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Buruli ulcer, caused by Mycobacterium ulcerans, is a neglected tropical disease endemic to over 30 countries, with increasing incidence in temperate, coastal Victoria, Australia. Strategies to control transmission are urgently required. This study systematically reviews the literature to identify and describe candidate prophylactic Buruli ulcer vaccines. This review highlights that Mycobacterium bovis Bacillus Calmette-Guérin (BCG) vaccine is the only vaccine studied in randomised controlled trials and confirms its importance as a benchmark for comparison against putative vaccines in pre-clinical studies. Nevertheless, BCG alone is unable to offer long-term protection in humans. A number of experimental vaccines that exceed the protection provided by BCG in mice have emerged, particularly those utilising recombinant BCG expressing immunogenic M. ulcerans proteins. Although progress is promising, there remain key questions about the optimal approach to characterising the immunological correlates of protection in humans and strategies to investigate the safety and efficacy of such vaccines in humans. [ABSTRACT FROM AUTHOR]

• Infant BCG immunisation induces M. ulcerans -specific immune responses. • M. ulcerans - and M. tuberculosis -specific immune responses are qualitatively similar. • Magnitude of M. ulcerans -specific immune responses was not influenced by BCG strain. • These in-vitro findings support the protective effect observed epidemiologically. Bacillus Calmette–Guérin (BCG) vaccine provides partial protection against Buruli ulcer caused by Mycobacterium ulcerans in epidemiological studies. This study aimed to quantify M. ulcerans -specific immune responses induced by BCG immunisation. Intracellular cytokine analysis of in-vitro experiments done 10 weeks after BCG immunisation in 130 Australian infants randomised to one of three BCG vaccine strains given either at birth (BCG-Denmark, BCG-Japan, or BCG-Russia) or at two months of age (BCG-Denmark). Proportions of polyfunctional CD4+ T-cells were higher in M. ulcerans -stimulated compared to unstimulated control samples. These proportions were not influenced by the vaccine strain or timing of the immunisation. The M. ulcerans -specific immune responses showed similar patterns to those observed in M. tuberculosis -stimulated samples, although they were of lower magnitude. Our data show that BCG immunisation induces M. ulcerans -specific immune responses in infants, likely explaining the cross-protective effect observed in epidemiological studies. (ACTRN12608000227392) [ABSTRACT FROM AUTHOR]

Mycobacterium ulcerans causes Buruli ulcer, a chronic and destructive necrotizing ulcer in humans. Effective vaccination should be one of the best methods for the prevention of this ulcer. However, no effective vaccines have been developed against M. ulcerans infection. In an effort to develop such a vaccine, we examined protective immunity against M. ulcerans infection in a mouse footpad-infection model. Prior infection of mice with a virulent strain of M. ulcerans or a mycolactone-deficient strain of M. ulcerans resulted in limited protection against subsequent challenge by a virulent strain of M. ulcerans . Protection was not induced in mice immunized with a formalin-treated killed whole-cell preparation of M. ulcerans . By contrast, a dewaxed whole-cell vaccine, prepared by dewaxing M. ulcerans with organic solvents that removed mycolactones and waxy cell walls from the cells, induced significant protection in mice. Our observations should facilitate development of effective vaccines against Buruli ulcer for control of this disease. [ABSTRACT FROM AUTHOR]