Gene expression in epithelial cells in response to pneumovirus infection.
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Respiratory syncytial virus (RSV) and pneumonia virus of mice (PVM) are viruses of the family Paramyxoviridae, subfamily pneumovirus, which cause clinically important respiratory infections in humans and rodents, respectively. The respiratory epithelial target cells respond to viral infection with specific alterations in gene expression, including production of chemoattractant cytokines, adhesion molecules, elements that are related to the apoptosis response, and others that remain incompletely understood. Here we review our current understanding of these mucosal responses and discuss several genomic approaches, including differential display reverse transcription-polymerase chain reaction (PCR) and gene array strategies, that will permit us to unravel the nature of these responses in a more complete and systematic manner. (+info)
Eosinophils, eosinophil ribonucleases, and their role in host defense against respiratory virus pathogens.
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Eosinophils remain among the most enigmatic of cells, as our appreciation of their detrimental activities--e.g., asthma and allergic disease--far outweighs our understanding of their beneficial effects. Among the major secretory effector proteins of eosinophils are the ribonucleases eosinophil-derived neurotoxin (EDN) and eosinophil cationic protein (ECP) in primates and their orthologs, the eosinophil-associated ribonucleases (EARs) in rodents. The rapid diversification observed among these ribonucleases suggested that the ultimate target(s) might be similarly efficient at generating sequence diversity while maintaining an unalterable susceptibility to ribonucleolytic cleavage. This has prompted us to consider a role for these proteins and by extension, for eosinophils, in host defense against single-stranded RNA virus pathogens. We detail our studies of the antiviral activity of eosinophils and eosinophil ribonucleases against respiratory syncytial virus (RSV) in vitro and the related, natural rodent pathogen, pneumonia virus of mice (PVM), in vivo, and consider the possibility that antiviral host defense and the dysregulated responses leading to asthma represent opposing sides of an eosinophil-mediated double-edged sword. (+info)
Glucocorticoid administration accelerates mortality of pneumovirus-infected mice.
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The use of glucocorticoids for the treatment of symptoms associated with respiratory syncytial virus (RSV) infection has been questioned. To evaluate the sequelae of glucocorticoid administration in the setting of pneumovirus infection in vivo, hydrocortisone was administered to mice infected with pneumonia virus of mice (PVM), a pneumovirus and natural rodent pathogen that is closely related to RSV and replicates the signs and symptoms of severe human RSV infection. Results showed that hydrocortisone spared the pulmonary neutrophilia but resulted in ablation of the pulmonary eosinophilia, despite continued production of the relevant chemoattractant, macrophage inflammatory protein-1alpha. Hydrocortisone also led to diminished production of inducible nitric oxide synthase and accumulation of reactive nitrogen species in lung tissue and bronchoalveolar lavage fluid and diminished lymphocyte recruitment. PVM-infected mice responded to hydrocortisone with enhanced viral replication and accelerated mortality. These results suggest several mechanisms to explain why glucocorticoid therapy may be of limited benefit in the overall picture of pneumovirus infection. (+info)
Differential expression of proinflammatory cytokine genes in vivo in response to pathogenic and nonpathogenic pneumovirus infections.
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Pneumonia virus of mice (PVM; Paramyxoviridae, subfamily Pneumovirinae) is an important pathogen for the study of physiologically relevant acute inflammatory responses in rodent hosts. In contrast to the severe symptomatology observed in response to infection with PVM strain J3666, infection with strain 15 resulted in few clinical symptoms, limited cellular inflammatory response, and no production of macrophage inflammatory protein-1alpha or monocyte chemoattractant peptide (MCP)-1. Microarray analysis of transcripts from lung tissue indicates that PVM J3666 infection promotes up-regulation of specific proinflammatory genes, most notably interferon (IFN)-1beta, IFN response genes, and chemokines MCP-1, MCP-3, RANTES (regulated on activation, normally T cell-expressed and secreted), and eotaxin. Of these, only RANTES expression increased in response to infection with strain 15, with no increased expression of IFN or IFN response genes, despite ongoing viral replication. These results suggest that pneumovirus replication alone is insufficient to promote antiviral inflammation and that evaluation of the more divergent strain-specific pneumovirus proteins may provide some intriguing leads toward the molecular basis of this differential response. (+info)
Altered pathogenesis of severe pneumovirus infection in response to combined antiviral and specific immunomodulatory agents.
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We report here the responses of mice with symptomatic pneumovirus infection to combined antiviral and specific immunomodulatory agents. Mice infected with pneumonia virus of mice, a natural mouse pathogen that replicates the signs and symptoms of severe infection with respiratory syncytial virus (RSV), responded to the antiviral agent ribavirin when it was administered in the setting of endogenous (gene deletion) or exogenous (antibody-mediated) blockade of the MIP-1alpha proinflammatory signaling cascade. Although neither treatment is effective alone, together they offer a dramatic reduction in symptoms and pathology, the most impressive of which is a significant reduction in morbidity and mortality. The findings presented are consistent with the notion of unique and independent contributions of virus replication and ongoing inflammation to the pathogenesis of severe respiratory virus infection, and they provide the impetus for the study of this treatment regimen in RSV-infected humans. (+info)
Identification of amino acids that are critical to the processivity function of respiratory syncytial virus M2-1 protein.
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The M2-1 protein of respiratory syncytial virus (RSV) is a transcription processivity factor that is essential for virus replication. The function of RSV M2-1 protein can be examined by using an RSVlacZ minigenome assay in vitro since the expression of the lacZ gene is dependent on M2-1. The M2-1 protein of pneumonia virus of mice (PVM), also a member of the Pneumovirus genus, functions poorly in the RSVlacZ minigenome assay despite conservation of the Cys(3)-His(1) motif at its N terminus and an overall 40% amino acid identity with RSV M2-1. To identify the amino acids responsible for the differences between these two proteins, two chimeric proteins were constructed. The RSV/PVM (RP) M2-1 chimera that contains the N-terminal 30 amino acids from RSV and the remaining C-terminal 148 amino acids from PVM maintained a level of activity at an ca. 36% of RSV M2-1. However, the PVM/RSV (PR) M2-1 chimera with the N-terminal 29 amino acids from PVM and 164 amino acids from RSV had an activity of <5% of RSV M2-1, indicating that the functional determinants are mainly located in the N terminus of M2-1. Mutagenesis of the N terminus of PR M2-1 and RSV M2-1 identified that Leu-16 and Asn-17 of RSV M2-1 are critical to the M2-1 function. In addition, several charged residues in the N terminus of RSV M2-1 also contributed to the functional integrity of M2-1. (+info)
Chimeric pneumovirus nucleocapsid (N) proteins allow identification of amino acids essential for the function of the respiratory syncytial virus N protein.
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The nucleocapsid (N) protein of the pneumovirus respiratory syncytial virus (RSV) is a major structural protein which encapsidates the RNA genome and is essential for replication and transcription of the RSV genome. The N protein of the related virus pneumonia virus of mice (PVM) is functionally unable to replace the RSV N protein in a minigenome replication assay. Using chimeric proteins, in which the immediate C-terminal part of the RSV N protein was replaced with the equivalent region of the PVM N protein, it was shown that six amino acid residues near the C terminus of the N protein (between residues 352-369) are essential for its function in replication and for the ability of the N protein to bind to the viral phosphoprotein, P. (+info)
Reevaluation of the virulence of prototypic strain 15 of pneumonia virus of mice.
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Prototypic strain 15 of pneumonia virus of mice (PVM) has been described as being nonpathogenic in mice, in contrast to the mouse-passaged, highly virulent strain J3666. Previous sequence analysis also indicated that strain 15 encodes an attachment G protein that is truncated at the amino terminus, which for the amino terminally anchored protein deletes the cytoplasmic tail. However, we found that PVM strain 15 obtained from the American Type Culture Collection was highly virulent in mice and was essentially indistinguishable on that basis from strain J3666. Sequence analysis showed that this preparation of virus encodes a G protein with an intact cytoplasmic tail: the truncated predicted protein in the previous sequence appeared to be due to a single nucleotide insertion that disrupted the upstream end of the open reading frame and shifted the translational start site to the next downstream AUG. Taken together, the two studies indicate that strain 15 is an inherently virulent strain but that a nonpathogenic variant that was generated during passage in vitro and encodes a truncated G protein exists. Interestingly, the majority sequence of strain J3666 was found to encode a G protein with an extended cytoplasmic tail, suggesting that there is the potential for considerable plasticity in the cytoplasmic tail of the G protein of PVM. (+info)