SCINTIGRAPHIC DIAGNOSIS OF SYPHILITIC LESIONS IN RABBITS BY RADIOLABELED MONOCLONAL-ANTIBODIES SPECIFIC FOR TREPONEMA-PALLIDUM

Immunoscintigraphy with radiolabelled monoclonal antibodies has been w idely used to detect solid tumours. The purpose of this study was to i nvestigate its Potential for the specific localization of syphilitic l esions. F(ab')2 fragments were prepared from murine monoclonal antibod ies against Treponema pallidum produced in our laboratory and labelled with I-131. Bilateral testicular infections were created in rabbits b y inoculation with T. pallidum or Staphylococcus aureus. Seven to 10 d ays after inoculation, radiolabelled antibodies were injected intraven ously. Serial gamma images were then taken 2 h after the injection and at 24 h intervals thereafter. Beginning as early as 2 h post-injectio n, the testicles could be visualized with either specific or non-speci fic antibodies. Gamma images in the monoclonal antibody-treated, T. pa llidum-infected group persisted up to 48 h post-injection. Lesions wer e not discernible from background in the S. aureus-infected group inje cted with the monoclonal antibody and the S. aureus-infected and T. pa llidum-infected groups injected with the polyclonal antibody at 24 h p ost-injection or later. Therefore, due to its ability to differentiate between specific and non-specific antibody-generated images from 24 h post-injection, immunoscintigraphy using monoclonal antibodies specif ic for T. pallidum may be employed as one of the methods to diagnose d ifficult cases of syphilitic internal organ involvement as well as syp hilis infection in seronegative HIV-infected patients.