Genetic variability of hepatitis B virus in acute and in different phases of chronic infection in Brazil.

The selection pressure imposed by the host immune system impacts on hepatitis B virus (HBV) variability. This study evaluates HBV genetic diversity, nucleos(t)ide analogs resistance and HBsAg escape mutations in HBV patients under distinct selective pressures. One hundred and thirteen individuals in different phases of HBV infection were included: 13 HBeAg-positive chronic infection, 9 HBeAg-positive chronic hepatitis, 47 HBeAg-negative chronic infection (ENI), 29 HBeAg-negative chronic hepatitis (ENH) and 15 acute infected individuals. Samples were PCR amplified, sequenced and genetically analyzed for the overlapping POL/S genes. Most HBV carriers presented genotype A (84/113; 74.3%), subgenotype A1 (67/84; 79.7%), irrespective of group, followed by genotypes D (20/113; 17.7%), F (8/113; 7.1%) and E (1/113; 0.9%). Clinically relevant mutations in polymerase (tL180M/M204V) and in the Major Hydrophilic Region of HBsAg (sY100C, T118A/M, sM133T, sD144A and sG145R) were observed. Our findings, however, indicated that most polymorphic sites were located in the cytosolic loops (CYL1-2) and transmembrane domain 4 (TMD4) of HBsAg. Lower viral loads and higher HBV genetic diversity were observed in ENI and ENH groups (p < 0.001), suggesting that these groups are subjected to a higher selective pressure. Our results provide information on the molecular characteristics of HBV in a diverse clinical setting, and may guide future studies on the balance of HBV quasispecies at different stages of infection.

Could Herpesviridae be the cause of severe acute hepatitis of unknown origin in children?

INTRODUCTION: Severe acute hepatitis (SAH) is defined by a severe inflammation of hepatocytes in the liver parenchyma which can lead to an acute liver failure, a clinical condition with high mortality rate that can be triggered by several factors but is usually associated to hepatotropic viruses' infection. In 2022, cases of children with severe acute hepatitis of unknown origin hospitalized in Glasgow, Scotland, were reported. Possible causes of this condition include, but are not limited to, undiagnosed viral (and non-viral) infections, autoimmune hepatitis, drug and/or chemical toxicity, mitochondrial chain respiratory and metabolic disorders. AREAS COVERED: Herpesviruses can cause severe acute hepatitis, but little is known about the role and the mechanisms of herpesviruses as a causative agent of this type of hepatitis. We review the role of herpesviruses as causative agent of SAH in children and other possible mechanisms involved in this disease. EXPERT OPINION: Differential diagnosis for herpesvirus in SAH should be implemented in all settings. Alternative fluids, such as saliva and dried blood, could be used in the diagnosis to overwhelm the availability of biological specimens at sufficient volume. In the future, genetic studies could also be added to increase the knowledge about severe acute hepatitis in children.

Serological and molecular characterization of hepatitis B virus infection in chronic kidney disease patients from Rio de Janeiro, Brazil.

Chronic kidney disease (CKD) patients undergoing hemodialysis (HD) are more vulnerable to blood-borne viral infections due to frequent invasive procedures. Hepatitis B virus (HBV) infection in this cohort of patients has been a matter of concern worldwide. The objective of this cross-sectional study was to evaluate the frequency of serological markers for hepatitis B, and the occurrence of overt and occult HBV infection (OBI) and its molecular characterization in serum samples from 644 CKD patients in HD units located in Rio de Janeiro, Brazil, from 2013 to 2017. HBV DNA was investigated in HBsAg reactive and "anti-HBc alone" samples to determine infecting genotypes and genetic relatedness between sequences. The prevalence of serological markers HBsAg+, anti-HBc alone, anti-HBc+/anti-HBs+, anti-HBs+, anti-HBc/anti-HBs/HBsAg were 5.9%, 2.8%, 30.7%, 26.6%, 34.0%, respectively. HBV DNA was detected in 39.5% (15/38) of the HBsAg+ and in 5/18 (27.8%) of the "anti-HBc alone" individuals, indicating a high prevalence of OBI within this group. We found a higher prevalence of HBV/A1 (65%), followed by HBV/D3 (20%), and HBV/A2 (15%). Bayesian MCC tree with a highly supported clade, genetic distance comparison, and identical nucleotide sequences suggested a nosocomial spread of HBV in some units. The high prevalence of HBV infection and low number of individuals immune to infection reinforces the need for vaccination in this group. The presence of closely related strains in the same HD unit reinforces the importance of continuous improvement of safety control measures and laboratory surveillance of serological markers to prevent the risk of infection and transmission of HBV.

Serological and molecular characterization of hepatitis B virus infection in chronic kidney disease patients from Rio de Janeiro, Brazil

ABSTRACT Chronic kidney disease (CKD) patients undergoing hemodialysis (HD) are more vulnerable to blood-borne viral infections due to frequent invasive procedures. Hepatitis B virus (HBV) infection in this cohort of patients has been a matter of concern worldwide. The objective of this cross-sectional study was to evaluate the frequency of serological markers for hepatitis B, and the occurrence of overt and occult HBV infection (OBI) and its molecular characterization in serum samples from 644 CKD patients in HD units located in Rio de Janeiro, Brazil, from 2013 to 2017. HBV DNA was investigated in HBsAg reactive and "anti-HBc alone" samples to determine infecting genotypes and genetic relatedness between sequences. The prevalence of serological markers HBsAg+, anti-HBc alone, anti-HBc+/anti-HBs+, anti-HBs+, anti-HBc/anti-HBs/HBsAg were 5.9%, 2.8%, 30.7%, 26.6%, 34.0%, respectively. HBV DNA was detected in 39.5% (15/38) of the HBsAg+ and in 5/18 (27.8%) of the "anti-HBc alone" individuals, indicating a high prevalence of OBI within this group. We found a higher prevalence of HBV/A1 (65%), followed by HBV/D3 (20%), and HBV/A2 (15%). Bayesian MCC tree with a highly supported clade, genetic distance comparison, and identical nucleotide sequences suggested a nosocomial spread of HBV in some units. The high prevalence of HBV infection and low number of individuals immune to infection reinforces the need for vaccination in this group. The presence of closely related strains in the same HD unit reinforces the importance of continuous improvement of safety control measures and laboratory surveillance of serological markers to prevent the risk of infection and transmission of HBV.

Hepatitis B virus genotypes prevalence in patients from hepatology services in Ceará, Brazil.

INTRODUCTION: Hepatitis B virus (HBV) infection is a public health problem; therefore, we aimed to report HBV genotypes in Ceará, Brazil. METHODS: A total of 103 HBsAg-positive samples were subjected to HBV genotyping and subgenotyping. RESULTS: The following genetic compositions of samples were found: F-54% (F2-83.33%), A-40% (A1-65%), D-6%, C2-1%, E-1%, and G-1%. CONCLUSIONS: Some genotypes are only prevalent in certain parts of the world; however, the State of Ceará is a hub for migration and has one of the most important liver transplantation centers in Brazil, which can explain the prevalence of the F genotype.

Hepatitis B virus genotypes prevalence in patients from hepatology services in Ceará, Brazil

Abstract INTRODUCTION: Hepatitis B virus (HBV) infection is a public health problem; therefore, we aimed to report HBV genotypes in Ceará, Brazil. METHODS: A total of 103 HBsAg-positive samples were subjected to HBV genotyping and subgenotyping. RESULTS: The following genetic compositions of samples were found: F-54% (F2-83.33%), A-40% (A1-65%), D-6%, C2-1%, E-1%, and G-1%. CONCLUSIONS: Some genotypes are only prevalent in certain parts of the world; however, the State of Ceará is a hub for migration and has one of the most important liver transplantation centers in Brazil, which can explain the prevalence of the F genotype.

Prevalence of hepatitis B and D virus infection in a district of Mato Grosso, bordering Amazonas and Rondônia states.

INTRODUCTION: Brazil's western Amazon basin has the highest prevalence of hepatitis B virus (HBV) infection in the country. Coinfection with hepatitis D virus (HDV) is also endemic. To estimate the prevalence of HBV and HDV markers in a population inhabiting the northwest portion of Mato Grosso state in the western Amazon. METHODS: We performed a cross-sectional study of the seroprevalence of antibodies against HBV core antigen (anti-HBc) in the Três Fronteiras District northwest of Mato Grosso. Anti-HBc-positive subjects were tested for HBV surface antigen (HBsAg). Those positive for this marker were tested for HDV antibodies. Anti-HBc-negative participants were tested for anti-HBsAg. All tests were performed by EIA. RESULTS: A total of 623 individuals in the community were assessed; the majority (67.6%) were male, with a mean age of 30.8 ± 15.4 years. Two hundred and fourteen individuals (34.3%) were anti-HBc-positive, and 47 (7.5%) were HBsAg carriers. Only one individual was anti-HDV-positive. Among the 409 individuals without HBV infection, 18.3% were anti-HBsAg-positive. There was no association between HBV infection and known risk factors. CONCLUSIONS: The study area had intermediate-to-high endemicity for HBV infection, but a low prevalence of HDV. Our serological results suggesting low vaccination-induced protection indicate a need for reinforced immunization programs in the populations of northwest Mato Grosso.

A New Method for Next-Generation Sequencing of the Full Hepatitis B Virus Genome from A Clinical Specimen: Impact for Virus Genotyping.

Hepatitis B virus (HBV) is an enveloped virus that induces chronic liver disease. HBV has been classified into eight genotypes (A-H) according to its genome sequence by using Sanger sequencing or reverse hybridization. Sanger sequencing is often restricted to analyzing the S gene and is inaccurate for detecting minority genetic variants, whereas reverse hybridization detects only known mutations. Next-generation sequencing (NGS) is a robust tool for clinical virology with different protocols available. The objective of this study was to develop a new method for the study of viral genetic polymorphisms or more accurate genotyping using genome amplification followed by NGS. Plasma obtained from five chronically infected HBV individuals was used for viral DNA isolation. HBV full-genome PCR amplification was the enrichment method for NGS. Primers were used to amplify all HBV genotypes in three overlapping amplicons, following a tagmentation step and Illumina NGS. For phylogenetic analysis, sequences were extracted from the HBVdb database. We were able to amplify a full HBV genome; further, NGS was shown to be a robust method and allowed better genotyping, mainly in patients carrying mixed genotypes, classified according to other techniques. This new method may be significant for whole genome analyses, including other viruses.

Rotavirus A shedding and HBGA host genetic susceptibility in a birth community-cohort, Rio de Janeiro, Brazil, 2014-2018.

Recent studies have investigated whether the human histo-blood group antigen (HBGAs) could affect the effectiveness of the oral rotavirus vaccines, suggesting secretor positive individuals develop a more robust response. We investigated the Rotavirus A (RVA) shedding in association with the host susceptibility profile in children from a birth community-cohort in Rio de Janeiro, Brazil, from 2014 to 2018. A total of 132 children were followed-up between 0 to 11-month-old, stool samples were collected before/after the 1st/2nd RV1 vaccination doses and saliva samples were collected during the study. RVA shedding was screened by RT-qPCR and G/P genotypes determined by multiplex RT-PCR and/or Sanger nucleotide sequencing. The sequencing indicated an F167L amino acid change in the RV1 VP8* P[8] in 20.5% of shedding follow-ups and these mutant subpopulations were quantified by pyrosequencing. The HBGA/secretor status was determined and 80.3% of the children were secretors. Twenty-one FUT2 gene SNPs were identified and two new mutations were observed. The mutant F167L RV1 VP8* P[8] was detected significantly more in Le (a+b+) secretors (90.5%) compared to non-secretors and even to secretors Le (a-b+) (9.5%). The study highlights the probable association between RV1 shedding and HBGAs as a marker for evaluating vaccine strain host susceptibility.

Prevalence of hepatitis B and D virus infection in a district of Mato Grosso, bordering Amazonas and Rondônia states

Abstract INTRODUCTION: Brazil's western Amazon basin has the highest prevalence of hepatitis B virus (HBV) infection in the country. Coinfection with hepatitis D virus (HDV) is also endemic. To estimate the prevalence of HBV and HDV markers in a population inhabiting the northwest portion of Mato Grosso state in the western Amazon. METHODS: We performed a cross-sectional study of the seroprevalence of antibodies against HBV core antigen (anti-HBc) in the Três Fronteiras District northwest of Mato Grosso. Anti-HBc-positive subjects were tested for HBV surface antigen (HBsAg). Those positive for this marker were tested for HDV antibodies. Anti-HBc-negative participants were tested for anti-HBsAg. All tests were performed by EIA. RESULTS: A total of 623 individuals in the community were assessed; the majority (67.6%) were male, with a mean age of 30.8 ± 15.4 years. Two hundred and fourteen individuals (34.3%) were anti-HBc-positive, and 47 (7.5%) were HBsAg carriers. Only one individual was anti-HDV-positive. Among the 409 individuals without HBV infection, 18.3% were anti-HBsAg-positive. There was no association between HBV infection and known risk factors. CONCLUSIONS: The study area had intermediate-to-high endemicity for HBV infection, but a low prevalence of HDV. Our serological results suggesting low vaccination-induced protection indicate a need for reinforced immunization programs in the populations of northwest Mato Grosso.

Detection and molecular characterisation of a diagnosis escape variant associated with occult hepatitis B virus in Brazil

BACKGROUND Many studies have identified mutations in the hepatitis B surface antigen (HBsAg) as important factors limiting the ability of commercial serological assays to detect this viral antigen. However, an association between mutations in the HBsAg gene and the occurrence of occult HBV infection (OBI) in patients has not been established. OBJECTIVES To detect hepatitis B virus (HBV) DNA in patients with anti-HBc as a unique serological marker, a previously published, cost-effective TaqMan-based real-time polymerase chain reaction (PCR) test with minor groove binding probes was adapted for use in this study. The current study also aimed to investigate HBsAg mutations and genotypes of HBV in OBI at the Viral Hepatitis Ambulatory Clinic in Rio de Janeiro to determine any possible association. METHODS Intra-assay and inter-assay reproducibility were determined, and the mean coefficient of variation values obtained were 2.07 and 3.5, respectively. Probit analysis indicated that the 95% detection level was 25 IU/mL. The prevalence of OBI was investigated in 35 serum samples with an ‘anti-HBc alone’ profile from individuals who attended our clinic between 2011 and 2013. FINDINGS HBV DNA was detected in only one sample, resulting in an OBI rate of 2.9%. Nucleotide sequencing of the pre-S/S region was performed to genotype and analyse mutations within the HBsAg gene of this HBV DNA. The HBV in the OBI case was classified as sub-genotype A1, and a sequence analysis of the small S gene revealed 12 mutations in the major hydrophilic region compared to the consensus A1 sequence. Most of these mutations occurred in amino acid residues that have been reported as clinically relevant because they have been implicated in vaccine escape and/or inability to detect HBsAg by commercial serological assays. MAIN CONCLUSIONS Our study suggests the importance of specific HBsAg mutations, different from those in D, B, and C genotypes, in sub-genotype A1 HBV associated with OBI.

Detection and molecular characterisation of a diagnosis escape variant associated with occult hepatitis B virus in Brazil.

BACKGROUND: Many studies have identified mutations in the hepatitis B surface antigen (HBsAg) as important factors limiting the ability of commercial serological assays to detect this viral antigen. However, an association between mutations in the HBsAg gene and the occurrence of occult HBV infection (OBI) in patients has not been established. OBJECTIVES: To detect hepatitis B virus (HBV) DNA in patients with anti-HBc as a unique serological marker, a previously published, cost-effective TaqMan-based real-time polymerase chain reaction (PCR) test with minor groove binding probes was adapted for use in this study. The current study also aimed to investigate HBsAg mutations and genotypes of HBV in OBI at the Viral Hepatitis Ambulatory Clinic in Rio de Janeiro to determine any possible association. METHODS: Intra-assay and inter-assay reproducibility were determined, and the mean coefficient of variation values obtained were 2.07 and 3.5, respectively. Probit analysis indicated that the 95% detection level was 25 IU/mL. The prevalence of OBI was investigated in 35 serum samples with an 'anti-HBc alone' profile from individuals who attended our clinic between 2011 and 2013. FINDINGS: HBV DNA was detected in only one sample, resulting in an OBI rate of 2.9%. Nucleotide sequencing of the pre-S/S region was performed to genotype and analyse mutations within the HBsAg gene of this HBV DNA. The HBV in the OBI case was classified as sub-genotype A1, and a sequence analysis of the small S gene revealed 12 mutations in the major hydrophilic region compared to the consensus A1 sequence. Most of these mutations occurred in amino acid residues that have been reported as clinically relevant because they have been implicated in vaccine escape and/or inability to detect HBsAg by commercial serological assays. MAIN CONCLUSIONS: Our study suggests the importance of specific HBsAg mutations, different from those in D, B, and C genotypes, in sub-genotype A1 HBV associated with OBI.

Identification of two phylogenetic lineages of equine hepacivirus and high prevalence in Brazil.

Non-primate hepacivirus (NPHV), as described in horses, is the virus most genetically related to hepatitis C virus (HCV). Although detected worldwide, limited data on genomic variability and distribution of NPHV are available in Latin America. The aim of this study was to investigate the genetic diversity and prevalence of equine NPHV in Brazil. Thirteen percent of 202 equines from three Brazilian states were positive for NPHV genome by reverse transcriptase PCR. Nucleotide sequences of the partial NS5B genome presented the greatest diversity described to date (25.6%), which is comparable to the upper limit of diversity for HCV subtype classification for the same region. Phylogenetic analysis revealed that Brazilian NPHV sequences along with isolates worldwide form two strongly supported clades (pp = 1.0) suggesting the existence of two distinct lineages.

Hepatitis B virus genotypes in Southeast Brazil and its relationship with histological features.

Data concerning the relationship between hepatitis B virus (HBV) genotypes and liver histology are scarce. The aim of this study was to compare HBV non-B and non-C genotypes according to demographic features, clinical status, HBV-DNA levels and liver histology in Rio de Janeiro. One hundred twenty one consecutive chronic HBV-infected patients were enrolled during two-year period and data were prospectively collected. Sera were tested for HBV genotyping using restriction fragment length polymorphism. Liver biopsy was obtained from patients with either increased alanine aminotransferase (ALT) or HBV-DNA levels. Genotype A was the most common, found in 82 (68%) patients, followed by F in 19 (15%), D in 17 (14%), B in one (1%) and C in two (2%). There was no association between HBV genotypes A, D and F and gender (p = 0.37), age (p = 0.78), race (p = 0.22), mode of infection (p = 0.94), HB "e" antigen status (p = 0.37) and HBV-DNA levels (p = 0.47). The ALT levels were lower in genotype D (75%) compared with A (47%) and F (55%) (p = 0.05). Liver biopsy showed lower inflammation [histological activity index (HAI) = 4] and fibrosis (F) (= 0) scores in genotype D than in genotypes A (HAI = 5, p < 0.001; F = 2, p = 0.008) or F (HAI = 5, p = 0.009; F = 2, p = 0.01). Genotype A was the most prevalent in chronic HBV-infected patients and genotype D patients presented with less intense liver disease.

Hepatitis B virus genotypes in Southeast Brazil and its relationship with histological features

Data concerning the relationship between hepatitis B virus (HBV) genotypes and liver histology are scarce. The aim of this study was to compare HBV non-B and non-C genotypes according to demographic features, clinical status, HBV-DNA levels and liver histology in Rio de Janeiro. One hundred twenty one consecutive chronic HBV-infected patients were enrolled during two-year period and data were prospectively collected. Sera were tested for HBV genotyping using restriction fragment length polymorphism. Liver biopsy was obtained from patients with either increased alanine aminotransferase (ALT) or HBV-DNA levels. Genotype A was the most common, found in 82 (68%) patients, followed by F in 19 (15%), D in 17 (14%), B in one (1%) and C in two (2%). There was no association between HBV genotypes A, D and F and gender (p = 0.37), age (p = 0.78), race (p = 0.22), mode of infection (p = 0.94), HB "e" antigen status (p = 0.37) and HBV-DNA levels (p = 0.47). The ALT levels were lower in genotype D (75%) compared with A (47%) and F (55%) (p = 0.05). Liver biopsy showed lower inflammation [histological activity index (HAI) = 4] and fibrosis (F) (= 0) scores in genotype D than in genotypes A (HAI = 5, p < 0.001; F = 2, p = 0.008) or F (HAI = 5, p = 0.009; F = 2, p = 0.01). Genotype A was the most prevalent in chronic HBV-infected patients and genotype D patients presented with less intense liver disease.

Antiviral therapy against chronic hepatitis B in Brazil: high rates of lamivudine resistance mutations and correlation with HBV genotypes

The effectiveness of antiviral treatments of chronic hepatitis B has been poorly studied in Brazil. Here, hepatitis B virus (HBV) DNA positivity, drug resistance mutations and their association with HBV genotypes were evaluated in chronically HBV-infected patients under different drug regimens in Brazil. The study involved 129 patients under interferon or nucleos(t)ide analogue therapy for a median treatment time of 12 months. One hundred and five (81%) of these patients were treated with lamivudine (LAM), either in monotherapy or in combination with newer drugs, such as entecavir (ETV) or tenofovir (TDF). High (37.5-100%) rates of HBV DNA positivity were observed with all but one drug regimen (LAM + ETV). However, patients that were treated with ETV alone, TDF alone or with LAM combination therapies had a mean viral load that was 3-4 log lower than patients treated with LAM monotherapy. Of the patients treated with LAM, 47% developed resistance mutations. HBV genotypes A (59.1%), D (30.3%) and F (9.1%) were found. There was no association between the presence of LAM resistance mutations and genotypes, HBeAg status or treatment duration. Nevertheless, the rtM204V mutation was observed more frequently (12/13, 92%) in genotype A than in the others (p = 0.023). Six out of nine isolates that contained the rtM204I mutation belonged to genotype D and half of them displayed a single mutation. Genotype D isolates with the rtM204V variant preferentially displayed a triple mutation, while genotype A preferentially displayed a double mutation (p = 0.04).

Antiviral therapy against chronic hepatitis B in Brazil: high rates of lamivudine resistance mutations and correlation with HBV genotypes.

The effectiveness of antiviral treatments of chronic hepatitis B has been poorly studied in Brazil. Here, hepatitis B virus (HBV) DNA positivity, drug resistance mutations and their association with HBV genotypes were evaluated in chronically HBV-infected patients under different drug regimens in Brazil. The study involved 129 patients under interferon or nucleos(t)ide analogue therapy for a median treatment time of 12 months. One hundred and five (81%) of these patients were treated with lamivudine (LAM), either in monotherapy or in combination with newer drugs, such as entecavir (ETV) or tenofovir (TDF). High (37.5-100%) rates of HBV DNA positivity were observed with all but one drug regimen (LAM + ETV). However, patients that were treated with ETV alone, TDF alone or with LAM combination therapies had a mean viral load that was 3-4 log lower than patients treated with LAM monotherapy. Of the patients treated with LAM, 47% developed resistance mutations. HBV genotypes A (59.1%), D (30.3%) and F (9.1%) were found. There was no association between the presence of LAM resistance mutations and genotypes, HBeAg status or treatment duration. Nevertheless, the rtM204V mutation was observed more frequently (12/13, 92%) in genotype A than in the others (p = 0.023). Six out of nine isolates that contained the rtM204I mutation belonged to genotype D and half of them displayed a single mutation. Genotype D isolates with the rtM204V variant preferentially displayed a triple mutation, while genotype A preferentially displayed a double mutation (p = 0.04).

Caracterização molecular de isolados do vírus da hepatite B em pacientes submetidos a tratamento antiviral e pacientes com infecção oculta / Molecular characterization of isolates of the virus of hepatitis B in patients undergoing antiviral therapy and patients with occult infection

Nos últimos anos, dois assuntos relacionados a infecção pelo vírus da hepatite B (HBV) vêm sendo foco de muitos debates e estudos por pesquisadores ao redor do mundo: o tratamento antiviral contra a hepatite B crônica e a infecção oculta pelo HBV. O estudo da ocorrência de mutações de resistência aos medicamentos antivirais mais potentes, os análogos de núcleos(t)ídeos (NAs), que representa o maior entrave para o sucesso do tratamento, passou a ter fundamental importância para o entendimento da dinâmica da terapia a longo prazo e para soluções para contornar este problema. A hepatite B oculta é um tema que preocupa pesquisadores do mundo inteiro pelo fato de algumas questões pertinentes ainda não tenham sido esclarecidas, como o impacto clínico da infecção oculta e seu papel na transmissão do vírus. A presente tese teve como objetivo realizar a caracterização molecular dos isolados do HBV em diversas populações de indivíduos com hepatite B: pacientes com infecção crônica submetidos a diferentes tratamentos antivirais (avaliando os tipos de tratamento antiviral atualmente utilizados no Brasil, a eficiência global de cada tratamento em reduzir os níveis de DNA do HBV e a freqüência de isolados com mutação de resistência aos medicamentos), pacientes com infecção aguda (observando a distribuição de genótipos e analisando a presença de subpopulações virais através do pirosequenciamento), e pacientes com infecção oculta pelo HBV (comparando a prevalência da infecção oculta pelo HBV em pacientes anti-HCV positivo e anti-HCV-negativo submetidos à hemodiálise) Como principais resultados obtidos nos quatro manuscritos produzidos, tivemos (i) a LAM como a terapia antiviral mais comum em uso no Brasil, com mais de 80 por cento dos pacientes analisados estando em tratamento com esta droga seja em monoterapia ou em terapia combinada com outra droga; (ii) o tratamento com IFN-alfa como o menos eficiente em reduzir o DNA do HBV e, em relação aos NAs, não foi encontrada uma diferença significativa entre a terapia com LAM e a terapia com os demais agentes orais em relação à eficiência em aduzir o DNA do HBV no soro dos pacientes, no entanto, as cargas virais nos pacientes tratados com LAM foram muito mais altas do que nos pacientes tratados com as drogas mais recentes; (iii) uma alta freqüência de isolados com mutações de resistência à LAM em pacientes submetidos à monoterapia (quase 50 por cento) ou à terapia combinada (78 por cento); (iv) uma alta incidência de isolados com a tripla mutação de resistência à LAM (6/27; 22 por cento) e uma diferença no perfil dos variantes YMDD entre os principais genótipos do HBV circulando no Brasil. Em conclusão, a alta freqüência de isolados com mutações de resistência à LAM pode limitar o uso de drogas como o ETV e a LdT para terapia de resgate em função da ocorrência de resistência cruzada entre essas drogas. As alterações de aminoácidos no HBsAg (sE164D mais sI195M) causadas pela tripla mutação de resistência à LAM, conhecidas por reduzir a afinidade de ligação deste antígeno com o anti-HBs, pode representar um sério problema epidemiológico caso esses isolados passem a circular no ambiente disseminados pela população em geral. Tais substituições podem ter contribuído para o caráter oculto da infecção por diminuírem a detecção do HBsAg por testes sorológicos, sugerindo ser esta a causa mais provável da ocorrência da infecção oculta nos pacientes em hemodiálise.