Involvement of IL-16 in the induction of airway hyper-responsiveness and up-regulation of IgE in a murine model of allergic asthma

Experiments were designed to investigate the role of IL-16 in a mouse model of allergic asthma. OVA-sensitized mice were repeatedly exposed to OVA or saline aerosols. Bronchoalveolar lavage fluid (BALF) was collected after the last aerosol, and the presence of IL-16 was evaluated using a migration assay with human lymphocytes. Migration of lymphocytes was significantly increased in the presence of cell-free BALF from OVA-challenged mice compared with BALF from saline-challenged controls. This response was significantly inhibited after addition of antibodies to IL-16, demonstrating the presence of IL-16 in BALF of OVA-challenged animals. Immunohistochemistry was performed and revealed IL-16 immunoreactivity particularly in airway epithelial cells but also in cellular infiltrates in OVA-challenged mice. IL-16 immunoreactivity was absent in nonsensitized animals; however, some reactivity was detected in epithelial cells of sensitized but saline-challenged mice, suggesting that sensitization induced IL-16 expression in airway epithelium. Treatment of mice with antibodies to IL-16 during the challenge period significantly suppressed up-regulation of OVA-specific IgE in OVA-challenged animals. Furthermore, antibodies to IL-16 significantly inhibited the development of airway hyper-responsiveness after repeated OVA inhalations, whereas the number of eosinophils in bronchoalveolar lavage or airway tissue was not affected. In conclusion, IL-16 immunoreactivity is present in the airways after sensitization. After repeated OVA inhalation, IL-16 immunoreactivity is markedly increased and IL-16 is detectable in BALF. Furthermore, IL-16 plays an important role in airway hyper-responsiveness and up-regulation of IgE but is not important for eosinophil accumulation in a mouse model of allergic asthma.     

Modulation of airway hyperresponsiveness and eosinophilia by selective histamine and 5-HT receptor antagonists in a mouse model of allergic asthma

1. Since both histamine and 5-hydroxytryptamine (5-HT) can be released by murine mast cells, we investigated the possible role of these autacoids on airway hyperresponsiveness (AHR), eosinophil infiltration and serum-IgE levels in a murine model of allergic asthma. 2. Ovalbumin-sensitized mice were exposed to either ovalbumin (2 mg ml(-1)) or saline aerosols on 8 consecutive days. Starting one day before the challenge, animals were injected i.p. twice a day with a 5-HT-type 1 (5-HT1) or type 2 (5-HT2) receptor antagonist (methiotepine, 1.25 or 2.0 mg kg(-1) and ketanserin, 12 mg kg(-1), respectively) or a histamine-type 1 (H1) or type 2 (H2) receptor antagonist (mepyramine, 12 or 20 mg kg(-1) and cimetidine, 10 or 25 mg kg(-1), respectively). Furthermore, animals were injected with a combination of cimetidine and ketanserin or with an alpha-adrenoceptor antagonist (phentolamine, 5 mg kg(-1)). 3. In vehicle-treated ovalbumin-challenged animals airway responsiveness to intravenous injections of methacholine in vivo was significantly (9 fold increase, P<0.01) increased when compared to vehicle-treated saline-challenged animals. Furthermore, ovalbumin challenge of vehicle-treated animals induced a significant increase in both eosinophil numbers in bronchoalveolar lavage (BAL) fluid (0+/-0, vehicle/saline and 15.0+/-5.9 x 10(4) cells vehicle/ovalbumin, P<0.05) and ovalbumin-specific IgE levels in serum (157+/-69 and 617+/-171 units ml(-1), respectively, P<0.05) compared to saline-challenged mice. Virtually no eosinophils could be detected in saline-challenged animals after all different treatments. 4. Treatment with ketanserin or cimetidine resulted in a partial but significant decrease of the ovalbumin-induced AHR compared to ovalbumin-challenged controls (P<0.05) and reduced eosinophil infiltration after ovalbumin challenge by 60% and 58%, respectively. The combination of cimetidine and ketanserin almost completely abolished AHR whereas eosinophilia was decreased by 49%. No effects of these antagonists were observed on IL-16 levels in BAL fluid or on serum antigen-specific IgE levels. Treatment with either the H1-receptor, the 5-HT1-receptor or the alpha-adrenoceptor antagonist, did not decrease the observed ovalbumin-induced airway responsiveness or eosinophilia in vehicle-treated animals. Higher doses of either methiotepine (2.0 mg kg(-1)) or mepyramine (20 mg kg(-1)) did decrease ovalbumin-induced eosinophil infiltration (by 67%, P<0.05 and 73%, respectively), whereas no effects of these antagonists were observed on ovalbumin-specific IgE levels in serum. 5. From these data it can be concluded that both histamine and 5-HT play a role in antigen-induced AHR and eosinophilia in the mouse.     

Characterization of cytokine production in murine Trypanosoma cruzi infection by in situ immunocytochemistry: lack of association between susceptibility and type 2 cytokine production

The ability of subcutaneous pretreatment with an immunogenic peptide derived from Fel d I, the major cat protein, to suppress the development of allergic responses was examined in a mouse model of antigen-induced sensitization. BALB/c mice exposed to aerosolized Fel d I chain 1 peptide developed antigen-specific IgE responses, immediate cutaneous reactivity to the peptide, and increased airway responsiveness (AR). Both subcutaneous and intraperitoneal administration of the peptide prior to sensitization caused a 50% reduction in cutaneous reactivity which was associated with a decrease in serum anti-Fel d I chain 1 IgE and IgG1 antibody responses and an increase in specific IgG. Pretreatment with the peptide also suppressed spleen and lymph node proliferative responses to the peptide. However, only subcutaneous peptide injections could prevent the development of increased AR. Transfer of spleen cells from subcutaneously peptide-treated mice to sensitized recipients reduced serum antigen-specific IgE and IgG1 antibody responses and skin test reactivity, and prevented alterations in AR. These data suggest that IgE (and IgG1) responses and airway hyperresponsiveness induced by allergen sensitization via the airways can be modulated by subcutaneous administration of peptide. Further, the results define a model for investigating the modulatory effects of subcutaneous administration of immunogenic peptides or protein on an ongoing allergic response.     

CD23 deficient mice develop allergic airway hyperresponsiveness following sensitization with ovalbumin

The low affinity receptor for IgE (CD23) is reported to regulate immune and inflammatory events and as a result, it may have a role in the development of allergic airway inflammation and hyperresponsiveness (AHR). To test this hypothesis CD23-deficient mice were studied following different modes of allergic sensitization. Mice were actively sensitized either intraperitoneally with ovalbumin (OA)/alum or via the airways (10 days exposure to OA aerosol with no adjuvant). Passive sensitization was performed by intravenous injections of OA-specific IgE. Airway responsiveness, serum IgE and IgG levels were assessed together with airway inflammation. Passive sensitization followed by airway challenges resulted in increased OA-specific lgG and IgE in the serum of wild-type mice only, while both the CD23+/+ and CD23-/- groups developed tracheal smooth muscle hyperresponsiveness to electrical field stimulation, indicating that IgE/CD23-mediated immune functions may not be necessary for the development of allergic changes. Active sensitization of both CD23-/- and CD23+/+ mice resulted in increased serum levels of OA-specific IgE and lgG, airway eosinophilia and significant AHR when compared with nonsensitized mice. The genetic deficiency of CD23-/- mice not only failed to prevent but was associated with a significant increase of these responses. These results indicate that CD23 may not be essential for the development of allergen-induced AHR and further, that its presence may have some inhibitory effects on the allergic response.     

Inhibitory effect of low molecular weight heparin on the bronchoconstriction in ovalbumin-sensitized guinea pigs after antigen exposure

To elucidate the effect of low molecular weight heparin (LMWH) on the bronchoconstriction, we examined the serial changes of the resistance of respiratory system (Rrs) in ovalbumin (OA)-sensitized guinea pigs after antigen exposure. After sensitization of guinea pigs with repeated OA inhalation, Rrs was measured at immediate asthmatic response (IAR) and late asthmatic response (LAR) with or without LMWH inhalation. Alteration in the number of inflammatory cells of the lung by LMWH inhalation was examined in the broncholaveolar lavage fluid (BALF) and in the histological sections of airway walls. Peak Rrs at 1 min up to 9 min, except 8 min, after antigen exposure significantly decreased by the pretreatment with LMWH inhalation as compared with saline inhalation. Peak Rrs at LAR (after 4 hours up to 24 hours, except 6 hours) also showed a significant decrease in the pretreatment with LMWH inhalation. Pretreatment of LMWH exhibited a decrease of eosinophil percentage in BALF (5.5 +/- 1.2% from 8.2 +/- 0.4% in saline inhalation) and a decrease of infiltrated eosinophil count in airway walls (71.0 +/- 7.3 from 155 +/- 15.8 in saline inhalation). These data show LMWH might play an important role as an inhibitory factor to bronchial asthma.     

Cross-protection of mice immunized with different influenza A (H2) strains and challenged with viruses of the same HA subtype

Cross-protection of mice immunized with inactivated preparations of human and avian influenza A (H2) viruses was determined after lethal infection with mouse-adapted (MA) variants of human A/Jap x Bell/57 (H2N1) and avian A/NJers/78 (H2N3) viruses. The MA variants differed from the original strains by acquired virulence for mice and changes in the HA antigenicity. These studies indicated that mice vaccinated with human influenza A (H2) viruses were satisfactorily protected against challenge with A/Jap x Bell/57-MA variant; the survival rate was in the range of 61%-88.9%. Immunization of mice with the same viral preparations provided lower levels of protection against challenge with A/NJers/78-MA variant. Vaccination of mice with the avian influenza A (H2) viruses induced better protection than with human strains against challenge with both MA variants. Challenge with A/NJers/78-MA variant revealed that 76.2%-95.2% of animals were protected when vaccinated with avian influenza virus strains isolated before 1980, and that the protection reached only 52.4%-60.0% in animals vaccinated with strains isolated in 1980-1985. The present study revealed that cross-protection experiments in a mouse model could provide necessary information for the development of appropriate influenza A (H2) virus vaccines with a potential for these viruses to reappear in a human population.     

Clavicular osteomyelitis as a complication of head and neck surgery

To investigate the development of airway hyperresponsiveness in infantile guinea pigs, animals (10 days old) were immunized twice and challenged by inhalation of 1% ovalbumin for 10 min with 7 days intervals. Similar to adult guinea pigs, infantile ones developed an increased airway responsiveness to acetylcholine 24 hr after antigen challenge. There was a marked increase in the number of total leukocytes, eosinophils and lymphocytes in bronchoalveolar lavage fluid (BALF). Suplatast tosilate (suplatast) and pemirolast potassium (pemirolast) given orally throughout the experiments suppressed the development of airway hyperresponsiveness in infantile animals. They showed similar potency in the suppression of eosinophil accumulation in BALF and lung tissue, while suplatast inhibited lymphocyte accumulation stronger than pemirolast. Collectively, the present model of airway hyperresponsiveness in infantile guinea pigs may be useful in predicting the efficacy of antiallergic agents in the treatment of asthmatic children.     

Inhalation of platelet-activating factor induced guinea pig airway hyperresponsiveness: role of eosinophils activation

Exposure of guinea pigs to aerosols of 200 micrograms/ml platelet-activating factor 24 h later, airway hyperresponsiveness to histamine induced and number of eosinophils and hypodense eosinophils in bronchoalveolar lavage fluid (BALF) increased, comparing with the control group. The number of eosinophils in BALF was corelated with PC20 value in PAF-treated group (r = -0.62, P < 0.05). However, the percentage of hypodense eosinophil in BALF had closer relation to airway responsiveness (r = -0.84, P < 0.01). The content of peroxidase in hypodense eosinophils in BALF for guinea pigs treated by inhalation of PAF was lowered markedly than that in normodense eosinophil (P < 0.05). The result suggested that chemotaxis and activation of eosinophils by PAF might play an important role in airway hyperresponsiveness.     

Dissociation of airway responsiveness and bronchoalveolar lavage (BAL) cell composition in sensitized guinea-pigs after daily inhalation of ovalbumin

The association between inflammatory cell influx, cell activation status and change of airway responsiveness to acetylcholine (ACh) after daily inhalation of ovalbumin (OA) in sensitized guinea-pigs was investigated. Starting 3 weeks after sensitization (OA at 50 mg/kg s.c.+i.p.) guinea-pigs were exposed daily to 2% OA (10 min; under cover of 0.5 mg/kg mepyramine i.p. 15 min before OA) for 2 weeks. Concentration-response curves (CRCs) for inhaled ACh were performed 24 h after the last OA-challenge and 24 h after another single OA-inhalation 1 week later. CRCs for inhaled ACh were neither affected 24 h after the last OA challenge (daily for two weeks) nor 24 h after another OA-inhalation one week later. In contrast, bronchoalveolar lavage (BAL) from repeatedly OA- sensitized/-challenged guinea-pigs immediately after the last CRC showed a significant increase of total cell count by about tenfold and increases in eosinophils by about 20-fold, neutrophils by 30-fold, macrophages by about fivefold and lymphocytes by about tenfold (P < 0.05, multiple Wilcoxon-test). In contrast, markers of cell activation (EPO, MPO) were significantly decreased (P < 0.05). Methylprednisolone almost completely prevented these changes in increased cell numbers and decreased cell activation (vs OA contr., P < 0.05). The lack of increased airway hyperresponsiveness despite a massive inflammatory cell influx suggests other factors controlling airway responsiveness than inflammation.     

Are there alternative avian influenza viruses for generation of stable attenuated avian-human influenza A reassortant viruses?

The present study evaluated gull influenza A viruses as donors of attenuating genes for the production of live, attenuated influenza A H1N1 and H3N2 avian-human (ah) reassortant viruses for use as vaccines to prevent disease due to influenza A viruses in humans. The previously evaluated duck influenza A viruses were abandoned as donors of attenuating avian influenza virus genes because clinical evaluation of H1N1 and H3N2 ah reassortant virus vaccines derived from duck viruses documented residual virulence of H1N1 reassortants for seronegative infants and young children. Gull influenza A viruses occupy an independent ecologic niche and are rarely isolated from species other than gulls. The possibility of using gull influenza A viruses as donors of internal gene segments in ah reassortant viruses was evaluated in the present study using three different gull viruses and three human influenza A viruses. Gull-human H3N2 reassortant influenza A viruses with the desired 6-2 genotype (six internal avian influenza virus genes and the two human influenza virus surface glycoprotein genes) were readily generated and were found to be attenuated for squirrel monkeys and chimpanzees. However, ah reassortant viruses with gull and human influenza A H1N1 genes were difficult to generate, and reassortants that had the desired genotype of six gull virus genes with human influenza A H1 and N1 genes were not isolated despite repeated attempts. The gull PB2, NP and NS genes were not present in any of the gull-human H1N1 reassortants generated. The under-representation of these three gene segments suggests that reassortants bearing one or more of these three gene segments might have reduced viability indicative of a functional incompatibility in their gene products. The difficulties encountered in the generation of a 6-2 gull-human H1N1 reassortant virus are sufficient to conclude that the gull influenza A viruses tested would not be useful as donors of sets of six internal genes to attenuate human influenza A viruses. This study also identifies influenza virus gene segments that appear to be incompatible for generation of reassortants. Elucidation of the molecular basis of this restriction may provide information on intergenic interactions involved in virion assembly or packaging.     

Protection against a lethal avian influenza A virus in a mammalian system

The question of how best to protect the human population against a potential influenza pandemic has been raised by the recent outbreak caused by an avian H5N1 virus in Hong Kong. The likely strategy would be to vaccinate with a less virulent, laboratory-adapted H5N1 strain isolated previously from birds. Little attention has been given, however, to dissecting the consequences of sequential exposure to serologically related influenza A viruses using contemporary immunology techniques. Such experiments with the H5N1 viruses are limited by the potential risk to humans. An extremely virulent H3N8 avian influenza A virus has been used to infect both immunoglobulin-expressing (Ig+/+) and Ig-/- mice primed previously with a laboratory-adapted H3N2 virus. The cross-reactive antibody response was very protective, while the recall of CD8(+) T-cell memory in the Ig-/- mice provided some small measure of resistance to a low-dose H3N8 challenge. The H3N8 virus also replicated in the respiratory tracts of the H3N2-primed Ig+/+ mice, generating secondary CD8(+) and CD4(+) T-cell responses that may contribute to recovery. The results indicate that the various components of immune memory operate together to provide optimal protection, and they support the idea that related viruses of nonhuman origin can be used as vaccines.     

Proton resonance assignments and ligand exchange kinetics in high-spin and mixed-spin myoglobin complexes using two-dimensional exchange spectroscopy

Local lymph node activation and increased total serum IgE levels are suggested to be predictive parameters of airway hypersensitivity caused by low molecular weight (LMW) chemicals. Whether increases of total serum IgE are indicative of actual induction of specific airway reactions (morphological and functional) after inhalation challenge was examined in the present study. In Brown Norway (BN) and Wistar rats, serum IgE concentrations were examined following topical exposure of chemicals with known diverse sensitization potential in humans: trimellitic anhydride (TMA), a dermal and respiratory sensitizer; dinitrochlorobenzene (DNCB), a dermal sensitizer with no known potential to cause respiratory allergy; and methyl salicylate, a skin irritant devoid of sensitizing properties. Functional and histopathological changes in the respiratory tract were examined after subsequent inhalatory challenge with these chemicals. Of the three tested chemicals, only topical exposure to TMA resulted in a significant increase in total serum IgE concentrations in the high-IgE-responding BN rat. Upon subsequent inhalatory challenge of these rats, TMA induced specific airway reactions which included a sharp decrease in respiratory rate during challenge, followed by an increase in breathing rate with a concomitant decrease in tidal volume 24 and 48 h after inhalatory challenge, and histopathological changes in the larynx and lungs of animals necropsied 48 h after challenge. Interestingly, despite low IgE levels, TMA induced histopathological changes in the larynx and lungs of Wistar rats too. Laryngeal changes were also observed in Wistar rats upon sensitization and challenge with DNCB. These data suggest that increased total serum IgE after topical sensitization is associated with immediate-type specific airway reactivity after inhalation challenge in BN rats and thus may be a valuable parameter in testing for respiratory sensitization potential of LMW compounds. Histopathological examination upon subsequent inhalation challenge of sensitized low-IgE-responders may provide information on other allergic inflammatory airway reactions.     

Inhaled procaterol inhibits histamine-induced airflow obstruction and microvascular leakage in guinea-pig airways with allergic inflammation

BACKGROUND: Beta2-adrenoceptor agonists (beta2-agonists) are shown to inhibit airway microvascular leakage in experimental animals. This effect may change in animals with chronic airway inflammation. OBJECTIVE: We examined whether inhaled beta2-agonists inhibit microvascular leakage in guinea-pig airways with chronic allergic inflammation. METHODS: Three weeks after the sensitization with ovalbumin (OA; 6 mg/mL), each guinea pig was challenged with inhaled OA once a day for 1 or 3 weeks. Control animals without sensitization with OA also inhaled vehicle for OA (saline) for 3 weeks. One day after the last challenge, different doses of inhaled procaterol (1, 3 or 10 microg/mL) or vehicle was given to animals for 10 min after an anaesthesia. Fifteen minutes after the end of inhalation, the animals were given i.v. Evans blue dye (EB dye; 20 mg/kg), a marker of microvascular leakage, and then i.v. histamine (3 or 30 microg/kg) or vehicle. Lung resistance, a parameter of airflow obstruction, was measured for 6 min and the lungs were removed to calculate the amount of extravasated EB dye into the airways. RESULTS: A significant increase in eosinophil infiltration into the airways was seen in sensitized and challenged animals compared with control animals without sensitization. Among animals receiving antigenic exposure for either 0 (control), 1 or 3 weeks, 10 microg/mL procaterol significantly inhibited 30 microg/kg histamine-induced increase in EB dye extravasation to a similar degree (ranged from 28.7 to 69.8% inhibition) as well as that in lung resistance (more than 90% inhibition in all groups). The minimal dose of procaterol to inhibit 3 microg/kg histamine-induced microvascular leakage was not different between nonsensitized control animals and those sensitized and challenged for 3 weeks at all airway levels. CONCLUSION: Inhaled beta2-adrenoceptor agonists may be also potent in attenuating microvascular leakage even in the airways with chronic allergic inflammation.     

Antiviral activity of plant flavonoid, 5,7,4'-trihydroxy-8-methoxyflavone, from the roots of Scutellaria baicalensis against influenza A (H3N2) and B viruses

We investigated effects of isoscutellarein-8-methylether (5,7,4'-trihydroxy-8-methoxyflavone, F36) from the roots of Scutellaria baicalensis on the single-cycle replication of mouse-adapted influenza viruses A/Guizhou/54/89 (H3N2 subtype) and B/Ibaraki/2/85 in Madin-Darby canine kidney (MDCK) cells. The agent suppressed replication of these viruses from 6 to 12 h after incubation in a dose-dependent manner by 50% at 20 microM and 90% at 40 microM, respectively. F36 (50 microM) reduced the release of B/Ibaraki virus in the medium by 90-93% when it was added to the MDCK cells at 0 to 4 h after incubation. The cell-associated virus determined by sialidase activity was also reduced by the treatment at 0 to 4 h. F36 (120 microM) inhibited the low pH-dependent membrane fusion of both the viruses with the liposome containing mixed gangliosides from bovine brain. However, the agent little affected the hemagglutination and RNA-dependent RNA polymerase activities of these viruses in vitro. These results suggest that F36 inhibits the replication of A/Guizhou and B/Ibaraki viruses at least partly by inhibiting the fusion of viral envelopes with the endosome/lysosome membrane which occurs at the early stage of the virus infection cycle. F36 (0.5 mg/kg) showed no antiviral activity against A/Guizhou and B/Ibaraki viruses in mice when administered intranasally 5 min prior to virus inoculation, whereas it significantly inhibited their proliferation in the mouse lung when administered intranasally 7 times (total 3.5 mg/kg) from 18 h before to 54 h after virus infection.     

Airway responsiveness to hyperosmolar saline challenge in cystic fibrosis: a pilot study

Hyperosmolar aerosols are used to assess airway responsiveness in subjects with asthma. Using a 10% NaCl aerosol, we investigated airway responsiveness in 23 cystic fibrosis (CF) subjects (12 females, 11 males; 19.1 +/- 3.3 years) who had asthma-like symptoms. The pre-challenge predicted forced expiratory volume in 1 second (FEV1) was 74.7 +/- 21.5. The aerosol was generated by a MistO2gen 143A ultrasonic nebulizer and inhaled for 0.5, 1, 2, 4, 8, 8, and 8 minutes or part thereof. Spirometry was performed before and 1 minute after each inhalation period. The challenge was stopped when a > or = 20% fall from the baseline FEV1 was recorded, after the last inhalation period, or when requested by the subject. We recorded different responses to 10% NaCl among subjects. In 7, the FEV1 fell progressively throughout the challenge in a manner similar to asthmatics. By contrast, in 15 subjects the FEV1 was higher at the completion of challenge compared to during challenge, i.e., the fall in FEV1 was transient. In 7 of these subjects, the final FEV1 at the end of the challenge was higher than the pre-challenge FEV1. We conclude that inhaled 10% hyperosmolar saline causes either progressive and sustained or transient airway narrowing during challenge in the majority of CF subjects. The cause of the transient airway narrowing requires further investigation.     

Characterization of influenza A/HongKong/156/97 (H5N1) virus in a mouse model and protective effect of zanamivir on H5N1 infection in mice

A recent outbreak of influenza in Hong Kong was caused by a highly virulent virus of avian origin. Concern that the appearance of such a virus in the human population may be a harbinger of a new pandemic has brought increased attention to the issue of antivirals available for treatment of influenza. A/HongKong/156/97 (H5N1), the first virus of H5N1 subtype isolated from a human host, is highly virulent in the mouse model and can infect mouse lungs without requiring adaptation. High mortality and evidence of systemic disease, including spread to the brain after intranasal inoculation, are observed. Zanamivir, a novel neuraminidase inhibitor, is effective at decreasing replication of the virus in vitro. In a model of lethal challenge in mice, zanamivir reduces lung titers of the virus and decreases morbidity and mortality.     

Human influenza virus A/HongKong/156/97 (H5N1) infection

Introduction of influenza viruses with gene segments of avian origin into the human population may result in the emergence of new pathogenic human influenza viruses. The recent infection of a 3-year-old boy with an influenza A (H5N1) virus of avian origin can be considered as an example of such an event. However, this virus, influenza A/Hong Kong/156/97 (H5N1) and the 17 additional H5N1 viruses isolated from humans by the end of 1997 lack the ability to spread efficiently amongst humans and therefore have limited pandemic potential. However, the possibility of reassortment of these viruses with currently circulating human viruses illustrates the need for pandemic preparedness.     

Requirements for allergen-induced airway hyperreactivity in T and B cell-deficient mice

BACKGROUND: The pathogenesis of asthma is believed to reflect antigen-induced airway inflammation leading to the recruitment of eosinophils and activation of mast cells through cell-associated IgE. Controversies persist however, regarding the relative importance of different pathogenic cells and effector molecules. MATERIALS AND METHODS: A variety of gene-targeted mice were examined for the induction of cholinergic airway hyperresponsiveness (AH), allergic airway inflammation, mucus production, and serum IgE reactivity following intratracheal challenge with a potent allergen. AH was determined using whole-body plethysmography following acetylcholine challenge. Where possible, results were confirmed using neutralizing antibodies and cell-specific reconstitution of immune deficient mice. RESULTS: T and B cell-deficient, recombinase-activating-gene-deficient mice (RAG -/-) failed to develop significant allergic inflammation and AH following allergen challenge. Reconstitution of RAG -/- mice with CD4+ T cells alone was sufficient to restore allergen-induced AH, allergic inflammation, and goblet cell hyperplasia, but not IgE reactivity. Sensitized B cell-deficient mice also developed airway hyperreactivity and lung inflammation comparable to that of wild-type animals, confirming that antibodies were dispensable. Treatment with neutralizing anti-IL-4 antibody or sensitization of IL-4-deficient mice resulted in loss of airway hyperreactivity, whereas treatment with anti-IL-5 antibody or sensitization of IL-5-deficient mice had no effect. CONCLUSIONS: In mice, CD4+ T cells are alone sufficient to mediate many of the pathognomonic changes that occur in human asthma by a mechanism dependent upon IL-4, but independent of IL-5, IgE, or both. Clarification of the role played by CD4+ T cells is likely to stimulate important therapeutic advances in treatment of asthma.     

The haemagglutinins of influenza A (H1N1) viruses in the 'O' or 'D' phases exhibit biological and antigenic differences

Influenza A (H1N1) viruses when initially isolated in mammalian cell cultures (MDCK cells) had different agglutination reactions with chicken and guinea-pig erythrocytes compared to the same viruses after passage. On first isolation the virus HA resembled the 'O' phase viruses described originally by Burnet and Bull and agglutinated mammalian but not avian erythrocytes. After passage, the virus HA resembled a classical 'D' phase virus and agglutinated both avian and mammalian erythrocytes. Monoclonal and polyclonal antisera detected antigenic differences between the HAs of the viruses in the 'O' and 'D' phases. The 'O' phase virus HA reacted preferentially with antibodies in post infection human antisera. Viruses in the 'O' phase replicated poorly in the allantoic cavity of embryonated hens' eggs whilst 'D' phase virus replicated in both MDCK cells and in embryonated hens' eggs. At least three distinguishable subpopulations of influenza A (H1N1) viruses may co-exist in clinical throat swab material, including viruses possessing HAs in the 'O' and 'D' phases and other 'D' phase viruses cultivable in embryonated hens' eggs but antigenically distinguishable from the corresponding 'D' phase virus in MDCK cells.     

Ability of temperature-sensitive mutants of the recombinant influenza S/N (H2N1) virus to induce immunity to parental (H0N1 and H2N2) viruses

The behavior in mice of two thermosensitive (ts) mutants (denoted ts217 and ts700) of the recombinant influenza virus S/N (H2N1) was studied. The parental thermoresistant (tr) virus and both of the mutants were capable of inducing protection against pneumotropic A/Singapore (H2N2) and A/WS (H0N1) challenge viruses. Immunity against the Singapore virus, with which the S/N virus shared the hemagglutinin, developed earlier than against the WS virus, with which the S/N virus shared the neuraminidase. The tr and ts217 viruses were immunologically more active than the ts700 virus. The first two viruses grew markedly better in mouse lungs than did the latter. In the course of ts217 virus replication in vivo, revertants capable of growing at 39 degrees C appeared readily. On the other hand, the ts700 virus proved to be genetically stable. These data seem to provide evidence of a linkage between the stability of the ts phenotype, reproductive capacity in mouse lungs, and immunogenicity in the viruses examined.