Production and in vivo use of recombinant ovine IL-1β as an immunological adjuvant

To determine the potential of ovine interleukin 1 (IL-1) as a vaccine adjuvant in sheep, we have expressed and purified recombinant ovine IL-1β (rovIL-1β) from bacterial cultures using a modified form of the ovine IL-1β cDNA. Adjuvant trials using the model protein avidin demonstrated that rovIL-1β when administered in association with a compound providing a slow-release mechanism, resulted in significant enhancement of specific serum antibody levels in both mice and sheep. In a dose-response experiment in sheep, intradermal immunization with avidin plus either 10 or 100 μg of rovIL-1β in aluminium hydroxide resulted in antibody levels four- to eightfold higher than immunizations without rovIL-1β. The addition of rovIL-1β also resulted in a more severe DTH response to avidin indicating that rovIL-1β is able to enhance both humoral and cell-mediated responses to avidin. The highest antibody titres were observed when sheep received rovIL-1β in both the primary and secondary immunizations although the addition of rovIL-1β in only one of the immunizations still resulted in a significant increase in antibody levels. Additional experiments showed that rovIL-1β and avidin must be administered in a site drained by the same lymph node for the adjuvant effect of rovIL-1β to be observed.