RESUMO
Fifteen strains of mAb specific for HA of the A/Hong Kong/482/97 (H5N1) influenza virus were generated. The HA antigenic sites of the human A/Hong Kong/482/97 (H5N1) influenza virus were defined by using yeast cell surface-displaying system and anti-H5 HA mAb. Evolution analysis of H5 HA identified residues that exhibit diversifying selection in the antigenic sites and demonstrated surprising differences between residue variation of H5 HA and H3 HA. A conserved neutralizing epitope in the H5 HA protein recognized by mAb H5M9 was found using viruses isolated from 1997-2006. Seven single amino acid substitutions were introduced into the HA antigenic sites, respectively, and the alteration of antigenicity was assessed. The structure obtained by homology-modeling and molecular dynamic methods showed that a subtle substitution at residue 124 propagates throughout its nearby loop (152-159). We discuss how the structural changes caused by point mutation might explain the altered antigenicity of the HA protein. The results demonstrate the existence of immunodominant positions in the H5 HA protein, alteration of these residues might improve the immunogenicity of vaccine strains.
Assuntos
Variação Antigênica , Epitopos/imunologia , Glicoproteínas de Hemaglutininação de Vírus da Influenza/imunologia , Virus da Influenza A Subtipo H5N1/imunologia , Aminoácidos/genética , Aminoácidos/imunologia , Anticorpos Monoclonais/genética , Anticorpos Monoclonais/imunologia , Membrana Celular/metabolismo , Cristalografia por Raios X , Mapeamento de Epitopos , Epitopos/química , Epitopos/genética , Evolução Molecular , Citometria de Fluxo , Glicoproteínas de Hemaglutininação de Vírus da Influenza/química , Glicoproteínas de Hemaglutininação de Vírus da Influenza/genética , Humanos , Virus da Influenza A Subtipo H5N1/genética , Modelos Moleculares , Mutação , Conformação Proteica , Estrutura Terciária de Proteína , Leveduras/genética , Leveduras/metabolismoRESUMO
An asymptomatic case of severe acute respiratory syndrome (SARS) occurred early in 2004, during a community outbreak of SARS in Guangzhou, China. This was the first time that a case of asymptomatic SARS was noted in an individual with antigenemia and seroconversion. The asymptomatic case patient and the second index case patient with SARS in the 2003-2004 outbreak both worked in the same restaurant, where they served palm civets, which were found to carry SARS-associated coronaviruses. Epidemiological information and laboratory findings suggested that the findings for the patient with asymptomatic infection, together with the findings from previously reported serological analyses of handlers of wild animals and the 4 index case patients from the 2004 community outbreak, reflected a likely intermediate phase of animal-to-human transmission of infection, rather than a case of human-to-human transmission. This intermediate phase may be a critical stage for virus evolution and disease prevention.