An understanding of the nature of immune protection and the role of immune effector products such as
interferon-gamma (IFN-gamma) in the control of
infectious disease is fundamental to the rational design of effective
vaccines and immunotherapeutic
reagents. Murine monoclonal and sheep polyclonal
antibodies (mAbs and pAbs) to feline IFN-gamma (fIFN-gamma) were generated firstly to facilitate further research into the role of cellular immune responses in the control of feline
infectious disease, and secondly to enable evaluation of the efficacy of novel immunotherapeutic approaches. A hybridoma clone, D9, secreting
IgG1 antibodies was selected for expansion and the mAbs affinity purified in vitro. Polyclonal
antibodies were raised in a sheep against recombinant fIFN-gamma and affinity purified. The sensitivity of the D9 mAb and the sheep anti-fIFN-gamma pAb was determined using an indirect fIFN-gamma
enzyme-linked
immunosorbent assay (ELISA) and immunoblots. These
antibodies were assessed for their ability to detect the production of fIFN-gamma by specific feline T cell populations ex vivo following coculture with
mitogen or feline leukaemia virus (FeLV)
antigens for 4 h in the presence of the
protein secretion inhibitor
brefeldin A (BFA). Production of fIFN-gamma was evaluated using flow cytometry to simultaneously detect PE-labelled surface molecules and
fluorescein isothiocyanate (
FITC)-labelled intracellular fIFN-gamma. Using this approach, our initial studies revealed an upregulation in virus-specific fIFN-gamma-secreting CD4(+)T cells in the lymph nodes of FeLV latently infected cats.