Hamborg Mette, Rose Fabrice, Jorgensen Lene, Bjorklund Katrine, Pedersen Helene B, Christensen Dennis, Foged Camilla
Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen Universitetsparken 2, DK-2100 Copenhagen Ø, Denmark.
Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen Universitetsparken 2, DK-2100 Copenhagen Ø, Denmark.
Biochim Biophys Acta. 2014 Aug;1838(8):2001-10. doi: 10.1016/j.bbamem.2014.04.013. Epub 2014 Apr 25.
The reverse vaccinology approach has recently resulted in the identification of promising protein antigens, which in combination with appropriate adjuvants can stimulate customized, protective immune responses. Although antigen adsorption to adjuvants influences vaccine efficacy and safety, little is generally known about how antigens and adjuvants interact at the molecular level. The aim of this study was to elucidate the mechanisms of interactions between the equally sized, but oppositely charged model protein antigens α-lactalbumin and lysozyme, and i) the clinically tested cationic liposomal adjuvant CAF01 composed of cationic dimethyldioctadecylammonium (DDA) bromide and trehalose-6,6'-dibehenate (TDB) or ii) the neutral adjuvant formulation NAF01, where DDA was replaced with zwitterionic distearoylphosphatidylcholine (DSPC). The effect of liposome charge, bilayer rigidity, isoelectric point and antigen-to-lipid ratio was investigated using dynamic light scattering, transmission electron microscopy, differential scanning calorimetry, intrinsic fluorescence and Langmuir monolayers. The net anionic α-lactalbumin adsorbed onto the cationic liposomes, while there was no measureable attractive interaction with the zwitterionic liposomes. In contrast, the net cationic lysozyme showed very little interaction with either types of liposome. Adsorption of α-lactalbumin altered its tertiary structure, affected lipid membrane packing below and above the phase transition temperature, and neutralized the liposomal surface charge, resulting in reduced colloidal stability and liposome aggregation. Langmuir studies revealed that α-lactalbumin was not squeezed out of DDA monolayers upon compression, which suggests additional hydrophobic interactions. Such interactions are thus likely to affect the way vaccine antigens are presented to antigen-presenting cells, and may play an important role for the efficacy of the vaccine-induced immune response. These studies thus exemplify the importance of characterizing the molecular interactions between the vaccine antigen and adjuvant along with immunogenicity and efficacy studies.
反向疫苗学方法最近已鉴定出有前景的蛋白质抗原，这些抗原与合适的佐剂联合使用可刺激定制的保护性免疫反应。尽管抗原吸附到佐剂上会影响疫苗的效力和安全性，但人们通常对抗原和佐剂在分子水平上如何相互作用知之甚少。本研究的目的是阐明大小相同但电荷相反的模型蛋白质抗原α-乳白蛋白和溶菌酶与以下物质之间的相互作用机制：i）由阳离子二甲基二辛基溴化铵（DDA）和海藻糖-6,6'-二山嵛酸酯（TDB）组成的经临床测试的阳离子脂质体佐剂CAF01，或ii）中性佐剂配方NAF01，其中DDA被两性离子二硬脂酰磷脂酰胆碱（DSPC）取代。使用动态光散射、透射电子显微镜、差示扫描量热法、内源荧光和朗缪尔单层膜研究了脂质体电荷、双层刚性、等电点和抗原与脂质比的影响。带净负电荷的α-乳白蛋白吸附到阳离子脂质体上，而与两性离子脂质体没有可测量的吸引相互作用。相比之下，带净正电荷的溶菌酶与两种类型的脂质体的相互作用都非常小。α-乳白蛋白的吸附改变了其三级结构，影响了相变温度上下的脂质膜堆积，并中和了脂质体表面电荷，导致胶体稳定性降低和脂质体聚集。朗缪尔研究表明，压缩时α-乳白蛋白不会从DDA单层膜中挤出，这表明存在额外的疏水相互作用。因此，这种相互作用可能会影响疫苗抗原呈递给抗原呈递细胞的方式，并可能对疫苗诱导的免疫反应的效力起重要作用。因此，这些研究例证了在进行免疫原性和效力研究的同时，表征疫苗抗原与佐剂之间分子相互作用的重要性。
