Effect of anti-nerve growth factor on early and late airway responses in allergic rats

Background: The increased production of nerve growth factor (NGF) has been associated with allergen-induced airway hyperresponsiveness and enhanced airway inflammation in experimental models of asthma. The aim of this study was to investigate whether a local application of anti-NGF to the lungs may affect the allergen-specific early (EAR) and late (LAR) airway responses to ovalbumin (Ova) of Ova-sensitized brown Norway rats. Methods: Rats were sensitized systemically with Ova and were boosted twice intratracheally with Ova aerosol using a microsprayer. Two hours before every boost, the animals were pretreated either with aerosolized anti-NGF or with a control antibody. On day 21, all animals were challenged with inhalational Ova aerosol and pulmonary resistance was recorded in anesthetized, orotracheally intubated animals during the early and late asthmatic responses. In addition, differential cell counts from bronchoalveolar lavage and serum immunoglobulin E (IgE) levels were determined 48 h post-Ova challenge. Results: Pretreatment with anti-NGF significantly attenuated the EAR but had no significant effect on the LAR. Serum IgE levels and inflammatory cell influx into the lungs were not affected by anti-NGF pretreatment. Conclusion: The data from this study suggest that NGF is directly involved in the development of the EAR without affecting the inflammatory airway response or LAR.