PDE6B and tuberculosis: The RD1 locus has been the recent subject of attention following its discovery as a major factor in the attenuation of BCG (Pym et al. 2002; Lewis et al. 2003) and the potential of an M. tuberculosis RD1-defective strain as a candidate vaccine for tuberculosis (Hsu et al. 2003; Pym et al. 2003).