Transcriptome Analysis of Neisseria meningitidis inHuman Whole Blood and Mutagenesis Studies Identify Virulence Factors Involved inBlood Survival

摘要

During infection Neisseria meningitidis (Nm) encounters multiple environments within the host, which makes rapid adaptation a crucial factor for meningococcal survival. Despite the importance of invasion into the bloodstream in the meningococcal disease process, little is known about how Nm adapts to permit survival and growth in blood. To address this, we performed a time-course transcriptome analysis using an ex vivo model of human whole blood infection. We observed that Nm alters the expression of ≈30% of ORFs of the genome and major dynamic changes were observed in the expression of transcriptional regulators, transport and binding proteins, energy metabolism, and surface-exposed virulence factors. In particular, we found that the gene encoding the regulator Fur, as well as all genes encoding iron uptake systems, were significantly up-regulated. Analysis of regulated genes encoding for surface-exposed proteins involved in Nm pathogenesis allowed us to better understand mechanisms used to circumvent host defenses. During blood infection, Nm activates genes encoding for the factor H binding proteins, fHbp and NspA, genes encoding for detoxifying enzymes such as SodC, Kat and AniA, as well as several less characterized surface-exposed proteins that might have a role inblood survival. Through mutagenesis studies of a subset of up-regulated genes wewere able to identify new proteins important for survival in human blood andalso to identify additional roles of previously known virulence factors inaiding survival in blood. Nm mutant strains lacking the genes encoding thehypothetical protein NMB1483 and the surface-exposed proteins NalP, Mip andNspA, the Fur regulator, the transferrin binding protein TbpB, and the L-lactatepermease LctP were sensitive to killing by human blood. This increased knowledgeof how Nm responds to adaptation in blood could also be helpful to developdiagnostic and therapeutic strategies to control the devastating disease causeby this microorganism.