CHANGES IN AIRWAY INFLAMMATORY CELL-POPULATIONS IN STANDARD-BRED RACEHORSES AFTER INTERFERON-ALPHA ADMINISTRATION

Natural human interferon-alpha (nHuIFN alpha) was administered to acti vely training Standardbred racehorses with inflammatory airway disease (IAD). Inflammatory airway disease was characterized by poor exercise performance and inflammation and exudate in the upper and lower airwa y. Placebo, 50, 150, or 450 units (U) of nHuIFN alpha was administered orally for 5 consecutive days to eight horses per treatment group in a double-blind, randomized block design. Response to nHuIFN alpha was monitored by semiquantitative endoscopic examination score and cytolog ic examination of bronchoalveolar lavage fluid (BALF) performed at bas eline (Day 1), Day 8 and Day 15 after initiation of nHuIFN alpha admin istration. Neutrophil, macrophage, lymphocyte, and nucleated cell coun ts in BALF were lower (P < 0.05), compared with BALF cell counts in pl acebo-treated horses, 8 days after administration of 50 U and 150 U nH uIFNL alpha, and 15 days after administration of 50 U nHuIFN alpha. Ne utrophil, lymphocyte and nucleated cell counts were lower than cell co unts from placebo-treated horses, 8 days following administration of 4 50 UnHuIFN alpha. The proportion CD4-, CD5-, and CD8-positive lymphocy tes in BALF was not affected by administration of nHuIFN alpha. Oral a dministration of low-dose nHuIFN alpha reduced inflammation of the low er respiratory tract in Standardbred racehorses with VAD.