Targeted killing of virally infected cells by radiolabeled antibodies to viral proteins

Background: The HIV epidemic is a major threat to health in the developing and western worlds. A modality that targets and kills HIV-1-infected cells could have a major impact on the treatment of acute exposure and the elimination of persistent reservoirs of infected cells. The aim of this proof-of-principle study was to demonstrate the efficacy of a therapeutic strategy of targeting and eliminating HIV-1-infected cells with radiolabeled antibodies specific to viral proteins in vitro and in vivo. Methods and Findings: Antibodies to HIV-1 envelope glycoproteins gp120 and gp41 labeled with radioisotopes bismuth 213 (²¹³Bi) and rhenium 188 (¹⁸⁸Re) selectively killed chronically HIV-1-infected human T cells and acutely HIV-1-infected human peripheral blood mononuclear cells (hPBMCs) in vitro. Treatment of severe combined immunodeficiency (SCID) mice harboring HIV-1-infected hPBMCs in their spleens with a ²¹³Bi- or ¹⁸⁸Re-labeled monoclonal antibody (mAb) to gp41 resulted in a 57% injected dose per gram uptake of radiolabeled mAb in the infected spleens and in a greater than 99% elimination of HIV-1-infected cells in a dose-dependent manner. The number of HIV-1-infected thymocytes decreased 2.5-fold in the human thymic implant grafts of SCID mice treated with the ¹⁸⁸Re-labeled antibody to gp41 compared with those treated with the ¹⁸⁸Re-control mAb. The treatment did not cause acute hematologic toxicity in the treated mice. Conclusions: The current study demonstrates the effectiveness of HIV-targeted radioimmunotherapy and may provide a novel treatment option in combination with highly active antiretroviral therapy for the eradication of HIV.