High antibody titres induced by protein subunit vaccines against Buruli ulcer usingMycobacterium ulceransantigens Hsp18 and MUL_3720
Abstract
Background
Mycobacterium ulceransis the causative agent of a debilitating skin and soft tissue infection known as Buruli ulcer (BU). There is no vaccine against BU. The purpose of this study was to investigate the vaccine potential of two previously described immunogenicM. ulceransproteins, MUL_3720 and Hsp18, using a mouse tail infection model of BU.
Methods
Recombinant versions of the two proteins were each electrostatically coupled with a previously described lipopeptide adjuvant. Seven C57BL/6 and seven BALB/c mice were vaccinated and boosted with each of the formulations. Vaccinated mice were then challenged withM. ulceransvia subcutaneous tail inoculation. Vaccine performance was assessed by time-to-ulceration compared to unvaccinated mice.
Results
The MUL_3720 and Hsp18 vaccines induced high titres of antigen-specific antibodies that were predominately subtype IgG1. However, all mice developed ulcers by day-40 post-M. ulceranschallenge. No significant difference was observed in the time-to-onset of ulceration between the experimental vaccine groups and unvaccinated animals.
Conclusions
These data align with previous vaccine experiments using Hsp18 and MUL_3720 that indicated these proteins may not be appropriate vaccine antigens. This work highlights the need to explore alternative vaccine targets and different approaches to understand the role antibodies might play in controlling BU.
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