Host-directed adjunctive therapy with pravastatin against chronic TB in mice

Mycobacterium tuberculosis (Mtb) is known to subvert immune responses to establish infection and cause disease. Thus, host-directed therapy (HDT), as adjunctive treatment to traditional antitubercular regimens, is an attractive strategy. Statins are a class of drugs used to lower cholesterol levels by inhibiting the 3-hydroxy-3-methylglutaryl coenzyme A reductase, a crucial enzyme in the cholesterol biosynthesis pathway. Here, we conducted a preclinical animal study aimed at comparing the bactericidal activities of the standard TB regimen (rifampin, isoniazid, pyrazinamide and ethambutol; RHZE) with or without escalating doses of pravastatin against chronic TB in BALB/c mice. Antibiotics were given five times weekly for 8 weeks (continuous phase) beginning 6 weeks after infection. Treatment with RHZE plus pravastatin at doses ranging from 30 mg/kg to 180 mg/kg demonstrated a dose-dependent increase in bactericidal activity, reducing lung bacillary counts by 0.2–0.6 log10, 0.3–0.6 log10 and 0.3–0.8 log10 compared to RHZE alone at weeks 2, 4 and 8, respectively. After 8 weeks of treatment, the degree of lung inflammation correlated with the bactericidal activity of each drug regimen. In order to gain insight into the anti-TB mechanism of action of pravastatin in vivo, the lungs of mice treated with pravastatin adjunctive therapy and those treated with RHZE alone were analyzed by whole-genome microarrays and RT-PCR. Mouse sera were studied by multiplex enzyme-linked immunosorbent assays. Treatment with pravastatin for 1 month had a profound effect on the global transcription in mouse lungs. Mtb-infected BALB/c mice were treated with the standard TB regimen (RHZE= rifampicin 10 mg/kg+ isoniazid 10 mg/kg + pyrazinamide 150 mg/kg+ ethambutol 100 mg/kg) with or without increasing doses of pravastatin (30, 90, 180 mg/kg). Treatment was given orally five times weekly for 4 weeks (continuous phase) beginning 6 weeks after infection