Important Role for Mycobacterium tuberculosis UvrD1 in Pathogenesis and Persistence apart from Its Function in Nucleotide Excision Repair

Mycobacterium tuberculosis survives and replicates in macrophages, where it is exposed to reactive oxygen and nitrogen species that damage DNA. In this study, we investigated the roles of UvrA and UvrD1, thought to be parts of the nucleotide excision re-pair pathway ofM. tuberculosis. Strains in which uvrD1was inactivated either alone or in conjunction with uvrAwere con-structed. Inactivation of uvrD1 resulted in a small colony phenotype, although growth in liquid culture was not significantly af-fected. The sensitivity of the mutant strains to UV irradiation and to mitomycin C highlighted the importance of the targeted genes for nucleotide excision repair. The mutant strains all exhibited heightened susceptibility to representatives of reactive oxy-gen intermediates (ROI) and reactive nitrogen intermediates (RNI). The uvrD1 and the uvrA uvrD1mutants showed decreased intracellular multiplication following infection of macrophages. Most importantly, the uvrA uvrD1mutant was markedly atten-uated following infection of mice by either the aerosol or the intravenous route. Tuberculosis remains a major world health problem, causing1.75 million deaths annually (54). Furthermore, it has been estimated that one-third of the world’s population is latently in-fected with Mycobacterium tuberculosis (16). Approximately 10% of those latently infected will develop active disease, but this risk is significantly increased by factors weakening the immune re-sponse, such as HIV infection (52). If latent infection in individ