The physicochemical properties of an antigen (Ag) influence the type, specificity, as well as duration of emerging immune responses. Like immune responses arising to nominal protein Ags, reactivities to protozoan parasites, Plasmodium falciparum and P. berghei, the causative agents of human and mouse malaria, respectively, are shaped by the form of the parasite. While repeated natural exposures to infectious Plasmodium sporozoites (spzs) typically induce malaria, immunizations with radiation or genetically attenuated forms of Plasmodium spzs induce sterile and durable protective immunity. The immune mechanisms that are responsible for these diametrically opposite outcomes are still not well understood. It has been observed that infectious spzs engage in mechanisms that evade immune recognition and thus prevent protective immune responses from occurring. The responses that develop are characteristic of anti-disease immunity; acquisition of protective immunity against infection is a prolonged process, and it decays once exposure to the parasite ceases. In contrast, repeated exposures to attenuated Plasmodium spzs induce antibodies and CD4 T cells directed primarily to the spz surface Ags and effector and memory CD8 T cells that localize in the liver and are specific for Plasmodium liver-stage Ags. Understanding the precise mechanisms, including early interactions between the spzs and Ag-presenting cells that lead to the manner of Ag processing and presentation, are of key importance as such information would substantially contribute to the successful development of malaria vaccine.

中文翻译：

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抗原的形式及其分子背景很重要：传染性与减毒疟原虫子孢子

抗原 (Ag) 的理化特性会影响新出现的免疫反应的类型、特异性和持续时间。与对名义蛋白 Ags 产生的免疫反应一样，对原生动物寄生虫、恶性疟原虫和伯氏疟原虫（分别是人类和小鼠疟疾的病原体）的反应性是由寄生虫的形式形成的。虽然反复自然暴露于传染性疟原虫子孢子 (spzs) 通常会诱发疟疾，但使用辐射或基因减毒形式的疟原虫进行免疫接种spzs 诱导无菌和持久的保护性免疫。导致这些截然相反的结果的免疫机制仍不清楚。已经观察到传染性 spzs 参与逃避免疫识别的机制，从而防止发生保护性免疫反应。产生的反应是抗疾病免疫的特征；获得针对感染的保护性免疫是一个漫长的过程，一旦停止接触寄生虫，它就会衰退。相比之下，反复暴露于减毒疟原虫spzs 诱导抗体和 CD4 T 细胞主要针对 spz 表面抗原和效应和记忆 CD8 T 细胞，这些细胞定位于肝脏并且对疟原虫具有特异性肝期抗原。了解精确的机制，包括导致 Ag 加工和呈递方式的 spz 和 Ag 呈递细胞之间的早期相互作用，是至关重要的，因为这些信息将大大有助于疟疾疫苗的成功开发。