Clinical features of parainfluenza infections among young children hospitalized for acute respiratory illness in Amman, Jordan.

BACKGROUND: Parainfluenza virus (PIV) is a leading cause of acute respiratory illness (ARI) in children. However, few studies have characterized the clinical features and outcomes associated with PIV infections among young children in the Middle East. METHODS: We conducted hospital-based surveillance for ARI among children < 2 years of age in a large referral hospital in Amman, Jordan. We systematically collected clinical data and respiratory specimens for pathogen detection using reverse transcription polymerase chain reaction. We compared clinical features of PIV-associated ARI among individual serotypes 1, 2, 3, and 4 and among PIV infections compared with other viral ARI and ARI with no virus detected. We also compared the odds of supplemental oxygen use using logistic regression. RESULTS: PIV was detected in 221/3168 (7.0%) children hospitalized with ARI. PIV-3 was the most commonly detected serotype (125/221; 57%). Individual clinical features of PIV infections varied little by individual serotype, although admission diagnosis of 'croup' was only associated with PIV-1 and PIV-2. Children with PIV-associated ARI had lower frequency of cough (71% vs 83%; p < 0.001) and wheezing (53% vs 60% p < 0.001) than children with ARI associated with other viruses. We did not find a significant difference in supplemental oxygen use between children with PIV-associated infections (adjusted odds ratio [aOR] 1.12, 95% CI 0.66-1.89, p = 0.68) and infections in which no virus was detected. CONCLUSIONS: PIV is frequently associated with ARI requiring hospitalization in young Jordanian children. Substantial overlap in clinical features may preclude distinguishing PIV infections from other viral infections at presentation.

Sendai Virus Induces Persistent Olfactory Dysfunction in a Murine Model of PVOD via Effects on Apoptosis, Cell Proliferation, and Response to Odorants.

BACKGROUND: Viral infection is a common cause of olfactory dysfunction. The complexities of studying post-viral olfactory loss in humans have impaired further progress in understanding the underlying mechanism. Recently, evidence from clinical studies has implicated Parainfluenza virus 3 as a causal agent. An animal model of post viral olfactory disorders (PVOD) would allow better understanding of disease pathogenesis and represent a major advance in the field. OBJECTIVE: To develop a mouse model of PVOD by evaluating the effects of Sendai virus (SeV), the murine counterpart of Parainfluenza virus, on olfactory function and regenerative ability of the olfactory epithelium. METHODS: C57BL/6 mice (6-8 months old) were inoculated intranasally with SeV or ultraviolet (UV)-inactivated virus (UV-SeV). On days 3, 10, 15, 30 and 60 post-infection, olfactory epithelium was harvested and analyzed by histopathology and immunohistochemical detection of S-phase nuclei. We also measured apoptosis by TUNEL assay and viral load by real-time PCR. The buried food test (BFT) was used to measure olfactory function of mice at day 60. In parallel, cultured murine olfactory sensory neurons (OSNs) infected with SeV or UV-SeV were tested for odorant-mixture response by measuring changes in intracellular calcium concentrations indicated by fura-4 AM assay. RESULTS: Mice infected with SeV suffered from olfactory dysfunction, peaking on day 15, with no loss observed with UV-SeV. At 60 days, four out of 12 mice infected with SeV still had not recovered, with continued normal function in controls. Viral copies of SeV persisted in both the olfactory epithelium (OE) and the olfactory bulb (OB) for at least 60 days. At day 10 and after, both unit length labeling index (ULLI) of apoptosis and ULLI of proliferation in the SeV group was markedly less than the UV-SeV group. In primary cultured OSNs infected by SeV, the percentage of cells responding to mixed odors was markedly lower in the SeV group compared to UV-SeV (P = 0.007). CONCLUSION: We demonstrate that SeV impairs olfaction, persists in OE and OB tissue, reduces their regenerative ability, and impairs the normal physiological function of OSNs without gross cytopathology. This mouse model shares key features of human post-viral olfactory loss, supporting its future use in studies of PVOD. Further testing and development of this model should allow us to clarify the pathophysiology of PVOD.

ORMDL3 variants associated with bronchiolitis susceptibility in a Chinese population.

Recent studies revealed common genetic risks for both viral bronchiolitis and asthma. Genome-wide association studies revealed that rs7216389 in the ORMDL3 gene is associated with childhood asthma. We conducted a case-control study examining the associations between ORMDL3 polymorphisms (rs7216389, rs12603332, and rs11650680) and bronchiolitis susceptibility/viral findings among 247 infant bronchiolitis cases and 190 healthy controls. We genotyped single nucleotide polymorphisms by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry and detected respiratory viruses with multiplex reverse transcriptase-polymerase chain reaction. Only the genotype and allele frequencies of rs7216389 significantly differed between bronchiolitis and controls. The frequencies of the TT homozygote and the T allele of rs7216389 were significantly higher in the bronchiolitis patients (P = 0.0325; P = 0.0089, respectively). Polymorphisms were not associated with bronchiolitis severity. Cases were further stratified by viral infection, but no significant differences in the ORMDL3 genotype between the virus-detected group (e.g., respiratory syncytial virus alone, respiratory virus alone, virus detected) and no-virus-detected group were observed. Bronchiolitis is associated with the ORMDL3 gene in Chinese children, and there were no significant associations between genetic variations and disease severity or respiratory viruses. The TT homozygote and the T allele of rs7216389 in ORMDL3 increased bronchiolitis risk. The rs7216389 polymorphism may be a predictor for identifying infants with predisposition to virus-induced wheezing to persistent asthma.

Comparison of temporal transcriptomic profiles from immature lungs of two rat strains reveals a viral response signature associated with chronic lung dysfunction.

Early life respiratory viral infections and atopic characteristics are significant risk factors for the development of childhood asthma. It is hypothesized that repeated respiratory viral infections might induce structural remodeling by interfering with the normal process of lung maturation; however, the specific molecular processes that underlie these pathological changes are not understood. To investigate the molecular basis for these changes, we used an established Sendai virus infection model in weanling rats to compare the post-infection transcriptomes of an atopic asthma susceptible strain, Brown Norway, and a non-atopic asthma resistant strain, Fischer 344. Specific to this weanling infection model and not described in adult infection models, Sendai virus in the susceptible, but not the resistant strain, results in morphological abnormalities in distal airways that persist into adulthood. Gene expression data from infected and control lungs across five time points indicated that specific features of the immune response following viral infection were heightened and prolonged in lungs from Brown Norway rats compared with Fischer 344 rats. These features included an increase in macrophage cell number and related gene expression, which then transitioned to an increase in mast cell number and related gene expression. In contrast, infected Fischer F344 lungs exhibited more efficient restoration of the airway epithelial morphology, with transient appearance of basal cell pods near distal airways. Together, these findings indicate that the pronounced macrophage and mast cell responses and abnormal re-epithelialization precede the structural defects that developed and persisted in Brown Norway, but not Fischer 344 lungs.

The p value of HPIV3-mediated autophagy inhibition.

Autophagy, a vesicular pathway involving the lysosomal degradation of cytosolic contents, is frequently hijacked by intracellular pathogens to optimize their infectivity. In this issue of Cell Host & Microbe, Ding et al. (2014) show that human parainfluenza virus exploits autophagy by targeting SNAREs and preventing the SNAP29-Stx17 interaction, an otherwise crucial event in autophagosome-lysosome fusion.

Phosphoprotein of human parainfluenza virus type 3 blocks autophagosome-lysosome fusion to increase virus production.

Autophagy is a multistep process in which cytoplasmic components, including invading pathogens, are captured by autophagosomes that subsequently fuse with degradative lysosomes. Negative-strand RNA viruses, including paramyxoviruses, have been shown to alter autophagy, but the molecular mechanisms remain largely unknown. We demonstrate that human parainfluenza virus type 3 (HPIV3) induces incomplete autophagy by blocking autophagosome-lysosome fusion, resulting in increased virus production. The viral phosphoprotein (P) is necessary and sufficient to inhibition autophagosome degradation. P binds to SNAP29 and inhibits its interaction with syntaxin17, thereby preventing these two host SNARE proteins from mediating autophagosome-lysome fusion. Incomplete autophagy and resultant autophagosome accumulation increase extracellular viral production but do not affect viral protein synthesis. These findings highlight how viruses can block autophagosome degradation by disrupting the function of SNARE proteins.

Toll-like receptor-2/6 and Toll-like receptor-9 agonists suppress viral replication but not airway hyperreactivity in guinea pigs.

Respiratory virus infections cause airway hyperreactivity (AHR). Preventative strategies for virus-induced AHR remain limited. Toll-like receptors (TLRs) have been suggested as a therapeutic target because of their central role in triggering antiviral immune responses. Previous studies showed that concurrent treatment with TLR2/6 and TLR9 agonists reduced lethality and the microbial burden in murine models of bacterial and viral pneumonia. This study investigated the effects of TLR2/6 and TLR9 agonist pretreatment on parainfluenza virus pneumonia and virus-induced AHR in guinea pigs in vivo. Synthetic TLR2/6 lipopeptide agonist Pam2CSK4 and Class C oligodeoxynucleotide TLR9 agonist ODN2395, administered in combination 24 hours before virus infection, significantly reduced viral replication in the lung. Despite a fivefold reduction in viral titers, concurrent TLR2/6 and TLR9 agonist pretreatment did not prevent virus-induced AHR or virus-induced inhibitory M2 muscarinic receptor dysfunction. Interestingly, the TLR agonists independently caused non-M2-dependent AHR. These data confirm the therapeutic antiviral potential of TLR agonists, while suggesting that virus inhibition may be insufficient to prevent virus-induced airway pathophysiology. Furthermore, TLR agonists independently cause AHR, albeit through a distinctly different mechanism from that of parainfluenza virus.

[Study of the susceptibility of mice to Sendai strain Tianjin].

To explore the infectivity characteristics and susceptibility of Sendai strain Tianjin in 129Sv, DBA/2, Kunming and BALB/c mice and determine the optimal small rodent animal model for strain Tianjin research, the Sendai strain Tianjin was propagated for 72h in 9-11 day-old chicken embryos, the allantoic fluids were then harvested and the virus titer (1:1280) was detected by hemagglutination assay. Four different kinds of mice were intranasally inoculated with 5 microl and the diluted 30 microl virus solution. The weight loss of mice was monitored for 12 consecutive days and the survival rate was observed. Kunming and BALB/c mice were sacrificed on the first day prior to infection and on the fourth and seventh days post infection of the diluted 30 microl Sendai strain Tianjin. Their left lobes of lung were fixed with 4% formalin for histopathologic examination. The maximum percentage of average weight loss of 129Sv, DBA/2 were 13.0%, 4.7% with 100% survival rate when 129Sv, DBA/2, Kunming and BALB/c were inoculated with 5 microl virus solution, while the mice were inoculated with diluted 30 microl virus solution, the maximum percentage of average weight loss reached 21.7%, 30.3%, 16.7% and 9.7% with the survival rate of 20%, 0%, 80% and 100%. Lung infections of mice Kunming on the fourth and seventh day post infection were more severe than that of BALB/c, showing a large number of inflammatory cell exudation and thickening of the submucosa. It suggested that DBA/2 was the most susceptible to the infection of strain Tianjin. The mice susceptibility ranked as DBA/2>129Sv>Kunming>BALB/c. Mice DBA/2 and 129Sv could be used as the optimal small rodent animal models in the research of pathogenicity and vaccine of Sendai strain Tianjin.

IκB kinase ε-dependent phosphorylation and degradation of X-linked inhibitor of apoptosis sensitizes cells to virus-induced apoptosis.

X-linked inhibitor of apoptosis (XIAP) is a potent antagonist of caspase 3-, 7-, and 9-dependent apoptotic activities that functions as an E3 ubiquitin ligase, and it targets caspases for degradation. In this study, we demonstrate that Sendai virus (SeV) infection results in the IKKε- or TBK1-mediated phosphorylation of XIAP in vivo at Ser430, resulting in Lys(48)-linked autoubiquitination at Lys322/328 residues, followed by the subsequent proteasomal degradation of XIAP. Interestingly, IKKε expression and XIAP turnover increases SeV-triggered mitochondrion-dependent apoptosis via the release of caspase 3, whereas TBK1 expression does not increase apoptosis. Interestingly, phosphorylation also regulates XIAP interaction with the transcription factor IRF3, suggesting a role in IRF3-Bax-mediated apoptosis. Our findings reveal a novel function of IKKε as a regulator of the virus-induced triggering of apoptosis via the phosphorylation-dependent turnover of XIAP.

Reduced inflammation and altered innate response in neonates during paramyxoviral infection.

BACKGROUND: Human infants are frequently hospitalized due to infection with the paramyxovirus respiratory syncytial virus (RSV). However, very little is known about the neonatal response to paramyxoviral infection. Here, a neonatal model of paramyxoviral infection is developed using the mouse pathogen Sendai virus (SeV). RESULTS: Adult mice infected with SeV developed a predominantly neutrophilic inflammatory cell influx and a concomitant reduction in lung function, as determined by oxygen saturation. In contrast, neonates with SeV had significantly reduced inflammation and normal lung function. Surprisingly, infected neonates had similar viral loads as adult mice. A reduced neutrophil influx in the neonates may be due in part to reduced expression of both CXCL2 and intracellular adhesion molecule-1 (ICAM-1). Expression of IFN-γ and TNF-α increased in a dose-dependent manner in adult lungs, but neonates did not increase expression of either of these cytokines, even at the highest doses. Importantly, the expression of the RIG-I-like receptors (RLRs) was delayed in the neonatal mice, which might have contributed to their reduced inflammation and differential cytokine expression. CONCLUSIONS: Neonatal mice developed similar SeV titers and cleared the virus with similar efficiency despite developing a dramatically lower degree of pulmonary inflammation compared to adults. This suggests that inflammation in the lung may not be required to control viral replication. Future studies will be needed to determine any effect the reduced inflammation may have on the development of a protective memory response in neonates.

Cough reflex sensitivity is increased in guinea pigs with parainfluenza virus infection.

The purpose of this study was to investigate for the change in cough reflex sensitivity (CRS) caused by parainfluenza virus type 3 (PIV3) infection. Guinea pigs were randomized into a vehicle control, an asthma control, or 1 of 4 PIV3-inoculated groups (referred to as postinfection day [PID] 6, 12, 28, and 42 groups). Evidence of viral protein and nucleic acid within the lung confirmed successful PIV3 infection. Plethysmography was used to assess CRS and airway reaction and airway inflammation was assessed via bronchoalveolar lavage fluid cytology and lung histopathology. Compared with the vehicle control group, CRS was significantly increased in all PID groups (P <.05) in concert with an obvious airway hyperresponsiveness in the PID 6 group. Though a small increase in CRS in the asthma control group was noted, it was not significant compared to the vehicle control group. Total cell counts from the bronchoalveolar lavage fluid of all PIV3-inoculated groups increased markedly and the number of lymphocytes was significantly increased in the PID 6 and PID 12 groups. The lung pathology of PIV3-inoculated animals showed airway inflammation without pneumonia in the acute infectious phase. The temporal and spatial variation of CRS may be the essential mechanism of cough caused by PIV3.

Bradykinin-induced lung inflammation and bronchoconstriction: role in parainfluenze-3 virus-induced inflammation and airway hyperreactivity.

Inhaled bradykinin causes bronchoconstriction in asthmatic subjects but not nonasthmatics. To date, animal studies with inhaled bradykinin have been performed only in anesthetized guinea pigs and rats, where it causes bronchoconstriction through sensory nerve pathways. In the present study, airway function was recorded in conscious guinea pigs by whole-body plethysmography. Inhaled bradykinin (1 mM, 20 s) caused bronchoconstriction and influx of inflammatory cells to the lungs, but only when the enzymatic breakdown of bradykinin by angiotensin-converting enzyme and neutral endopeptidase was inhibited by captopril (1 mg/kg i.p.) and phosphoramidon (10 mM, 20-min inhalation), respectively. The bronchoconstriction and cell influx were antagonized by the B(2) kinin receptor antagonist 4-(S)-amino-5-(4-{4-[2,4-dichloro-3-(2,4-dimethyl-8-quinolyloxymethyl)phenylsulfonamido]-tetrahydro-2H-4-pyranylcarbonyl}piperazino)-5-oxopentyl](trimethyl)ammonium chloride hydrochloride (MEN16132) when given by inhalation (1 and 10 µM, 20 min) and are therefore mediated via B(2) kinin receptors. However, neither intraperitioneal MEN16132 nor the peptide B(2) antagonist icatibant, by inhalation, antagonized these bradykinin responses. Sensitization of guinea pigs with ovalbumin was not sufficient to induce airway hyperreactivity (AHR) to the bronchoconstriction by inhaled bradykinin. However, ovalbumin challenge of sensitized guinea pigs caused AHR to bradykinin and histamine. Infection of guinea pigs by nasal instillation of parainfluenza-3 virus produced AHR to inhaled histamine and lung influx of inflammatory cells. These responses were attenuated by the bradykinin B(2) receptor antagonist MEN16132 and H-(4-chloro)DPhe-2'(1-naphthylalanine)-(3-aminopropyl)guanidine (VA999024), an inhibitor of tissue kallikrein, the enzyme responsible for lung synthesis of bradykinin. These results suggest that bradykinin is involved in virus-induced inflammatory cell influx and AHR.

Residues in the heptad repeat a region of the fusion protein modulate the virulence of Sendai virus in mice.

While the molecular basis of fusion (F) protein refolding during membrane fusion has been studied extensively in vitro, little is known about the biological significance of membrane fusion activity in parainfluenza virus replication and pathogenesis in vivo. Two recombinant Sendai viruses, F-L179V and F-K180Q, were generated that contain F protein mutations in the heptad repeat A region of the ectodomain, a region of the protein known to regulate F protein activation. In vitro, the F-L179V virus caused increased syncytium formation (cell-cell membrane fusion) yet had a rate of replication and levels of F protein expression and cleavage similar to wild-type virus. The F-K180Q virus had a reduced replication rate along with reduced levels of F protein expression, cleavage, and fusogenicity. In DBA/2 mice, the hyperfusogenic F-L179V virus induced greater morbidity and mortality than wild-type virus, while the attenuated F-K180Q virus was much less pathogenic. During the first week of infection, virus replication and inflammation in the lungs were similar for wild-type and F-L179V viruses. After approximately 1 week of infection, the clearance of F-L179V virus was delayed, and more extensive interstitial inflammation and necrosis were observed in the lungs, affecting entire lobes of the lungs and having significantly greater numbers of syncytial cell masses in alveolar spaces on day 10. On the other hand, the slower-growing F-K180Q virus caused much less extensive inflammation than wild-type virus, presumably due to its reduced replication rate, and did not cause observable syncytium formation in the lungs. Overall, the results show that residues in the heptad repeat A region of the F protein modulate the virulence of Sendai virus in mice by influencing both the spread and clearance of the virus and the extent and severity of inflammation. An understanding of how the F protein contributes to infection and inflammation in vivo may assist in the development of antiviral therapies against respiratory paramyxoviruses.

Persistent activation of an innate immune response translates respiratory viral infection into chronic lung disease.

To understand the pathogenesis of chronic inflammatory disease, we analyzed an experimental mouse model of chronic lung disease with pathology that resembles asthma and chronic obstructive pulmonary disease (COPD) in humans. In this model, chronic lung disease develops after an infection with a common type of respiratory virus is cleared to only trace levels of noninfectious virus. Chronic inflammatory disease is generally thought to depend on an altered adaptive immune response. However, here we find that this type of disease arises independently of an adaptive immune response and is driven instead by interleukin-13 produced by macrophages that have been stimulated by CD1d-dependent T cell receptor-invariant natural killer T (NKT) cells. This innate immune axis is also activated in the lungs of humans with chronic airway disease due to asthma or COPD. These findings provide new insight into the pathogenesis of chronic inflammatory disease with the discovery that the transition from respiratory viral infection into chronic lung disease requires persistent activation of a previously undescribed NKT cell-macrophage innate immune axis.

Parainfluenza type 3 outbreaks in Izmir children, Turkey.

The present study was aimed to investigate characteristics of lower respiratory tract infections caused by parainfluenza type 3 viruses. Nasopharyngeal smears were taken from 178 patients with lower respiratory infections for the diagnosis of respiratory syncytial virus, adenovirus, influenza and parainfluenza viruses between December 2004 and April 2005. Parainfluenza type 3 was isolated from the viral specimens of 96 (53.9%) patients and it was noticeable that the parainfluenza type 3 outbreak occurs during winter. Obviously, improving the aetiological diagnosis of viral infections might avoid unnecessary therapy, antibiotics in particular, and would allow for preventive isolation of infected patients.

Sendai virus budding in the course of an infection does not require Alix and VPS4A host factors.

Closing the Sendai virus C protein open reading frames (rSeV-DeltaC virus) results in the production of virus particles with highly reduced infectivity. Besides, the Sendai virus C proteins interact with Alix/AIP1 and Alix suppression negatively affects Sendai virus like particle (VLP) budding. Similarly, the Sendai virus M protein has been shown to interact with Alix. On this basis, it has been suggested that Sendai virus budding involves recruitment of the multivesicular body formation machinery. We follow, here, the production of SeV particles upon regular virus infection. We find that neither Alix suppression nor dominant negative-VPS4A expression, applied separately or in combination, affects physical or infectious virion production. This contrasts with the observed decrease of SV5 virion production upon dominant negative-VPS4A expression. Finally, we show that suppression of more than 70% of a GFP/C protein in the background of a rSeV-DeltaC virus infection has no effect either on SeV particle production or on virus particle infectivity. Our results contrast with what has been published before. Possible explanations for this discrepancy are discussed.

Altered allergen-induced eosinophil trafficking and physiological dysfunction in airways with preexisting virus-induced injury.

Although both asthmatics and allergic rhinitics develop an acute inflammatory response to lower airway allergen challenge, only asthmatics experience airway obstruction resulting from chronic environmental allergen exposure. Hypothesizing that asthmatic airways have an altered response to chronic allergic inflammation, we compared the effects of repeated low-level exposures to inhaled Alternaria extract in sensitized rats with preexisting chronic postbronchiolitis airway dysfunction versus sensitized controls with normal airways. Measurements of air space (bronchoalveolar lavage) inflammatory cells, airway goblet cells, airway wall collagen, airway wall eosinophils, airway alveolar attachments, and pulmonary physiology were conducted after six weekly exposures to aerosolized saline or Alternaria extract. Postbronchiolitis rats, but not those starting with normal airways, had persistent increases in airway wall eosinophils, goblet cell hyperplasia in small airways, and loss of lung elastic recoil after repeated exposure to aerosolized Alternaria extract. Despite having elevated airway wall eosinophils, the postbronchiolitis rats had no eosinophils in bronchoalveolar lavage at 5 days after the last allergen exposure, suggesting altered egression of tissue eosinophils into the air space. In conclusion, rats with preexisting airway pathology had altered eosinophil trafficking and allergen-induced changes in airway epithelium and lung mechanics that were absent in sensitized control rats that had normal airways before the allergen exposures.

T cell memory in the lung airways.

The respiratory tract poses a substantial challenge to the immune system due to its large surface area, an extensive vasculature that is in very close proximity to the external environment, and repeated exposure to potentially pathogenic organisms in the air. Yet many lung pathogens are controlled by appropriate immune responses. The underlying mechanisms of the adaptive cellular immune response in protecting the respiratory tract are poorly understood. Recently, it has emerged that memory CD4(+) and CD8(+) T cells are present in the lung airways, and evidence is mounting that these cells play a key role in pulmonary immunity to pathogen challenge by immediately engaging the pathogen at the site of infection when pathogen loads are low. For example, in the case of respiratory virus infections, there is evidence that both CD4(+) and CD8(+) memory cells in the lung airways mediate substantial control of a secondary respiratory virus infection in the lungs. Here we address recent developments in our understanding of lung airway memory T cells and their role in infectious disease.

Sendai virus-induced alterations in lung structure/function correlate with viral loads and reveal a wide resistance/susceptibility spectrum among mouse strains.

The Paramyxoviridae family includes some of the most important and ubiquitous disease-causing viruses of infants and children, most of which cause significant infections of the respiratory tract. Evidence is accumulating in humans that genetic factors are involved in the severity of clinical presentation. As a first step toward the identification of the genes involved, this study was undertaken to establish whether laboratory mouse strains differ in susceptibility to Sendai virus, the murine counterpart of human type-1 parainfluenza virus which, historically, has been used extensively in studies that have defined the basic biological properties of paramyxoviruses in general. With this purpose in mind, double-chamber plethysmography data were collected daily for 7 days after inoculation of Sendai virus in six inbred strains of mice. In parallel, histological examinations and lung viral titration were carried out from day 5 to day 7 after inoculation. Pulmonary structure/function values closely reflected the success of viral replication in the lungs and revealed a pattern of continuous variation with resistant, intermediate, and susceptible strains. The results unambiguously suggest that BALB/c (resistant) and 129Sv (susceptible) strains should be used in crossing experiments aimed at identifying the genes involved in resistance to Paramyxoviridae by the positional cloning approach.

Airway function and reactivity, leukocyte influx and nitric oxide after inoculation with parainfluenza-3 virus: effects of dexamethasone or rolipram.

Guinea-pigs were inoculated with parainfluenza type 3 (PI3) virus (5.2 x 10(7)) or medium (125 microl each nostril). The PDE4-inhibitor, rolipram (1 mg kg(-1)), the corticosteroid, dexamethasone (20 mg kg(-1)), or vehicle were administered (i.p.) 24 h and 0.5 h before inoculation and for 4 days thereafter. Respiratory function, recorded in conscious guinea-pigs as specific airways conductance (sGaw) by whole-body plethysmography, was unaffected over 4 days by inoculation with medium or PI3. Inhaled histamine (nose-only, 1 mM, 20 s) 24 h before inoculation produced no response but 4 days after PI3 inoculation, a significant (P<0.001) bronchoconstriction occurred, indicating airway hyperreactivity (AHR). Dexamethasone or rolipram treatment inhibited the AHR. Four days after PI3- or medium-inoculation, animals underwent bronchoalveolar lavage (BAL) for total and differential (macrophages, eosinophils and neutrophils) cell counts and determination of nitric oxide (NO) as nitrite and nitrate. Compared with medium-inoculated animals, BAL fluid removed 4 days after PI3 inoculation had significantly increased macrophages, eosinophils and neutrophils. Dexamethasone or rolipram significantly (P<0.05) reduced the PI3-induced airways influx of macrophages (by 40% and 47%), eosinophils (79% and 84%) and neutrophils (58% and 61%). PI3-inoculation significantly (P<0.05) increased BALF combined NO metabolites (84.8+/-2.2 microM 100 microl(-1)), compared with medium-inoculated (56.0+/-5.8) or naive animals (45.7+/-2.0). Treating the PI3-infected guinea-pigs with dexamethasone or rolipram significantly (P<0.001) reduced the raised NO metabolites by 34% and 37%, respectively. These results support a role for steroids and PDE4-inhibitors in the management of inflammation and airways hyperreactivity arising from viral infection of the airways.