The fundamental study for polymyxins as novel and safe mucosal adjuvants

目前迫切需要开发安全有效的佐剂以增强疫苗诱导的抗原特异性免疫应答。我们在这里证明，鼻内免疫与临床使用的多肽抗生素，多粘菌素B（PMB）和粘菌素（CL），沿着卵清蛋白（OVA），增加OVA特异性体液免疫反应，在粘膜和全身隔室剂量依赖性的方式。在8个月的观察期间，发现通过加强免疫的增强持续存在。此外，与单独给予OVA的小鼠相比，用OVA加不同剂量的PMB或CL鼻内免疫的小鼠在鼻腔和嗅球中既没有显示出炎症反应，也没有显示出肾损伤。这些数据表明，多粘菌素可能作为一种新的和安全的粘膜佐剂诱导体液免疫反应。发现多粘菌素的佐剂性不依赖于由其杀菌活性释放的内毒素，如PMB在脂多糖（LPS）-低应答小鼠和LPS -敏感小鼠中的类似增强作用所示。然而，尽管存在预先存在的抗PMB抗体，我们观察到鼻内给予多粘菌素时，其佐剂功能没有降低。此外，在用OVA加PMB或CL鼻内免疫的小鼠中，OVA特异性Ab的滴度显著高于用多粘菌素类似物（如多粘菌素B九肽和甲磺酸粘杆菌素）给药的小鼠中的那些。PMB或CL刺激肥大细胞培养上清释放的β-氨基己糖苷酶和组胺水平也显著高于其类似物刺激的水平。这些结果表明，疏水性碳链和亲水性阳离子环肽都有助于PMB和CL的粘膜佐剂作用

There is currently an urgent need to develop safe and effective adjuvants for enhancing vaccine-induced antigen -specific immune responses. We demonstrate here that intranasal immunization with clinically used polypeptide antibiotics, polymyxin B (PMB) and colistin (CL), along with ovalbumin (OVA), increases OVA-specific humoral immune responses in a dose-depe ndently manner at both mucosal and systemic compartments. Enhanced immunity by boosting was found to persist during 8 months of observation. Moreover, mice intranasally immunized with OVA plus various doses of PMB or CL showed neither inflammatory responses in the nasal cavity and olfactory bulbs nor renal damages, compared to those given OVA alone. These data suggest that polymyxins may serve as novel and safe mucosal adjuvants to induce humoral immune responses. The polymyxin adjuvanticity was found to be independent of endotoxins liberated by its bactericidal activity, as indicated by similar enhancing effects of PMB in lipopolysaccharide (LPS)-hyporesponsive and LPS -susceptible mice. However, despite the presence of preexisting anti-PMB antibodies, we ob served no reduction in the adjuvant function of polymyxins when they were given intranasally. Furthermore, the titers of OVA-specific Abs in mice intranasally immunized with OVA plus PMB or CL were significantly higher than those in mice administered with polymyxin analogues, such as polymyxin B nonapeptide and colistin methanesulfonate. The levels of released β-hexosaminidase and histamine in mast cell culture supernatants stimulated by PMB or CL were also significantly higher than those stimulated by their analogues. These results suggest that both the hydrophobic carbon chain and hydrophilic cationic cyclic peptide contribute to the mucosal adjuvanticity of PMB and CL