RESUMO
BACKGROUND Occult hepatitis B virus (HBV) - characterized by the absence of detectable HBsAg in the presence of HBV DNA - represents a potential threat for blood safety. OBJECTIVES This study was conducted with the aim to investigate the serological and molecular characterization of occult HBV infection (OBI) among blood donors in Mozambique. METHODS 1,502 blood donors were tested for HBsAg. All HBsAg-negative individuals were tested for HBV DNA. Antibodies against HBV core, surface and HBe antigen (anti-HBc, anti-HBs, HBeAg) were measured in HBV DNA positive individuals. FINDINGS 1435 serum samples were HBsAg negative and 16 positive for HBV DNA, 14 confirmed to have OBI, corresponding to a frequency of 0.98%. Of the 14 OBI infections identified, 13/14 (92.8%) were positive for anti-HBc, 4/14 (28.5%) for anti-HBs, and no samples were reactive for HBeAg. Of the 14 OBI cases, nine samples (64.2%) were sequenced for the S/P region. Eight samples (88.9%) belonged to genotype A1 and one (11.1%) to genotype E. One escape mutation (T123A) associated with OBI and various amino acid substitutions for genotype A1 and E were observed. MAIN CONCLUSIONS Our results show the importance of using nucleic acid amplification test to detect occult hepatitis B infection in blood donors in Mozambique.
Assuntos
Humanos , Masculino , Feminino , Adulto , Doadores de Sangue , Vírus da Hepatite B/isolamento & purificação , Vírus da Hepatite B/genética , Técnicas de Amplificação de Ácido Nucleico/métodos , Hepatite B/diagnóstico , Antígenos de Superfície da Hepatite B/genética , Filogenia , DNA Viral , Reação em Cadeia da Polimerase , Estudos Transversais , MoçambiqueRESUMO
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.
Assuntos
DNA Viral/isolamento & purificação , DNA Viral/genética , Hepatite B/genética , Hepatite B/virologia , Antígenos de Superfície da Hepatite B/genética , Sensibilidade e Especificidade , Reação em Cadeia da Polimerase em Tempo RealAssuntos
Humanos , Vacinas contra Hepatite B/imunologia , Vírus da Hepatite B/genética , Hepatite B/virologia , Evasão da Resposta Imune/genética , Mutação/genética , DNA Viral/genética , Anticorpos Anti-Hepatite B/imunologia , Antígenos de Superfície da Hepatite B/genética , Vírus da Hepatite B/imunologia , Hepatite B/imunologia , Hepatite B/prevenção & controle , Imunização PassivaRESUMO
Estudo Histórico Social que tem como objeto notícias sobre o Levantamento de Recursos e Necessidades de Enfermagem no Brasil, publicadas na Revista Brasileira de Enfermagem entre 1955 e 1958. A fonte primária foi constituída pelos exemplares da Revista Brasileira de Enfermagem, publicados dentro do recorte temporal do estudo. As fontes secundárias foram constituídas por livros, artigos, dissertações e teses relativas à história da Enfermagem. A análise dos dados teve apoio das fontes secundárias e do pensamento do sociólogo Pierre Bourdieu. Os dados evidenciaram que a Revista Brasileira de Enfermagem, além de oportunizar a divulgação de notícias acerca do Levantamento, proporcionou visibilidade ao mesmo mediante a veiculação dessas notícias e, por fim, teve o efeito simbólico de conferir poder e prestígio à Enfermagem Brasileira.
Social historical study that has as object news related to the Assessment of the Resources and Needs of Nursing in Brazil published in the Revista Brasileira de Enfermagem between 1955 and 1958. The primary source is constituted of copies of Revista Brasileira de Enfermagem published within the selected period of the study. The secondary sources are constituted of books, papers, dissertations and thesis related to the Nursing history. The data analysis was supported by the secondary sources and the thought of the sociologist Pierre Bourdieu. The results evidenced that Revista Brasileira de Enfermagem, in addition to making possible the dissemination of news about the Assessment provided visibility to it and, at last, had the symbolic effect of giving power and prestige to the Brazilian Nursing.
Estudio Histórico Social que tiene como objeto noticias referentes al Levantamiento de Recursos y Necesidades de Enfermería en Brasil publicadas en la Revista Brasileira de Enfermagem entre 1955 y 1958. La fuente primaria se constituye de los ejemplares de la Revista Brasileira de Enfermagem publicados dentro del recorte temporal do estudio. Las fuentes secundarias están constituidas de libros, artículos disertaciones y tesis relativas a la historia de la Enfermería. El análisis de los datos tuvo apoyo de las fuentes secundarias y del pensamiento del Sociólogo Pierre Bourdieu. Los resultados evidencian que la Revista Brasileira de Enfermagem, además de posibilitar la divulgación de noticias acerca del Levantamiento proporcionó visibilidad al mismo mediante la divulgación de esas noticias y, por fin, tuve el efecto simbólico de conferir poder y prestigio a la Enfermería Brasileña.
Assuntos
Animais , Feminino , Camundongos , Antígenos de Superfície da Hepatite B/genética , Vacinas contra Hepatite B/genética , Proteínas do Envelope Viral/genética , Proteínas do Envelope Viral/imunologia , Vacinas contra Hepatite Viral/genética , Fusão Gênica Artificial , Sequência de Bases , Hepacivirus/genética , Hepacivirus/imunologia , Vírus da Hepatite B/genética , Vírus da Hepatite B/imunologia , Imunização , Técnicas In Vitro , Dados de Sequência Molecular , Vacinas de DNA/genéticaRESUMO
No abstract available.
Assuntos
Feminino , Humanos , Masculino , DNA Circular/análise , Hepatite B/patologia , Antígenos de Superfície da Hepatite B/genética , Vírus da Hepatite B/metabolismoRESUMO
To assess the correlation between serum HBsAg titers and hepatitis B virus [HBV] DNA levels in patients with hepatitis B envelop antigen-negative [HBeAg -ve] HBV genotype-D [HBV/D] infection. A total of 106 treatment- nave, HBeAg -ve HBV/D patients were included; 78 in the inactive carrier [IC] state and 28 in the active hepatitis [AH] stage. HBV DNA load and HBsAg titers were tested using TaqMan real-time polymerase chain reaction [PCR] and automated chemiluminescent microparticle immunoassay, respectively. The median [range] log10 HbsAg titer was significantly lower in the IC group compared with AH group, 3.09 [-1 to -4.4] versus 3.68 [-0.77 to 5.09] IU/mL, respectively; P < 0.001. The suggested cutoff value of HBsAg titer to differentiate between the two groups was 3.79 log10 IU/mL. In addition, there was a significant positive correlation between HBsAg and HBV DNA levels in the whole cohort, AH, and IC groups [r = 0.6, P < 0.0001; r = 0.591, P = 0.001; and r = 0.243, P = 0.032, respectively]. Serum HBsAg titers may correlate with HBV DNA in treatment-nave HBeAg -ve HBV/D patients, and supports the use of HBsAg levels in clinical practice as a predictor of serum HBV DNA levels.
Assuntos
Humanos , Masculino , Feminino , Antígenos de Superfície da Hepatite B/genética , DNA Viral/sangue , Vírus da Hepatite B/imunologia , Hepatite B Crônica/sangue , Hepatite B Crônica/imunologia , Genoma Viral/genética , Proteínas do Envelope ViralRESUMO
The hepatitis B virus (HBV) polymerase gene has overlapping reading frames with surface genes, which allows to alter the amino acid codon of the surface genes. In adefovir (ADV) treated chronic hepatitis B patients carrying rtA181T/rtA181V mutations, overlap with surface gene mutations such as sW172stop/sL173F has been reported. However, the clinical consequences of such surface mutations have not been determined. The aim of this study was to determine the surface gene sequence in ADV-resistant patients carrying the A181T/V mutation and to describe the clinical significance. Of the 22 patients included in this study, 13 were ADV-resistant with rtA181T/V mutations (polymerase mutation group, Group P) and nine were antiviral treatment-naive (control group, Group C). The Pre-S1 gene mutation, V60A, was detected in 11 patients (Group P=8, Group C=3). A start codon mutation in the Pre-S2 gene was found in five patients (Group P=3, Group C=2). An S gene mutation, sA184V, was found in nine patients, all of whom were in group P. Although sW172stop and sL173F mutations were detected, reduced HBsAg titer was not observed. Further study of these mutations and their clinical implications are needed.
Assuntos
Adulto , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Adenina/análogos & derivados , Sequência de Aminoácidos , Substituição de Aminoácidos , Antivirais/uso terapêutico , Códon de Iniciação , DNA Polimerase Dirigida por DNA/genética , Demografia , Farmacorresistência Viral/genética , Genótipo , Antígenos de Superfície da Hepatite B/genética , Hepatite B Crônica/tratamento farmacológico , Dados de Sequência Molecular , Organofosfonatos/uso terapêutico , Mutação Puntual , Proteínas Virais/genéticaRESUMO
The obtainment of transgenic edible plants carrying recombinant antigens is a desired issue in search for economic alternatives viewing vaccine production. Here we report a strategy for genetic transformation of lettuce plants (Lactuca sativa L.) using the surface antigen HBsAg of hepatitis B virus. Transgenic lettuce seedlings were obtained through the application of a regulated balance of plant growth regulators. Genetic transformation process was acquired by cocultivation of cotyledons with Agrobacterium tumefaciens harboring the recombinant plasmid. It is the first description of a lettuce Brazilian variety "Vitória de Verão" genetically modified.
Assuntos
Antígenos de Superfície da Hepatite B/genética , Vacinas contra Hepatite B/genética , Lactuca/genética , Plantas Geneticamente Modificadas/genética , DNA Recombinante , Lactuca/imunologia , Reguladores de Crescimento de Plantas , Plantas Geneticamente Modificadas/imunologia , Plântula/genética , Plântula/imunologia , Vacinas de Plantas ComestíveisRESUMO
The S gene region of the hepatitis B virus (HBV) is responsible for the expression of surface antigens and includes the 'a'-determinant region. Thus, mutation(s) in this region would afford HBV variants a distinct survival advantage, permitting the mutant virus to escape from the immune system. The aim of this study was to search for mutations of the S gene region in different patient groups infected with genotype D variants of HBV, and to analyse the biological significance of these mutations. Moreover, we investigated S gene mutation inductance among family members. Forty HBV-DNA-positive patients were determined among 132 hepatitis B surface antigen (HbsAg) carriers by the first stage of seminested PCR. Genotypes and subtypes were established by sequencing of the amplified S gene regions. Variants were compared with original sequences of these serotypes, and mutations were identified. All variants were designated as genotype D and subtype ayw3. Ten kinds of point mutations were identified within the S region. The highest rates of mutation were found in chronic hepatitis patients and their family members. The amino acid mutations 125 (M -> T) and 127 (T -> P) were found on the first loop of 'a'-determinant. The other consequence was mutation inductance in a family member. We found some mutations in the S gene region known to be stable and observed that some of these mutations affected S gene expression.
Assuntos
Sequência de Aminoácidos , Sequência de Bases , DNA Viral/genética , Feminino , Genes Virais , Hepatite B/transmissão , Antígenos de Superfície da Hepatite B/genética , Vírus da Hepatite B/classificação , Humanos , Transmissão Vertical de Doenças Infecciosas , Masculino , Dados de Sequência Molecular , Mutação , Homologia de Sequência de Aminoácidos , TurquiaRESUMO
Hepatitis B is a global serious disease caused by hepatitis B virus (HBV). There is no known cure for hepatitis B. The best way to deal with the disease is by preventing with hepatitis B vaccine. However, the current protein-based vaccines made up of recombinant hepatitis B surface antigen (HBsAg) are ineffective in chronic HBV carriers and a significant number of the vaccinees do not mount the protective immune response. Novel DNA-based immunization may overcome the deficits of the protein-based immunization and may provide more effective prophylactic and therapeutic outcomes. In this study, we constructed a recombinant plasmid carrying gene encoding the HBV surface antigen (HBs) linked to DNA segment encoding full-length murine interleukin-18, i.e. pcDNA-HBs-IL-18. Immunogenicity of the DNA construct was carried out in BALB/c mice in comparison with mock, i.e. pcDNA3.1+ and vaccines comprised of pRc/CMV-HBs and pRc/CMV-HBs plus pcDNA-IL-18. All vaccinated mice revealed significant serum anti-HBs IgG response after two intramuscular injections of the vaccines at 28 day interval as compared to the level of mock. Co-administration of pRc/CMV-HBs and pcDNA-IL-18 elicited arbitrarily higher levels of anti-HBs IgG than the levels in mice immunized with pRc/CMV-HBs alone and mice that received pcDNA-HBs-IL-18 although not statistically different. Further experiments are needed to investigate the subisotypes of the IgG antibody, the kinetics of cytokine and the cell-mediated immune response. For this communication, the prototype HBs-IL-18 DNA vaccine was successfully constructed and the gene encoding murine IL-18 was successfully cloned. The latter can be co-injected with the antigen coding DNA or used as a fusion partner to the DNA for priming the immune response. The recombinant HBs and full-length IL-18 proteins have potential for other research purposes. They may be used also as standard proteins in the protein quantification assay.
Assuntos
Animais , Anticorpos Antivirais/imunologia , Hepatite B/genética , Antígenos de Superfície da Hepatite B/genética , Vacinas contra Hepatite B/genética , Vírus da Hepatite B/genética , Humanos , Imunidade Celular , Imunoglobulina G/imunologia , Interleucina-18/genética , Camundongos , Camundongos Endogâmicos BALB C , Proteínas Recombinantes de Fusão/genética , Vacinas de DNA/genéticaRESUMO
BACKGROUND/AIMS: Perinatal infection with hepatitis B virus (HBV) may occur despite immunoprophylaxis. One of the important mechanisms for perinatal prophylaxis failure, might include HBV surface gene variants. Therefore, we screened Korean children, in whom perinatal prophylaxis failed, for HBV surface gene variants. METHODS: Thirty-one children with perinatal HBV prophylaxis failure were selected. To amplify the major hydrophilic region of the HBV surface gene, nested PCR with primers targeted to nucleotides 237 to 706 was performed, and then sequencing was done. RESULTS: All cases were shown to be PCR positive for HBV-DNA and genotype C. Nine out of 31 (29%) with perinatal prophylaxis failure had a nucleotide substitution at the major hydrophilic region of the gene; but only two cases (6.5%) had an amino acid substitution. One case was infected by wild type and variants of I126S, and the other by wild type and S114A+I126S, respectively. CONCLUSIONS: In Korea, compared to the previous studies of other nations, gene surface variants such as G145R do not appear to play an important role in perinatal immunoprophylaxis failure.
Assuntos
Criança , Pré-Escolar , Feminino , Humanos , Lactente , Masculino , Gravidez , Hepatite B/prevenção & controle , Antígenos de Superfície da Hepatite B/genética , Vacinas contra Hepatite B/imunologia , Análise de Sequência de DNA , Análise de Sequência de Proteína , VacinaçãoRESUMO
A prevalência mundial do vírus da Hepatite B é estimada em cerca 350 milhões de infectados cronicamente, tendo distribuição bastante variada com prevalências baixas desde inferiores a dois por cento, como Europa Ocidental, América do Norte, Nova Zelândia, Austrália e Japão ù até altas, superiores a oito por cento como encontradas na África, Sudeste Asiático e China. No Brasil, a prevalência média é em torno de 8%. São descritos atualmente sete variações genotípicas do HBV, nomeadas de A a G, e quatro subtipos principais de antígenos de superfície: "adw", "ayw", "adr "e "ayr", existindo um grande interesse em identificar quais os subtipos e genotipos mais prevalentes a fim de correlacioná-los com manifestações clínicas e distribuição geográfica. Apesar do diagnóstico sorológico ser normalmente bastante sensível e específico, este não detecta casos de Hepatite B mutantes, cada vez mais freqüentes atualmente devido a escape e resistência de vacinação, terapias anti-virais, imunossupressão dentre outras. São descritas alterações genômicas no gene de superfície (envelope); gene X; gene do "core"; gene polimerase e gene "pré-core". As principais mutações ocorrem nos genes de superfície e nos genes "pré-core/core", podendo também ser conhecidas como hepatite oculta, uma vez que os marcadores de infecção ativa (AgHBs) e replicação viral (AgHBe) podem estar negativos. Assim, deve-se suspeitar de mutação viral nos casos em que a sorologia para a hepatite B indica imunidade ou parada da replicação com o quadro clínico evoluindo mal, excluído outras causas de hepatites.
Assuntos
Humanos , Hepatite B , Vírus da Hepatite B , Mutação , Países Desenvolvidos , Genótipo , Saúde Global , Antígenos de Superfície da Hepatite B/genética , Antígenos de Superfície da Hepatite B/imunologia , Vírus da Hepatite B/genética , Vírus da Hepatite B/imunologia , Hepatite B/epidemiologia , Hepatite B/imunologia , Hepatite B/virologia , PrevalênciaRESUMO
The S protein of hepatitis B virus is the principal component of virus envelope and the primary target of anti-HBs response. Mutants or variants that escape neutralization by anti-HBs have been selected during immunoprophylaxis of HBV after birth and liver transplantation. We investigated a case of a Korean child who was vaccinated at birth against hepatitis B and also given hepatitis B immunoglobulin, but nevertheless later became infected with the virus. Hepatitis B virus-specific deoxyribonucleic acid covering the region of genome encoding the predominant "a" determinant of hepatitis surface antigen was amplified using polymerase chain reaction, and the nucleotide sequence was determined. We present for the first time in Korea the independent emergence of an escape mutant with substitution of arginine for glycine at amino acid 145 and proline for glutamate at amino acid 120 in "a" determinant after immunization.
Assuntos
Humanos , Lactente , Masculino , Clonagem Molecular , DNA Viral/análise , Epitopos de Linfócito B/genética , Antígenos de Superfície da Hepatite B/genética , Vacinas contra Hepatite B/efeitos adversos , Vírus da Hepatite B/genética , Antígenos E da Hepatite B/sangue , Coreia (Geográfico) , Mutagênese Sítio-Dirigida , Mutação , Reação em Cadeia da Polimerase/métodos , Análise de Sequência de DNARESUMO
In order to develop an experimental DNA vaccine for the prevention and treatment of hepatitis B virus infection, hepatitis B virus surface antigen (HBsAg) DNA was subcloned into an E. coli-eukaryotic cell shuttle vector and was expressed in the Baculovirus expression system. Intramuscular, intradermal, and intraperitoneal injections of 30 microg of the plasmid DNA expressing HBsAg induced humoral and cellular immune responses in ICR mice. The first IgG antibodies were detected after ten days and specific IgG antibody titers peaked after two months of a single intramuscular DNA injection. Anti-HBs antibody titers gradually increased and peaked at four months following intradermal DNA injection, and in case of intraperitoneal injection they peaked at seven months. Generation of HBs-specific helper T lymphocytes was also investigated through the production of interleukin-2 by T helper cells. Boosting effects of HBs DNA were investigated without much results. In general, DNA-mediated HBs immunization induced humoral and cellular immune responses in mice that appears to simulate immune responses in human during the course of HBV vaccination.
Assuntos
Humanos , Masculino , Camundongos , Animais , Clonagem Molecular , DNA Viral/imunologia , Hepatite B/prevenção & controle , Anticorpos Anti-Hepatite B/imunologia , Antígenos de Superfície da Hepatite B/genética , Vacinas contra Hepatite B/imunologia , Interleucina-2/biossíntese , Camundongos Endogâmicos ICR , Plasmídeos/imunologia , Baço/imunologia , Baço/citologia , Vacinação , Vacinas de DNA/imunologiaRESUMO
Although many hepatitis B virus (HBV) mutants have been found in all open reading frames since the precore defective mutant was initially reported, systematic investigations of diverse HBV mutant populations in hepatitis B patients have not been performed. Therefore, we examined whether heterogeneous mutant populations simultaneously exist in Korean hepatitis B patients. In order to detect hepatitis B virus mutants, we amplified a conserved core region and a surface antigen region of HBV DNA by PCR from sera of 27 Korean chronic hepatitis B patients, and then performed single strand conformational polymorphism analysis followed by DNA sequencing analysis. The results showed that heterogeneous HBV mutants in both regions were present in a single as well as in various hepatitis B patients. Sequence analysis revealed a defective interfering particle with missense mutation in the core region. We also found that two subtypes of adr and adw coexisted in a single patient. In addition, a point mutation causing a stop codon in the surface antigen region was observed. We are further analyzing the clinical implications of HBV mutants to identify their roles in the pathogenesis of chronic hepatic disorders induced by HBV.
Assuntos
Adulto , Feminino , Humanos , Masculino , Sequência de Bases , Sequência Conservada , Heterogeneidade Genética , Antígenos de Superfície da Hepatite B/genética , Vírus da Hepatite B/genética , Hepatite B Crônica/virologia , Pessoa de Meia-Idade , Dados de Sequência Molecular , Mutação , Reação em Cadeia da Polimerase , Polimorfismo Conformacional de Fita Simples , Análise de Sequência de DNARESUMO
La introducción de ADN foráneo en los primeros estadíos de desarrollo embrionario del ratón con vistas a obtener animales transgénicos, permite crear nuevos modelos animales para el estudio de enfermedades humanas. Con la finalidad de crear un modelo de portador sano del virus de la hepatitis B (VHB), fueron microinyectados embriones unicelulares murinos con un plasmidio recombinante que contenía el genoma completo del VHB excepto el gen codificante para las proteínas del core viral, bajo el control del promotor propio del VHB. Se obtuvieron ratones transgénicos que presentaban integración y expresión del material génico viral. La expresión del gen del antígeno de superficie del VHB (HBsAg) fue cuantificada y se confirmó la segregación del transgen a la generación filial F1. Se concluye que estos ratones transgénicos pueden representar un modelo de portador asintomático de la hepatitis B.
Assuntos
Camundongos , Animais , Antígenos de Superfície da Hepatite B/genética , Expressão Gênica , Camundongos TransgênicosRESUMO
El virus Vaccinia ha sido empleado como vector para la fabricación de vacunas recombinantes vivas, entre las cuales se ha reportado la fabricación de un virus recombinante capaz de expresar el antígeno de superficie del virus de la hepatitis tipo B (HBSAg) durante el proceso de replicación del virus. En nuestro laboratorio se construyó un virus Vaccinia recombinante, también capaz de expresar el HBSAg. Los transcriptos específicos de HBSAg fueron caracterizados. La propiedad del virus Vaccinia recombinante de expresar el HBSAg, fue probada en ratones y conejos, obteniéndose en estos animales títulos de anticuerpos contra el HBSAg después de haber sido inoculados con los virus recombinantes
Assuntos
Antígenos de Superfície da Hepatite B/genética , Vaccinia virus/genéticaRESUMO
Mediante técnicas de ingeniería genética se ha logrado obtener líneas estables de células animales que sintetizan y secretan eficientemente partículas de antígeno de superficie del virus de la hepatitis B. Estas partículas presentan al microscopio electrónico un tamaño de 22 nm y son estructuralmente e inmunogénicamente similares a las obtenidas de plasma de enfermos crónicos, por lo que constituyen una excelente fuente de antígeno para la elaboración de una vacuna contra el virus