Asthma exacerbations are a major cause of ER visits and hospitalizations with annual direct costs of approximately $50 billion /year in the USA. Viral infections, in particular rhinoviral (RV) infections, are a major precipitant of asthma exacerbations in allergic asthmatics. As there are over 100 RV serotypes and, for now, no RV vaccine, novel strategies to inhibit RV induced airway inflammation are needed to prevent asthma exacerbations associated with increased airway hyper-reactivity (AHR). State of the art research recently demonstrated that RV infection in allergic humans and mice can induce neutrophils to undergo NETosis ? a newly recognized inflammatory process involving the expulsion of Neutrophil Extracellular Traps (NET's) comprising linearized double stranded (ds)DNA bearing cytotoxic histones and granule proteins such as myeloperoxidase and elastase. Furthermore, NET's can be sensed by the innate or adaptive immune system to boost type-2 immunity and enhance the severity of asthma exacerbations. Degradation of NETs by DNase or inhibition of elastase by alpha 1-antitrypsin (AAT) have both proven effective at preventing allergic asthma exacerbations in animal models but neither is a direct inhibitor of NETosis. Serpin B1 (sB1) is a protein both structurally and functionally related to AAT (both inhibit the neutrophil serine proteinases [NSP's] elastase, cathepsin G and proteinase 3 implicated in inflammation and airway hyper-reactivity [AHR]) that is abundantly produced inside monocytes and neutrophils but unlike AAT directly blocks NETosis and regulates the expansion of Th17 cytokine producing cells in vitro. However, Serplus Technology LLC has recently shown that human and mouse sB1's are subject to inactivation by reactive oxygen species (ROS) that convert the protein into an elastase substrate. To prevent this inactivation we have created an oxidation resistant sB1 (OxR sB1) that retains elastase inhibitory activity in the presence of ROS and hypothesize that it will be an effective in vivo inhibitor of both elastase and NETosis during inflammatory episodes and will block RV induced NETosis thus diminishing Th2-mediated T-cell responses to more effectively control allergic asthma exacerbations. We will test if OxR sB1 can prevent RV induced airway inflammation and AHR in house dust mite sensitized mice and, if successful, undertake further preclinical and clinical development such that it may improve control of RV induced asthma exacerbations in allergic asthmatics. The proposed research in phase I will focus on (Aim 1) the purification and biochemical characterization of oxidation resistant mouse sb1a and (Aim 2) providing proof-of-principle in an animal model of RV induced asthma. The outcome of these studies will guide the design of future efficacy studies in animals and humans.
Viral infections, in particular rhinoviral (RV) infections, are a major precipitant of asthma exacerbations in allergic asthmatics and as there are over 100 RV serotypes and no RV vaccine as yet, novel strategies to inhibit the RV induced airway inflammation and increased airway hyper- reactivity (AHR) are urgently required. Serpin B1 is an endogenous regulator of neutrophil protease activity and Neutrophil Extracellular Trap (NET) formation? key inflammatory processes important for induction of exacerbations in asthmatic humans and mice. We have discovered that sB1 is subject to inactivation by reactive oxygen species (ROS) and have made an ROS resistant form of sB1 which we seek to prove can function in the asthmatic lung as an effective inhibitor of inflammatory proteases, cytokine production, and NETosis to ameliorate airway inflammation and reduce AHR thus offering an additional therapeutic candidate to prevent or treat the underlying pathology of asthma exacerbations.
