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 TNFalpha (hrTNFalpha) may generate antibodies (Ab) to epitopes present in TNFalpha from other species. Here, we demonstrate that F5 anti-hrTNFalpha monoclonal antibody (mAb) recognizes feline TNFalpha while E8 anti-hrTNFalpha mAb failed to do so. In order to demonstrate that E8 and F5 mAb recognize different epitopes in the hrTNFa molecule, a constant concentration of E8 and variable concentrations of F5 were incubated with solid phase bound hrTNFalpha. Binding of E8 and F5 to hrTNFalpha was determined with anti-mu and gamma chain specific Ab. F5 bound equally to hrTNFalpha in the presence or absence of E8 and the same amount of E8 bound to hrTNFalpha, in spite of the presence of F5. When using the E8 and F5 mAb for capturing the TNFa 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 TNFalpha by F5 mAb ( p = 0.001). By a cytotoxic assay on L929 fibroblasts, we indeed demonstrated the feline TNFalpha production after the LPS stimulus. In an inhibition assay, the human and feline cytokines competed for F5, although the inhibition of native human TNFalpha binding to F5 was significant but only about 20% ( p = 0.001). In conclusion, most likely the F5 anti-hrTNFalpha mAb recognizes an epitope in feline TNFalpha. Its immunomodulatory potential in the feline model remains to be studied.