Contribution of Hfq to gene regulation and virulence in Histophilus somni

• Published in: Infection and immunity 2024-03, Vol.92 (3), p.e0003824
• Main Authors: Cao, Dianjun, Subhadra, Bindu, Lee, Yue-Jia, Thoresen, Merrilee, Cornejo, Santiago, Olivier, Alicia, Woolums, Amelia, Inzana, Thomas J
• Format: Article
• Language: English
• Subjects: Animals; Bacteriology; Cattle; Haemophilus somnus - genetics; Mice; Molecular Pathogenesis; Monocytes; Pasteurellaceae - genetics; Proteins - metabolism; Virulence - genetics; Virulence Factors - genetics; Virulence Factors - metabolism
• ISSN: 0019-9567; 1098-5522; 1098-5522
• DOI: 10.1128/iai.00038-24

is one of the predominant bacterial pathogens responsible for bovine respiratory and systemic diseases in cattle. Despite the identification of numerous virulence factors, little is known about the regulation of such factors. The post-transcriptional regulatory protein Hfq may play a crucial role in regulation of components that affect bacterial virulence. The contribution of Hfq to phenotype and virulence was investigated following creation of an deletion mutant of strain 2336 (designated 2336Δ ). A comparative analysis of the mutant to the wild-type strain was carried out by examining protein and carbohydrate phenotype, RNA sequence, intracellular survival in bovine monocytes, serum susceptibility, and virulence studies in mouse and calf models. 2336Δ exhibited a truncated lipooligosaccharide (LOS) structure, with loss of sialylation. The mutant demonstrated increased susceptibility to intracellular and serum-mediated killing compared to the wild-type strain. Transcriptomic analysis displayed significant differential expression of 832 upregulated genes and 809 downregulated genes in 2336Δ compared to strain 2336, including significant downregulation of and , which contribute to LOS oligosaccharide synthesis and sialylation. A substantial number of differentially expressed genes were associated with polysaccharide synthesis and other proteins that could influence virulence. The 2336Δ mutant strain was attenuated in a mouse septicemia model and somewhat attenuated in a calf intrabronchial challenge model. was recovered less frequently from nasopharyngeal swabs, endotracheal aspirates, and lung tissues of calves challenged with 2336Δ compared to the wild-type strain, and the percentage of abnormal lung tissue in calves challenged with 2336Δ was lower than in calves challenged with the wild-type strain. In conclusion, our results support that Hfq accounts for the regulation of virulence factors.