Studying the protective efficacy of radiation-attenuated Plasmodium sporozoites as anti-infective malaria vaccine during concurrent infection with Mycobacterium tuberculosis

疟疾仍然是人类面临的主要威胁之一。疟疾研究的一个主要目标是开发新的疫苗。40多年来，人们已经知道，辐射减弱子孢子(RAS)免疫在小鼠和人身上对随后的疟原虫攻击具有无菌保护作用。在小鼠身上的研究已经阐明了CD8+T细胞在RAS免疫中对肝期疟原虫感染的保护作用。此外，需要极高数量的CD8+T细胞来提供杀菌保护。有人提出，从短期保护到长期保护需要高抗原负载，记忆性T细胞反应的持久性至少部分取决于肝脏中抗原库的持久性。对其他病原体的免疫反应可以干扰疫苗诱导的记忆性T细胞反应，从而干扰对疟原虫感染的充分反应能力。在疟疾流行的地区，许多人接触结核分枝杆菌(Mtb)，这是结核病(TB)的病原体。在小鼠混合感染模型中，我们发现伯氏肺炎子孢子传播后血液中寄生虫的初始出现延迟了预先感染Mtb的动物，这表明当Mtb同时存在时，肝脏发育受到损害。这表明非特异性免疫激活可以影响肝脏中的子孢子数量。此外，我们有初步数据表明，当结核分枝杆菌同时存在时，接种基因减毒的寄生虫疫苗时，对野生型子孢子攻击的保护部分被取消。有趣的是，卡介苗接种对RAS介导的预防疟疾感染的重大影响早在30多年前就已被证明。总之，这些研究将我们的研究假设带到了我们的研究假设中，即结核分枝杆菌感染导致免疫环境的调节，并阻碍原虫肝脏阶段介导的保护。鉴于结核病在疟疾流行地区的高流行率，这将对全子孢子疫苗接种方法产生重大影响。RAS免疫仍然是诱导无菌保护的黄金标准，并已进入临床试验。这项赠款提案的目标是使用我们的联合感染模型来研究在同时存在结核分枝杆菌的情况下，RAS免疫的保护效力是如何调节的。具体地说，我们将研究结核分枝杆菌感染对RAS诱导的短期和长期记忆反应的影响。此外，我们还将比较感染和未感染结核分枝杆菌的动物在免疫后不同时间点野生型攻击的短期和长期保护效果。我们将进一步研究挑战后的适应性反应，以找出疫苗诱导的反应在结核分枝杆菌合并感染期间是否可以增强。我们的研究结果可能会对未来的人类研究产生重要影响，并将对该领域做出重大贡献。

Malaria remains one of the main threats to mankind. A major goal in malaria research is the development of new vaccines. It has been known for more than 40 years that immunization with radiation attenuated sporozoites (RAS) confers sterile protection against subsequent Plasmodium challenge in mouse and man. Studies in mice have elucidated a leading role for CD8+ T cells in protection against liver-stage Plasmodium infection upon RAS immunization. Moreover, extremely high numbers of memory CD8+ T cells are required to provide sterilizing protection. It has been proposed that a high antigen load is needed to progress from short- to long-term protection and that the persistence of a memory T cell response depends at least in part on the persistence of an antigen-depot in the liver.Immune responses to other pathogens can interfere with vaccine-induced memory T cell responses and thus, with the ability to respond adequately to Plasmodium infections. In areas where malaria is endemic, many people are exposed to Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (Tb). In a murine co-infection model we found that the initial occurrence of parasites in the blood (prepatency) following P. berghei sporozoite transmission was delayed in animals pre-infected with Mtb, indicating impaired liver stage development when Mtb is concurrent. This suggests that unspecific immune activation can influence sporozoite numbers in the liver. Moreover, we have preliminary data indicating that protection against wild type sporozoite challenge upon vaccination with genetically attenuated parasites is partially abrogated when Mtb is concurrent. Interestingly, a significant impact of BCG vaccination on RAS-mediated protection against malaria infection has been demonstrated already more than 30 years ago. Together, these studies bring us to our research hypothesis that Mtb infection causes modulation of the immunological environment and impedes plasmodial liver-stage mediated protection. Given the high prevalence of Tb in malaria endemic areas, this would have major implications on whole-sporozoite vaccination approaches. RAS immunization still represents the gold standard for induction of sterile protection and has moved to clinical trials. The goal of this grant proposal is to use our co-infection model to investigate how the protective efficacy of RAS immunization is modulated in the context of concurrent Mtb. Specifically we will study the impact of Mtb infection on RAS-induced short and long-term memory responses. Moreover, we will compare short- and long-term protection by wild type challenge at different time points after immunization in Mtb infected and non-infected animals. We will further investigate adaptive responses post challenge to find out if vaccine-induced responses can be boosted during Mtb co-infection. The results of our study may have important implications for future human studies and will contribute significantly to the field.