Hansen Philipp, Haubenthal Thomas, Reiter Caroline, Kniewel Jana, Bosse-Plois Karla, Niemann Hartmut H, von Bargen Kristine, Haas Albert
Institute for Cell Biology, University of Bonn, Bonn, Germany.
Department of Chemistry, Bielefeld University, Bielefeld, Germany.
Microbiol Spectr. 2023 Feb 14;11(2):e0341722. doi: 10.1128/spectrum.03417-22.
irulence-ssociated rotein (VapA) of Rhodococcus equi is a pathogenicity factor required for the multiplication of virulent strains within spacious macrophage vacuoles. The production of VapA is characteristic for isolates from pneumonic foals. VapB and VapN proteins in isolates from infected pig (VapB) and cattle (VapN) have amino acid sequences very similar to VapA and consequently have been assumed to be its functional correlates. Using model membrane experiments, phagosome pH acidification analysis, lysosome size measurements, protein partitioning, and degradation assays, we provide support for the view that VapA and VapN promote intracellular multiplication of by neutralizing the pH of the -containing vacuole. VapB does not neutralize vacuole pH, is not as membrane active as VapA, and does not support intracellular multiplication. This study also shows that the size of the sometimes enormous -containing vacuoles or the partitioning of purified Vaps into organic phases are not features that have predictive value for virulence of , whereas the ability of Vaps to increase phagosome pH is coupled to virulence. Rhodococcus equi is a major cause of life-threatening pneumonia in foals and occasionally in immunocompromised persons. Virulence-associated protein A (VapA) promotes multiplication in lung macrophages, which are the major host cells during foal infection. In this study, we compare cellular, biochemical, and biophysical phenotypes associated with VapA to those of VapB (typically produced by isolates from pigs) or VapN (isolates from cattle). Our data support the hypothesis that only some Vaps support multiplication in macrophages by pH neutralization of the phagosomes that inhabit.
马红球菌的毒力相关蛋白（VapA）是强毒株在宽敞的巨噬细胞液泡内增殖所必需的致病因子。VapA的产生是肺炎驹分离株的特征。来自感染猪（VapB）和牛（VapN）的分离株中的VapB和VapN蛋白的氨基酸序列与VapA非常相似，因此被认为是其功能相关物。通过模型膜实验、吞噬体pH酸化分析、溶酶体大小测量、蛋白质分配和降解测定，我们支持以下观点：VapA和VapN通过中和含菌液泡的pH来促进菌的细胞内增殖。VapB不能中和液泡pH，其膜活性不如VapA，也不支持细胞内增殖。这项研究还表明，有时巨大的含菌液泡的大小或纯化的Vaps在有机相中的分配并不是对马红球菌毒力具有预测价值的特征，而Vaps增加吞噬体pH的能力与毒力相关。马红球菌是驹致命性肺炎的主要病因，偶尔也会导致免疫功能低下者患病。毒力相关蛋白A（VapA）促进菌在肺巨噬细胞中的增殖，肺巨噬细胞是驹感染期间的主要宿主细胞。在这项研究中，我们将与VapA相关的细胞、生化和生物物理表型与VapB（通常由猪分离株产生）或VapN（牛分离株）的表型进行了比较。我们的数据支持这样的假设，即只有一些Vaps通过中和其所占据的吞噬体的pH来支持巨噬细胞中的增殖。
