-related liver disease in Latin America, which contrast with those reported in other regions of the world.

HBV infection in HIV-infected subjects in the state of Piauí, Northeast Brazil

In this study, the prevalence, genotype frequency, and risk factors for HBV infection in 768 HIV-infected subjects living in Piauí were determined. Forty-six (6.0 %) HIV-positive subjects were reactive for HBsAg and positive for HBV-DNA. Genotypes A (71.8 %), F (23.9 %) and D (4.3 %) were identified. Multivariate analysis revealed an association between HIV-HBV coinfection and male gender, older age groups, unprotected sex, reporting more than ten sexual partners throughout life, STD, and tattooing. This study shows the importance of monitoring sites and professionals who perform tattooing and practice safe sex to prevent the spread of HIV and HBV infections.

Distribution of hepatitis B virus subgenotype F2a in São Paulo, Brazil

Background

HBV genotype F is primarily found in indigenous populations from South America and is classified in four subgenotypes (F1 to F4). Subgenotype F2a is the most common in Brazil among genotype F cases. The aim of this study was to characterize HBV genotype F2a circulating in 16 patients from São Paulo, Brazil. Samples were collected between 2006 and 2012 and sent to Hospital Israelita Albert Einstein. A fragment of 1306 bp partially comprising HBsAg and DNA polymerase coding regions was amplified and sequenced. Viral sequences were genotyped by phylogenetic analysis using reference sequences from GenBank (n=198), including 80 classified as subgenotype F2a. Bayesian Markov chain Monte Carlo simulation implemented in BEAST v.1.5.4 was applied to obtain the best possible estimates using the model of nucleotide substitutions GTR+G+I.

Findings

It were identified three groups of sequences of subgenotype F2a: 1) 10 sequences from São Paulo state; 2) 3 sequences from Rio de Janeiro and one from São Paulo states; 3) 8 sequences from the West Amazon Basin.

Conclusions

These results showing for the first time the distribution of F2a subgenotype in Brazil. The spreading and the dynamic of subgenotype F2a in Brazil requires the study of a higher number of samples from different regions as it is unfold in almost all Brazilian populations studied so far. We cannot infer with certainty the origin of these different groups due to the lack of available sequences. Nevertheless, our data suggest that the common origin of these groups probably occurred a long time ago.

Hepatitis B virus subgenotype C2- and B2-associated mutation patterns may be responsible for liver cirrhosis and hepatocellular carcinoma, respectively

The objective of this study was to examine hepatitis B virus (HBV) subgenotypes and mutations in enhancer II, basal core promoter, and precore regions of HBV in relation to risks of liver cirrhosis (LC) and hepatocellular carcinoma (HCC) in Southeast China. A case-control study was performed, including chronic hepatitis B (CHB; n=125), LC (n=120), and HCC (n=136). HBV was genotyped by multiplex polymerase chain reaction and subgenotyped by restriction fragment length polymorphism. HBV mutations were measured by DNA sequencing. HBV genotype C (68.2%) predominated and genotype B (30.2%) was the second most common. Of these, C2 (67.5%) was the most prevalent subgenotype, and B2 (30.2%) ranked second. Thirteen mutations with a frequency >5% were detected. Seven mutation patterns (C1653T, G1719T, G1730C, T1753C, A1762T, G1764A, and G1799C) were associated with C2, and four patterns (C1810T, A1846T, G1862T, and G1896A) were associated with B2. Six patterns (C1653T, G1730C, T1753C, A1762T, G1764A, and G1799C) were obviously associated with LC, and 10 patterns (C1653T, G1730C, T1753C, A1762T, G1764A, G1799C, C1810T, A1846T, G1862T, and G1896A) were significantly associated with HCC compared with CHB. Four patterns (C1810T, A1846T, G1862T, and G1896A) were significantly associated with HCC compared with LC. Multivariate regression analyses showed that HBV subgenotype C2 and C2-associated mutation patterns (C1653T, T1753C, A1762T, and G1764A) were independent risk factors for LC when CHB was the control, and that B2-associated mutation patterns (C1810T, A1846T, G1862T, and G1896A) were independent risk factors for HCC when LC was the control.

Distribution of HBV genotypes in Latin America

Approximately 2 billion people worldwide are infected with HBV, and 350 million people are chronic carriers. HBV is classified into nine genotypes (A to I). Genotype F is the most prevalent in the Spanish-speaking countries and in the Amerindian population in South America. HBV genotype F was primarily found in indigenous populations from South America and is divided into four subgenotypes (F1 to F4). Subgenotype F1 is further divided into F1a (found in Costa Rica and El Salvador) and F1b (found in in Alaska, Argentina and Chile). Subgenotypes F2 and F3 cocirculate in the north of South America: F2a is found in Brazil and Venezuela, F2b is described only in Venezuela, F3 is frequent in Colombia, Venezuela and Panama, and F4 is reported from the central and south areas of South America, including Bolivia, Argentina and southern Brazil. HBV genotypes and subgenotypes have distinct geographical distributions. It is currently under discussion whether they are associated with different prognoses, considering the patterns of severity of liver diseases in various populations. Furthermore, global human migrations affect the pattern of genotype distribution, introducing genotypes differing from those found in the original inhabitants.

Distribution of HBV genotypes F and H in Mexico and Central America

The distribution of HBV genotypes is associated with populations of specific geographical regions of the world. We show data from the GenBank sequence database and medical reports, which indicate that HBV genotype H (HBV/H) is mainly distributed in Mexico, whereas HBV genotype F (HBV/F) is distributed in countries from Central America. The phylogenetic analysis and historical records suggest that HBV/H has been present in Mexico even before the arrival of the Spaniards. Interestingly, occult hepatitis B is a common finding in both natives and patients with chronic liver disease in Mexico. This suggests that an immunogenic background could be important during the natural history of liver diseases. The estimated large number of HBV/H-infected patients in Mexico does not correlate with the total number of patients with chronic liver disease and cirrhosis reported in the country. This may be because of the fact that HBV infection is often masked by alcoholic liver disease, HCV coinfection and/or obesity. Here, we analyse the data concerning the distribution of HBV/F and HBV/H genotypes in Central America and Mexico. Specifically, we focus on the effect of molecular epidemiology and pathogenesis of HBV/H. These recent findings reveal new areas of study with therapeutic potential in viral liver diseases.

Origin of HBV and its arrival in the Americas--the importance of natural selection on time estimates

BACKGROUND

The strong geographic structure shown by the global pattern of HBV lineages suggests an ancient origin for this virus; however, estimates based on the molecular clock suggest a very recent origin for the Native American genotypes F and H. In this study, we contribute to this debate by estimating the divergence times of genotypes F and H and by discussing how evolutionary rates estimated from recent samples may underestimate the divergence time of more ancient nodes in HBV phylogenies.

METHODS

A total of 108 complete HBV genotype F and H genomes were compared to 44 reference genomes from other genotypes. Time estimates were based on a Bayesian method with evolutionary rates taken from the literature. To assess the pattern of substitutions in recent versus old branches we mapped the phylogenetic distribution of all mutations occurring in genotypes F and H using a maximum likelihood approach and compared the number of synonymous and non-synonymous mutations in young and old branches of HBV genotype F and H phylogeny using a χ² test.

RESULTS

Estimated divergence times between genotypes F and H depend heavily on the evolutionary rate. While fast rates suggest a recent separation of these genotypes (approximately 800 years ago), slow rates suggest an earlier divergence (up to approximately 13,000 years ago). There is a clear excess of non-synonymous substitutions in the most recent branches of HBV phylogeny (P=4.87×10⁻¹⁵), most likely suggesting the action of purifying selection.

CONCLUSIONS

These results suggest that rates estimated based on recent samples will overestimate the evolutionary rate and underestimate the coalescence times for ancient nodes in HBV phylogeny.

Dating the origin and dispersal of hepatitis B virus infection in humans and primates

The origin of hepatitis B virus (HBV) infection in humans and other primates remains largely unresolved. Understanding the origin of HBV is crucial because it provides a framework for studying the burden, and subsequently the evolution, of HBV pathogenicity with respect to changes in human population size and life expectancy. To investigate this controversy we examined the relationship between HBV phylogeny and genetic diversity of modern humans, investigated the timescale of global HBV dispersal, and tested the hypothesis of HBV-human co-divergence. We find that the global distribution of HBV genotypes and subgenotypes are consistent with the major prehistoric modern human migrations. We calibrate the HBV molecular clock using the divergence times of different indigenous human populations based on archaeological and genetic evidence and show that HBV jumped into humans around 33,600 years ago; 95% higher posterior density (HPD): 22,000-47,100 years ago (estimated substitution rate: 2.2 × 10(-6) ; 95% HPD: 1.5-3.0 × 10(-6) substitutions/site/year). This coincides with the origin of modern non-African humans. Crucially, the most pronounced increase in the HBV pandemic correlates with the global population increase over the last 5,000 years. We also show that the non-human HBV clades in orangutans and gibbons resulted from cross-species transmission events from humans that occurred no earlier than 6,100 years ago.

CONCLUSION

Our study provides, for the first time, an estimated timescale for the HBV epidemic that closely coincides with dates of human dispersals, supporting the hypothesis that HBV has been co-expanding and co-migrating with human populations for the last 40,000 years. (HEPATOLOGY 2013).

Epidemiology and molecular characterization of hepatitis B virus infection in isolated villages in the Western Brazilian Amazon

Individuals from three isolated, rural communities in the western Brazilian Amazon were evaluated for serological markers of hepatitis B virus (HBV) infection, HBV genotype, and the presence of risk factors for infection and transmission. Of the 225 individuals studied, 79.1% had serological evidence of HBV infection; 10.2% individuals were chronic carriers for HBV surface antigen (HBsAg-positive). Analysis of risk factors indicates that HBV is transmitted mainly horizontally within the family from a chronic "active" carrier for hepatitis B "e" antigen (HBeAg-positive), though a strong possibility of vertical transmission remains. The predominance of HBV genotype F, with a higher genomic similarity between the isolates, indicated a relatively recent introduction of HBV, from a common source, to the area. This study sheds light on the HBV epidemiology in the Brazilian Amazon region and highlights the need for greater emphasis on HBV control and immunization programs.

HBsAg variants: diagnostic-escape and diagnostic dilemma

A wide variety of commercial assays is available for the detection of hepatitis B surface antigen (HBsAg). Clearly, the sensitivity of an assay to detect a variant is dependent on the anti-HBs usage. Thus, it is not surprising that there are examples of variants that cannot be detected by all assays. Data from Europe, Asia and Africa about HBsAg variants which are not recognized by either monoclonal or polyclonal antibodies specific for wild-type group 'a' determinant, but positive by DNA polymerase chain reaction (PCR) in chronic patients and from vaccinated children are increasing. This would impose a challenge for public health issues of hepatitis B virus. In this review we tried to summarize the discrepancies between results of HBsAg assays and to explain some rationales for these inconsistencies.

Genomic analysis of hepatitis B virus reveals antigen state and genotype as sources of evolutionary rate variation

Hepatitis B virus (HBV) genomes are small, semi-double-stranded DNA circular genomes that contain alternating overlapping reading frames and replicate through an RNA intermediary phase. This complex biology has presented a challenge to estimating an evolutionary rate for HBV, leading to difficulties resolving the evolutionary and epidemiological history of the virus. Here, we re-examine rates of HBV evolution using a novel data set of 112 within-host, transmission history (pedigree) and among-host genomes isolated over 20 years from the indigenous peoples of the South Pacific, combined with 313 previously published HBV genomes. We employ Bayesian phylogenetic approaches to examine several potential causes and consequences of evolutionary rate variation in HBV. Our results reveal rate variation both between genotypes and across the genome, as well as strikingly slower rates when genomes are sampled in the Hepatitis B e antigen positive state, compared to the e antigen negative state. This Hepatitis B e antigen rate variation was found to be largely attributable to changes during the course of infection in the preCore and Core genes and their regulatory elements.

HBV genotypes: relevance to natural history, pathogenesis and treatment of chronic hepatitis B

Although chronic HBV infection is the leading cause of chronic liver disease and death worldwide, there are substantial differences in its clinical courses regarding prevalence, mode of transmission, characteristics of each phase, responses to antiviral therapy, and development of cirrhosis and hepatocellular carcinoma, according to geographical areas (Asia versus Western Europe and North America versus Africa). Furthermore, the clinical course in infected individuals depends on a complex interplay among various factors including viral, host, environmental and other factors. Recently, understanding of molecular characteristics of the prevailing HBV genotypes, frequently accompanied mutations and their clinical implications might explain these geographical differences more pertinently. Hence, in this article, we review the global epidemiology and the natural history of HBV infection, with emphasis on summarizing the different HBV genotypes according to regions.

Full-length genomic sequence of hepatitis B virus genotype C2 isolated from a native Brazilian patient

The hepatitis B virus (HBV) is among the leading causes of chronic hepatitis, cirrhosis and hepatocellular carcinoma. In Brazil, genotype A is the most frequent, followed by genotypes D and F. Genotypes B and C are found in Brazil exclusively among Asian patients and their descendants. The aim of this study was to sequence the entire HBV genome of a Caucasian patient infected with HBV/C2 and to infer the origin of the virus based on sequencing analysis. The sequence of this Brazilian isolate was grouped with four other sequences described in China. The sequence of this patient is the first complete genome of HBV/C2 reported in Brazil.

Unusual presentation of hepatitis B serological markers in an Amerindian community of Venezuela with a majority of occult cases

Background

Occult hepatitis B infection (OBI) is characterized by the presence of hepatitis B virus (HBV) DNA in the absence of HBsAg in the serum of patients. The aim of this study was to characterize HBV infection among a Piaroa community, an Amerindian group which exhibits significant evidence of exposure to HBV but relatively low presence of HBsAg, and to explore the presence of OBI in this population.

Results

Of 150 sera, with 17% anti-HBc and 1.3% HBsAg prevalence, 70 were tested for the presence of HBV DNA. From these, 25 (36%) were found positive for HBV DNA by PCR in the core region. Two of these 25 sera were HBsAg positive, indicating an overt infection. Of the remaining 68 sera tested, 23 exhibited OBI. Of these, 13 were HBV DNA out of 25 anti-HBc positive (52%) and 10 HBV DNA positive, out of 43 anti-HBc negative (23%), with a statistical significance of p = 0.03. Viral DNA and HBsAg were present intermittently in follow up sera of 13 individuals. Sequence analysis in the core region of the amplified DNA products showed that all the strains belonged to HBV genotype F3. The OBI isolates displayed 96-100% nucleotide identity between them. One isolate exhibited the co-circulation of a wild type variant with a variant with a premature stop codon at the core protein, and a variant exhibiting a deletion of 28 amino acids.

Conclusions

The frequency of OBI found in this Amerindian group warrants further studies in other communities exhibiting different degrees of HBV exposure.

Etiology and Viral Genotype in Patients with End-Stage Liver Diseases admitted to a Hepatology Unit in Colombia

Hepatitis B virus (HBV) and hepatitis C virus (HCV) infections are the principal risk factor associated to end-stage liver diseases in the world. A study was carried out on end-stage liver disease cases admitted to an important hepatology unit in Medellin, the second largest city in Colombia. From 131 patients recruited in this prospective study, 71% of cases were diagnosed as cirrhosis, 12.2% as HCC, and 16.8% as cirrhosis and HCC. Regarding the risk factors of these patients, alcohol consumption was the most frequent (37.4%), followed by viral etiology (17.6%). Blood and/or hepatic tissue samples from patients with serological markers for HCV or HBV infection were characterized; on the basis of the phylogenetic analysis of HCV 5' UTR and HBV S gene, isolates belonged to HCV/1 and HBV/F3, respectively. These results confirm the presence of strains associated with poor clinical outcome, in patients with liver disease in Colombia; additionally, HBV basal core promoter double mutant was identified in HCC cases. Here we show the first study of cirrhosis and/or HCC in Colombian and HBV and HCV molecular characterization of these patients. Viral aetiology was not the main risk factor in this cohort but alcohol consumption.

Dynamics of hepatitis D (delta) virus genotype 3 in the Amazon region of South America

Hepatitis delta virus (HDV) is widely distributed and associated with fulminant hepatitis epidemics in areas with high prevalence of HBV. Several studies performed in the 1980s showed data on HDV infection in South America, but there are no studies on the viral dynamics of this virus. The aim of this study was to conduct an evolutionary analysis of hepatitis delta genotype 3 (HDV/3) prevalent in South America: estimate its nucleotide substitution rate, determine the time of most recent ancestor (TMRCA) and characterize the epidemic history and evolutionary dynamics. Furthermore, we characterized the presence of HBV/HDV infection in seven samples collected from patients who died due to fulminant hepatitis from Amazon region in Colombia and included them in the evolutionary analysis. This is the first study reporting HBV and HDV sequences from the Amazon region of Colombia. Of the seven Colombian patients, five were positive for HBV-DNA and HDV-RNA. Of them, two samples were successfully sequenced for HBV (subgenotypes F3 and F1b) and the five samples HDV positive were classified as HDV/3. By using all HDV/3 available reference sequences with sampling dates (n=36), we estimated the HDV/3 substitution rate in 1.07 × 10(-3) substitutions per site per year (s/s/y), which resulted in a time to the most recent common ancestor (TMRCA) of 85 years. Also, it was determined that HDV/3 spread exponentially from early 1950s to the 1970s in South America. This work discusses for the first time the viral dynamics for the HDV/3 circulating in South America. We suggest that the measures implemented to control HBV transmission resulted in the control of HDV/3 spreading in South America, especially after the important raise in this infection associated with a huge mortality during the 1950s up to the 1970s. The differences found among HDV/3 and the other HDV genotypes concerning its diversity raises the hypothesis of a different origin and/or a different transmission route.

Hepatitis B virus in Buenos Aires, Argentina: genotypes, virological characteristics and clinical outcomes

Hepatitis B virus (HBV) is classified into eight major genotypes, A-H, which are geographically distributed worldwide. The aim of this work was to describe the clinical characteristics associated with the HBV genotypes circulating in Buenos Aires city. The study included 139 patients infected with HBV, whose clinical courses were classified as acute symptomatic self-limiting hepatitis, inactive carrier state and chronic active hepatitis (HBV e-antigen (HBeAg)-positive and HBeAg-negative). The HBV genotypes were determined in 128 patients by PCR-restriction fragment length polymorphism and phylogenetic analysis. Biochemical, virological, clinical and histological features were analysed. A differential distribution of genotypes between acute symptomatic and chronic infections was found. Among the acute cases, genotype F was predominant (65.2%, 30/46) and genotype D was rare (4.3%, 2/46), whereas among the chronic infections, a homogeneous distribution of genotypes A (26.8%, 22/82), D (31.7%, 26/82) and F (36.6%, 30/82), with an unusual presence of genotypes B (1.2%, 1/82) and C (3.7%, 3/82), was observed. Regarding the liver histology of chronically infected patients, genotype F tended to display higher histological activity indexes. Mutations related to HBV surface antigen immunoreactivity, antiviral resistance and HBeAg-negative status were studied. This work constitutes, to our knowledge, the first description of the clinical characteristics related to HBV genotypes in Argentina, where the distribution of genotypes in patients with acute infection has not been reported previously. Finally, it was established that genotype F is the prevalent genotype among the acute symptomatic infections in Buenos Aires city, and that it shows a tendency to cause an adverse disease outcome among the chronic cases.

Hepatitis B virus genotypes

Hepatitis B virus (HBV) is a member of the hepadnavirus family and can lead to severe liver disease. HBV has a very high genetic variability. Currently, eight genotypes of HBV have been recognized, and most genotypes are now divided into subgenotypes with distinct virological and epidemiological properties. In addition, recombination among HBV genotypes increases the variability of HBV. This review summarizes current knowledge of the epidemiology of genetic variability in hepadnaviruses and, due to rapid progress in the field, updates several recent reviews on HBV genotypes and subgenotypes.

Occult hepatitis B in the genotype H-infected Nahuas and Huichol native Mexican population

Mexico is considered to be a low endemic country for HBV infection. However, a high anti-HBc against a low hepatitis B surface antigen (HBsAg) seroprevalence is the reported characteristic of native Mexicans. HBV diagnosis and genotype distribution was examined in native populations (Nahuas and Huichol, n = 306), and compared to a non-native population (Mestizos, n = 17). Overall, 6% of the natives were positive for HBsAg and 33% had detectable anti-HBc. HBsAg prevalence was lower in Nahuas compared to Huichols (1.4% vs. 9.4%, P < 0.002). Occult hepatitis B was detected in 14.2% (41/289) of natives, who either tested positive (5.88%, 17/289 HBsAg-negative) or negative for anti-HBc marker (8%, 24/289 HBsAg-negative). Age-adjusted anti-HBc seroprevalence and HBsAg quantitation revealed a sub-optimal sensitivity of conventional immunoassays. Nahuas had HBV/H and Huichol had HBV/A as the predominant genotypes followed by genotypes D, C, B, A, and D, G and H, respectively. A less variable HBV/H was characteristic in Mestizos, compared to a much variable HBV/H identified among the Nahuas. In conclusion, these findings indicate a high HBV endemicity among native Mexican groups where occult B infection is common. The different distribution of HBV genotypes among natives suggests multiple reservoirs of HBV from which these genotypes spread into the local communities. High anti-HBc seroprevalence against a low HBsAg prevalence rate may be due to the limited sensitivity of the immunoassays for the detection of HBsAg that are available in Mexico and/or unknown immunogenetic characteristics of native Mexicans.

Epidemiology of hepatitis B and C viruses: a global overview

This article reviews the prevalence, disease burden, genotype distribution, and transmission patterns of hepatitis B virus (HBV) and hepatitis C virus in the 6 World Health Organization regions. The global epidemiology of hepatitis B and C demonstrates a predominantly declining prevalence of the diseases. Improvement in the control of hepatitis B has been largely achieved with implementation of a more universal HBV vaccine program, although a large gap still remains in the effort toward global prevention of hepatitis B. The transmission of hepatitis C has been greatly impacted by mandatory screening of blood donors in most countries in the world, although intravenous drug use continues to be a major source of infection. Public education regarding the risks of exposure to infected paraphernalia as well as household items such as razors is necessary in the continuing effort to curb this disease.

Worldwide genetic diversity of HBV genotypes and risk of hepatocellular carcinoma

Hepatitis B viruses (HBV) are responsible for over 50% of the worldwide attributable risk of hepatocellular carcinoma (HCC) and this figure increases even further in regions of high endemicity. Systematic sequencing of HBV genomes has identified that this common virus existed as eight distinct genotypes (denoted A-H), each regrouping variants with less than 8% divergence in their DNA sequence. These genotypes differ by their geographic distribution in populations around the globe. There is evidence that HBV genotypes also differ by their pathogenic properties, including their risk of persistence as chronic infection and their capacity to induce precursor disease or cancer. On the other hand, HBV genes may undergo mutations that become selected during the course of chronic infection and progressive liver disease. The most significant of these mutations in the context of HCC are those occurring in the pre-core (Pre-C) and basal core promoter (BCP) regions. These mutations may upregulate HBV expression and increase its virulence. These mutations may occur in all HBV genotypes but are more common in genotypes associated with more severe disease and cancer, in particular genotype C. Understanding the molecular basis of pathological variations between HBV variants is critical for prediction of disease severity. It will also be important to determine whether differences among genotypes may have an impact on the long-term protective efficacy of universal HBV vaccination.

Evolutionary history and phylogeography of human viruses

Understanding the evolutionary history of human viruses, along with the factors that have shaped their spatial distributions, is one of the most active areas of study in the field of microbial evolution. I give an overview of our current knowledge of the genetic diversity of human viruses using comparative studies of viral populations, particularly those with RNA genomes, to highlight important generalities in the patterns and processes of viral evolution. Special emphasis is given to the major dichotomy between RNA and DNA viruses in their epidemiological dynamics and the different types of phylogeographic pattern exhibited by human viruses. I also consider a central paradox in studies of viral evolution: Although epidemiological theory predicts that RNA viruses have ancestries dating back millennia, with major ecological transitions facilitating their emergence, the genetic diversity in currently circulating viral populations has a far more recent ancestry, indicative of continual lineage turnover.

The influence of hepatitis B virus genotype and subgenotype on the natural history of chronic hepatitis B

BACKGROUND

Chronic infection with hepatitis B virus (HBV) is associated with a high lifetime risk of developing hepatocellular carcinoma (HCC) and cirrhosis of the liver.

PURPOSE

To review the studies published to date regarding the association of HBV genotypes and subgenotypes in the development of adverse sequelae from HBV.

METHODS

Review of the literature for articles describing studies of HBV genotype/subgenotypes and development of HCC, cirrhosis, and liver-related death.

RESULTS

Eight genotypes of HBV (A through H), which differ from each other in viral genome sequence by more than 8%, and multiple subgenotypes, which differ from each other by 4-8% have been identified. Recently, studies investigating the association between the risks of developing HCC and cirrhosis by specific HBV genotypes and subgenotypes have reported marked differences in outcome. Certain HBV genotypes and subgenotypes, including genotype C, B2-5, and F1, appear to be associated with a higher risk of developing HCC, and others, including genotypes B1, B6, and A2, appear to be associated with a lower risk of complications of HBV. Our understanding of the role of HBV genotypes and subgenotypes on the outcome of HBV infection is limited, as few population-based prospective studies have been performed and most studies compare only the outcome in areas where two genotypes predominate whereas others have not examined subgenotypes.

CONCLUSIONS

Studies to date suggest that HBV genotypes/subgenotypes have important influences on the outcome of chronic HBV infection, but more population-based prospective studies examining multiple genotypes are needed.

Alta prevalencia de la infección por el virus de hepatitis B en la comunidad indígena Japreira, Estado Zulia, Venezuela

A fin de conocer la prevalencia de la infección por el virus de hepatitis B (VHB) en la comunidad indígena Japreira, Venezuela, y determinar las pautas de su adquisición en función de la edad y sexo, se seleccionaron 149 individuos de un total de 300. Se detectó por métodos serológicos la presencia de anticuerpos totales del VHB (anti-HBc total), y en las positivas se investigó la presencia del antígeno de superficie (HBsAg) y del antígeno "e" del VHB (HBeAg). La prevalencia de anti-HBc total fue de 72,9% en el sexo femenino y 81,1% en el masculino, la prevalencia de HBsAg fue elevada (61,1%) en el sexo masculino, sólo cuatro de los portadores de HBsAg fueron positivos para HBeAg. Los resultados obtenidos indican un grado elevado de endemia para esta infección y que su diseminación comienza a temprana edad. El factor involucrado en la adquisición y diseminación del virus seria la vía sexual. Hacinamiento, contacto intercorpóreo con fluidos biológicos, prácticas sociales, y características de la cepa viral circulante podrían estar involucradas en la alta cronicidad observada en la comunidad indígena Japreira.

Subgenotype diversity of hepatitis B virus American genotype F in Amerindians from Venezuela and the general population of Colombia

The objective of this study was the evaluation of the genetic diversity found in HBV circulating among Venezuelan Amerindians and the general population in Colombia. Phylogenetic analysis of the S region in 194 isolates showed that genotype F is highly predominant in Colombia and Venezuela. This might be related to the genetic background of the population. F3 is the main subgenotype which circulates in both countries. Phylogenetic analysis of 61 complete genome sequences of HBV American genotypes confirms the presence of two genotypes F and H, and 4 F subgenotypes. In Venezuela, subgenotypes F1, F2, and F3 circulate in East and West Amerindians, while only F3 was found among South Amerindians. Japreira community derived from Yucpa Amerindians around 150 years ago. However, several Japreira HBV sequences were forming a clade that can be classified as subgenotype 2b, differing from Yucpa sequences that belong mainly to subgenotype F3. The apparent absence of correlation between the phylogenetic groupings of HBV isolates with the ethnical origin in aboriginal populations might be suggesting a recent origin of HBV American subgenotypes, or a genetic drift effect.

Hepatitis B virus genotypes circulating in Brazil: molecular characterization of genotype F isolates

Background

Hepatitis B virus (HBV) isolates have been classified in eight genotypes, A to H, which exhibit distinct geographical distributions. Genotypes A, D and F are predominant in Brazil, a country formed by a miscegenated population, where the proportion of individuals from Caucasian, Amerindian and African origins varies by region. Genotype F, which is the most divergent, is considered indigenous to the Americas. A systematic molecular characterization of HBV isolates from different parts of the world would be invaluable in establishing HBV evolutionary origins and dispersion patterns. A large-scale study is needed to map the region-by-region distribution of the HBV genotypes in Brazil.

Results

Genotyping by PCR-RFLP of 303 HBV isolates from HBsAg-positive blood donors showed that at least two of the three genotypes, A, D, and F, co-circulate in each of the five geographic regions of Brazil. No other genotypes were identified. Overall, genotype A was most prevalent (48.5%), and most of these isolates were classified as subgenotype A1 (138/153; 90.2%). Genotype D was the most common genotype in the South (84.2%) and Central (47.6%) regions. The prevalence of genotype F was low (13%) countrywide. Nucleotide sequencing of the S gene and a phylogenetic analysis of 32 HBV genotype F isolates showed that a great majority (28/32; 87.5%) belonged to subgenotype F2, cluster II. The deduced serotype of 31 of 32 F isolates was adw4. The remaining isolate showed a leucine-to-isoleucine substitution at position 127.

Conclusion

The presence of genotypes A, D and F, and the absence of other genotypes in a large cohort of HBV infected individuals may reflect the ethnic origins of the Brazilian population. The high prevalence of isolates from subgenotype A1 (of African origin) indicates that the African influx during the colonial slavery period had a major impact on the circulation of HBV genotype A currently found in Brazil. Although most genotype F isolates belonged to cluster II, the presence of some isolates belonging to clusters I (subgroup Ib) and IV suggests the existence of two or more founder viral populations of genotype F in Brazil.