CCL4 and infection: For example, the expression of CCL2, CCL4 and CCL7 was induced to higher levels in cells infected with the Mtb:Δ-sigH mutant (4.18, 6.23 and 4.3-fold respectively), relative to cells infected with Mtb (1.9, 3.5 and 2.9-fold respectively) or Mtb:Δ-sigH:CO (1.7, 3.3 and 3.7-fold respectively), at the 0 hr post-infection time-point (Figure 2A).