Histamine-releasing factor in severe asthma and rhinovirus-associated asthma exacerbation

Abstract

Background: Histamine-releasing factor (HRF) is implicated in allergic diseases. We previously showed its pathogenic role in murine models of asthma.

Objective: We aim to present data analysis from 3 separate human samples (sera samples from asthmatic patients, nasal washings from rhinovirus [RV]-infected individuals, and sera samples from patients with RV-induced asthma exacerbation) and 1 mouse sample to investigate correlates of HRF function in asthma and virus-induced asthma exacerbations.

Methods: Total IgE and HRF-reactive IgE/IgG as well as HRF in sera from patients with mild/moderate asthma or severe asthma (SA) and healthy controls (HCs) were quantified by ELISA. HRF secretion in culture media from RV-infected adenovirus-12 SV40 hybrid virus transformed human bronchial epithelial cells and in nasal washings from experimentally RV-infected subjects was analyzed by Western blotting. HRF-reactive IgE/IgG levels in longitudinal serum samples from patients with asthma exacerbations were also quantified.

Results: HRF-reactive IgE and total IgE levels were higher in patients with SA than in HCs, whereas HRF-reactive IgG (and IgG₁) level was lower in asthmatic patients versus HCs. In comparison with HRF-reactive IgE^low asthmatic patients, HRF-reactive IgE^high asthmatic patients had a tendency to release more tryptase and prostaglandin D₂ on anti-IgE stimulation of bronchoalveolar lavage cells. RV infection induced HRF secretion from adenovirus-12 SV40 hybrid virus transformed bronchial epithelial cells, and intranasal RV infection of human subjects induced increased HRF secretion in nasal washes. Asthmatic patients had higher levels of HRF-reactive IgE at the time of asthma exacerbations associated with RV infection, compared with those after the resolution. This phenomenon was not seen in asthma exacerbations without viral infections.

Conclusions: HRF-reactive IgE is higher in patients with SA. RV infection induces HRF secretion from respiratory epithelial cells both in vitro and in vivo. These results suggest the role of HRF in asthma severity and RV-induced asthma exacerbation.

Keywords: Asthma; HRF; IgE; IgG; asthma exacerbation; rhinovirus.

Fig. 1.

Increased HRF-reactive IgE in severe asthmatics and reduced HRF-reactive IgG in asthmatics. (A-D) Total IgE and HRF-reactive IgE and IgG in sera were quantified by ELISA. (D) Ratio of HRF-reactive IgE to HRF-reactive IgG. HC, healthy control (n=18); MA, mild/moderate asthma (n=16); SA, severe asthma (n=16). P values by Mann-Whitney U test (A-D).

Fig. 2.

HRF secretion is induced by RV in vitro and in vivo. (A) BEAS-2B cells were stimulated with HDM (100 μg/ml) or RV-1B (0.1 MOI) for 88 h. HDM>RV, cells stimulated with HDM for 72 h, then incubated with RV for another 16 h; HDM+RV, cells stimulated with HDM for 72 h and with HDM plus RV for the last 16 h. Secreted HRF was analyzed by SDS-PAGE (10% polyacrylamide gel) under nonreducing (upper panel) or reducing (lower panel) conditions and western blotting. 1*, HRF monomer; 2*, dimer; HMW-HRFs, high molecular weight HRFs (Mr > 148 kD); med, medium; US, unstimulated. (B) Mild asthmatics (19–39 years in age) and normal subjects (20–27 years) were inoculated with RV-16 on day 0. Nasal washes were analyzed by SDS-PAGE (4–12% gradient Tris-glycine SDS gel) under nonreducing conditions and western blotting for HRF. Note that the use of a gradient gel allowed a better resolution in the high molecular weight range. n*, HRF n-mer.

Fig. 3.

Increased HRF-reactive IgE during RV-induced asthma exacerbations. Sera from pediatric asthma patients during exacerbation (Exac) with RV infection (A, n=10) or non-viral causes (B, n=10) and after resolution (Resol) were subjected to ELISA to quantify HRF-reactive IgE. C,D Comparisons of HRF-reactive IgE (C) and HRF-reactive IgG (D) within RV+ or virus- groups were made using Wilcoxon Matched Pairs test. Comparison between RV+ vs. virus- samples was made by Mann-Whitney U test. Data are presented as mean ± SEM.