Coxiella burnetii lipopolysaccharide (C. burnetii LPS)

Coxiella burnetii lipopolysaccharide (LPS) is the primary virulence factor of the Gram-negative intracellular bacterium responsible for Q fever. It is unique among bacterial endotoxins due to its extreme structural diversity, existing in two distinct forms: the full-length Phase I LPS found in virulent natural isolates and the truncated Phase II LPS found in laboratory-passaged, avirulent strains. The Phase I LPS contains rare sugars such as virenose and dihydrohydroxystreptose, which are essential for masking the bacteria from host immune recognition by acting as a TLR4 antagonist and preventing phagosome-lysosome fusion. In clinical practice, this molecule is the cornerstone of Q fever diagnostics, as the ratio of antibodies against Phase I and Phase II LPS helps distinguish between acute and chronic infections. Furthermore, it is the critical antigenic component of the Q-Vax vaccine, though its high immunogenicity necessitates pre-vaccination screening to avoid severe hypersensitivity reactions in individuals with prior exposure.

Other names

Coxiella burnetii Phase I lipopolysaccharideCoxiella burnetii Phase II lipopolysaccharideQ fever antigenC. burnetii endotoxin

Coxiella burnetii lipopolysaccharide serves as a primary target for vaccine-induced neutralizing antibodies and diagnostic assays. In the context of infection, the Phase I LPS acts as a physical shield and a Toll-like receptor 4 (TLR4) antagonist, preventing the host immune system from detecting and eliminating the bacteria. Therapeutic strategies focus on using the LPS as an antigen in vaccines to prime the immune system or developing antibodies that can bypass the protective LPS layer to facilitate bacterial clearance.