2592. Lung Function as an Indicator of Vaccine Enhanced RSV Disease in Cotton Rats

Abstract Background Respiratory syncytial virus (RSV) infection is the leading cause of lower respiratory tract infections in infants and young children. Seronegative children previously vaccinated with formalin-inactivated live RSV formulated with aluminum (FIRSV) developed vaccine enhanced RSV disease (VERD), which is characterized by fever, wheezing, bronchopneumonia, and airway hyperresponsiveness (AHR). We investigated whether impaired lung function can serve as a marker for VERD in an animal model of RSV infection. Methods Uninfected and RSV-infected cotton rats intranasally challenged with 106 pfu of RSV A2 were anesthetized with pentobarbital and tracheostomized. A cannula was placed in the trachea and animals were connected to flexiVent™ (Scireq), which is a computer-controlled piston ventilator that analyzes pressure and volume signals in response to an oscillatory waveform applied at the animal’s airways. Vecuronium bromide was administered to ventilated animals to prevent independent breathing. To measure AHR, animals were exposed to increasing doses of inhaled methacholine, and methacholine-induced bronchoconstriction was measured. Results Two independent studies showed that RSV-infected cotton rats (n = 4) exhibited increased total respiratory system resistance (Rrs) and airway resistance (Rn) following methacholine challenge on days 4 and 6 post-infection compared with uninfected cotton rats (n = 4). Conclusion RSV-induced impairment in lung function can be exploited for the development of a more robust and objective method for assessing vaccine safety in a cotton rat model of respiratory disease compared with traditional histopathological analysis. Disclosures All authors: No reported disclosures.