RESUMO
The precore-core and S genes of HBV were directly sequenced from serum samples of 42 patients with chronic hepatitis B (16 hepatitis Be antigen [HBeAg]+and 26 anti-HBe+). Viral genotype A was identified in 12 cases, genotype D in 11 and genotype F in 19 cases. Precore mutations, mainly M1 (G1896A, stop at codon 28) were similarly found among viral genotypes A and D: seven cases (58%) and six cases (55%), respectively. The selection of M1 mutants from genotype D resulted in a more stable encapsidation signal but was less stable for genotype A precore mutants. Oddly enough, the encapsidation signal of M1 precore mutants from genotype F sequences were evenly distributed among less stable (genotype A M1 mutants) and more stable encapsidation signal (genotype D M1 mutants). This study shows that the selection of precore mutants that preclude the HBeAg expression, including the M1 mutation, does not necessarily depend on the stabilization of the encapsidation signal or the viral genotype In addition, the particular behavior of genotype F genomes at precore region is described.
Assuntos
Antígenos do Núcleo do Vírus da Hepatite B/genética , Antígenos de Superfície da Hepatite B/genética , Hepatite B Crônica/virologia , Precursores de Proteínas/genética , Adolescente , Adulto , Idoso , Sequência de Bases , DNA Viral , Feminino , Genoma Viral , Genótipo , Vírus da Hepatite B/classificação , Vírus da Hepatite B/genética , Hepatite B Crônica/sangue , Humanos , Masculino , Pessoa de Meia-Idade , Dados de Sequência Molecular , Mutagênese , RNA Viral , Homologia de Sequência do Ácido NucleicoRESUMO
Hepatitis B virus infection is responsible of an important number of world morbimortality. This is associated to severe liver outcome such as cirrhosis and hepatocellular carcinoma. Diverse factors influence the severity of liver injury produced by Hepatitis B Virus (HBV): the emergence of HBV mutants unable to secrete "e" antigen (pre-core mutants), the virus and host genetic heterogenicity and immune system competence. Particularly, the presence of pre-core mutants in chronic carriers is associated a low response to interferon therapy. We present paper is to present evidence as to the presence of these mutants in chronically infected, HBeAg negative patients (HBsAg positive) in Argentina. Viral DNAs were extracted from sera of nine patients, amplified by PCR and characterized by restriction enzyme assay. All of them appear to be pre-core mutants according with serological markers and a very low level of viral DNA detected in serum. Further genetic characterization of one of them by nucleotide sequence analysis of the pre-core region let allowed us to show modifications at codon 15 and 28 both of them previously described for pre-core mutants.
Assuntos
Antígenos de Superfície da Hepatite B/genética , Antígenos E da Hepatite B/genética , Vírus da Hepatite B/genética , Hepatite B/virologia , Sequência de Bases , Doença Crônica , Enzimas de Restrição do DNA/sangue , DNA Viral/sangue , DNA Viral/genética , Amplificação de Genes , Genoma Viral , Hepatite B/sangue , Hepatite B/terapia , Anticorpos Anti-Hepatite B/sangue , Anticorpos Anti-Hepatite B/imunologia , Antígenos de Superfície da Hepatite B/sangue , Antígenos E da Hepatite B/sangue , Humanos , Interferon-alfa/uso terapêutico , Dados de Sequência Molecular , Mutação , Reação em Cadeia da Polimerase , Mapeamento por RestriçãoRESUMO
The genomic coding region of the hepatitis B surface antigen (HBsAg) was partially sequenced from 12 HBsAg-positive sera of carriers residing in Buenos Aires, Argentina. A phylogenetic analysis groups the 12 isolates into genotypes A (n = 4), B (n = 1), D (n = 2), and F (n = 5). The occurrence of genotypes A and D is not unexpected, considering the mainly European origin of the studied population. The high prevalence of genotype F and its genetic composition support the suggestion that F strains originated in native populations of the New World.
Assuntos
Vírus da Hepatite B/genética , Hepatite B/virologia , Sequência de Aminoácidos , Argentina/epidemiologia , Sequência de Bases , Genes Virais , Genótipo , Hepatite B/epidemiologia , Humanos , Dados de Sequência Molecular , PrevalênciaRESUMO
Differences in pathogenesis and the probability of becoming a chronic carrier depend on the age at which hepatitis B virus (HBV) infection is acquired, ranging from 82% in infants less than 6 months of age to 15 to 30% in older children. HBV genotypes from 22 pediatric patients from two areas that differ in prevalence have been determined. Phylogenetic analysis shows a clear difference between the genotype distribution in Buenos Aires, a low-prevalence area, and that found in Gualeguay, Entre Ríos, a high-prevalence area. While the analysis allocated the sequences in the Buenos Aires group to genotypes A (36%), D (9%), and F (55%), the Gualeguay group presented exclusively genotype A isolates with very low nucleotide divergence, which suggests a strong founder viral population. The high prevalence of genotype F in the Buenos Aires group and its high intragroup heterogeneity agree with the American origin of this genotype.
Assuntos
Vírus da Hepatite B/genética , Vírus da Hepatite B/isolamento & purificação , Hepatite B/epidemiologia , Hepatite B/virologia , Argentina/epidemiologia , Sequência de Bases , Criança , Pré-Escolar , Primers do DNA/genética , DNA Viral/genética , Variação Genética , Genótipo , Vírus da Hepatite B/classificação , Hepatite Crônica/epidemiologia , Hepatite Crônica/virologia , Humanos , Lactente , Epidemiologia Molecular , Dados de Sequência Molecular , Filogenia , Reação em Cadeia da Polimerase , Homologia de Sequência do Ácido NucleicoRESUMO
La infección por el virurs de la Hepatitis B (HBV) es causa importante de morbi-mortalidad en el mundo, hallándose asociada con afecciones hepáticas graves tales como cirrosis y/o carcinoma hepatocelular primario (HCC). Entre los diversos factores que influyen en la severidad del daño hepático pueden señalarse, la emergencia de mutantes pre-core (HBeAg defectuosa), la heterogeneidad genética del virus y del hospedador y la competencia del sistema inmune. En particular la presencia de mutantes pre-core en portadores crónicos se asocia, además, con una baja respuesta a la terapia con interferón alfa. En este trabajo presentamos evidencias de la presencia de dichas mutantes en pacientes cronicamente infectados HBeAg negativos (HB Agi positivo) en la Argentina. Al suero de estos pacientes se les extrajo el ADN viral que fue amplificado por PCR y caracterizado por análisis con enzimas de restricción. Finalmente uno de estos sueros fue secuenciado en la región pre-core evidenciando la presencia de mutaciones en los codones 15 y 28 de dicha región característicos de estas mutantes