Wafa Emad I, Geary Sean M, Goodman Jonathan T, Narasimhan Balaji, Salem Aliasger K
Department of Pharmaceutical Sciences and Experimental Therapeutics, College of Pharmacy, University of Iowa, Iowa City, IA 52242, USA.
Department of Chemical and Biological Engineering, College of Engineering, Iowa State University, Ames, IA 50011, USA.
Acta Biomater. 2017 Mar 1;50:417-427. doi: 10.1016/j.actbio.2017.01.005. Epub 2017 Jan 4.
The goal of this research was to study the effect of polyanhydride chemistry on the immune response induced by a prophylactic cancer vaccine based on biodegradable polyanhydride particles. To achieve this goal, different compositions of polyanhydride copolymers based on 1,8-bis-(p-carboxyphenoxy)-3,6-dioxaoctane (CPTEG), 1,6-bis-(p-carboxyphenoxy)-hexane (CPH), and sebacic anhydride (SA) were synthesized by melt polycondensation, and polyanhydride copolymer particles encapsulating a model antigen, ovalbumin (OVA), were then synthesized using a double emulsion solvent evaporation technique. The ability of three different compositions of polyanhydride copolymers (50:50 CPTEG:CPH, 20:80 CPTEG:CPH, and 20:80 CPH:SA) encapsulating OVA to elicit immune responses was investigated. In addition, the impact of unmethylated oligodeoxynucleotides containing deoxycytidyl-deoxyguanosine dinucleotides (CpG ODN), an immunological adjuvant, on the immune response was also studied. The immune response to cancer vaccines was measured after treatment of C57BL/6J mice with two subcutaneous injections, seven days apart, of 50μg OVA encapsulated in particles composed of different polyanhydride copolymers with or without 25μg CpG ODN. In vivo studies showed that 20:80 CPTEG:CPH particles encapsulating OVA significantly stimulated the highest level of CD8 T lymphocytes, generated the highest serum titers of OVA-specific IgG antibodies, and provided longer protection against tumor challenge with an OVA-expressing thymoma cell line in comparison to formulations made from other polyanhydride copolymers. The results also revealed that vaccination with CpG ODN along with polyanhydride particles encapsulating OVA did not enhance the immunogenicity of OVA. These results accentuate the crucial role of the copolymer composition of polyanhydrides in stimulating the immune response and provide important insights on rationally designing efficacious cancer vaccines.
Compared to soluble cancer vaccine formulations, tumor antigens encapsulated in biodegradable polymeric particles have been shown to sustain antigen release and provide long-term protection against tumor challenge by improving the immune response towards the antigen. Treatment of mice with cancer vaccines based on different polyanhydride copolymers encapsulating OVA resulted in stimulation of tumor-specific immune responses with different magnitudes. This clearly indicates that polyanhydride chemistry plays a substantial role in stimulating the immune response. Vaccination with 20:80 CPTEG:CPH/OVA, the most hydrophobic formulation, stimulated the strongest cellular and humoral immune responses and provided the longest survival outcome without adding any other adjuvant. The most important finding in this study is that the copolymer composition of polyanhydride particle-based vaccines can have a direct effect on the magnitude of the antitumor immune response and should be selected carefully in order to achieve optimal cancer vaccine efficacy.
本研究的目的是探讨聚酸酐化学对基于可生物降解聚酸酐颗粒的预防性癌症疫苗诱导的免疫反应的影响。为实现这一目标，通过熔融缩聚合成了基于1,8-双（对羧基苯氧基）-3,6-二氧杂辛烷（CPTEG）、1,6-双（对羧基苯氧基）-己烷（CPH）和癸二酸酐（SA）的不同组成的聚酸酐共聚物，然后使用双乳液溶剂蒸发技术合成了包裹模型抗原卵清蛋白（OVA）的聚酸酐共聚物颗粒。研究了三种不同组成的包裹OVA的聚酸酐共聚物（50:50 CPTEG:CPH、20:80 CPTEG:CPH和20:80 CPH:SA）引发免疫反应的能力。此外，还研究了含有脱氧胞苷-脱氧鸟苷二核苷酸（CpG ODN）的未甲基化寡脱氧核苷酸作为免疫佐剂对免疫反应的影响。在用由不同聚酸酐共聚物组成的颗粒包裹的50μg OVA，加或不加25μg CpG ODN，对C57BL/6J小鼠进行两次皮下注射（间隔7天）后，测量对癌症疫苗的免疫反应。体内研究表明，与由其他聚酸酐共聚物制成的制剂相比，包裹OVA的20:80 CPTEG:CPH颗粒显著刺激了最高水平的CD8 T淋巴细胞，产生了最高血清滴度的OVA特异性IgG抗体，并在面对表达OVA的胸腺瘤细胞系的肿瘤攻击时提供了更长时间的保护。结果还显示，用CpG ODN与包裹OVA的聚酸酐颗粒一起接种疫苗并没有增强OVA的免疫原性。这些结果突出了聚酸酐共聚物组成在刺激免疫反应中的关键作用，并为合理设计有效的癌症疫苗提供了重要见解。
与可溶性癌症疫苗制剂相比，包裹在可生物降解聚合物颗粒中的肿瘤抗原已被证明可维持抗原释放，并通过改善对抗原的免疫反应提供针对肿瘤攻击的长期保护。用基于不同聚酸酐共聚物包裹OVA的癌症疫苗治疗小鼠导致了不同程度的肿瘤特异性免疫反应的刺激。这清楚地表明聚酸酐化学在刺激免疫反应中起着重要作用。用最疏水的制剂20:80 CPTEG:CPH/OVA接种疫苗，在不添加任何其他佐剂的情况下刺激了最强的细胞和体液免疫反应，并提供了最长的生存结果。本研究中最重要的发现是，基于聚酸酐颗粒的疫苗的共聚物组成可直接影响抗肿瘤免疫反应的程度，为实现最佳癌症疫苗疗效应仔细选择。
