Development of monoclonal antibodies (MAbs) to feline interferon (fIFN)-γ as tools to evaluate cellular immune responses to feline infectious peritonitis virus (FIPV)

Feline infectious peritonitis virus (FIPV) can cause a lethal disease in cats, feline infectious peritonitis (FIP). The antibody-dependent enhancement (ADE) of FIPV infection has been recognised in experimentally infected cats, and cellular immunity is considered to play an important role in preventing the onset of FIR To evaluate the importance of cellular immunity for FIPV infection, monoclonal antibodies (MAbs) against feline interferon (fIFN)-gamma were first created to establish flFN-gamma detection systems using the MAbs. Six anti-fIFN-gamma MAbs were created. Then, the difference in epitope which those MAbs recognise was demonstrated by competitive enzyme-linked immunosorbent assay (ELISA) and IFN-gamma neutralisation tests. Detection systems for fIFN-gamma (sandwich ELISA, ELISpot assay, and two-colour flow cytometry) were established using anti-fIFN-gamma MAbs that recognise different epitopes. In all tests, fIFN-gamma production from peripheral blood mononuclear cells (PBMCs) obtained from cats experimentally infected with an FIPV isolate that did not develop the disease was significantly increased by heat-inactivated FIPV stimulation in comparison with medium alone. Especially, CD8(+)fIFN-gamma(+) cells, but not CD4(+)fIFN-gamma(+) cells, were increased. In contrast, fIFN-gamma production from PBMCs isolated from cats that had developed PIP and specific pathogen-free (SPF) cats was not increased by heat-inactivated FIPV stimulation. These results suggest that cellular immunity plays an important role in preventing the development of FIR Measurement of fIFN-gamma production with the anti-fIFN-gamma MAbs created in this study appeared to be useful in evaluating cellular immunity in cats. (C) 2011 ISFM and AAFP. Published by Elsevier Ltd. All rights reserved.