Department of Microbiology, University of Georgiagrid.213876.9, Athens, Georgia, USA.
mBio. 2022 Feb 22;13(1):e0278521. doi: 10.1128/mbio.02785-21. Epub 2022 Jan 11.
Systemic cryptococcosis is fatal without treatment. Globally, this disease kills 180,000 of the 225,000 infected people each year, even with the use of antifungal therapies. Currently, there is no vaccine to prevent cryptococcosis. Previously, we discovered that Znf2, a morphogenesis regulator that directs Cryptococcus yeast-to-hyphal transition, profoundly affects cryptococcal interaction with the host-overexpression of drives filamentous growth, attenuates cryptococcal virulence, and elicits protective host immune responses. Importantly, immunization with cryptococcal cells overexpressing , either in live or heat-inactivated form, offers significant protection to the host from a subsequent challenge by the otherwise lethal wild-type H99 strain. We hypothesize that cellular components enriched in cells are immunoprotective. Here, we discovered that serum from protected animals vaccinated with inactivated cells recognizes cryptococcal antigens that reside within the capsule. Consistently, capsule is required for immunoprotection offered by cells. Interestingly, the serum from protective animals recognizes antigens in both wild-type yeast cells and cells, with higher abundance in the latter. Consequently, even the heat-inactivated wild-type cells become immunoprotective with an increased vaccination dose. We also found that disruption of a chromatin remodeling factor Brf1, which is important for initiation of filamentation by Znf2, reduces the antigen level in cells. Deletion of drastically reduces the protective effect of cells in both live and heat-killed forms even though the Δ strain itself is avirulent. Collectively, our findings underscore the importance of identifying the subset of cryptococcal surface factors that are beneficial in host protection. Cryptococcosis claims close to 200,000 lives annually. There is no vaccine clinically available for this fungal disease. Many avirulent mutant strains do not provide protection against cryptococcosis. We previously discovered that hyphal strains elicit protective host immune responses both in the live and heat-inactivated forms. Here we seek to understand the mechanism underlying the host protection provided by cells. We discovered increased accumulation of antigens located within the caspusle of cells and consequently the requirement of the capsule for strain-elicited host protection. Furthermore, genetically blocking the ability of cells to grow in the hyphal form significantly reduces antigen accumulation and impairs the ability of strain to provide host protection. Our findings highlight the importance of identifying the Znf2-regulated capsular surface factors that are fundamental in host protection.
系统性隐球菌病如果不治疗是致命的。全球范围内，每年有 18 万人死于这种疾病，即使使用抗真菌疗法也是如此。目前，还没有预防隐球菌病的疫苗。此前，我们发现 Znf2 是一种形态发生调节剂，可指导隐球菌从酵母形态向菌丝形态的转变，它对隐球菌与宿主的相互作用有深远影响——过表达 Znf2 可驱动丝状生长、减弱隐球菌的毒力，并引发保护性的宿主免疫反应。重要的是，用表达 的隐球菌细胞（无论是活的还是热失活的）进行免疫接种，可显著保护宿主免受随后由致命性野生型 H99 菌株引起的感染。我们假设在过表达 的细胞中富集的细胞成分具有免疫保护作用。在这里，我们发现用热失活的 细胞免疫接种的保护性动物的血清可识别位于荚膜内的隐球菌抗原。一致地，荚膜是由 细胞提供的免疫保护所必需的。有趣的是，保护性动物的血清可识别野生型酵母细胞和 细胞中的抗原，后者的丰度更高。因此，即使是热失活的野生型细胞，随着接种剂量的增加也会变得具有免疫保护作用。我们还发现，破坏染色质重塑因子 Brf1（它对 Znf2 引发丝状生长很重要）可降低 细胞中的抗原水平。即使Δ 菌株本身无毒力， 缺失也会大大降低 细胞在活细胞和热杀死细胞形式中的保护作用。总的来说，我们的研究结果强调了确定有利于宿主保护的隐球菌表面因子亚群的重要性。 隐球菌病每年导致近 20 万人死亡。目前还没有针对这种真菌病的临床可用疫苗。许多无毒力突变株不能提供针对隐球菌病的保护。我们之前发现，丝状 株在活细胞和热失活形式下都能引发保护性的宿主免疫反应。在这里，我们试图了解 细胞提供宿主保护的机制。我们发现 细胞中位于荚膜内的抗原积累增加，因此荚膜是 菌株引发的宿主保护所必需的。此外，遗传阻断 细胞生长为菌丝形态的能力会显著减少抗原积累，并削弱 菌株提供宿主保护的能力。我们的研究结果强调了确定在宿主保护中起基础性作用的 Znf2 调节的荚膜表面因子的重要性。
