Hanoux Vincent, Wijkhuisen Anne, Alexandrenne Coralie, Créminon Christophe, Boquet Didier, Couraud Jean-Yves
CEA/DSV/iBiTec-S/SPI/LIAS, Laboratoire d'Ingénierie des Anticorps pour la Santé, CEA de Saclay, Bâtiment 136, F-91191 Gif sur Yvette, France.
Mol Immunol. 2009 Mar;46(6):1076-83. doi: 10.1016/j.molimm.2008.09.033. Epub 2008 Nov 13.
Immunization with anti-idiotypic (anti-Id) antibodies, used as surrogate antigens, has led to promising results, notably in active immunotherapy of cancers, essentially because it breaks immunological tolerance against self-tumor-associated antigens. The aim of the present study was to provide a proof-of-principle that this vaccination approach could be envisaged also in the field of prion diseases, caused by the accumulation of an aggregated pathological isoform of the highly tolerogenic self-prion protein (PrP), and for which no therapy is available. We investigated the possibility of raising anti-Id antibodies mimicking the human PrP (hPrP), using as immunogens either a peptide derived from the paratope of an anti-PrP mAb or the entire antibody. To this end, we cloned and sequenced SAF61 mAb, an anti-PrP antibody already produced in the laboratory, directed against a critical epitope of PrP involved in the aggregation process. A synthetic peptide (denoted CDR3L) was designed from the identification of a 17-amino-acid sequence encompassing the CDR3 region of the light chain whose hydropathic profile was opposed to that of PrP epitope. CDR3L peptide was directly demonstrated to bind hPrP, confirming the role of hydropathic complementarity in antigen-antibody interactions. When injected into rabbits, CDR3L generated anti-SAF61 anti-Id polyclonal antibodies that exclusively recognized SAF61 mAb but were unable to compete with hPrP for antibody binding. By contrast, immunizations with the entire SAF61 mAb generated anti-Id antibodies specifically competing with soluble or membrane-bound hPrP (in EIA or flow cytometry experiments, respectively) for binding not only SAF61 mAb but also other anti-PrP mAbs directed against similar epitopes, i.e. behaving as "internal images" of this disease-related PrP epitope. These results could open the way to raising PrP-like mAbs, which might serve as surrogate antigens in a new active immunotherapeutic approach to prion diseases.
用抗独特型（抗Id）抗体作为替代抗原进行免疫，已取得了令人鼓舞的成果，尤其是在癌症的主动免疫治疗中，主要是因为它打破了针对自身肿瘤相关抗原的免疫耐受。本研究的目的是提供一个原理证明，即这种疫苗接种方法也可设想用于朊病毒疾病领域，朊病毒疾病是由高度耐受原性的自身朊病毒蛋白（PrP）的聚集病理性异构体的积累引起的，目前尚无治疗方法。我们研究了使用抗PrP单克隆抗体互补决定区的肽或整个抗体作为免疫原，产生模拟人PrP（hPrP）的抗Id抗体的可能性。为此，我们克隆并测序了SAF61单克隆抗体，这是一种实验室已产生的抗PrP抗体，针对参与聚集过程的PrP关键表位。通过鉴定包含轻链CDR3区域的17个氨基酸序列设计了一种合成肽（称为CDR3L），其亲水性图谱与PrP表位相反。直接证明CDR3L肽能结合hPrP，证实了亲水性互补在抗原-抗体相互作用中的作用。当注射到兔子体内时，CDR3L产生了抗SAF61抗Id多克隆抗体，该抗体仅识别SAF61单克隆抗体，但不能与hPrP竞争抗体结合。相比之下，用整个SAF61单克隆抗体进行免疫产生的抗Id抗体不仅能与SAF61单克隆抗体特异性竞争结合，还能与针对相似表位的其他抗PrP单克隆抗体特异性竞争结合（分别在酶免疫分析或流式细胞术实验中与可溶性或膜结合的hPrP竞争），即表现为这种疾病相关PrP表位的“内影像”。这些结果可能为产生PrP样单克隆抗体开辟道路，这些抗体可作为一种新的朊病毒疾病主动免疫治疗方法中的替代抗原。
