Wiedinger Kari, Pinho Daniel, Bitsaktsis Constantine
Seton Hall University, South Orange, NJ, USA.
Seton Hall University, 400 South Orange Ave, South Orange, NJ 07079, USA.
Ther Adv Vaccines. 2017 Feb;5(1):15-24. doi: 10.1177/2051013617691041. Epub 2017 Feb 13.
The introduction of the pneumococcal conjugate and polysaccharide vaccines have been valuable tools for combating invasive pneumococcal infection in children and healthy adults. Despite the available vaccination strategies, pneumococcal pneumonia and associated diseases continue to cause substantial morbidity and mortality, particularly in individuals with chronic disease and ageing populations. Next-generation pneumococcal vaccines will need to be highly immunogenic across patient populations providing both mucosal and systemic protective immunity. Mucosal immunization is an effective strategy for stimulating the immune response at the site of pathogen entry while increasing systemic immunity. In this study we utilized intranasal immunization with pneumococcal surface protein A (PspA), in combination with the mucosal adjuvant cholera toxin B (CTB), to characterize the immune components providing protection against challenge.
Mice were immunized intranasally with CTB and PspA individually, and in combination, followed by lethal bacterial challenge with , strain A66.1. Animals were monitored for survival and tested for lung bacterial burden, cytokine production as well as -specific antibody titer in mouse sera. The primary immunological contributor to the observed protection was confirmed by cytokine neutralization and serum passive transfer.
The combination of CTB and PspA provided complete protection against bacterial challenge, which coincided with a significant decrease in lung bacterial burden. Increases in the T-helper (Th) 1 cytokines, interferon (IFN)-γ and interleukin (IL)-2 were observed in the lung 24 h post-challenge while decreases in proinflammatory mediators IL-6 and tumor necrosis factor (TNF)-α were also recorded at the same time point. The adjuvanted PspA immunization induced significant titers of -specific antibody in the serum of mice prior to infection. Serum adoptive transfer passively protected animals against subsequent challenge while IFN-γ neutralization had no impact on the outcome of immunization, suggesting a primary role for antibody-mediated protection in the context of this immunization strategy.
Mucosal immunization with CTB and PspA induced a local cellular immune response and systemic humoral immunity which resulted in effective reduction of pulmonary bacterial burden and complete protection against challenge. While induction of the pleiotropic cytokine IFN-γ likely contributes to control of infection through activation of effector pathways, it was not required for protection. Instead, immunization with PspA and CTB-induced specific antibodies in the serum prior to infection that were sufficient to protect against mucosal challenge.
肺炎球菌结合疫苗和多糖疫苗的引入是对抗儿童和健康成人侵袭性肺炎球菌感染的重要工具。尽管有可用的疫苗接种策略，但肺炎球菌肺炎及相关疾病仍继续导致大量发病和死亡，尤其是在患有慢性疾病的个体和老年人群中。下一代肺炎球菌疫苗需要在患者群体中具有高度免疫原性，提供黏膜和全身保护性免疫。黏膜免疫是一种在病原体进入部位刺激免疫反应同时增强全身免疫的有效策略。在本研究中，我们利用肺炎球菌表面蛋白A（PspA）鼻内免疫，并联合黏膜佐剂霍乱毒素B（CTB），以表征提供抵御攻击保护作用的免疫成分。
小鼠分别单独或联合用CTB和PspA进行鼻内免疫，随后用A66.1菌株进行致死性细菌攻击。监测动物的存活情况，并检测肺部细菌负荷、细胞因子产生以及小鼠血清中的特异性抗体滴度。通过细胞因子中和和血清被动转移证实了观察到的保护作用的主要免疫贡献者。
CTB和PspA的联合提供了针对细菌攻击的完全保护，这与肺部细菌负荷的显著降低相一致。在攻击后24小时，在肺部观察到辅助性T细胞（Th）1细胞因子、干扰素（IFN）-γ和白细胞介素（IL）-2增加，同时在同一时间点也记录到促炎介质IL-6和肿瘤坏死因子（TNF）-α减少。佐剂化的PspA免疫在感染前诱导小鼠血清中产生显著滴度的特异性抗体。血清过继转移被动保护动物免受后续攻击，而IFN-γ中和对免疫结果没有影响，表明在这种免疫策略中抗体介导的保护起主要作用。
用CTB和PspA进行黏膜免疫诱导了局部细胞免疫反应和全身体液免疫，从而有效降低了肺部细菌负荷并提供了针对攻击的完全保护。虽然多效性细胞因子IFN-γ的诱导可能通过激活效应途径有助于控制感染，但保护并不需要它。相反，在感染前用PspA和CTB免疫诱导血清中产生特异性抗体，足以抵御黏膜攻击。
