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Introduction: The role of damage-associated molecular pattern HMGB1 signalling in a murine BALB/c model of severe respiratory melioidosis (Burkholderia pseudomallei infection) was explored in this study. Methods: Time course experiments were performed. Results: It was established that HMGB1 was released in concert with increasing weight of organs and increasing concentration of liver enzymes in the blood a short time after cytokine release. Differences in the cytokine response between organs were observed, where the lungs contained higher concentrations of chemokines and interleukin 17, while the spleen produced more interferon-gamma, which is essential in the host defence against B. pseudomallei. This is evidence as to why the disease is seemingly more severe in the respiratory form. The effect of depleting HMGB1 using an antibody was also evaluated. It was found that this treatment significantly reduced bacterial load in the liver, spleen, and, to a greater degree, in the lungs. Cytokine quantification indicated that this reduction in bacterial load is likely due to the treatment reducing the release of a variety of pro-inflammatory cytokines. Conclusion: It is concluded that anti-HMGB1 treatment would be effective alongside other therapeutics, where it would reduce the characteristic over-inflammation associated with late stage infection.

Melioidosis is a severe infectious disease caused by Burkholderia pseudomallei. It is refractory to antibiotic treatment and there is currently no licensed vaccine. In this report we detail the construction and protective efficacy of a polysaccharide-protein conjugate composed of B. pseudomallei lipopolysaccharide and the Hc fragment of tetanus toxin. Immunisation of mice with the lipopolysaccharide-conjugate led to significantly reduced bacterial burdens in the spleen 48 hours after challenge and afforded significant protection against a lethal challenge with B. pseudomallei. The conjugate generated significantly higher levels of antigen-specific IgG1 and IgG2a than in lipopolysaccharide-immunised mice. Immunisation with the conjugate also demonstrated a bias towards Th1 type responses, evidenced by high levels of IgG2a. In contrast, immunisation with unconjugated lipopolysaccharide evoked almost no IgG2a demonstrating a bias towards Th2 type responses. This study demonstrates the effectiveness of this approach in the development of an efficacious and protective vaccine against melioidosis.

Glycoconjugate-based vaccines have proved to be effective at producing long-lasting protection against numerous pathogens. Here, we describe the application of bacterial protein glycan coupling technology (PGCT) to generate a novel recombinant glycoconjugate vaccine. We demonstrate the conjugation of the Francisella tularensis O-antigen to the Pseudomonas aeruginosa carrier protein exotoxin A using the Campylobacter jejuni PglB oligosaccharyltransferase. The resultant recombinant F. tularensis glycoconjugate vaccine is expressed in Escherichia coli where yields of 3 mg l−1 of culture were routinely produced in a single-step purification process. Vaccination of BALB/c mice with the purified glycoconjugate boosted IgG levels and significantly increased the time to death upon subsequent challenge with F. tularensis subsp. holarctica. PGCT allows different polysaccharide and protein combinations to be produced recombinantly and could be easily applicable for the production of diverse glycoconjugate vaccines.