A cotton rat model of human parainfluenza 3 laryngotracheitis: virus growth, pathology, and therapy.

Parainfluenza virus type 3 (PIV3) infection led to laryngotracheitis in cotton rats. Laryngeal virus titers peaked at 10(5.0)-10(6.0) plaque-forming units (pfu)/g of tissue from days 2 through 5 after inoculation with 10(5.5) pfu of PIV3. Lymphocytic and neutrophilic inflammatory infiltrates were present in the subglottic and proximal tracheal regions, whereas respiratory epithelial cells were blunted with loss of cilia. Topical therapy with moderate doses of triamcinolone acetonide, an anti-inflammatory glucocorticoid, greatly reduced the extent of lesions. Interferon-gamma messenger RNA production was increased by infection and was suppressed by the highest dose of glucocorticoid. Topical glucocorticoid therapy, with or without concurrent topical immunotherapy with antibody to PIV3, did not lead to a rebound of viral replication.