RESUMO
Introduction of a novel influenza virus into the human population leads to the occurrence of pandemic events, such as the one caused by pandemic influenza A (H1N1) 2009 virus. The severity of infections caused by this virus in young adults was greater than that observed in patients with seasonal influenza. Fatal cases have been associated with an abnormal innate, proinflammatory immune response. A critical role for natural killer cells during the initial responses to influenza infections has been suggested. In this study, we assessed the association of killer-cell immunoglobulin-like receptors (KIRs) with disease severity by comparing KIR gene content in patients with mild and severe pandemic influenza virus infections to a control group. We found that activator (KIR3DS1 and KIR2DS5) and inhibitory (KIR2DL5) genes, encoded in group B haplotypes containing the cB01, cB03 and tB01 motifs, are associated with severe pandemic influenza A (H1N1) 2009 infections. Better understanding of how genetic variability contributes to influenza virus pathogenesis may help to the development of immune intervention strategies aiming at controlling the severity of disease.
Assuntos
Vírus da Influenza A Subtipo H1N1 , Influenza Humana/genética , Receptores KIR2DL5/genética , Receptores KIR3DS1/genética , Receptores KIR/genética , Adolescente , Adulto , Idoso , Motivos de Aminoácidos , Criança , Pré-Escolar , Feminino , Frequência do Gene , Genótipo , Haplótipos , Humanos , Influenza Humana/epidemiologia , Influenza Humana/patologia , Masculino , México/epidemiologia , Pessoa de Meia-Idade , Pandemias , Isoformas de Proteínas/genética , Índice de Gravidade de Doença , Adulto JovemRESUMO
OBJECTIVES: To determine the contribution of influenza and respiratory syncytial virus (RSV) as the cause of lower respiratory tract infection (LRTI) associated hospitalizations during the first year of the influenza A(H1N1) 2009 pandemic and to assess the severity of illness during the second pandemic wave. METHODS: Patients admitted with LRTI from April 2009 through March 2010 were assessed for the presence of influenza and RSV. Pandemic influenza virus was detected by means of a nested RT-PCR assay and/or the CDC's real time-PCR protocol. RSV was detected using a one-step RT-PCR assay. The characteristics of patients admitted during the first and second pandemic outbreaks were compared. RESULTS: 657 patients with LRTI were admitted during the study period. Pandemic influenza virus was detected in 180 and RSV in 133. Influenza was the most common cause of infection in adults, while RSV was more common in children. There were no differences in disease severity between the first and second pandemic outbreaks. CONCLUSIONS: Pandemic influenza virus was associated to increased numbers of hospitalizations and deaths; particularly in adults. The severity of the first and second pandemic outbreaks was similar. RSV continues to be the main pathogen responsible for hospitalizations in young children.
