Detection of experimental infections with 99mTc-labeled monoclonal antibodies against TNF-α and interleukin-8

Abstract This study was designed to assess monoclonal antibodies (MAbs) directed against tumor necrosis factor-α (TNF-α) (anti-TNF) or interleukin-8 (anti-IL-8) as radioactive agents for the detection of Staphylococcus aureus - or Klebsiella pneumoniae -infected thighs in mice. At 5 min (acute infection) or 20 h (established) post-infection, 20 μg of the 99m Tc-labeled MAbs were injected. At various time intervals, the accumulation of the radiotracer in the infected thighs was assessed and expressed as a target-to-nontarget (TNT) ratio. The binding of 99m Tc-labeled MAbs to circulating mononuclear cells and granulocytes was quantitated 20 h after injection. The pharmacokinetics of the MAbs, in relation to the control agents 99m Tc-labeled polyclonal human immunoglobulin (IgG) and a 99m Tc-labeled nonspecific IgG1 MAb, were also studied. In acute infections, 99m Tc-anti-TNF accumulated to a higher extent ( p S. aureus -infected thighs in mice until 4 h after the injection than 99m Tc-IgG and was higher at 0.25 h in K. pneumoniae -infected mice ( p 99m Tc-IgG. In established S. aureus and K. pneumoniae infections, 99m Tc-anti-IL-8 detected the infection more intensely than 99m Tc-IgG until 1 h after injection. In both S. aureus and K. pneumoniae infections, localization of sites of infection correlates ( p 99m Tc-labeled MAbs to granulocytes and mononuclear cells in both acute and established infections. It was concluded that 99m Tc-labeled MAbs, directed against TNF-α and IL-8, accumulate in bacterial infections in mice to a higher extent than does 99m Tc-IgG after infection and is related to the binding of the antibodies to blood leukocytes. With these 99m Tc-labeled MAbs, information might be gained about the development of an infection.