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目的Palivizumab(PZ)是目前临床使用的惟一一个预防人类感染性疾病的单克隆抗体,本研究评估不同逃逸株在棉鼠体内对PZ预防的抗性。方法在细胞培养系统中筛选获得PZ逃逸株,测定其全长F基因序列,用微量中和法评估逃逸株对PZ的抗性,在棉鼠模型体内观察逃逸株对PZ预防的抗性差异。结果筛选获得的PZ逃逸株于F蛋白内第268位氨基酸(F212)和272位氨基酸(MP4、MS312、MS412和MS512)发生替换。用Westernblot检测发现所有逃逸株PZ识别位点抗原性改变。F212复制能力受损,而其他逃逸株复制能力与A2母株接近。与A2原型株比较,MP4和MS412在体内外对PZ的中和活性具完全抗性。F212体外对PZ中和活性显示不完全抗性,但大剂量PZ在棉鼠体内仍能有效预防F212感染。结论不同PZ逃逸株体内对PZ的预防效应可能具有不同程度的抗性,某些逃逸株即使在PZ筛选压力下产生,亦不一定导致临床后果。
Purpose Palivizumab (PZ) is the only monoclonal antibody currently used clinically to prevent human infectious disease. This study evaluated the resistance of different escape strains to PZ prophylaxis in cotton rats. Methods The Escherichia coli PZ escape strain was screened in cell culture system. The full-length F gene sequence was screened. The resistance of escaping strains to PZ was evaluated by micro-neutralization method. The resistance of escaping strains to PZ was observed in cotton rat model. Results The Escherichia coli PZ escape strain was replaced by amino acid 268 (F212) and amino acid 272 (MP4, MS312, MS412 and MS512) in F protein. Western blot analysis showed that all escape strains PZ recognition site antigenic change. F212 was impaired in replication while other escape strains replicated in the A2 parent. Compared with the A2 prototype strain, MP4 and MS412 have complete resistance to the neutralization activity of PZ in vitro and in vivo. F212 in vitro showed incomplete resistance to PZ neutralizing activity, but large doses of PZ can still effectively prevent F212 infection in cotton rats. Conclusion The preventive effects of PZ on different PZ escape strains may have different degrees of resistance. Some escape strains may not result in clinical consequences even under the PZ screening pressure.