Vaccination of cotton rats with a chimeric FG glycoprotein of human respiratory syncytial virus induces minimal pulmonary pathology on challenge.

The cotton rat model of human respiratory syncytial virus (RSV) infection was used to study the safety and efficacy of a chimeric FG glycoprotein that was expressed in insect cells using a baculovirus vector. Histologic and virologic examination of vaccinated rat lungs was done after challenge with RSV. When rats were challenged 1 month after vaccination, severe pulmonary inflammation characterized by both a mononuclear and polymorphonuclear cell infiltrate and 30%-40% involvement of lung tissue was observed with a formalin-inactivated RSV vaccine. The FG glycoprotein induced minimal lung inflammation (involving 2%-5% of the lung), while negative controls had 1%-3% lung involvement. Two doses with as little as 20 ng of FG glycoprotein formulated in an aluminum hydroxide adjuvant completely protected the cotton rats from RSV challenge. Thus the chimeric FG glycoprotein is highly immunogenic and induces minimal pulmonary inflammation in the cotton rat model.