Specific immune responses of dairy cattle after primary inoculation with recombinant bovine interferon-γ as an adjuvant when vaccinating against mastitis

Abstract

Objective. To examine whether specific immunity in the mammary gland and blood of dairy cattle was enhanced after primary innoculation with a test antigen keyhole limpet hemocyanin (KLH) and recombinant bovine interferon-γ (rBoIFN-γ) as an adjuvant. Design. Holstein dairy cows received IM injections of KLH in conjunction with saline solution (n = 4), Freund's incomplete adjuvant (FIA; n = 4), or rBoIFN-γ (n = 3). Milk and blood samples were collected during a 1-month period and analyzed for KLH antibody content. Isolated blood mononuclear cells were examined for their ability to proliferate and produce interleukin 2 (IL-2) after mitogen and/or KLH stimulation in vitro. The phenotype of isolated blood mononuclear cells also was characterized through flow cytometric analysis. Results. The adjuvant rBoIFN-γ induced serum KLH antibody titers similar to those induced by administration of FIA. However, FIA induced significantly more KLH antibodies in milk. Administration of rBoIFN-γ enhanced T-lymphocyte activity, as indicated by the greater expression of high-affinity IL-2 receptors and the increased response to the mitogens concanavalin A, phytohemagglutinin, and IL-2, compared with FIA or saline treatment. Lymphocyte and monocyte movement from the blood also was altered after rBoIFN-γ treatment, which can have a profound influence on secondary immune responses, such as antibody production. Conclusions. rBoIFN-γ may safely enhance specific immunity in the bovine mammary gland and may be an effective adjuvant in mastitis immunization protocols.