Abstract
Haemophilus parasuis is a common opportunistic pathogen known for its ability to colonize healthy piglets and causes Glässer's disease. The lipooligosaccharide (LOS) of H. parasuis is a potential virulence-associated factor. In this study, two putative glycosyltransferases that might be involved in LOS synthesis in H. parasuis SC096 were identified (lgtB and lex-1). Mutants were constructed to investigate the roles of the lgtB and lex-1 genes. The LOS from the ΔlgtB or Δlex-1 mutant showed truncated structure on silver-stained SDS-PAGE gel compared to the wild-type strain. The ΔlgtB and Δlex-1 mutants were significantly more sensitive to 50% porcine serum, displaying 15.0 and 54.46% survival rates, respectively. Complementation of the lex-1 mutant restored the serum-resistant phenotype. Additionally, the ΔlgtB and Δlex-1 strains showed impaired ability to adhere to and invade porcine kidney epithelial cells (PK-15). The above results suggested that the lgtB and lex-1 genes of the H. parasuis SC096 strain participated in LOS synthesis and were involved in serum resistance, adhesion and invasion.
Highlights
Haemophilus parasuis is an important porcine pathogen and the etiological agent of Glässer’s disease, which is characterized by fibrinous polyserositis, polyarthritis, and meningitis
The backbone of the lipid A moiety is substituted at position 6′ with a 2,4-linked Kdo disaccharide, lgtB and lex-1 in H. parasuis which serves as an acceptor for the transfer of the first heptose residue to position 5 of the first Kdo residue; this transfer is accomplished by the heptosyltransferase family (Gronow et al, 2005)
The results suggested that lgtB and lex-1 may be associated with serum resistance
Summary
Haemophilus parasuis is an important porcine pathogen and the etiological agent of Glässer’s disease, which is characterized by fibrinous polyserositis, polyarthritis, and meningitis. It is a commensal organism found in the upper respiratory tract of swine that causes systemic symptoms in conditions with decreased resistance (Oliveira and Pijoan, 2004). In H. parasuis, deletion of the opsX, rfaF, and waaQ genes, which encode the three heptosyltransferases, produced severely truncated LOS structures, decreased resistance to complementmediated killing in serum and a decreased ability to adhere to and invade porcine kidney epithelial (PK-15) and porcine umbilical vein-derived endothelial cells (PUVECs) (Xu et al, 2013). Other glycosyltransferases associated with LOS biosynthesis and pathogenesis have yet to be investigated
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