Development of an Aerosol Model of Cryptococcus Reveals Humidity as an Important Factor Affecting the Viability of Cryptococcus during Aerosolization

Cryptococcus is an emerging global health threat that is annually responsible for over 1,000,000 infections and one third of all AIDS patient deaths. There is an ongoing outbreak of cryptococcosis in the western United States and Canada. Cryptococcosis is a disease resulting from the inhalation of the infectious propagules from the environment. The current and most frequently used animal infection models initiate infection via liquid suspension through intranasal instillation or intravenous injection. These models do not replicate the typically dry nature of aerosol exposure and may hinder our ability to decipher the initial events that lead to clearance or the establishment of infection. We have established a standardized aerosol model of murine infection for the human fungal pathogen Cryptococcus. Aerosolized cells were generated utilizing a Collison nebulizer in a whole-body Madison Chamber at different humidity conditions. The aerosols inside the chamber were sampled using a BioSampler to determine viable aerosol concentration and spray factor (ratio of viable aerosol concentration to total inoculum concentration). We have effectively delivered yeast and yeast-spore mixtures to the lungs of mice and observed the establishment of disease. We observed that growth conditions prior to exposure and humidity within the Madison Chamber during exposure can alter Cryptococcus survival and dose retained in mice.隐球菌（Cryptococcus）是一类新兴的全球健康威胁，每年造成超100万例感染，占艾滋病患者死亡总数的三分之一。目前美国西部与加拿大地区正流行隐球菌病（cryptococcosis）。隐球菌病是因吸入环境中的传染性繁殖体而引发的疾病。当前最常用的动物感染模型均通过液体悬液经鼻内滴注或静脉注射启动感染，此类模型无法复现气溶胶暴露典型的干燥特性，可能阻碍我们解析引发病原体清除或感染建立的初始事件。 我们针对人类真菌病原体隐球菌建立了标准化的小鼠（murine）肺部感染气溶胶模型。实验中，我们在不同湿度条件下，于全身暴露式麦迪逊舱（Madison Chamber）内使用科林逊雾化器（Collison nebulizer）制备雾化菌体；舱内气溶胶采用生物采样器（BioSampler）进行采样，以测定活菌气溶胶浓度及喷雾因子（活菌气溶胶浓度与总接种物浓度的比值）。 我们成功将酵母菌与酵母孢子混合物递送至小鼠肺部，并观察到感染的建立。研究发现，暴露前的菌体培养条件及暴露期间麦迪逊舱内的湿度，均可影响隐球菌的存活能力及在小鼠体内的留存剂量。