Division of Molecular Microbiology and Immunology, CSIR-Central Drug Research Institute, Lucknow 226031, India.
Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India.
ACS Infect Dis. 2024 Aug 9;10(8):3013-3025. doi: 10.1021/acsinfecdis.4c00362. Epub 2024 Jul 22.
sporozoites invade hepatocytes, transform into liver stages, and replicate into thousands of merozoites that infect erythrocytes and cause malaria. Proteins secreted from micronemes play an essential role in hepatocyte invasion, and unneeded micronemes are subsequently discarded for replication. The liver-stage parasites are potent immunogens that prevent malarial infection. Late liver stage-arresting genetically attenuated parasites (GAPs) exhibit greater protective efficacy than early GAP. However, the number of late liver-stage GAPs for generating GAPs with multiple gene deletions is limited. Here, we identified Scot1 (Sporozoite Conserved Orthologous Transcript 1), which was previously shown to be upregulated in sporozoites, and by endogenous tagging with mCherry, we demonstrated that it is expressed in the sporozoite and liver stages in micronemes. Using targeted gene deletion in , we showed that Scot1 is essential for late liver-stage development. KO sporozoites grew normally into liver stages but failed to initiate blood-stage infection in mice due to impaired apicoplast biogenesis and merozoite formation. Bioinformatic studies suggested that Scot1 is a metal-small-molecule carrier protein. Remarkably, supplementation with metals in the culture of infected KO cells did not rescue their phenotype. Immunization with KO sporozoites in C57BL/6 mice confers protection against malaria via infection. These proof-of-concept studies will enable the generation of Scot1 mutants that could be exploited to generate GAP malaria vaccines.
疟原虫的子孢子侵入肝细胞，转化为肝期，复制成数千个裂殖子，感染红细胞并引起疟疾。微线体分泌的蛋白质在肝细胞入侵中起着至关重要的作用，随后不需要的微线体被丢弃用于复制。肝期寄生虫是有效的免疫原，可以预防疟疾感染。晚期肝期停滞的遗传减毒寄生虫（GAP）比早期 GAP 具有更高的保护效果。然而，用于产生具有多个基因缺失的 GAP 的晚期肝期 GAP 的数量有限。在这里，我们鉴定了 Scot1（孢子保守同源转录物 1），它之前在子孢子中被上调，并且通过内源标记 mCherry，我们证明它在微线体中表达在子孢子和肝期。通过靶向基因缺失，我们表明 Scot1 对于晚期肝期发育是必需的。Scot1 KO 子孢子正常生长为肝期，但由于类质体生物发生和裂殖子形成受损，无法在小鼠中启动血液期感染。生物信息学研究表明，Scot1 是一种金属小分子载体蛋白。值得注意的是，在感染的 Scot1 KO 细胞的培养物中补充金属并不能挽救它们的表型。用 C57BL/6 小鼠中的 Scot1 KO 子孢子免疫可通过感染提供对疟疾的保护。这些概念验证研究将使产生 Scot1 突变体成为可能，这些突变体可用于生成 GAP 疟疾疫苗。
