Staphylococcus aureus Mastitis: Pathogenesis and Treatment with Bovine Interleukin-1β and Interleukin-2

Abstract

Polymorphonuclear leukocytes play a central role in the pathogenesis of bovine mastitis. Intramammary challenge with Staphylococcus aureus was shown to induce both quantitative and qualitative changes in mammary gland polymorphonuclear leukocytes. Intramammary infusion of recombinant bovine interleukin-1β and interleukin-2 elicited a similar cellular response. Staphylococcus aureus, interleukin-1β, and interleukin-2 all increased the number of somatic cells after intramammary infusion and activated the inducible superoxide production in milk polymorphonuclear leukocytes. Interleukin-2 also activated phagocytosis of these cells, and their activation was maintained for 3 to 5 d after intramammary administration. Inter-leukin-1β and interleukin-2 were moderately effective in the therapy of experimental S. aureus mastitis. Approximately 54% of the glands treated with interleukin-1β responded to therapy by transiently clearing the milk of S. aureus, 30% of which relapsed, and a total of 38% of the treated glands remained cured. In contrast, 83% of glands treated with interleukin-1β responded to therapy, but 50% of these quarters relapsed. A total of 42% of the quarters treated with interleukin-1β remained cured. Homologous recombinant cytokines are effective immunomodulators that augment natural defensive mechanisms similar to the normal response to pathogens and may prove to be suitable alternatives to, or may be used in combination with, antibiotics as effective mastitis therapeutic agents. © 1991, American Dairy Science Association. All rights reserved.