Aim: We examined whether HLA-DRB1*1501 and four VDR SNPs influence the macrophage response to infection with Mycobacterium tuberculosis (Mtb) via innate immune versus drug treatment or drug delivery mechanisms.
Materials & methods: Monocyte-derived macrophages from 24 healthy donors were infected with Mtb in vitro. Survival of intracellular bacilli and secretion of cytokines and nitric oxide by the infected cells were monitored with and without exposure to isoniazid and rifabutin.
Results: Haplotype analysis was conducted, and an arbitrary score of genetic 'susceptibility' (S ) score ranging from -3 to +3 was assigned to donors based on the presence or absence of genetic markers. S scores correlated more strongly with Mtb survival (r = 0.68) than TNF and nitric oxide (NO; r = ∼0.01-0.11). A specific haplotype was significantly associated with decreased Mtb survival (p < 0.05), increased NO and decreased IL-10/IL-4. Macrophages with S scores ≥ 2 secreted significantly (p < 0.05) more IL-10 and IL-4, and less NO upon infection, and supported Mtb survival. Microparticulate drugs showed higher bactericidal activity than free drugs, irrespective of S score.
Conclusion: S score predicts colonization of macrophages by Mtb, as does haplotype analysis. Drug-containing microparticles are superior to free drugs across diverse genetic backgrounds.