To address the possibility that the protective differences exerted by ESAT-6 and TB10.4 were a result of a different level of gene expression at different stages of the infection, we compared the expression of esxA, esxH, acr (alpha-crystallin) and fhpB (Ag85B) at week 3 and week 20 p.i. (Figure 5B). The gene discussed is ACR; the disease is infection.