The Canadian healthy infant longitudinal development birth cohort study: biological samples and biobanking

BACKGROUND

It is hypothesised that complex interactions between genetic and environmental factors give rise to allergy and asthma in childhood. The Canadian Healthy Infant Longitudinal Development (CHILD) study was designed to explore these factors.

METHODS

CHILD is a longitudinal, general population birth cohort study following infants from mid-pregnancy to age 5 years. Over this time period, biological samples, questionnaires, clinical measures and environmental data are collected.

RESULTS

A total of 3624 families have been recruited, and many thousands of samples and questionnaires have been collected, annotated, and archived. This report outlines the rationale and methodology for collecting and storing diverse biological samples from parents and children in this study, and the mechanisms for their release for analyses.

CONCLUSIONS

The CHILD sample and data repository is a tremendous current and future resource and will provide a wealth of information not only informing studies of asthma and allergy, but also potentially in many other aspects of health relevant for Canadian infants and children.

CpG-oligodeoxynucleotides inhibit RSV-enhanced allergic sensitisation in guinea pigs

Experimental respiratory syncytial virus (RSV) infection of guinea pigs is associated with enhanced allergic sensitisation to inhaled ovalbumin (OA) and low-level viral persistence in the lungs. Based on the T-helper (Th)1/Th2 paradigm, in which a Th2 shift is characteristic of an allergic response and less effective anti-viral immunity, the effects of immunotherapy with synthetic cytosine phosphate-guanine-oligodeoxynucleotides (CpG-ODN), which are potent Th1 stimuli, on OA sensitisation with and without RSV infection were evaluated. Measurements included quantitative histology for airway inflammation by T-cells and eosinophils, semiquantitative RT-PCR for lung Th1/Th2 balance (interferon (IFN)-gamma/interleukin (IL)-5 mRNA ratios), and serology for circulating titres of OA-specific immunoglobulin (Ig)G1 antibodies. RSV antigens were identified in lung tissue sections by immunohistochemistry. CpG-ODN immunotherapy did not prevent OA sensitisation of guinea pigs; however, in RSV-infected, OA-sensitised animals, CpG-ODN administration was associated with significant reductions of airway T-cells and eosinophils, increased lung IFN-gamma/IL-5 ratios, and decreased OA-specific IgG1 antibody titres to levels observed in uninfected, OA-sensitised animals. Viral antigens were identified in a similar proportion of the lungs of RSV-infected animals, irrespective of CpG-ODN immunisation status. In conclusion, cytosine phosphate-guanine-oligodeoxynucleotides immunotherapy protects guinea pigs against respiratory syncytial virus-enhanced ovalbumin sensitisation and might be a relevant intervention in the context of post-bronchiolitis allergic sensitisation in children.

The association between respiratory viruses and symptoms in 2-week-old infants at high risk for asthma and allergy

OBJECTIVES

The role of viral respiratory tract infections in the onset of childhood asthma and allergy is controversial, partly because of limited understanding about postnatal viral exposures. We investigated the prevalence of 3 common respiratory viruses and associated respiratory symptoms in 2-week-old infants at high risk for having asthma and allergy.

STUDY DESIGN

Frozen nasal specimens from 2-week-old children at high risk (n = 495) underwent reverse transcription-polymerase chain reaction (RT-PCR) for picornavirus-, parainfluenza-, and respiratory syncytial virus-specific nucleic acid. RT-PCR findings were related to respiratory symptoms (cold, cough, and wheeze) and to characteristics implicated with increased risk for asthma and allergy.

RESULTS

Viral RT-PCR was positive in 199 (40.2%) of 495 specimens examined, with picornavirus and parainfluenza significantly associated with respiratory symptoms. Viral prevalence was significantly higher in children born during the winter and summer months.

CONCLUSIONS

A high percentage (40.2%) of infants at high risk for asthma and allergy had been exposed to common respiratory viruses at 2 weeks of age. RT-PCR is a powerful diagnostic method that can be used in epidemiologic studies examining the role of viral respiratory tract infections in the pathogenesis of pediatric asthma and allergy.

The pathology of asthma: brief review

The presence of chronic airway inflammation in asthmatic patients has been known for over a century, but the relationship of this inflammatory process to the pathogenesis of reversible airflow obstruction and non-specific bronchial hyperresponsiveness remains unclear. In recent years, the increasing ability to sample the lower respiratory tract of living asthmatic patients, coupled with revolutionary advances in immunology and molecular biology, has resulted in extensive evaluation of inflammatory cells and mediators implicated in the pathogenesis of asthma. In addition, there is increasing recognition that airway remodeling, characterized by thickening of all compartments of the airway wall, may have profound consequences on the mechanics of airway narrowing in asthma and contribute to the chronicity and progression of the disease. In this brief review, I will describe the gross and microscopic pathology of asthma, the process of airway remodeling and its functional consequences, and speculate on future directions to improve our understanding of the structural changes of asthma and their pathogenic role.

Effects of respiratory syncytial virus persistence on airway responsiveness and inflammation in guinea-pigs

Recurrent wheezing and asthma often develop after acute respiratory syncytial virus (RSV) bronchiolitis, but the mechanisms of these sequelae are poorly understood. Using a guinea-pig model of human RSV lung infection, the effects of long-term viral persistence on three hallmarks of asthma: nonspecific airway responsiveness, airway inflammation and airway remodelling were examined. Guinea-pigs were studied 100 days after intranasal instillation of either human RSV or uninfected vehicle, using: 1) acetylcholine challenge to test for airway hyperresponsiveness (AHR); 2) lung histology to quantify the numbers of airway eosinophils and metachromatic cells (mast cells/basophils); 3) airway morphometry of the areas of the airway subepithelial connective tissue, smooth muscle and adventitia, to test for airway remodelling; and 4) immunohistochemistry to identify lung cells containing RSV antigens. The RSV-inoculated group had significantly elevated AHR and airway eosinophils compared to uninfected control animals (p<0.05). There were no significant differences between the two groups in terms of numbers of airway metachromatic cells, or the areas of subepithelial connective tissue, smooth muscle or adventitia. Viral proteins were identified by immunohistochemistry within several types of lung cells. In conclusion, long-term persistence of respiratory syncytial virus in the guinea-pig lung is associated with airway hyperresponsiveness and airway eosinophilia, and these changes may be pertinent to the pathogenesis of postbronchiolitis wheezing and asthma in children.

Community study using a polymerase chain reaction panel to determine the prevalence of common respiratory viruses in asthmatic and nonasthmatic children

We developed a sensitive polymerase chain reaction (PCR) panel, suitable for the detection of seven common respiratory viruses, to study the prevalence of viruses in nasal swabs obtained from clinically stable asthmatic children (n = 21), non-physician diagnosed asthmatic children with exercise-induced bronchoconstriction (EIB) (n = 16), and nonasthmatic, non-EIB controls (n = 33). The PCR panel detected viruses in 43/70 (61.4%) specimens but there were no significant differences in prevalence of these viruses between the three groups of children. These results indicate that clinically stable asthmatic and nonasthmatic children frequently harbor viruses in the upper respiratory tract.

Role of viruses in the onset of asthma and allergy: lessons from animal models

There are several potential mechanisms by which viral respiratory tract infections in childhood might trigger the onset of sensitization to allergens and asthma. To study these potential mechanisms, researchers have developed a number of animal models. In this paper, results of animal experiments are discussed under three headings: (i) chronic sequelae of acute viral infections; (ii) viral infections and sensitization to aeroallergens; and (iii) persistent viral infections. The use of animal models to study the role of viral infections in the induction of allergic sensitization and airway responsiveness has provided intriguing new insights that may be relevant to the pathogenesis of human disease.

Effect of respiratory syncytial virus on subsequent allergic sensitization to ovalbumin in guinea-pigs

Children with acute respiratory syncytial virus (RSV) bronchiolitis often develop recurrent wheezing, asthma and allergic sensitization, but the role of RSV in the pathogenesis of these sequelae is unclear. This study examined whether RSV infection potentiates subsequent allergic sensitization, airway hyperresponsiveness (AHR) and airway inflammation induced by repeated exposures to aerosolized ovalbumin (OA) in guinea-pigs. Guinea-pigs received either RSV or sham inoculum, followed by exposures to OA- or saline-containing aerosols to form the following groups: 1) noninfected, nonsensitized controls (sham/saline group); 2) RSV-infected, nonsensitized animals (RSV/ saline group); 3) noninfected, OA-sensitized animals (sham/OA group); 4) RSV infection and first OA exposure on the same day (RSV/OA group), and 5) RSV infection six days prior to first OA exposure (RSV6/OA group). Three days after the final aerosol exposure, circulating OA-specific immunoglobulin (Ig)G1 antibody titres and AHR to inhalation acetylcholine challenge were measured and morphometry performed to evaluate allergic inflammation of the airways. OA-exposed animals developed OA-specific IgG1 antibodies, AHR and airway eosinophilia (sham/OA, RSV/OA and RSV6/OA groups. RSV infection alone induced significant AHR and airway eosinophilia (RSV/saline group). RSV infection, and concomitant exposure to OA (RSV/OA group) enhanced OA-specific IgG1 antibodies, but not airway eosinophilia or AHR. Such increases were not observed in the RSV6/OA group. In conclusion, respiratory syncytial virus potentiates the production of ovalbumin-specific immunoglobulin G1 antibodies in guinea-pigs, but circulating titres of these antibodies do not reflect the extent of airway hyperresponsiveness or airway inflammation. In addition, respiratory syncytial virus infection alone can produce slight increases in airway hyperresponsiveness that are associated with increased numbers of eosinophils in the airways.

Common respiratory viruses in lower airways of patients with acute hypersensitivity pneumonitis

Hypersensitivity pneumonitis (HP), a lung disease with "flulike" symptoms, results from repeated exposures to well defined, nonpathogenic antigens. This study examined whether respiratory viruses are present in the lower airways, the likely site of hypersensitivity reaction, in patients with HP. The polymerase chain reaction (PCR) method was used to test for 10 common respiratory viruses in bronchoalveolar lavage (BAL) cells obtained from patients with acute HP and from unexposed healthy volunteers. Immunocytochemistry was subsequently used to localize viral proteins within BAL cells. The results of PCR showed that influenza A virus was the most frequently detected virus in the BAL cells of our study patients (six of 13) and control subjects (two of six). Influenza A proteins were detected within alveolar macrophages in nine of 13 patients and in two of six control subjects. The number of total BAL cells, but not lymphocytes, was higher in patients with documented influenza A proteins than in patients with no influenza A proteins (p = 0.017) and correlated with the proportion of influenza-A-positive alveolar macrophages (r = 0.7; p = 0.036). This report documents the presence of viruses in the lower airways of patients with acute HP. The findings may imply a potential role for influenza A in the modulation of HP during antigen exposure.

PCR detection of viral nucleic acid in fatal asthma: is the lower respiratory tract a reservoir for common viruses?

BACKGROUND

There is indirect evidence implicating viral respiratory tract infections in the pathogenesis of fatal asthma. However, it is unknown whether viruses are present within the lower respiratory tract in fatal asthma.

OBJECTIVES

To apply a nine-virus polymerase chain reaction (PCR) panel to postmortem specimens of lower airway secretions and compare the prevalence of viral nucleic acid among patients who died of asthma, asthmatic patients who died of other causes and persons who died without lung disease.

PATIENTS AND METHODS

Postmortem specimens of lower airway secretions from patients who died of asthma (fatal asthma [n=10]), asthmatic patients who died of other causes (n=4) and nonasthma controls (n=6) underwent PCR for nine common respiratory viruses. The prevalence of each virus was compared among the three groups.

RESULTS

PCR was positive for at least one virus in 19 of 20 cases, and multiple viruses were detected in 14 of 20 cases. The prevalence of each virus was similar in the three groups studied.

CONCLUSIONS

In fatal asthma, lower airway secretions do not show a specific pattern of viral nucleic acid. Intriguingly, these results suggest that the lower respiratory tract may act as a potential reservoir for common respiratory viruses.

Usefulness of bronchoalveolar lavage for diagnosis of acute and persistent respiratory syncytial virus lung infections in guinea pigs

To investigate whether bronchoalveolar lavage (BAL) fluid specimens can be used to diagnose acute and persistent respiratory syncytial virus (RSV) lung infections in guinea pigs, we tested BAL fluid and lung tissue specimens for evidence of viral infection, and compared BAL cytology between infected and uninfected animals. RSV-inoculated guinea pigs were studied during acute bronchiolitis (days 3 and 7 postinoculation), convalescence (Day 14 postinoculation), and persistent infection (Days 28 and 60 postinoculation), and were compared to the sham-infected control animals. BAL and lung tissue specimens were cultured for virus and tested by immunocytochemistry for viral protein. A reverse transcription-polymerase chain reaction (RT-PCR) method was used to test for viral nucleic acid. Total and differential BAL cell counts were compared between RSV-inoculated and control animals on each study day. In BAL specimens, replicating RSV was isolated by culture in one out of four of the animals on Day 3 postinoculation; immunocytochemistry for RSV antigens was positive in all virus-exposed animals from Days 3-14 postinoculation, and viral nucleic acid was detected by RT-PCR in one-fourth of the animals on Day 3 postinoculation. In contrast, replicating virus, viral antigens, and viral nucleic acid were documented in lung tissues obtained from the same RSV-infected animals on all study days. BAL specimens of RSV-inoculated animals contained more eosinophils on all study days (two-tailed P value < 0.01) compared to the controls. The results of this animal study demonstrate that BAL fluid is not useful for diagnosis of persistent RSV infection. However, BAL fluid may be helpful for the documentation of acute RSV lung infection when immunocytochemistry may provide a more accurate test for virus detection than RT-PCR or viral culture.

Permissiveness of guinea pig alveolar macrophage subpopulations to acute respiratory syncytial virus infection in vitro

BACKGROUND AND OBJECTIVES

Alveolar macrophages (AMs) are targets for respiratory syncytial virus (RSV) infection in vivo and in vitro. However, only a minority of AMs are permissive to acute RSV infection in vitro, and it is unknown whether this permissiveness may be related to the degree of cellular maturation that is achieved in vivo.

METHODS

By using density gradient centrifugation, in which the degree of AM maturation is inversely related to buoyant density, we prepared three subpopulations of guinea pig AMs (designated as hypodense, intermediate-density, and high-density AMs). Twenty-four hours after exposure to RSV in vitro, the percentage of RSV-positive cells in each subpopulation was determined by immunocytochemistry; intracellular virus was released from cells by sonication and quantified by plaque assay, and intracellular localization of RSV proteins was evaluated by immunogold electron microscopy.

RESULTS

High-density AMs had a significantly higher proportion of RSV-positive cells than hypodense AMs (p < 0.001), with intermediate-density AMs having intermediate values. The amounts of intracellular virus significantly increased from hypodense to intermediate density to high-density AMs (p < 0.001). Hypodense cells showed immunogold labeling principally within phagolysosomes, whereas intermediate-density and high-density cells showed immunolabeling of free cytoplasmic viral proteins and nucleocapsids.

CONCLUSIONS

The permissiveness of guinea pig AMs to acute RSV infection in vitro is inversely related to their degree of maturation achieved in vivo. In addition, these results suggest that immature, high-density AMs support RSV replication whereas more mature, hypodense AMs may restrict viral replication.

Two enteropathogenic Escherichia coli type III secreted proteins, EspA and EspB, are virulence factors

Enteropathogenic Escherichia coli (EPEC) belongs to a family of related bacterial pathogens, including enterohemorrhagic Escherichia coli (EHEC) O157:H7 and other human and animal diarrheagenic pathogens that form attaching and effacing (A/E) lesions on host epithelial surfaces. Bacterial secreted Esp proteins and a type III secretion system are conserved among these pathogens and trigger host cell signal transduction pathways and cytoskeletal rearrangements, and mediate intimate bacterial adherence to epithelial cell surfaces in vitro. However, their role in pathogenesis is still unclear. To investigate the role of Esp proteins in disease, mutations in espA and espB were constructed in rabbit EPEC serotype O103 and infection characteristics were compared to that of the wild-type strain using histology, scanning and transmission electron microscopy, and confocal laser scanning microscopy in a weaned rabbit infection model. The virulence of EspA and EspB mutant strains was severely attenuated. Additionally, neither mutant strain formed A/E lesions, nor did either one cause cytoskeletal actin rearrangements beneath the attached bacteria in the rabbit intestine. Collectively, this study shows for the first time that the type III secreted proteins EspA and EspB are needed to form A/E lesions in vivo and are indeed virulence factors. It also confirms the role of A/E lesions in disease processes.

Allergic sensitization increases airway reactivity in guinea pigs with respiratory syncytial virus bronchiolitis

BACKGROUND

Respiratory syncytial virus (RSV) causes acute bronchiolitis in children and has been implicated in the pathogenesis of recurrent wheezing and asthma. However, few children exposed to RSV experience acute bronchiolitis or its sequelae, suggesting a subgroup of susceptible children. An allergic diathesis may predispose children to subsequent airway disease.

OBJECTIVE

This study was carried out to determine whether a preexisting allergic state, induced by repeated inhalational exposures to ovalbumin, potentiates nonspecific airway responsiveness to acetylcholine and increases airway inflammation during acute RSV bronchiolitis in guinea pigs.

METHODS

Forty guinea pigs were randomized into four groups: nonsensitized, noninfected (ovalbumin-, RSV-); sensitized, noninfected (ovalbumin+, RSV-); nonsensitized, infected (ovalbumin-, RSV+); sensitized, infected (ovalbumin+, RSV+). Depending on grouping, animals were exposed to either repeated aerosols of ovalbumin or saline solution and were subsequently inoculated with either human RSV or uninfected culture medium. Six days after inoculation, animals underwent acetylcholine challenge, and lung specimens were prepared for histologic scoring of airway inflammation.

RESULTS

Maximal increases in pulmonary resistance (centimeters of water per milliliter per second) to acetylcholine were greater for RSV alone (12.4 +/- 3.9) and ovalbumin alone (13.7 +/- 3.9) compared with controls (4.3 +/- 1.1), but significantly greater increases occurred in ovalbumin+, RSV+ animals (34.0 +/- 11.0). These ovalbumin+, RSV+ animals demonstrated the combined histologic changes noted with RSV alone and ovalbumin alone including airway epithelial necrosis, mononuclear and granulocyte infiltrates, airway wall edema, hyperplasia of bronchus-associated lymphoid tissue, and goblet cell metaplasia.

CONCLUSION

Prior allergic sensitization potentiates the physiologic and structural changes induced by acute RSV bronchiolitis. These results suggest that an allergic diathesis may increase the severity of RSV infections in children.

Inflammation of small airways in asthma

This study was designed to examine the inflammatory process in the central and peripheral airways of surgically resected lungs from asthmatic and nonasthmatic subjects. Lung specimens were inflated with cryoprotective, rapidly frozen, and systematically sampled. Cryosections prepared from frozen tissue blocks were fixed in acetone/methanol and immunostained with monoclonal antibodies by using the alkaline phosphatase-anti-alkaline phosphatase technique to detect CD3 (T cells), major basic protein (total eosinophils), EG2 (activated eosinophils), anti-tryptase (mast cells), anti-elastase (neutrophils), and CD68 (macrophages). All airways from patients with asthma demonstrated a significant increase in the numbers of T cells and total and activated eosinophils compared with airways from nonasthmatic subjects (p < 0.001). In the patients with asthma, the numbers of activated eosinophils but not T cells were significantly greater in airways with an internal perimeter less than 2 mm compared with those with an internal perimeter greater than 2 mm (p < 0.05). There were also significantly higher numbers of major basic protein-positive eosinophils, when expressed as a fraction of the alveolar wall tissue, in patients with asthma compared with control subjects (p < 0.05). In asthmatic airways with an internal perimeter of more than 2 mm, there was a greater number of activated eosinophils in the tissue between the epithelium and the smooth muscle compared with the tissue between the smooth muscle layer and lung parenchyma (p < 0.05). In contrast, there was a greater number of total eosinophils in the outer airway layer compared with the inner airway layer (p < 0.05). These results show that there is a similar but more severe inflammatory process present in the peripheral compared with the central airways of patients with asthma, which is consistent with the fact that the smaller airways are a major site of obstruction in asthma.

Expression of bcl-2 and Epstein-Barr virus LMP1 in lymphocytic interstitial pneumonia

BACKGROUND

Epstein-Barr virus (EBV) genome has been demonstrated in lung tissues of patients with lymphocytic interstitial pneumonia (LIP) but its role in the pathogenesis of this condition is unclear. In vitro studies have shown that EBV can immortalise and transform cells by upregulation of the cellular proto-oncogene, B cell leukaemia-2 (bcl-2), via the viral latent membrane protein, LMP1. The purpose of this study was to determine whether bcl-2 expression is upregulated in the lungs of patients with LIP and whether EBV LMP1 has a role in this bcl-2 expression.

METHODS

Immunohistochemical analysis using alkaline phosphatase anti-alkaline phosphatase (APAAP) was performed on formalin fixed, paraffin embedded lung tissues from 13 patients with LIP using anti-LMP1 and anti-bcl-2 monoclonal antibodies. Lung tissues from nine patients with idiopathic pulmonary fibrosis (IPF) and nine necropsy cases without pulmonary disease served as controls. LMP1 positivity was estimated as the number of LMP1 positive cells per unit area of lung tissue. Immunostaining for bcl-2 expression was assessed by a pictorial-based semiquantitative grading system.

RESULTS

Positive immunostaining for LMP1 was localised to airway epithelial cells of lung tissue. Ten out of 13 (77%) patients with LIP were positive for LMP1 compared with three of nine cases (33%) in each control group. LMP1 positivity of LIP cases was significantly greater than that of non-LIP cases: LIP versus IPF (mean difference, 95% confidence interval (CI)) 2.39 (1.54 to 3.24); LIP versus necropsy controls 2.62 (1.77 to 3.47). bcl-2 immunostaining was localised to lymphocytes within the alveolar septa and lymphoid aggregates of patients with LIP. The cumulative score for bcl-2 immunostaining was significantly higher in the lungs of patients with LIP than in those of patients with IPF and necropsy controls: LIP versus IPF and LIP versus necropsy controls (mean difference, 95% CI) 7.55 (7.18 to 7.92).

CONCLUSIONS

These immunohistochemical studies have shown the presence of EBV LMP1 protein in airway epithelial cells and overexpression of the cellular bcl-2 protein in lymphoid cells of lung tissue in patients with LIP. These geographically distinct staining patterns of immunostaining suggest that the involvement of EBV LMP1 in the upregulation of cellular bcl-2 is more complex in LIP than was thought from previous in vitro observations. The respective roles of EBV LMP1 and bcl-2 in the pathogenesis of LIP require further studies.

Persistence of respiratory syncytial virus (RSV) infection and development of RSV-specific IgG1 response in a guinea-pig model of acute bronchiolitis

Acute respiratory syncytial virus (RSV) bronchiolitis in children can result in sequelae of recurrent wheezing and asthma and production of RSV-specific immunoglobulin E (IgE), but the pathogenesis of these sequeleae is poorly understood. Guinea-pigs experimentally inoculated with human RSV show histological evidence of acute bronchiolitis and chronic persistence of viral antigens and genome in the lungs; whether this persistence is due to infectious replicating virus, and whether infected animals develop RSV-specific immunoglobulin G1 (IgG1) (the main class of antibody involved in guinea-pig allergic responses) is unknown. Guinea-pigs were inoculated intranasally with human RSV or with uninfected cell culture supernatant. At times ranging 1-60 days postinoculation, the viral titre in the lung was determined by immunoplaque assay (a method combining viral culture and immunocytochemistry). Serum titres of RSV-specific IgG1 antibodies were determined by enzyme-linked immunosorbent assay. Bronchiolar inflammation was assessed on coded lung sections, by using a semiquantitative, histological scoring system based on features of human acute bronchiolitis. Infectious RSV was cultured from the lungs of infected animals on all study days, with maximal viral replication observed on Day 3. RSV-specific IgG1 antibodies were detected in all RSV-inoculated animals from Day 7 onward, with the highest antibody titre measured on Day 28. RSV-inoculated guinea-pigs had maximal bronchiolar inflammation on Day 7, and had significantly increased polymorphonuclear cell infiltrates on Days 28 and 60. Respiratory syncytial virus chronically persists as infectious virus in the guinea-pig lung. Infected animals develop an anti-respiratory syncytial virus immunoglobulin G1 antibody response, histological evidence of acute bronchiolitis, and chronic airway inflammation. Persistent respiratory syncytial virus lung infection may be important in the pathogenesis of postbronchiolitis wheezing and asthma in children.

Increased airway reactivity in human RSV bronchiolitis in the guinea pig is not due to increased wall thickness

Bronchiolitis due to the respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infection in the first year of life. It has been suggested that RSV infection may cause subsequent asthma, but a mechanism for this relationship has not been demonstrated. Studies examining the presence of airway reactivity in infants with RSV bronchiolitis are limited by our inability to administer provocative agents such as histamine to such ill infants. This makes a small animal model of this condition a useful tool in which to investigate the pathophysiology of RSV bronchiolitis. We, therefore, evaluated airway responsiveness in vivo and airway morphometric changes in 20 guinea pigs infected by instilling 4,000 plaque-forming units of human RSV virus onto the nasal mucosa under halothane anaesthesia, while 20 control animals received an equivalent volume of sterile cell culture medium. Six days following instillation, 10 infected animals and 10 controls underwent measurements of pulmonary resistance (RL) following increasing doses of inhaled acetylcholine (Ach). These guinea pigs were then sacrificed and the lung and heart removed en bloc for morphometric studies. There were no differences in baseline RL between infected and control groups. At Ach concentrations of 15 and 50 mg/mL, RSV-infected animals had higher RL values than controls (P < 0.05). Fourteen days following RSV instillation no differences in Ach responses were detected in the 10 infected and 10 control animals studied. To determine whether the increase in airway reactivity 6 days after RSV instillation was associated with changes in airway wall morphometry, 125 airways (69 infected, 56 control) were studied. Analysis of wall area, wall area internal to the smooth muscle, or smooth muscle area standardized by the internal perimeter of the airway showed no significant differences between the infected and control airways. These results demonstrated that airway hyperresponsiveness correlated with previously reported histologic changes of acute bronchiolitis 6 days after guinea pigs were infected with human RSV, but neither hyperresponsiveness nor histological changes persisted following resolution of the primary infection. The increased airway reactivity and the previously observed histological changes seen at day 6 following infection was not due to increased airway wall thickness.

Amplification of human beta-actin gene by the reverse transcriptase-polymerase chain reaction: implications for assessment of RNA from formalin-fixed, paraffin-embedded material

The polymerase chain reaction (PCR) is a powerful method that allows enzymatic amplification of rate target nucleic acid sequences. It has been applied to the amplification of viral genomes from paraffin-embedded pathology specimens. However, interpretation of negative results requires amplification of a housekeeping gene such as beta-actin. In the present study we used specific oligonucleotide primers previously designed to amplify both the genomic DNA and the mRNA transcript from paraffin-embedded tissue. These products have predicted sizes of 250 BP and 154 BP, respectively, but our results showed that PCR amplification only (without reverse transcription) unexpectedly generated the 154-BP product. Further investigation of the nature of this product demonstrated that it originated from the amplification of DNA, not RNA. We conclude that the 154-BP product generated by these primers cannot be exclusively considered as beta-actin RNA product and should not be used to assess successful extraction of RNA, to ascertain its integrity, or to normalize for the total amount of RNA assayed by RT-PCR from paraffin-embedded tissue.

A nonradioactive method for rapid and sensitive detection of polymerase chain reaction products by use of bromo-deoxyuridine

A highly sensitive and nonradioactive method that allows for rapid detection of polymerase chain reaction (PCR) products, without the need for hybridization with oligonucleotide probes, is described. In this method, a 410-bp sequence of the human respiratory syncytial virus nucleocapsid cDNA was amplified by PCR in the presence of bromo-deoxyuridine-triphosphate, an analog of deoxythymidine-triphosphate. After agarose gel electrophoresis and Southern blotting, the PCR product was directly identified by immunoenzyme-chemiluminescent reaction after binding with an antibromodeoxyuridine antibody. The results show that substitution of bromo-deoxyuridine-triphosphate for deoxythymidine-triphosphate does not affect the efficiency of PCR, and as low as one copy-equivalent of the target DNA sequence could be detected within 2 hours, whereas it required 1 to 5 days to reach comparable sensitivity level after hybridization with a 32P-labeled oligonucleotide probe and autoradiography. Compared with the use of digoxygenin-11-deoxyuridine-triphosphate, the sensitivity of detection was 100-fold higher with the use of Bromo-deoxyuridine-triphosphate. When applied to the diagnosis by use of reverse transcription-PCR of respiratory syncytial virus infections in nasopharyngeal washes from children with symptoms of acute upper respiratory tract infection, the current method detected respiratory syncytial virus genome in 29 of 100 specimens, and there was a complete concordance with the results of hybridization of reverse transcription-PCR products by use of a radiolabeled oligonucleotide probe. Thus, in addition to its rapidity of detection and high sensitivity, this method provides safety of use and can be readily applied to the clinical diagnosis of viral respiratory tract infections.

Diagnosis of viral respiratory tract infections in children by using a reverse transcription-PCR panel

Reverse transcription-PCR (RT-PCR) is a sensitive method for detection of RNA virus nucleic acid sequences in clinical respiratory specimens. Previous studies have focused on RT-PCR for a single virus, but this approach is limited by the inability to establish a specific etiology when the RT-PCR result is negative and by the inability to document simultaneous infections involving more than one virus. The purpose of this study was to apply a panel of RT-PCR protocols for respiratory syncytial virus, parainfluenza virus, and picornaviruses to respiratory specimens from 80 children suspected to have acute viral respiratory tract infections and to correlate RT-PCR results with viral culture results and clinical diagnosis. In comparison with viral culture, the RT-PCR panel had a sensitivity of over 94% and showed evidence of simultaneous infections in a significantly greater proportion of specimens (20.0% versus 3.8%; P < 0.002). For specimens in which no viruses were detected by culture, the proportion of specimens with positive picornavirus RT-PCR results was significantly greater than the proportion of specimens with positive respiratory syncytial virus or parainfluenza virus RT-PCR results (P < 0.001). There were no statistically significant associations between RT-PCR results and clinical diagnosis. In summary, the RT-PCR panel provides an improved approach to obtain new insights into acute viral respiratory tract infections in children.

Adenovirus and Epstein-Barr virus in lung disease

The adenovirus and the Epstein-Barr virus are double-stranded DNA viruses capable of infecting the human respiratory tract and producing a wide spectrum of pulmonary disorders. We review the viral factors and viral-host interactions that may be involved in the pathogenesis of pulmonary disorders associated with adenoviral and Epstein-Barr virus infections, focusing on the possible role of acute, persistent, and latent infections. Adenovirus and Epstein-Barr virus have evolved a remarkable array of strategies to survive within the infected host, and an improved understanding of these strategies is essential to developing innovative therapies to effectively manipulate viral-host interactions.

Mechanisms of airway narrowing and hyperresponsiveness in viral respiratory tract infections

Viral respiratory tract infections are associated with an acute increase in airway responsiveness in normal subjects and patients with asthma. Airway responsiveness is also increased at least transiently in animals during acute viral infections. In this article, we discuss possible mechanisms whereby viral infections can increase airway responsiveness, emphasizing the effects of viral-induced airway epithelial damage during acute lytic infection and the mechanical consequences of airway inflammation and edema, both internal and external to the smooth muscle layer. We also describe possible mechanisms by which acute lytic viral infections could induce chronic sequelae in atopic individuals and contribute to the development of persistence of asthma. Finally, results of recent studies from our laboratory that document adenoviral genome in lungs of patients with chronic obstructive pulmonary disease (COPD) and long-term persistence of respiratory syncytial viral genome and protein in an animal model are discussed in terms of the possible role of latent and persistent viral infections in the pathogenesis of asthma and COPD.

Oncogenic osteomalacia: evidence for a humoral phosphaturic factor

Oncogenic osteomalacia is a syndrome characterized by phosphaturia, hypophosphatemia, reduced vitamin D levels, and osteomalacia. The cause is not known, but all patients have had a tumor; usually of mesenchymal origin. Removal of the tumor reverses the metabolic abnormalities. We report a patient with osteomalacia, severe hypophosphatemia, elevated alkaline phosphatase, low 1,25-dihydroxyvitamin D3, and phosphaturia. A tumor was identified in the infratemporal fossa. The tumor was removed, and all of the biochemical abnormalities resolved over the subsequent 8 months. The bone density returned to normal values. The tumor had the appearance of a paraganglioma and was used to establish a cell culture line called JH-55. Electron microscopy of the original tumor and the JH-55 cells demonstrated the presence of neurosecretory granules. A bioassay using opossum kidney cells was used to evaluate phosphate transport. Conditioned medium from the JH-55 cells inhibited phosphate reabsorption by the kidney tubular cells. Maximal inhibition required a 24-h incubation period and was not altered by the presence of an inhibitor of protein synthesis (10 micrograms/mL cycloheximide). Immunoassays revealed no detectable PTH-related peptide or intact PTH in the JH-55 medium. The cause of this paraneoplastic syndrome is not known, but all of the evidence is consistent with the action of a hormone that produces phosphaturia. This putative factor is distinct from other hormones that cause phosphaturia.

In situ hybridization for the Y chromosome reveals a donor origin for a posttransplant lymphoproliferative disorder in a sex-mismatched hepatic allograft

We report a case of posttransplant lymphoproliferative disorder diagnosed within 4 weeks of orthotopic liver transplantation from a male donor to a female recipient. To determine whether the posttransplant lymphoproliferative disorder was of donor or recipient origin, nonisotopic in situ hybridization for the human Y chromosome was performed on formalin-fixed, paraffin-embedded sections of the donor liver using a digoxigenin-labeled probe. The lymphoid cells hybridized with the Y chromosome probe, indicative of a male genotype consistent with posttransplant lymphoproliferative disorder of donor origin. This case illustrates that nonisotopic in situ hybridization for the Y chromosome can discriminate between donor and recipient cells in sex-mismatched organ transplants.

Persistence of respiratory syncytial virus genome and protein after acute bronchiolitis in guinea pigs

Children with acute respiratory syncytial virus (RSV) bronchiolitis often develop sequelae of recurrent wheezing and asthma. To determine whether RSV persists within the lung after resolution of acute bronchiolitis, we examined the lungs of guinea pigs 60 days after intranasal inoculation with either human RSV (n = 10) or uninfected cell culture supernatant (n = 11). Evidence of viral persistence within the lung was determined by viral culture to test for replicating virus, immunohistochemistry to test for viral protein, and the reverse transcriptase-polymerase chain reaction (RT-PCR) to test for viral genomic RNA. Lungs were also examined histologically for evidence of bronchiolar inflammation or increased numbers of mast cells in the airway walls. All viral cultures were negative; however, there was positive immunohistochemical staining of occasional alveolar macrophages in six of ten RSV-inoculated guinea pigs while RT-PCR was positive in seven of ten RSV-inoculated animals. The six guinea pigs with evidence of RSV by immunohistochemistry and RT-PCR showed excess bronchiolar polymorphonuclear cell infiltrates (p < 0.005) but no increase in the number of airway wall mast cells. These results show that RSV protein and genomic RNA can persist in the lungs of experimentally inoculated guinea pigs for at least 60 days after infection and that persistence of the virus within alveolar macrophages might contribute to the pathogenesis of chronic bronchiolar inflammation.

Production of acute bronchiolitis in guinea-pigs by human respiratory syncytial virus

Respiratory syncytial virus (RSV) is the most important cause of acute bronchiolitis in young children, and is implicated in the pathogenesis of paediatric asthma. The present studies were designed to develop a model of acute RSV bronchiolitis in young guinea-pigs, that could be used to study the mechanisms of the acute bronchiolitis and its sequelae. Anaesthetized, one month old guinea-pigs received either 4 x 10(3) plaque forming units of Long strain human RSV or uninfected cell culture medium intranasally. Bronchiolar inflammation was assessed 6 days (n = 10 RSV-inoculated; n = 10 controls) and 14 days (n = 10 RSV-inoculated; n = 9 controls) postinoculation using a semiquantitative histological scoring system. Viral replication within the lung was evaluated by culture, and the intrapulmonary distribution of viral antigens was evaluated by immunohistochemistry. The RSV-inoculated group showed histological evidence of acute bronchiolitis 6 days after inoculation, which subsided by Day 14. Replicating virus was cultured from the lungs of 9 out of 10 RSV-inoculated animals on Day 6, and 2 out of 10 animals on Day 14, with no growth from control animals. Viral antigens were identified primarily within airway epithelial cells on Day 6, and within alveolar macrophages on Day 14. Intranasal inoculation of human RSV into guinea-pigs provides a model of acute RSV bronchiolitis that may facilitate the study of both the pathogenesis of acute infection and the possible role of RSV in the subsequent development of nonspecific bronchial hyperresponsiveness in children.

Production of acute bronchiolitis in guinea-pigs by human respiratory syncytial virus

Respiratory syncytial virus (RSV) is the most important cause of acute bronchiolitis in young children, and is implicated in the pathogenesis of paediatric asthma. The present studies were designed to develop a model of acute RSV bronchiolitis in young guinea-pigs, that could be used to study the mechanisms of the acute bronchiolitis and its sequelae. Anaesthetized, one month old guinea-pigs received either 4 x 10(3) plaque forming units of Long strain human RSV or uninfected cell culture medium intranasally. Bronchiolar inflammation was assessed 6 days (n = 10 RSV-inoculated; n = 10 controls) and 14 days (n = 10 RSV-inoculated; n = 9 controls) postinoculation using a semiquantitative histological scoring system. Viral replication within the lung was evaluated by culture, and the intrapulmonary distribution of viral antigens was evaluated by immunohistochemistry. The RSV-inoculated group showed histological evidence of acute bronchiolitis 6 days after inoculation, which subsided by Day 14. Replicating virus was cultured from the lungs of 9 out of 10 RSV-inoculated animals on Day 6, and 2 out of 10 animals on Day 14, with no growth from control animals. Viral antigens were identified primarily within airway epithelial cells on Day 6, and within alveolar macrophages on Day 14. Intranasal inoculation of human RSV into guinea-pigs provides a model of acute RSV bronchiolitis that may facilitate the study of both the pathogenesis of acute infection and the possible role of RSV in the subsequent development of nonspecific bronchial hyperresponsiveness in children.

Detection of Epstein-Barr virus in lymphocytic interstitial pneumonia by in situ hybridization

The involvement of Epstein-Barr virus (EBV) in the pathogenesis of lymphocytic interstitial pneumonia (LIP) was investigated using an in situ hybridization technique. Archival lung tissue samples from 14 patients (six men and eight women with a mean age of 58 +/- 3 yr) in whom a diagnosis of LIP had been previously established were retrospectively examined and compared with samples from 10 patients (six men and four women with a mean age of 58 +/- 3 yr) with idiopathic pulmonary fibrosis (IPF) who served as control subjects. In patients with LIP, the immunophenotype of the lymphocytic infiltrate was determined by using monoclonal antibodies to both pan-B-cell and pan-T-cell markers. In situ hybridization studies were performed by using the BamHI-W region of the EBV genome as a probe and a colorimetric detection method. The immunophenotyping studies showed that the interstitial infiltrate in LIP was primarily made up of B-lymphocytes, particularly within the lymphoid aggregates, whereas T-lymphocytes were sparsely distributed along the alveolar septa. The in situ hybridization studies showed the presence of cells bearing the EBV genome in nine cases of LIP and in two cases of IPF (p less than 0.05, Fisher's exact test). In LIP, the EBV-positive cells were observed in both enlarged and normal septa and occasionally within the lymphoid aggregates. We conclude that EBV may promote the proliferation of B-lymphocytes in a substantial number of patients with LIP.

Immunocytochemical characterization of cells in rat glomerular culture

Identification and characterization of cells in glomerular tissue culture has been an ongoing concern of experimental renal biologists. We examined the immunocytochemical staining profiles of primary and passaged rat glomerular cultures using a battery of commercially available antisera. In all culture systems examined, two distinct cell populations could be distinguished. One cell type stained positively for desmin and had ultrastructurally smooth muscle features typical of contractile mesangial cells. The second cell type proliferated in a manner classically described for "epithelial" cells but, intriguingly, did not express any of the numerous epithelial markers tested. The second cell population may represent an undifferentiated reserve cell type. Immunocytochemical methods offer an independent modality to the evaluation of cells which proliferate in glomerular cell culture.