**9. BU vaccines**

There is currently no specific vaccine for BU [92]. But Bacillus Calmette–Guérin (BCG) vaccine has been used to check for cross-protection in *M. ulcerans* infection in Mycobacterium ulcerans *Disease and Host Immune Responses DOI: http://dx.doi.org/10.5772/intechopen.103843*

Uganda [50]. BCG is a purified protein derivative (PPD) from *Mycobacterium bovis* [63]. It is the main vaccination regimen for TB and some non-tuberculous mycobacteria (NTM) [63, 64]. It stimulates a strong Th1 immune response. This include IFNγsecreting CD4+ T cell response in recipient [64]. It was observed that BCG offered a protective effect between 47 to 50% among those tested in Uganda [50, 93]. However, this protection was short-lived, the reason is unclear [50, 94]. The main protective agent in BCG vaccine is the peptide Ag85A [92]. It is a highly conserved motif and plays a critical role in cell wall synthesis [95, 96]. Ag85A homologue from *M. ulcerans* have also been screened for cross-protection in BU disease and have shown prospect [96]. *M. ulcerans* surface protein −18 kDa small heat shock protein (MUL\_2232) [97] and MUL\_3720 [98] have also been used in vaccine formulation against *M. ulcerans* [99]. In a murine experiment, a recombinant (r) vaccine formulation (rMUL2232 and rMUL3720) failed to protect against BU even though antibodies were present [99]. It appears that *M. ulcerans* specific antibodies fail to protect against developing overt disease [100]. Although mycolactone is the culprit in this debilitating disease [6], vaccine based on it has been thought off as a "goose chase". The reason being, mycolatone is a polyketide, a lipid-like derivative and not necessary immunogenic [92]. Animal experiment by Robert *et al* 1997 did not find mycolactone an ideal candidate for diagnosis or vaccine [58].
