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  • Author or Editor: Everett C. Short Jr. x
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SUMMARY

Biological responses to recombinant dna-derived bovine interferon α (rBoifn-αI1) by bovine alveolar macrophages were examined by measuring viral yield reduction and 2′,5′-oligoadenylate synthetase (2′,5′-oas) production by ifn-treated cells. In vitro ifn pretreatment of alveolar macrophages reduced viral yield in cultures challenged exposed with parainfluenza-3 virus, compared with control cultures. In vitro treatment of alveolar macrophages with ifn also resulted in increased 2′,5′-oas activity. The 2′,5′-oas activity was measured in alveolar macrophages and blood mononuclear leukocytes of calves injected im with 3.6 × 106 U of rBoifn-αI1/kg of body weight. The ifn action was monitored by measuring 2′,5′-oas activity of blood mononuclear leukocytes beginning 6 days before and ending 24 hours after ifn treatment. The 2′,5′-oas activity in the blood mononuclear leukocytes sharply increased 24 hours after ifn treatment, indicating response to ifn. The alveolar macrophages collected from the same calves 24 hours after ifn administration also had increased 2′,5′-oas activity, compared with alveolar macrophages from the same calves collected 6 days before treatment. Increased 2′,5′-oas activity indicates: a possible mechanism of ifn action in cattle that may be responsible for viral yield reduction; potential use of high enzyme activity as a marker for ifn induction; and potential use of 2′,5′-oas activity as a marker for determining effects of ifn on bovine macrophages and other cells of the bovine immune system.

Free access
in American Journal of Veterinary Research

Summary

Cell extracts that were prepared from blood mononuclear leukocytes from 66 samples obtained from 6 clinically normal calves contained mean 2′,5′-oligoadenylate (2′,5′-oligo[A]) synthetase activity sufficient to synthesize 186 ± 82 pmol of 2′,5′-oligo(A)/h/106 cells. Calves had no measurable serum interferon (ifn) activity. Five calves were given im injections of 104, 105, 5 × 105, 106, and 107 U of bovine ifn-α1/kg of body weight at 2-week intervals. Five dosing sequences were used with a 5 × 5 Latin square design so that each calf received each dose once. Activity of 2′,5′-oligo(A) synthetase increased at 24 hours in response to all dosages of ifn and then declined following first-order kinetics, with an apparent half-life (t½) of 2.1 ± 0.5 days. The area under the concentration-time curve for 2′,5′-oligo(A) synthetase increased with dose of ifn more rapidly than did peak response. Serum ifn that was measured at 1-day intervals following administration of ifn was consistently measurable only at dosages above 106 U of ifn/kg. The t½ for circulating ifn was 12.4 ± 1.0 hours. Over all dosages, increases in 2′,5′-oligo(A) synthetase activity were measurable for 3.5 days longer than were increases in ifn following im injection of ifn. None of the calves developed detectable anti-ifn antibodies.

Free access
in American Journal of Veterinary Research