Respiratory syncytial virus M2-1 protein induces the activation of nuclear factor kappa B.

Respiratory syncytial virus (RSV) induces the production of a number of cytokines and chemokines by activation of nuclear factor kappa B (NF-kappaB). The activation of NF-kappaB has been shown to depend on viral replication in the infected cells. In this study, we demonstrate that expression of RSV M2-1 protein, a transcriptional processivity and anti-termination factor, is sufficient to activate NF-kappaB in A549 cells. Electromobility shift assays show increased NF-kappaB complexes in the nuclei of M2-1-expressing cells. M2-1 protein is found in nuclei of M2-1-expressing cells and in RSV-infected cells. Co-immunoprecipitations of nuclear extracts of M2-1-expressing cells and of RSV-infected cells revealed an association of M2-1 with Rel A protein. Furthermore, the activation of NF-kappaB depends on the C-terminus of the RSV M2-1 protein, as shown by NF-kappaB-induced gene expression of a reporter gene construct.

Respiratory syncytial virus deficient in soluble G protein induced an increased proinflammatory response in human lung epithelial cells.

Respiratory syncytial virus (RSV) is worldwide the single most important respiratory pathogen in infancy and early childhood. The G glycoprotein of RSV, named attachment protein, is produced by RSV-infected lung epithelial cells in both a membrane-anchored (mG protein) and a soluble form (sG protein) that is secreted by the epithelial cell. Currently, the biological role of the sG protein in primary RSV infection is still elusive. Therefore, we analyzed the inflammatory response of human lung epithelial cells (A549) infected either with wild-type RSV (RSV-WT) or a spontaneous mutant thereof deficient in the production of secreted G protein (RSV-DeltasG). Our data reveal that RSV-DeltasG, in comparison to RSV-WT, induced an increased cell surface expression of ICAM-1 on A549 cells and an enhanced release of the chemokines IL-8 and RANTES after 20 h postinfection. The increased protein expression pattern correlated with an enhanced mRNA level encoding for ICAM-1, IL-8, and RANTES, respectively. Furthermore, epithelial cells infected with RSV-DeltasG showed a more increased binding activity of the transcription factor NF-kappaB when compared to RSV-WT. In contrast, the mutant RSV-DeltasG replicated less efficiently in A549 cells than RSV-WT. Our data suggest that RSV, in the course of an ongoing infection, reduces by the production of sG protein the detrimental inflammatory response evolved by the infected resident lung epithelial cell and thereby supports its own replication.

Respiratory syncytial virus: G gene genotype and disease severity.

BACKGROUND: In a hospital-based study by Martinello (2002), specific G gene genotypes of respiratory syncytial virus subgroup A virus were associated with an increased severity of illness. AIM: We sought to confirm the association of G genotypes with disease severity in a population-based study. MATERIAL AND METHODS: Ninety-one type A respiratory syncytial viruses (identified in the 1999/2000 season by polymerase chain reaction and cell culture), collected in a German multicenter study (PRI.DE) were analyzed for G gene diversity (amino acids 1-165). Disease severity was classified according to World Health Organization criteria for pneumonia in outpatients and by a bronchiolitis score (Rodriguez, 1997) in inpatients. Multiple regression analysis was used to explain disease severity. RESULTS: Three clusters were identified (cluster 1, n = 35; cluster 2,n = 35; cluster 3, n = 21). Sixty-seven patients had severe disease. After controlling for other variables, illness severity was significantly greater for cluster 2 viruses (odds ratio, 7.0; 95% confidence interval, 1.6 49), compared with viruses in other clusters. Other known risk factors (male gender, age) were not associated with disease severity. Our cluster 2 is genetically distinct from the virulent genotype in Martinello's study. DISCUSSION: Previously reported associations between G genotypes and disease severity in hospitalized patients can be generalized across the spectrum of illnesses including outpatients. The association seems not to be linked to a specific G gene structure. Rather G gene diversity in combination with the susceptibility of the host cohort may form the basis of such associations. Because of the magnitude of the effect, the underlying mechanisms warrant further investigation.

Prospective population-based study of viral lower respiratory tract infections in children under 3 years of age (the PRI.DE study).

UNLABELLED: Population-based incidence data from Europe on the disease burden of lower respiratory tract infections (LRTI) due to respiratory syncytial viruses (RSV), parainfluenza viruses (PIV) and influenzaviruses (IV) are lacking, especially with respect to the disease burden. In a 2-year prospective multicentre study of children aged <3 years in Germany, we registered population-based cases as outpatients (n=2386), inpatients (n=2924), and nosocomially-acquired (n=141). Nasopharyngeal secretions were tested for viral RNA. The annual incidence for physician visits per 100 children for all LRTI was 28.7, RSV 7.7, PIV 3.8 and IV 1.1. Annual hospitalisation rates per 10(5) children were for all LRTI 2941, RSV 1117, PIV 261 and IV 123. Annual nosocomial cases per 10(5) hospital days were for all LRTI 79, RSV 29, PIV 9 and IV 1.5. All five children (0.27%) who died had an underlying disease and four were nosocomially acquired. CONCLUSION: Hospitalisation rates due to lower respiratory tract infections in healthy children were similar to those reported elsewhere; the rates for outpatient visits were approximately ten times higher.