RESUMEN
Interleukin-17 (IL-17), a member of the IL-17 cytokine family, plays a crucial role in mediating the immune response against extracellular bacteria and fungi in the lung. Although there is increasing evidence that IL-17 is involved in protective immunity against H1 and H3 influenza virus infections, little is known about the role of IL-17 in the highly pathogenic H5N1 influenza virus infection. In this study, we show that H5N1-infected IL-17 knockout (KO) mice exhibit markedly increased weight loss, more pronounced lung immunopathology and significantly reduced survival rates as compared with infected wild-type controls. Moreover, the frequency of B cells in the lung were substantially decreased in IL-17 KO mice after virus infection, which correlated with reduced CXCR5 expression in B cells and decreased CXCL13 production in the lung tissue of IL-17 KO mice. Consistent with this observation, B cells from IL-17 KO mice exhibited a significant reduction in chemokine-mediated migration in culture. Taken together, these findings demonstrate a critical role for IL-17 in mediating the recruitment of B cells to the site of pulmonary influenza virus infection in mice.
Asunto(s)
Linfocitos B/inmunología , Eliminación de Gen , Subtipo H5N1 del Virus de la Influenza A/inmunología , Interleucina-17/inmunología , Pulmón/virología , Infecciones por Orthomyxoviridae/inmunología , Animales , Linfocitos B/citología , Linfocitos B/metabolismo , Movimiento Celular/inmunología , Quimiocina CXCL13/biosíntesis , Quimiocina CXCL13/inmunología , Regulación hacia Abajo , Femenino , Citometría de Flujo , Humanos , Subtipo H5N1 del Virus de la Influenza A/patogenicidad , Gripe Humana/inmunología , Gripe Humana/patología , Gripe Humana/virología , Interleucina-17/deficiencia , Interleucina-17/genética , Pulmón/inmunología , Pulmón/patología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Infecciones por Orthomyxoviridae/mortalidad , Infecciones por Orthomyxoviridae/patología , Infecciones por Orthomyxoviridae/virología , Receptores CXCR5/biosíntesis , Receptores CXCR5/inmunología , Tasa de Supervivencia , Pérdida de PesoRESUMEN
BACKGROUND: Pregnant women infected by the pandemic influenza A (H1N1) 2009 virus had more severe disease and higher mortality but its pathogenesis is still unclear. PRINCIPAL FINDINGS: We showed that higher mortality, more severe pneumonitis, higher pulmonary viral load, lower peripheral blood T lymphocytes and antibody responses, higher levels of proinflammatory cytokines and chemokines, and worse fetal development occurred in pregnant mice than non-pregnant controls infected by either wild type (clinical isolate) or mouse-adapted mutant virus with D222G substitution in hemagglutinin. These disease-associated changes and the lower respiratory tract involvement were worse in pregnant mice challenged by mutant virus. Though human placental origin JEG-3 cell line could be infected and proinflammatory cytokines or chemokines were elevated in amniotic fluid of some mice, no placental or fetal involvement by virus were detected by culture, real-time reverse transcription polymerase chain reaction or histopathological changes. Dual immunofluorescent staining of viral nucleoprotein and type II alveolar cell marker SP-C protein suggested that the majority of infected alveolar epithelial cells were type II pneumocytes. CONCLUSION: The adverse effect of this pandemic virus on maternal and fetal outcome is largely related to the severe pulmonary disease and the indirect effect of inflammatory cytokine spillover into the systemic circulation.
Asunto(s)
Subtipo H1N1 del Virus de la Influenza A/aislamiento & purificación , Mutación , Infecciones por Orthomyxoviridae/fisiopatología , Animales , Anticuerpos Antivirales/biosíntesis , Quimiocinas/metabolismo , Citocinas/metabolismo , Ensayo de Inmunoadsorción Enzimática , Femenino , Subtipo H1N1 del Virus de la Influenza A/genética , Subtipo H1N1 del Virus de la Influenza A/fisiología , Pulmón/metabolismo , Ratones , Ratones Endogámicos BALB C , Infecciones por Orthomyxoviridae/inmunología , Infecciones por Orthomyxoviridae/mortalidad , Infecciones por Orthomyxoviridae/virología , Embarazo , Linfocitos T/inmunología , Carga Viral , Replicación ViralRESUMEN
Although the majority of infections by the pandemic influenza H1N1 (2009) virus is mild, a higher mortality occurs in young adults with no risk factors for complications. Some of these severe cases were infected by the virus with an aspartate to glycine substitution at 225 position (D225G, H3 numbering) in the hemagglutinin (HA). Previous studies with the highly virulent 1918 pandemic H1N1 virus suggested that such substitution was associated with a dual binding specificity of the virus for both alpha2,3- and alpha2,6-linked sialic acid receptors on host cells. Thus, the D225G mutant may cause more severe disease with its increased predilection for the lower respiratory tract, where the alpha2,3 sialic acid receptor is more prevalent, but this hypothesis has not been investigated. We obtained a mutant virus after four sequential passages in lungs of BALB/c mice with a wild-type pandemic influenza A H1N1 (2009) virus. One plaque purified mutant virus had a single non-synonymous D225G mutation in the HA gene. This mutant was more lethal to chick embryo and produced a viral load of about two log higher than that of the wild-type parental virus during the first 24 h. A pathogenicity test showed that the 50% lethal dose in mice (LD50) was reduced from over 2 x 10(6) plaque-forming units (PFU) with the parental virus to just 150 PFU with the mutant virus. The survival of mice challenged with the mutant virus was significantly decreased when compared with the parental virus (P < 0.0001). Significantly higher viral titers and elevated proinflammatory cytokines in lung homogenates of mice infected with the mutant virus were found, which were compatible with severe histopathological changes of pneumonitis. The only consistent mutation in the genomes of viral clones obtained from dying mice was D225G substitution.