Table_4_Production and Composition of Group B Streptococcal Membrane Vesicles Vary Across Diverse Lineages.XLSX

Although the neonatal and fetal pathogen Group B Streptococcus (GBS) asymptomatically colonizes the vaginal tract of ∼30% of pregnant women, only a fraction of their offspring develops invasive disease. We and others have postulated that these dimorphic clinical phenotypes are driven by strain variability; however, the bacterial factors that promote these divergent clinical phenotypes remain unclear. It was previously shown that GBS produces membrane vesicles (MVs) that contain active virulence factors capable of inducing adverse pregnancy outcomes. Because the relationship between strain variation and vesicle composition or production is unknown, we sought to quantify MV production and examine the protein composition, using label-free proteomics on MVs produced by diverse clinical GBS strains representing three phylogenetically distinct lineages. We found that MV production varied across strains, with certain strains displaying nearly twofold increases in production relative to others. Hierarchical clustering and principal component analysis of the proteomes revealed that MV composition is lineage-dependent but independent of clinical phenotype. Multiple proteins that contribute to virulence or immunomodulation, including hyaluronidase, C5a peptidase, and sialidases, were differentially abundant in MVs, and were partially responsible for this divergence. Together, these data indicate that production and composition of GBS MVs vary in a strain-dependent manner, suggesting that MVs have lineage-specific functions relating to virulence. Such differences may contribute to variation in clinical phenotypes observed among individuals infected with GBS strains representing distinct lineages.

尽管作为新生儿与胎儿病原体的B群链球菌（Group B Streptococcus, GBS）可在约30%的孕妇阴道中无症状定植，但仅有部分子代会罹患侵袭性疾病。本团队与其他研究者均推测，这种双态临床表型由菌株变异性驱动；然而，介导这些迥异临床表型的细菌因子仍未明确。既往研究表明，GBS可产生膜囊泡（membrane vesicles, MVs），其携带的活性毒力因子能够诱发不良妊娠结局。由于菌株变异与囊泡组成或产生量之间的关联尚不明确，本研究针对代表3个系统发育不同谱系的多种临床GBS菌株产生的MVs，采用无标记蛋白质组学技术，定量分析MV产生量并检测其蛋白质组成。研究发现，不同菌株的MV产生量存在差异，部分菌株的MV产生量相较其他菌株提升近两倍。对蛋白质组进行层次聚类与主成分分析后结果显示，MV组成具有谱系依赖性，且与临床表型无关。多种参与毒力或免疫调节的蛋白质（包括透明质酸酶、C5a肽酶与唾液酸酶）在MVs中存在差异丰度，这部分解释了上述组成差异。综上，本研究数据表明，GBS膜囊泡的产生量与组成呈菌株依赖性差异，提示MVs具有与毒力相关的谱系特异性功能。此类差异或可解释感染不同谱系GBS菌株的个体间所观察到的临床表型变异。