FIG. 3.

Vaccination of CD4^−/− mice with either BCG or the TB DNA cocktail resulted in a substantial improvement in lung histopathology and highly reduced numbers of acid-fast bacilli compared to naïve CD4^−/− controls. Lung sections were fixed and stained with either hematoxylin and eosin (a, b, and c) or Ziehl-Neelsen reagent (d, e, and f) 28 days postchallenge. (a) Numerous necrotic, suppurative lesions containing many neutrophils and overall severe and acute coalescing inflammation with little functional tissue were seen in nonvaccinated CD4^−/− mice. (d) An overwhelming number of acid-fast bacilli were also detected in the naïve controls. In contrast, lung sections from TB DNA cocktail (b and e)- and BCG (c and f)-vaccinated mice exhibited subacute lymphocytic granulomatous bronchopneumonia with no necrosis, and substantial amounts of intact functional tissue with few acid-fast bacilli were observed.