Glucocorticoid administration accelerates mortality of pneumovirus-infected mice

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.

Epithelial cells infected with respiratory syncytial virus are resistant to the anti-inflammatory effects of hydrocortisone

In this work we continue our study of the biochemical responses of respiratory epithelial cells to infection with human paramyxovirus pathogens. In our earlier studies, we detected elevated concentrations of the proinflammatory chemokines MIP-1alpha and IL-8 in upper and lower respiratory tract secretions from patients infected with respiratory syncytial virus (RSV). Here we demonstrate the same trend for individuals infected with parainfluenza virus (PIV), with elevated concentrations of MIP-1alpha and IL-8 (means of 309 +/- 51 and 2280 +/- 440 pg/ml/mg protein, respectively) detected in nasal wash samples from 17 patients with culture-positive PIV. Similar to our findings with RSV, cells of the HEp-2 epithelial line and primary cultures of human bronchial epithelial cells respond to PIV infection with production and release of both MIP-1alpha and IL-8. Addition of the glucocorticoid anti-inflammatory agent hydrocortisone (200-1000 ng/ml) attenuated the production of MIP-1alpha and IL-8 in PIV-infected cells while having minimal to no effect on the production of these mediators from cells infected with RSV. Neither virus infection resulted in a change in the total cellular concentration of glucocorticoid receptors, nor did hydrocortisone exert any differential effect on viral replication. As repression of chemokine production by epithelial cells is likely to result in diminished recruitment of proinflammatory leukocytes, these results may explain in part why glucocorticoid therapy reduces the symptoms associated with acute PIV infection, but have little to no effect in the overall outcome in the case of RSV.

Gene expression in epithelial cells in response to pneumovirus infection

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.

MIP-1alpha is produced but it does not control pulmonary inflammation in response to respiratory syncytial virus infection in mice

The intent of this study was to compare the cellular and biochemical inflammatory responses of mice infected with the paramyxovirus pathogens respiratory syncytial virus (RSV) and pneumonia virus of mice (PVM). Although RSV is not a natural pathogen of mice, it has been used extensively in mouse models of the human disease, as a limited respiratory infection can be established via intranasal inoculation of virus at high titer. In earlier work, we found that acute infection with the natural rodent pathogen, PVM, elicited a rapid and sustained pulmonary inflammatory response (peak, 1.7 x 10(6) leukocytes/ml BAL fluid) that was dependent on both local production of MIP-1alpha and signaling via its receptor, CCR1. We find here that MIP-1alpha is also produced in response to RSV, although relatively few leukocytes (<200 ml BAL fluid) are recruited to the lungs in response. Further experiments with CCR1-deficient mice confirm the finding that although MIP-1alpha is produced in response to RSV infection, leukocytes do not respond via this pathway. Among the explanations for these findings, we propose that there are other, as yet to be identified proinflammatory mediators elicited in response to PVM (but not in response to RSV) that serve to prime the leukocytes in vivo, thus enabling them to respond to MIP-1alpha signaling via CCR1. Furthermore, the differences in disease pathogenesis seen in response to each of these pneumovirus infections in mice raise questions regarding the extent to which primary RSV infection in mice can be used as a model of primary RSV infection in humans.

Cytokeratin 17 is expressed in cells infected with respiratory syncytial virus via NF-kappaB activation and is associated with the formation of cytopathic syncytia

We used differential display to detect enhanced expression of an mRNA fragment encoding cytokeratin 17 (Ck-17) in respiratory syncytial virus (RSV)-infected epithelial cells. Expression increased 12-fold by 96 h after infection but remained unchanged in cells challenged with virus in the presence of neutralizing anti-RSV fusion protein antibody. Immunoblots of RSV-infected cell lysates probed with an anti-keratin antibody demonstrated stable expression of total cytokeratins over time. When probed with an anti-Ck-17 monoclonal antibody, Ck-17 was first detected at 4 days after infection. In situ staining demonstrated that Ck-17 expression localized to regions of syncytia formation. Expression of Ck-17 mRNA also increased in response to intracellular RSV-F protein in the absence of active RSV infection. No increase in Ck-17 mRNA expression and no syncytia were observed in RSV-infected cells grown in the presence of the NF-kappaB inhibitor gliotoxin. These results suggest that RSV-induced transcriptional activation of the Ck-17 gene is dependent on an NF-kappaB-associated signaling pathway.

The chemokine macrophage-inflammatory protein-1 alpha and its receptor CCR1 control pulmonary inflammation and antiviral host defense in paramyxovirus infection

In this work, we explore the responses of specific gene-deleted mice to infection with the paramyxovirus pneumonia virus of mice (PVM). We have shown previously that infection of wild type mice with PVM results in pulmonary neutrophilia and eosinophilia accompanied by local production of macrophage-inflammatory protein-1 alpha (MIP-1 alpha). Here we examine the role of MIP-1 alpha in the pathogenesis of this disease using mice deficient in MIP-1 alpha or its receptor, CCR1. The inflammatory response to PVM in MIP-1 alpha-deficient mice was minimal, with approximately 10-60 neutrophils/ml and no eosinophils detected in bronchoalveolar lavage fluid. Higher levels of infectious virus were recovered from lung tissue excised from MIP-1 alpha-deficient than from fully competent mice, suggesting that the inflammatory response limits the rate of virus replication in vivo. PVM infection of CCR1-deficient mice was also associated with attenuated inflammation, with enhanced recovery of infectious virus, and with accelerated mortality. These results suggest that the MIP-1 alpha/CCR1-mediated acute inflammatory response protects mice by delaying the lethal sequelae of infection.

Cytokeratin 17 is expressed in cells infected with respiratory syncytial virus via NF-kappaB activation and is associated with the formation of cytopathic syncytia

We used differential display to detect enhanced expression of an mRNA fragment encoding cytokeratin 17 (Ck-17) in respiratory syncytial virus (RSV)-infected epithelial cells. Expression increased 12-fold by 96 h after infection but remained unchanged in cells challenged with virus in the presence of neutralizing anti-RSV fusion protein antibody. Immunoblots of RSV-infected cell lysates probed with an anti-keratin antibody demonstrated stable expression of total cytokeratins over time. When probed with an anti-Ck-17 monoclonal antibody, Ck-17 was first detected at 4 days after infection. In situ staining demonstrated that Ck-17 expression localized to regions of syncytia formation. Expression of Ck-17 mRNA also increased in response to intracellular RSV-F protein in the absence of active RSV infection. No increase in Ck-17 mRNA expression and no syncytia were observed in RSV-infected cells grown in the presence of the NF-kappaB inhibitor gliotoxin. These results suggest that RSV-induced transcriptional activation of the Ck-17 gene is dependent on an NF-kappaB-associated signaling pathway.

Pulmonary eosinophilia and production of MIP-1alpha are prominent responses to infection with pneumonia virus of mice

Human eosinophils secrete two distinct ribonucleases that have antiviral activity against pathogens of the family Paramyxoviridae. To examine the role of eosinophils and their ribonucleases in host defense against paramyxovirus pathogens in vivo, we have developed a mouse model involving a viral pathogen that naturally targets a rodent host. In this work we describe infection of Balb/c mice with pneumonia virus of mice (PVM, strain J3666), a paramyxovirus pathogen found frequently among rodent populations. We show here that pulmonary eosinophilia is an immediate response to infection with PVM, with bronchoalveolar lavage fluid containing 12-14% eosinophils obtained as early as day 3 postinoculation. Infection is accompanied by the production of macrophage inflammatory protein-1-alpha (MIP-1alpha), a chemokine that has been associated with the pulmonary eosinophilia observed in response to respiratory syncytial virus infection in humans and with enhanced clearance of influenza virus in mice. Interestingly, we observed no changes in expression of the chemoattractants eotaxin and RANTES in response to PVM infection, and interleukin-5 remained undetectable throughout. These responses-clinical pathology, viral recovery, pulmonary eosinophilia, and production of MIP-1alpha-will provide a means for exploring the role of eosinophils, eosinophil secretory ribonucleases, and eosinophil chemoattractants in host defense against PVM and related paramyxovirus pathogens in vivo.

Respiratory syncytial virus infection induces expression of the anti-apoptosis gene IEX-1L in human respiratory epithelial cells

By means of differential display reverse-transcriptase polymerase chain reaction, increased expression of the mRNA encoding the anti-apoptosis gene IEX-1L was found in respiratory epithelial cells infected with respiratory syncytial virus (RSV). IEX-1L mRNA expression increased 5-7-fold in RSV-infected cells at 72 h after infection but remained unchanged in cells exposed to irradiated, replication-incompetent RSV. Because IEX-1L is reported to protect cells from apoptosis induced by tumor necrosis factor (TNF)-alpha, the effect of TNF-alpha on epithelial cell apoptosis in the context of RSV infection was determined. Epithelial cells were exposed to vehicle, RSV, or irradiated RSV for 72 h, and then TNF-alpha was added to appropriate cultures. Cytochemical staining of cellular DNA with 4,6-diamidino-2-phenylindole demonstrated TNF-alpha-induced apoptosis in 23.4% of control cells but only 5% of RSV-infected cells. These data show that RSV infection protects epithelial cells from TNF-alpha-induced apoptosis and that this effect is temporally associated with IEX-1L gene expression.

Rapid evolution of the ribonuclease A superfamily: adaptive expansion of independent gene clusters in rats and mice

The two eosinophil ribonucleases, eosinophil-derived neurotoxin (EDN/RNase 2) and eosinophil cationic protein (ECP/RNase 3), are among the most rapidly evolving coding sequences known among primates. The eight mouse genes identified as orthologs of EDN and ECP form a highly divergent, species-limited cluster. We present here the rat ribonuclease cluster, a group of eight distinct ribonuclease A superfamily genes that are more closely related to one another than they are to their murine counterparts. The existence of independent gene clusters suggests that numerous duplications and diversification events have occurred at these loci recently, sometime after the divergence of these two rodent species ( approximately 10-15 million years ago). Nonsynonymous substitutions per site (d(N)) calculated for the 64 mouse/rat gene pairs indicate that these ribonucleases are incorporating nonsilent mutations at accelerated rates, and comparisons of nonsynonymous to synonymous substitution (d(N) / d(S)) suggest that diversity in the mouse ribonuclease cluster is promoted by positive (Darwinian) selection. Although the pressures promoting similar but clearly independent styles of rapid diversification among these primate and rodent genes remain uncertain, our recent findings regarding the function of human EDN suggest a role for these ribonucleases in antiviral host defense.

Respiratory syncytical virus-induced chemokine expression in the lower airways: eosinophil recruitment and degranulation

Characterization of chemokine expression patterns in virus-infected epithelial cells provides important clues to the pathophysiology of such infections. The aim of this study was to determine the chemokine response pattern of respiratory epithelium when infected with respiratory syncytial virus (RSV). Macrophage inflammatory protein-1-alpha (MIP-1-alpha), interleukin-8 (IL-8), and RANTES concentrations were measured from RSV-infected HEp-2, MRC-5, and WI-38 cell culture supernatants daily following infection. Additionally, MIP-1-alpha, IL-8, and RANTES concentrations were measured from lower respiratory secretions obtained from 10 intubated infants (0-24 mo) with RSV bronchiolitis, and from 10 control subjects. Our results indicate that respiratory epithelial cells respond to RSV infection by producing MIP-1-alpha, IL-8, and RANTES. Production of MIP-1-alpha required ongoing viral replication, whereas RANTES and IL-8 could be elicited by inactivated forms of the virus. MIP-1-alpha, RANTES, and IL-8 were also present in lower airway secretions obtained from patients with RSV bronchiolitis. Eosinophil cationic protein (ECP) and eosinophil-derived neurotoxin (EDN), the eosinophil secretory ribonucleases, were detected in lower airway secretions from RSV-infected patients; ECP concentrations correlated with MIP-1-alpha concentrations (r = 0.93). We conclude that MIP-1-alpha is present in the lower airways during severe RSV disease. The correlation between MIP-1-alpha and ECP concentrations suggests a role for eosinophil degranulation products in the pathogenesis of RSV bronchiolitis.

Enteroviral meningoencephalitis as a complication of X-linked hyper IgM syndrome

We describe 5 children from 2 families with mutations in the CD40 ligand (CD40L) gene leading to absent expression of CD40L on activated CD4 cells. All subjects presented with interstitial pneumonia with low serum IgG and normal serum IgM. One child had normal and one child had elevated serum IgA. Four had confirmed Pneumocystis carinii pneumonia. In spite of intravenous immunoglobulin treatment yielding therapeutic serum immunoglobulin levels, 3 children had enteroviral encephalitis. When assessed by flow cytometry, the 3 surviving affected male children had absent CD40L expression on activated CD4(+) T cells. The affected children from both families were shown to have the same single nucleotide insertion (codon 131) resulting in frameshift and early termination within exon 4 (extracellular domain). This observation demonstrates that persistent enteroviral infection is not only observed in X-linked agammaglobulinemia but may also occur in patients with X-linked hyper IgM syndrome.

Macrophage inflammatory protein-1alpha and RANTES are present in nasal secretions during ongoing upper respiratory tract infection

Macrophage inflammatory protein-1alpha (MIP-1alpha) and RANTES (regulated upon activation, normal T-cell expressed and secreted) were measured by enzyme-linked immunosorbent assay (ELISA) from virus-infected respiratory cell culture supernatants and from 100 nasal wash samples obtained from patients aged 8 d to 10 yr. The results of the nasal wash samples were analyzed in relation to the etiology of the viral infection. In vitro, respiratory syncytial virus (RSV) induced the production of MIP-1alpha, while both RSV and adenovirus were associated with the production of RANTES. Both MIP-1alpha and RANTES were detected in nasopharyngeal secretions from pediatric patients with acute upper respiratory tract RSV, adenovirus, influenza, and parainfluenza virus infection (p<0.001 by Fisher's exact test). As both of these chemokines have potent effects on the recruitment and degranulation of eosinophils and basophils, further understanding of their role in upper respiratory tract infections may provide valuable insights into the immunopathogenesis of respiratory viral infections.

Evolution of antiviral activity in the ribonuclease A gene superfamily: evidence for a specific interaction between eosinophil-derived neurotoxin (EDN/RNase 2) and respiratory syncytial virus

We have demonstrated that the human eosinophil-derived neurotoxin (EDN, RNase 2), a rapidly evolving secretory protein derived from eosinophilic leukocytes, mediates the ribonucleolytic destruction of extracellular virions of the single-stranded RNA virus respiratory syncytial virus (RSV). While RNase activity is crucial to antiviral activity, it is clearly not sufficient, as our results suggest that EDN has unique structural features apart from RNase activity that are necessary to promote antiviral activity. We demonstrate here that the interaction between EDN and extracellular virions of RSV is both saturatable and specific. Increasing concentrations of the antivirally inactivated, ribonucleolytically inactivated point mutant form of recombinant human EDN, rhEDNdK38, inhibits rhEDN's antiviral activity, while increasing concentrations of the related RNase, recombinant human RNase k6, have no effect whatsoever. Interestingly, acquisition of antiviral activity parallels the evolutionary development of the primate EDN lineage, having emerged some time after the divergence of the Old World from the New World monkeys. Using this information, we created ribonucleolytically active chimeras of human and New World monkey orthologs of EDN and, by evaluating their antiviral activity, we have identified an N-terminal segment of human EDN that contains one or more of the sequence elements that mediate its specific interaction with RSV.

Recombinant human eosinophil-derived neurotoxin/RNase 2 functions as an effective antiviral agent against respiratory syncytial virus

A dose-dependent decrease in infectivity was observed on introduction of eosinophils into suspensions of respiratory syncytial virus group B (RSV-B). This antiviral effect was reversed by ribonuclease inhibitor, suggesting a role for the eosinophil secretory ribonucleases. Recombinant eosinophil-derived neurotoxin (rhEDN), the major eosinophil ribonuclease, promoted a dose-dependent decrease in RSV-B infectivity, with a 40-fold reduction observed in response to 50 nM rhEDN. Ribonucleolytically inactivated rhEDN (rhEDNdK38) had no antiviral activity. Semiquantitative reverse transcriptase-polymerase chain reaction demonstrated loss of viral genomic RNA in response to rhEDN, suggesting that this protein promotes the direct ribonucleolytic destruction of extracellular virions. Ribonuclease A had no antiviral activity even at approximately 1000-fold higher concentrations, suggesting that rhEDN has unique features other than ribonuclease activity that are crucial to its effectiveness. These results suggest that rhEDN may have potential as a therapeutic agent for prevention or treatment of disease caused by RSV.

Immunoblot analysis of anti-Ureaplasma urealyticum antibody in pregnant women and newborn infants

The purpose of the present study was to determine the frequency in which antibody reactive to Ureaplasma urealyticum could be detected in a population of pregnant women and newborn infants. Serum samples from a prospective cohort of 80 healthy, U. urealyticum culture-positive and culture-negative pregnant women and a retrospective cohort of 522 infants born at between 25 and 42 weeks of gestation were studied by immunoblot analysis. Cultures of specimens from the lower genital tract were positive for U. urealyticum for 83% of the pregnant women, and serum immunoglobulin G (IgG) antibody which reacted to U. urealyticum was detectable in 93% of the pregnant women. Samples from five women (8%) had increases in the number of anti-U. urealyticum IgG bands over the course of the pregnancy. Samples from four of these five women had corresponding increases in the number of antibody bands present in IgA immunoblots. Six of the 522 samples from newborns or cord blood (1.1%) were positive for anti-U. urealyticum IgA; 5 of these 6 samples were also positive for IgM. The six anti-U. urealyticum IgA-positive infants were distributed as follows; 3 of 67 (4.5%) infants were delivered at 25 to 30 weeks of gestation, 3 of 176 (1.7%) infants were delivered at 31 to 34 weeks of gestation, and 0 of 279 infants were delivered at > or = 35 weeks of gestation. An antibody response to U. urealyticum can be detected in pregnant women and preterm infants and may serve as a marker of infection.

Respiratory syncytial virus and influenza A infections in the hospitalized elderly

Respiratory syncytial virus (RSV) infections in the institutionalized elderly have been described; however, there is little information on the impact of RSV infection on community-dwelling elderly. The purpose of this study was to determine the relative numbers of hospitalizations associated with RSV infection and compare the clinical manifestations with influenza A infection. Between November and April during 1989-1992, persons > or = 65 years old hospitalized with acute cardiopulmonary conditions or influenza-like illnesses were evaluated. Evaluation included viral culture, RSV antigen detection, and serologic analysis; 159 (10%) of 1580 had RSV infection and 221 (11%) of 2091 had influenza A. RSV and influenza A cases occurred simultaneously throughout the 3 years. Clinical manifestations were similar; however, patients with RSV infection were more likely to receive therapy for bronchospasm. Death rates were 10% and 6% for RSV infection and influenza A, respectively. RSV infection is the cause of serious disease in community-dwelling older persons.

Communitywide laboratory-based influenza surveillance focused on older persons, 1989-1992

We collected surveillance data as part of the Medicare Influenza Vaccine Demonstration to describe communitywide epidemiology of influenza, focusing on the elderly. Laboratory-based surveillance was established in medical practices, hospitals, and nursing homes in a two-county demonstration in upstate New York. Time course and intensity of epidemic influenza were compared between counties, between influenza A and B epidemics, and among several levels of surveillance involving elderly persons as well as children during the years 1989-1992. The counties experienced parallel epidemics during each of the three demonstration years. Influenza A/H3N2, predominant in 1989-1990 and 1991-1992, was equally intense among young and old, accounted for 11%-28% of acute cardiopulmonary hospitalizations of older persons, and caused focal outbreaks in 30%-40% of nursing homes in the respective epidemics. Influenza B, predominant in 1990-1991, showed modest impact among the elderly as compared with children. Influenza A/H1N1 occurred among children each year but was virtually absent among the elderly. Systematic surveillance during the "influenza season" consistently confirms widespread infection among older patients, both in the community and in institutions. However, much febrile respiratory illness in this age group during periods of epidemic influenza is culture-negative for influenza virus and thus may be caused by other respiratory pathogens.

The effects of a promoter of cell differentiation and selected hormones on human cytomegalovirus infection using an in vitro cell system

The influence of factors that can regulate cellular developmental or metabolic processes in host tissue on cytomegalovirus (CMV) replication in vitro was determined. Hydrocortisone treatment of cells before viral infection resulted in a 12- to 13-fold increase in the expression of immediate early proteins at 4 h after virus inoculation. The addition of a phorbol diester 1.5 h after CMV infection resulted in an 8- to 13-fold increase in production of viral progeny. In contrast, beta-human chorionic gonadotropin treatment generally resulted in a 25%-72% suppression of both CMV-specific proteins and progeny. Effects on CMV infection with either progesterone or estradiol were minor and generally suppressive. The stimulating or suppressive effects of these factors on CMV replication in vitro may be important to CMV reactivation in humans. Further study of regulatory factors may lead to the development of therapeutic approaches to the prevention of CMV reactivation in patients at risk for severe disease.

Rapid detection of herpes simplex virus in MRC-5 cells using low-speed centrifugation enhancement and immunoperoxidase staining 16 h post-inoculation

The performance of MRC-5 shell vial centrifugation-enhancement and direct immunoperoxidase staining was compared to the traditional WI38 tube cell culture for the detection of Herpes simplex virus on 123 clinical samples. The shell vial technology not only proved to be sensitive (100%) and specific (100%), but could offer up to 20% reduction in cost when compared to routine methods. In addition, a commercially prepared MRC-5 shell vial product proved to be superior with respect to cost, sensitivity, and reliability when compared to an in-house preparation.