Oral therapy with human interferon alpha in calves experimentally injected with infectious bovine rhinotracheitis virus.

Fifty-six calves, seronegative for infectious bovine rhinotracheitis (IBR) virus, were randomly divided into 7 equal groups (n = 8) and given 0.0, 0.05, 0.50, or 5.00 international units (IU) of natural or recombinant human interferon alpha per kg body weight (nHuIFN-alpha or rHuIFN-alpha, respectively) orally once daily for 4 consecutive days, starting 2 days before intranasal inoculation with virulent IBR virus. Calves given 0.05 IU nHuIFN-alpha/kg bwt had significantly greater weight gain at days 15 (P < 0.10) and 25 (P < 0.05) than the placebo-treated (0.0 IU) control group. The treatment groups given 0.05 and 0.5 IU nHuIFN-alpha/kg bwt nHuIFN-alpha had fewer days with temperature > 40 degrees C (P < 0.05 and P = 0.10, respectively), and lower mean rectal temperatures on days 8 and 11 (0.05 IU/kg bwt; P < 0.10) or on day 11 (0.5 IU/kg bwt; P < 0.10). None of the calves given 0.05 IU nHuIFN-alpha/kg bwt required antibiotic therapy. Calves given 0.50 IU/kg bwt of nHuIFN-alpha, or 0.05 IU/kg bwt of rHuIFN-alpha had fewer (P < 0.05) total days of antibiotic therapy compared to controls. These data indicate that low dose oral IFN-alpha treatment significantly reduced the clinical effects of IBR virus infection in feedlot cattle in an interferon dose-dependent fashion.