Invasive growth in tissues by the human fungal pathogen Candida albicans is promoted by a switch from budding to hyphal morphogenesis that is stimulated by multiple environmental factors that can vary at different sites of infection. To identify genes that promote invasive growth in the oral cavity to cause oropharyngeal candidiasis (OPC), we first identified C. albicans mutants that failed to invade agar medium. Analysis of nine severely defective mutants in a mouse model of OPC revealed that the strongest defects were seen for the rvs161Δ and rvs167Δ mutants, which lack amphiphysin proteins needed for endocytosis. The rvsΔ mutants initially adhered to the tongue but failed to invade efficiently and were lost from the oral cavity. Previous studies indicated that rvsΔ mutants formed filamentous hyphae in the kidney albeit with morphological abnormalities, suggesting that the rvsΔ mutants were influenced by factors that vary at different sites of infection. Consistent with this, increasing concentrations of CO2, an inducer of hyphal growth that is more abundant in internal organs than air, partially rescued the invasive-growth defects of the rvsΔ mutants in vitro Interestingly, preinduction of the rvsΔ mutants to form hyphae prior to introduction into the oral cavity restored their ability to cause OPC, identifying a key role for endocytosis in initiating invasive hyphal growth. These results highlight the influence of distinct environmental factors in promoting invasive hyphal growth in the oral cavity and indicate that blocking endocytosis could have therapeutic value in preventing the initiation of OPC.IMPORTANCE Oropharyngeal candidiasis (OPC) is a common fungal infection that is associated with severe morbidity. Another concern is that patients at risk for developing OPC often take long courses of antifungal drugs, which can lead to the emergence of drug-resistant C. albicans strains. We therefore identified nine mutants with defects in undergoing invasive hyphal growth in the oral cavity, increasing the number of genes known to be involved in OPC by more than 30%. The two strongest mutants, rvs161Δ and rvs167Δ, have defects in endocytosis. The rvsΔ mutants appear to have a specific defect in initiating invasive growth, as preinducing the cells to form hyphae prior to infection restored their ability to cause OPC. These results indicate that blocking endocytosis could have therapeutic value in preventing the initiation of OPC without leading to development of resistance against drugs currently used to treat fungal infections.

中文翻译：

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白色念珠菌rvs161Δ和rvs167Δ内吞突变在入侵口腔中有缺陷。

人类真菌病原体白色念珠菌在组织中的侵袭性生长是由芽生转变为菌丝形态发生而促进的，菌丝形态发生受到多种环境因素的刺激，这些环境因素在感染的不同部位可能有所不同。为了鉴定促进口腔中侵袭性生长以引起口咽念珠菌病（OPC）的基因，我们首先鉴定了未能入侵琼脂培养基的白色念珠菌突变体。对OPC小鼠模型中的9个严重缺陷的突变体进行分析后发现，发现rvs161Δ和rvs167Δ突变体的缺陷最强，它们缺少内吞所需的两亲性蛋白。rvsΔ突变体最初附着在舌头上，但未能有效侵入，并从口腔中消失。先前的研究表明，rvsΔ突变体在肾脏中形成丝状菌丝，尽管形态异常，这表明rvsΔ突变体受到感染部位不同的因素的影响。与此相一致的是，增加浓度的二氧化碳（一种在内部器官中比空气更丰富的菌丝生长的诱导剂）在体外部分挽救了rvsΔ突变体的侵袭性生长缺陷。进入口腔后，它们恢复了引起OPC的能力，从而确定了内吞作用在启动侵入性菌丝生长中的关键作用。这些结果突出了不同环境因素对促进口腔中侵袭性菌丝生长的影响，并表明阻断内吞作用在预防OPC的发生方面可能具有治疗价值。重要信息口咽念珠菌病（OPC）是与重度细菌感染相关的常见真菌感染。发病率。另一个令人担忧的问题是，处于发生OPC风险的患者经常服用长疗程的抗真菌药物，这可能导致出现耐药性白色念珠菌菌株。因此，我们确定了9个在口腔中经历侵入性菌丝生长缺陷的突变体，从而使已知参与OPC的基因数量增加了30％以上。两个最强的突变体rvs161Δ和rvs167Δ在胞吞作用方面存在缺陷。rvsΔ突变体在启动侵袭性生长方面似乎具有特定缺陷，因为在感染前预诱导细胞形成菌丝可恢复其引起OPC的能力。这些结果表明，阻断内吞作用可能具有预防OPC启动的治疗价值，而不会导致对目前用于治疗真菌感染的药物产生抗药性。