Nasal lavage VEGF and TNF-α levels during a natural cold predict asthma exacerbations.

BACKGROUND: Asthma exacerbations contribute to significant morbidity, mortality and healthcare utilization. Furthermore, viral infections are associated with asthma exacerbations by mechanisms that are not fully understood. OBJECTIVE: The aim of this analysis was to determine whether cytokine patterns in patients with colds could identify risks for subsequent asthma exacerbations. METHODS: We analysed cytokine levels in nasal lavage fluid (NLF) in 59 subjects (46 with asthma) with acute upper respiratory symptoms and after symptomatic resolution. Analyte choice was based on potential relevance to asthma exacerbations: antiviral (IFN-α, IFN-ß, IFN-γ, IFN-λ1, IP-10, TRAIL), cell recruiting (G-CSF, IL-1ß, IL-8, MCP-1, MCP-3, TNF-α), polarizing (CXCL13, IL-10, IL-13, IL-17, TSLP), and injury remodelling (fibronectin, IL-33, MMP-9, VEGF). RESULTS: The overall cytokine response induced during viral infections was not different between asthmatic and non-asthmatic individuals for a wide array of cytokines. However, mean levels of VEGF, TNF-α and IL-1ß were 1.7-, 5.1- and 4.7-fold higher in samples from asthma subjects who exacerbated in the first 3 weeks of the cold compared with those who did not exacerbate (P = 0.006, 0.01, 0.048, respectively). Using receiver operating characteristic curve-defined thresholds, high VEGF and TNF-α levels predicted a shorter time-to-exacerbation after NLF sampling (25% exacerbation rate: 3 vs. 45 days, and 3 vs. 26 days; P = 0.03, 0.04, respectively). CONCLUSION AND CLINICAL RELEVANCE: Although they produce similar cytokine responses to viral infection as non-asthmatics, asthmatics with higher levels of VEGF and TNF-α in NLF obtained during acute cold phases predicted subsequent asthma exacerbations in this cohort of patients with mild-to-moderate disease. In the future, stratifying the risk of an asthma exacerbation by cytokine profile may aid the targeting of personalized treatment and intervention strategies.

Interferon gene expression in sputum cells correlates with the Asthma Index Score during virus-induced exacerbations.

BACKGROUND: The majority of asthma exacerbations are related to viral respiratory infections. Some, but not all, previous studies have reported that low interferon responses in patients with asthma increase the risk for virus-induced exacerbations. OBJECTIVE: We sought to determine the relationship between lower airway inflammatory biomarkers, specifically interferon gene expression, and the severity or presence of an exacerbation in asthmatics experiencing a naturally occurring viral infection. METHODS: Sputum samples were analysed from subjects in an asthma exacerbation study who experienced a confirmed viral infection. Subjects were monitored for daily symptoms, medication use and peak expiratory flow rate until baseline. Sputum samples were assessed for cell counts and gene expression. RESULTS: Interferon gamma expression was significantly greater in patients with asthma exacerbations compared to non-exacerbating patients (P = 0.002). IFN-α1, IFN-ß1 and IFN-γ mRNA levels correlated with the peak Asthma Index (r = 0.58, P < 0.001; r = 0.57, P = 0.001; and r = 0.51, P = 0.004, respectively). Additionally, IL-13, IL-10 and eosinophil major basic protein mRNA levels were greater in patients with asthma exacerbations compared to non-exacerbating patients (P = 0.03, P = 0.06 and P = 0.02, respectively), and IL-13 mRNA correlated with the peak Asthma Index (P = 0.006). CONCLUSIONS: Our findings indicate that asthma exacerbations are associated with increased rather than decreased expression of interferons early in the course of infection. These findings raise the possibility that excessive virus-induced interferon production during acute infections can contribute to airway inflammation and exacerbations of asthma.