Effectiveness of sodium hypochlorite in preventing inoculation of periapical tissues with contaminated patency files.

The aim of this study was to analyze the effectiveness of 5.25% sodium hypochlorite (NaOCI) in preventing inoculation of periapical tissues with contaminated patency files. Twenty-eight extracted human permanent teeth with single canals were used in the study. Group I teeth were filled with NaOCl, and #15 stainless steel files contaminated with Streptococcus sanguis (ATCC #10556) were allowed to pass through the NaOCI into the culture medium. The teeth in group II were also filled with NaOCl, but the contaminated files used in group II canals were immersed in NaOCl for 10 s prior to being placed into the canals and cultured. The negative control group used sterile files (0% growth), the first positive control group used contaminated patency files in teeth with empty canals (100% growth), and the second positive control group placed contaminated files into broth next to teeth filled with NaOCl (to evaluate potential chlorine leakage; 100% growth). The experimental results showed no positive growth of S. sanguis for groups I and II, indicating that the NaOCl present in the canal after irrigation was sufficient to kill the test organism.

Effect of condoms on reducing the transmission of herpes simplex virus type 2 from men to women.

CONTEXT: Herpes simplex virus type 2 (HSV-2) is one of the most common sexually transmitted infections in the United States. No prospective study has shown the ability of condoms to reduce transmission of HSV-2. OBJECTIVE: To evaluate risk factors for HSV-2 acquisition and efficacy of condoms in prevention of HSV-2 transmission. DESIGN: Analysis of data from a randomized, double-blind, placebo-controlled trial conducted December 13, 1993, to June 28, 1996, of an ineffective candidate HSV-2 vaccine with 18 months of follow-up. SETTING: Eighteen clinical trial centers in the United States. PARTICIPANTS: A total of 528 monogamous couples discordant for HSV-2 infection, including an HSV-2-susceptible population of 261 men and 267 women. MAIN OUTCOME MEASURE: Acquisition of HSV-2 infection by susceptible partners, compared with those remaining free of HSV-2 with regard to demographic characteristics, sexual activity, and condom use. RESULTS: Twenty-six women (9.7%) vs 5 men (1.9%) acquired HSV-2, for a rate per 10 000 sex acts (episodes of sexual intercourse) of 8.9 vs 1.5, respectively (P<.001). In multivariable analysis, younger age (adjusted hazard ratio [HR] per 5 years, 1.57; 95% confidence interval [CI], 1.22-2.04), seropositivity for HSV-1 and HSV-2 vs HSV-2 alone in the source partner (adjusted HR, 2.34; 95% CI, 1.14-4.82), and more frequent sexual activity (adjusted HR per additional sex act per week, 1.10; 95% CI, 1.01-1.19) were associated with higher risk of HSV-2 acquisition. Condom use during more than 25% of sex acts was associated with protection against HSV-2 acquisition for women (adjusted HR, 0.085; 95% CI, 0.01-0.67) but not for men (adjusted HR, 2.02; 95% CI, 0.32-12.50). Risk of HSV-2 transmission declined from 8.5 per 100 person-years in the initial 150-day interval to 0.9 per 100 person-years in the final 150-day interval (P =.002 for trend), concurrent with a decrease in sexual activity and proportion of sex acts occurring when the source partner had genital lesions. CONCLUSIONS: Condom use offers significant protection against HSV-2 infection in susceptible women. Changes in sexual behavior, correlated with counseling about avoiding sex when a partner has lesions, were associated with reduction in HSV-2 acquisition over time. These data suggest that identification of discordant couples can reduce transmission of HSV-2, especially for heterosexual couples in which the male partner has HSV-2 infection.

Effects of antigen dose and immunization regimens on antibody responses to a cytomegalovirus glycoprotein B subunit vaccine.

The purpose of this phase I study was to evaluate the safety and immunogenicity of 2 doses of cytomegalovirus glycoprotein B (CMV gB)/MF59 vaccine at 3 different immunization schedules. Ninety-five volunteers were randomized to 6 groups. Antibodies to gB represent the majority of the CMV-specific neutralizing response. Three groups received 5 microgram of gB antigen combined with MF59 (a proprietary adjuvant) and 3 groups received a 30-microgram dose at 0, 1, and 2 months; 0, 1, and 4 months; or 0, 1, and 6 months. The vaccine was well tolerated, and there was no significant difference in antibody production between the 2 doses. The vaccine induced highest antibody titers when given at 0, 1, and 6 months. A low dose of CMV gB/MF59 may be the preferred dose for future studies.

An acellular pertussis vaccine in healthy adults: safety and immunogenicity. Pennridge Pediatric Associates.

Recent data indicate that Bordetella pertussis can be an important cause of illness in adolescents and adults. In a randomized observer- and subject-blinded study, adults (> or = 18 years of age) received an acellular pertussis (aP) vaccine containing genetically inactivated pertussis toxin (PT), filamentous hemagglutinin (FHA) and pertactin (PRN), or a saline placebo, and were monitored for safety and immunogenicity. IgG antibodies to PT, FHA, and PRN were measured by enzyme-linked immunosorbent assay (ELISA) and PT neutralization by a Chinese hamster ovary (CHO) cell assay. Local reactions, more common in the aP group, were mild and transient. One month after immunization, geometric mean ELISA antibody concentrations for the aP and placebo groups, respectively, were: anti-PT, 463 and 7.6; anti-FHA, 417 and 18; and anti-PRN, 855 and 14. The anti-PT neutralization titers for the aP and placebo groups were 1:3439 and 1:58 respectively. This aP vaccine is a safe and immunogenic candidate booster vaccine against pertussis for adults.

Recombinant glycoprotein vaccine for the prevention of genital HSV-2 infection: two randomized controlled trials. Chiron HSV Vaccine Study Group.

CONTEXT: In the last 3 decades, herpes simplex virus type 2 (HSV-2) infection seroprevalence and neonatal herpes have increased substantially. An effective vaccine for the prevention of genital herpes could help control this epidemic. OBJECTIVE: To evaluate the efficacy of a vaccine for prevention of HSV-2 infection. DESIGN: Two randomized, double-blind, placebo-controlled multicenter trials of a recombinant subunit vaccine containing 30 microg each of 2 major HSV-2 surface glycoproteins (gB2 and gD2) against which neutralizing antibodies are directed, administered at months 0, 1, and 6. Control subjects were given a citrate buffer vehicle. Participants were followed up for 1 year after the third immunization. SETTING AND PARTICIPANTS: We enrolled 2393 persons from December 10, 1993, to April 4, 1995, who were HSV-2 and human immunodeficiency virus seronegative. One trial with 18 centers enrolled 531 HSV-2-seronegative partners of HSV-2-infected persons; the other, with 22 centers, enrolled 1862 persons attending sexually transmitted disease clinics. A total of 2268 (94.8%) met inclusion criteria and were included in the analysis with 1135 randomized to placebo and 2012 to vaccine. MAIN OUTCOME MEASURE: Time to acquisition of HSV-2 infection, defined by seroconversion or isolation of HSV-2 in culture during the study period by randomization group. RESULTS: Time-to-event curves indicated a 50% lower acquisition rate among vaccine vs placebo recipients during the initial 5 months of the trial; however, overall vaccine efficacy was 9% (95% confidence interval, -29% to 36%). Acquisition rates of HSV-2 were 4.6 and 4.2 per 100 patient-years in the placebo and vaccine recipients, respectively (P =.58). Follow-up of vaccine recipients acquiring HSV-2 infection showed vaccination had no significant influence on duration of clinical first genital HSV-2 episodes (vaccine, median of 7.1 days; placebo, 6.5 days; P>.10) or subsequent frequency of reactivation (median monthly recurrence rate with vaccine, 0.2; with placebo, 0.3; P>.10). The vaccine induced high levels of HSV-2-specific neutralizing antibodies in vaccinated persons who did and did not develop genital herpes. CONCLUSIONS: Efficient and sustained protection from sexual acquisition of HSV-2 infection will require more than high titers of specific neutralizing antibodies. Protection against sexually transmitted viruses involving exposure over a prolonged period will require a higher degree of vaccine efficacy than that achieved in this study.

A randomized, controlled study in adults of the immunogenicity of a novel hepatitis B vaccine containing MF59 adjuvant.

The safety and immunogenicity of a novel hepatitis B virus (HBV) vaccine containing recombinant PreS2 and S antigens combined with MF59 adjuvant (HBV/MF59) was evaluated in healthy adults (N=230) who were randomized to receive 2 or 3 immunizations of either the study vaccine or a licensed control vaccine (Recombivax HB). After a single immunization, 105 of 118 (89%) recipients of HBV/MF59 achieved protective serum levels of anti-HBs antibody (> 10 mIU/ml), compared with 13 of 110 (12%) recipients of licensed vaccine (P < 0.001). The geometric mean titer (GMT) after 2 doses of HBV/MF59 given 2 months apart (13,422 mIU/ml) was more than 5-fold higher than that following 3 doses of licensed vaccine given over 6 months (2,346 mIU/ml; P < 0.001). The GMT following 3 injections of HBV/MF59 (249,917 mIU/ml) was 100-fold higher than licensed vaccine (P < 0.001). Anti-PreS2 antibodies were elicited in over 90% of the subset of HBV/MF59 recipients tested. Both vaccines were well tolerated; transient, mild-to-moderate local inflammation was the major postinjection reaction.

Safety, pharmacokinetics, and antiviral response of CD4-immunoglobulin G by intravenous bolus in AIDS and AIDS-related complex.

To assess the safety, pharmacokinetics, and antiviral effects of intravenous recombinant CD4 immunoglobulin G (CD4-IgG), a 12-week Phase One study with an optional maintenance phase was performed. Twenty-two subjects with advanced human immunodeficiency virus (HIV) infection were enrolled; 15 subjects completed the initial 12 weeks. CD4-IgG doses were 30, 100, or 300 micrograms/kg weekly; 1,000 micrograms/kg once, twice, or three times per week; or 3,000 micrograms/kg twice weekly. Serum concentrations of CD4-IgG increased linearly with dose, with average peak serum concentrations of 22 micrograms/ml with 1,000 micrograms/kg. CD4-IgG was well tolerated; one patient had self-limited tachycardia and flushing associated with CD4-IgG therapy. No changes were seen in CD4 cell counts, hematologic or coagulation studies, serum chemistries, HIV p24 antigen titers, or plasma HIV titers. No subject developed anti-CD4 antibodies. HIV isolates from five patients had IC90 values that were higher than the peak concentrations of CD4-IgG achieved in those patients. Additional studies that achieve higher CD4-IgG concentrations are necessary to evaluate the antiviral activity of this compound.

Treatment of steroid-dependent asthma with recombinant interferon-gamma.

We have recently reported that treatment of patients with severe atopic dermatitis with recombinant interferon-gamma (rIFN-gamma) resulted in clinical improvement as well as a reduction of circulating eosinophils. Since IgE-dependent late phase allergic reactions and eosinophilic infiltration are thought to play an important role in the pathogenesis of asthma, we conducted a two centre randomized double-blind placebo-controlled trial of rIFN-gamma in the treatment of steroid-dependent asthma. Patients were treated with daily subcutaneous injections of either 0.05 mg/m2 rIFN-gamma (n = 9) or placebo (n = 11) for 90 days. All patients completed the study without significant drug toxicity noted. Oral prednisone dose, forced expiratory volume in 1 second (FEV1), peak expiratory flow rates (PEFR) and circulating eosinophil counts were monitored throughout the trial. There was no significant difference between the two treatment groups in per cent reduction from baseline of daily prednisone (P = 0.51). There was also no significant difference between the two treatment groups in per cent change from baseline in FEV1 (P = 0.54) or in PEFR (P = 0.75). Total circulating eosinophil counts decreased by 31% in the rIFN-gamma group and increased by 8.5% in the placebo group (P = 0.09). We conclude that this treatment regimen was not effective in patients with steroid-dependent asthma.

Recombinant interferon gamma therapy for atopic dermatitis.

BACKGROUND: Atopic dermatitis is characterized by immunologic abnormalities including evidence for reduced interferon gamma production. Therapeutic options for treatment of atopic dermatitis are limited and unsatisfactory. Previous open trials have suggested efficacy for recombinant interferon-gamma (rIFN-gamma) in treatment of severe atopic dermatitis. We describe the results of treatment with rIFN-gamma, assessing clinical, immunologic, and laboratory safety parameters in 83 patients with moderate to severe atopic dermatitis. OBJECTIVE: Our purpose was to determine in a randomized, placebo-controlled, double-blind multicenter study the effects of recombinant human interferon gamma therapy in patients with atopic dermatitis. METHODS: Patients received 50 micrograms/m2 rIFN-gamma (n = 40) or placebo (n = 43) by daily subcutaneous injection for 12 weeks. Seventy-eight patients completed the treatment course; two patients receiving rIFN-gamma (one because of constitutional side effects) and three receiving placebo discontinued treatment before completion. Physician and patient overall response evaluations, clinical severity scores, body surface area involvement, and laboratory parameters were monitored throughout the trial. RESULTS: Patients in both treatment groups were similar except that the rIFN-gamma group was older and had a longer disease duration. Forty-five percent of rIFN-gamma-treated patients and 21% of placebo-treated patients achieved greater than 50% improvement in physicians' overall response evaluations (p = 0.016). As estimated by patients, responses also showed significant improvement in the rIFN-gamma group compared with the placebo group (53% vs 21%, p = 0.002). Significant reductions in erythema (p = 0.035) and in excoriations or erosions (p = 0.045) occurred in rIFN-gamma-treated patients. Other atopic symptoms such as conjunctivitis (p < 0.002) were also reduced in the rIFN-gamma group. Occasional headaches, myalgias, or chills occurred in 30% to 60% of rIFN-gamma-treated patients but were effectively prevented by pretreatment acetaminophen and by dosing at bedtime. Grade II granulocytopenia occurred in five rIFN-gamma patients but normalized with continued treatment. Reduction to alternate-day dosing was necessary for six patients in the rIFN-gamma group and two in the placebo group. Seven had mild elevations of hepatic transaminase levels that did not affect therapy. The mean eosinophil count was significantly reduced (p = 0.003), whereas a nonsignificant increase in serum IgE levels occurred in the active treatment group. CONCLUSION: This study demonstrated that rIFN-gamma given by daily subcutaneous injection over a 12-week period was safe, well accepted, and effective in reducing inflammation, clinical symptoms, and eosinophilia in severe atopic dermatitis.

A randomized prospective clinical trial to determine the efficacy of interferon-gamma in severely injured patients.

Many aspects of the normal immune response are depressed after severe injury. Reduced monocyte human leukocyte antigen-DR (HLA-DR) levels have closely correlated with the development of major infection. After a pilot study with recombinant interferon-gamma (rIFN-gamma) showed restoration of depressed HLA-DR levels after major injury, a multicenter, prospective, randomized, double-blind trial was conducted. Two hundred thirteen trauma patients who were at high risk of infection received either placebo or rIFN-gamma (100 micrograms) subcutaneously each day for 10 days after admission. One hundred ninety-three patients were evaluable with respect to primary end points. Patients treated with rIFN-gamma were older (p = 0.10) and had more severe modes of injury (p = 0.02). By the third day, both monocyte HLA-DR antigen expression and outcome predictive score were significantly better in the rIFN-gamma-treated group than in the placebo group (p = 0.0001 and p = 0.0006, respectively). Nine deaths occurred in patients treated with rIFN-gamma compared with 12 deaths in the placebo group (p = 0.46). Major infections requiring surgical drainage or debridement occurred in 17 patients treated with rIFN-gamma compared with 22 treated with placebo. No difference between treatment arms was noted in overall major or minor infection rates, but there were fewer severe infections that required reoperation or computer tomographic-guided drainage in patients receiving IFN-gamma. While these results suggest that rIFN-gamma may be useful in some aspects of infection in the patient with severe trauma, a larger trial with longer treatment will be needed to prove the comprehensive value of rIFN-gamma.

Phase 1 study of recombinant human CD4-immunoglobulin G therapy of patients with AIDS and AIDS-related complex.

The safety and pharmacokinetics of recombinant CD4-immunoglobulin G (rCD4-IgG) were evaluated in a phase 1 study with dose escalation. A total of 16 patients, 6 with AIDS and 10 with AIDS-related complex, were evaluated at two university-affiliated hospital clinics. rCD4-IgG was administered once weekly for 12 weeks to four patients each at doses of 0.03, 0.1, 0.3, and 1.0 mg/kg of body weight. Dosing was intravenous for two patients in the 1.0-mg/kg dose group and intramuscular for the remaining patients. Dosing was intravenous for two patients in the 1.0-mg/kg dose group and intramuscular for the remaining patients. Pharmacokinetic, toxicity, and immunologic variables were monitored with all patients. Administration of rCD4-IgG was well tolerated, with no important clinical or immunologic toxicities noted. No subjects required dose reduction or discontinuation of therapy due to toxicity. No consistent changes were seen in human immunodeficiency virus antigen levels in serum or CD4 lymphocyte populations. The volume of distribution was small, and compared with that of rCD4, the half-life of the hybrid molecule was markedly prolonged following intramuscular or intravenous administration. The rate and extent of absorption following intramuscular dosing were variable. Intramuscular administration of rCD4-IgG appears to be inferior to intravenous dosing from a pharmacokinetic standpoint, with lower peak concentrations and variable absorption. After intravenous administration, peak concentrations of rCD4-IgG in serum (20 to 24 micrograms/ml) that have shown antiviral activity in vitro against more sensitive clinical isolates of human immunodeficiency virus were achieved. The peak concentrations in serum after intramuscular administration were below these levels. Treatment with rCD4-IgG was well tolerated at the doses administered to patients in this study but did not result in significant changes in CD4 lymphocyte counts or p24 antigen levels in serum.

The safety and pharmacokinetics of recombinant soluble CD4 (rCD4) in subjects with the acquired immunodeficiency syndrome (AIDS) and AIDS-related complex. A phase 1 study.

STUDY OBJECTIVE: To evaluate the safety and pharmacokinetics of recombinant, soluble human CD4 (rCD4) in subjects with the acquired immunodeficiency syndrome (AIDS) and AIDS-related complex. The protein rCD4 binds to envelope protein, gp120, of the human immunodeficiency virus (HIV) and blocks HIV infection of CD4 lymphocytes in vitro. DESIGN: Phase 1 trial with dose escalation. SETTING: Two university-affiliated hospital clinics. SUBJECTS: Of 42 subjects enrolled, 29 had AIDS and 13 had AIDS-related complex. INTERVENTIONS: The rCD4 was administered by rapid intravenous infusion on day 1, followed by a 3-day washout, then once a day for 10 days, followed by a 7-day washout, and then three times a week for 8 weeks. Doses of 1, 10, 30, 100, and 300 micrograms/kg body weight per day of rCD4 were administered intravenously to 6 subjects at each dose level. Twelve additional patients received 300 micrograms/kg.d of rCD4: 6 by intramuscular and 6 by subcutaneous injection. All subjects were monitored for toxicity. Immunologic and virologic variables were also monitored. MEASUREMENTS AND MAIN RESULTS: Administration of rCD4 was not associated with important toxicity as determined by clinical monitoring or by serum chemistry, hematologic, or immunologic variables. No subjects required dose reduction or discontinuation of therapy due to rCD4-related toxicity. No consistent or sustained changes in CD4 lymphocyte populations or HIV antigen levels were observed. The volume of distribution of rCD4 was small, and clearance remained constant over the dose range studied. The bioavailability of intramuscular injection and subcutaneous injection was 51% and 45%, respectively. CONCLUSIONS: At the dose levels used in this study, rCD4 appears safe and well tolerated. Serum concentrations of rCD4 were achieved that were comparable to concentrations shown to have antiviral activity in vitro. Further studies are indicated to determine whether rCD4 or related molecules will be useful in treating HIV infection.

Butoconazole vaginal cream in the treatment of vulvovaginal candidiasis. Comparison with miconazole nitrate and placebo.

A double-blind, parallel study was conducted comparing a new imidazole derivative, butoconazole nitrate, with placebo and miconazole nitrate for the treatment of vulvovaginal candidiasis. Patients were randomly assigned to six treatment regimens. Butoconazole was found to be an effective antifungal agent in both the six- and three-day treatment schedules. The incidence of local side effects from both tested imidazoles was low.

Flunisolide aerosol for treatment of severe, chronic asthma in steroid-independent children.

The efficacy and safety of flunisolide aerosol were studied in 46 steroid-independent children with asthma inadequately controlled by nonsteroid drugs. This was a double-blind, placebo-controlled, parallel study lasting eight weeks. Patients were randomly assigned either flunisolide by inhalation, 0.5 mg twice a day, or placebo. Effectiveness was evaluated daily by symptom scores, by Wright peak flow measurements twice daily, and weekly by spirometry and physical examination. Adrenal function and throat cultures for Candida were evaluated before and after the test-drug treatment period. Flunisolide was administered to 25 patients and 21 received placebo. Most symptom scores were statistically significantly better in flunisolide-treated than in placebo-treated patients; these included severity of wheezing (P = .01), chest tightness (P = .01) and shortness of breath (P = .02), and frequency (P = .001) and severity of asthma attacks (P = .03). In addition, placebo-treated patients used significantly more bronchodilators than flunisolide-treated patients. In the final therapeutic effectiveness evaluation, 72% of flunisolide-treated patients received very good or good ratings, whereas only 29% of placebo-treated patients received these ratings (P = .005). No patient developed thrush, evidence of adrenal suppression, or other severe adverse reaction. Flunisolide aerosol was shown to be effective and safe in controlling asthma in children who were candidates for oral steroid therapy.

Short-term double-blind evaluation of flunisolide aerosol for steroid-dependent asthmatic children and adolescents.

The purpose of this study was to compare the effectiveness of flunisolide aerosol prescribed as .5 mg (two inhalations) twice daily and placebo in terms of oral steroid sparing ability in a population of 32 known steroid-dependent children and adolescents. Patients were stabilized on the lowest tolerated dose of daily AM or alternate AM oral corticosteroid for at least one month before entering the study. They were randomly assigned to either flunisolide or placebo treatment for the 12-week, double-blind trial. Patients were seen every two weeks for symptom assessment, physical examination, and pulmonary function testing. Tests of adrenal function were done initially and at the study's conclusion. The flunisolide group had improved asthma control compared with the placebo group. The daily oral steroid requirement decreased in 100 percent of the flunisolide group compared with 53 percent of the placebo group (P less than .01). Pulmonary function and endocrine function remained stable for both groups. There were no adverse effects. Flunisolide aerosol in doses of .5 mg twice daily appears to be topically active and to have oral steroid potential without apparent adverse effects.

Multicenter study of flunisolide aerosol in adult patients with steroid-dependent asthma.

Seventy-three adult, steroid-dependent asthmatic patients participated in a 16-wk, double-blind study testing the efficacy of flunisolide aerosol. Forty received flunisolide, and 33 received placebo. The mean daily prednisone requirement of patients receiving flunisolide fell 59.2% during the testing period, and that of the patients receiving placebo fell 19.7%. The median daily prednisone dose dropped 74.4% in the flunisolide group and 4.2% in the placebo group (p = 0.006). In the flunisolide group 75% tapered use of oral steroids 50% or more, and 27.5% stopped taking oral steroids completely. In the placebo group 36% tapered use of oral steroids 50% or more, and only 12% stopped taking them completely. Despite their reduction in systemic steroids, those patients receiving flunisolide achieved significantly greater reduction in the daily severity of wheezing (p = 0.014) and frequency of asthma attacks (p = 0.049) than did those receiving placebo. In the final evaluation of therapeutic response, 70% of patients receiving flunisolide were rated as having a very good or good response, and 30% were rated as having a fair or poor response. In contrast 33% of patients receiving placebo were rated as very good or good, and 67% were rated as fair or poor (p = 0.0009). No serious reactions were reported. Plasma cortisols showed an average increase of 42.9% in the flunisolide group but no change in the placebo group. Flunisolide aerosol is a well-tolerated and effective agent in the treatment of steroid-dependent asthma.

Episodic asthma as a bronchial provocation test.

This study, originally designed to investigate the efficacy of a new inhaled steroid, flunisolide, in New Orleans, demonstrated that episodic asthma (known as "New Orleans Asthma") still occurs in that city. Although its outbreaks are less frequent and severe than reported in previous years, they are still intense enough to affect asthmatics who are on maximal drug therapy. We found in this study that patients who were taking a sympathomimetic, methyl xanthine, and steroids both by inhalation (flunisolide) and by mouth (prednisone) required more prednisone during outbreaks. During such outbreaks the use of flunisolide not only delayed the need for more prednisone but also reduced the dosage needed. Furthermore, flunisolide had over-all prednisone-sparing benefits during the course of the whole 18-week study. Finally, throughout the study, asthma was less frequent in patients on flunisolide therapy, their over-all therapeutic response being significantly better than that of a control group. The authors conclude that New Orleans Asthma provides a natural provocation for extrinsic asthmatics in their normal milieu and thus provides an ideal situation for testing new anti-asthmatic treatments, especially in individuals with severe asthma in whom deliberate challenge may be unethical.