An anti-human recombinant tumor necrosis factor alpha (TNFα) monoclonal antibody recognizes an epitope in feline TNFα

It is likely that the murine response to human recombinant TNFα (hrTNFα) may generate antibodies (Ab) to epitopes present in TNFα from other species. Here, we demonstrate that F5 antihrTNFα monoclonal antibody (mAb) recognizes feline TNFα while E8 anti-hrTNFα mAb failed to do so. In order to demonstrate that E8 and F5 mAb recognize different epitopes in the hrTNFα molecule, a constant concentration of E8 and variable concentrations of F5 were incubated with solid phase bound hrTNFα. Binding of E8 and F5 to hrTNFα was determined with anti-μ and γ chain specific Ab. F5 bound equally to hrTNFα in the presence or absence of E8 and the same amount of E8 bound to hrTNFα, in spite of the presence of F5. When using the E8 and F5 mAb for capturing the TNFα from the equine, canine, feline and bovine species, in supernatants of an ex vivo lipopolysaccharide (LPS)stimulated whole blood cell culture, we only detected the feline TNFα by F5 mAb (p = 0.001). By a cytotoxic assay on L929 fibroblasts, we indeed demonstrated the feline TNFα production after the LPS stimulus. In an inhibition assay, the human and feline cytokines competed for F5, although the inhibition of native human TNFα binding to F5 was significant but only about 20% (p = 0.001). In conclusion, most likely the F5 anti-hrTNFα mAb recognizes an epitope in feline TNFα. Its immunomodulatory potential in the feline model remains to be studied. monoclonal antibodies / tumor necrosis factor alpha / cross-reactivity