AEGiS-11IAC: Interleukin-13 receptor: a new target for a Pseudomonas exotoxin based chimeric protein on AIDS-associated Kaposi's sarcoma cells.

11th International AIDS Conference

Vancouver, British Columbia — July 7-12, 1996

Interleukin-13 receptor: a new target for a Pseudomonas exotoxin based chimeric protein on AIDS-associated Kaposi's sarcoma cells.

Int Conf AIDS 1996 Jul 7-12; 11:222 (abstract no. Tu.A.272)
Husain SR, Obiri N, Gill P, Pastan I, Debinski W, Puri RK; Food and Drug Administration, Center for Biologics Evaluation and Research, Bethesda, MD, USA. Fax: 301-827-0449. E-mail: Husain@Al.CBER.FDA.GOV.

OBJECTIVES: To identify novel target on AIDS-Kaposi's sarcoma-derived (AIDS-KS) cells and to determine if these cells are suitable target for a novel recombinant chimeric protein composed of interleukin-13 (IL-13) and truncated Pseudomonas exotoxin (IL 13-PE38QQR).

METHODS: The expression of IL-13 receptor (IL-13R) on six AIDS-KS cell cultures was determined by binding studies. The structure of IL-13R and its interaction with related cytokine, IL-4, was investigated by affinity cross-linking. The cytotoxic activity of IL 13-PE38QQR on AIDS-KS was evaluated by protein synthesis inhibition assay.

RESULTS: All six AIDS-KS cell cultures expressed large numbers (approximately 3,000-15,000 sites/cell) of high affinity (Kd= 124 to 972 pM) IL-13R. Human endothelial (HUVEC) and fibroblast (BUD-8) cell lines expressed low numbers or no IL-13R. IL-13 competed efficiently for 125I-IL-13 binding on AIDS-KS cells while IL-4 showed little competition. Crosslinking studies revealed that 125I-IL-13 crosslinked to one major protein of approximately 65-70 kDa and this was abolished by excess IL-13 and partially by excess IL-4 in KS248 and NCB-59 AIDS-KS cell cultures. NCB-59, KS248 and KS220B KS cells were highly sensitive to the cytotoxic effect of IL 13-PE38QQR. The 50% inhibition in protein synthesis (IC50) in 6 AIDS-KS cultures was achieved at 2.5 to 263 ng/ml concentration of the chimeric toxin. The cytotoxic activity of IL 13-PE38QQR was completely blocked by an excess of IL-13 but not IL-4 indicating that IL-13R on AIDS-KS cells is distinct from IL-4R.

CONCLUSIONS: IL-13 receptor on AIDS-KS cells represent a novel plasma membrane protein(s) that could be utilized for diagnosis and/or targeting with cytotoxic agents, such as Pseudomonas exotoxin. Additional studies are warranted to investigate potential targeting of IL-13R in AIDS-KS in vivo.

Keywords: AEGIS, Sarcoma, Kaposi, Exotoxins, Receptors, Interleukin, Acquired Immunodeficiency Syndrome, Interleukin-13, Chimeric Proteins, Immunotoxins, Interleukin-4, Inhibitory Concentration 50, Recombinant Proteins, Antineoplastic Agents, Pseudomonas aeruginosa exotoxin A, interleukin-13 receptor, Human, ICA11

960707
TuA272