Heaton Brook E, Barkan Daniel, Bongiorno Paola, Karakousis Petros C, Glickman Michael S
Immunology Program, Sloan Kettering Institute, New York, New York, USA.
Division of Infectious Diseases, Memorial Sloan Kettering Cancer Center, New York, New York, USA.
Infect Immun. 2014 Aug;82(8):3177-85. doi: 10.1128/IAI.01540-14. Epub 2014 May 19.
Mycobacterium tuberculosis persistence within its human host requires mechanisms to resist the effector molecules of host immunity, which exert their bactericidal effects through damaging pathogen proteins, membranes, and DNA. Substantial evidence indicates that bacterial pathogens, including M. tuberculosis, require DNA repair systems to repair the DNA damage inflicted by the host during infection, but the role of double-strand DNA break (DSB) repair systems is unclear. Double-strand DNA breaks are the most cytotoxic form of DNA damage and must be repaired for chromosome replication to proceed. M. tuberculosis elaborates three genetically distinct DSB repair systems: homologous recombination (HR), nonhomologous end joining (NHEJ), and single-strand annealing (SSA). NHEJ, which repairs DSBs in quiescent cells, may be particularly relevant to M. tuberculosis latency. However, very little information is available about the phenotype of DSB repair-deficient M. tuberculosis in animal models of infection. Here we tested M. tuberculosis strains lacking NHEJ (a Δku ΔligD strain), HR (a ΔrecA strain), or both (a ΔrecA Δku strain) in C57BL/6J mice, C3HeB/FeJ mice, guinea pigs, and a mouse hollow-fiber model of infection. We found no difference in bacterial load, histopathology, or host mortality between wild-type and DSB repair mutant strains in any model of infection. These results suggest that the animal models tested do not inflict DSBs on the mycobacterial chromosome, that other repair pathways can compensate for the loss of NHEJ and HR, or that DSB repair is not required for M. tuberculosis pathogenesis.
结核分枝杆菌在其人类宿主内存活需要具备抵抗宿主免疫效应分子的机制,这些效应分子通过破坏病原体的蛋白质、膜和DNA来发挥杀菌作用。大量证据表明,包括结核分枝杆菌在内的细菌病原体需要DNA修复系统来修复感染期间宿主造成的DNA损伤,但双链DNA断裂(DSB)修复系统的作用尚不清楚。双链DNA断裂是最具细胞毒性的DNA损伤形式,必须进行修复才能进行染色体复制。结核分枝杆菌拥有三种基因上不同的DSB修复系统:同源重组(HR)、非同源末端连接(NHEJ)和单链退火(SSA)。NHEJ可修复静止细胞中的DSB,可能与结核分枝杆菌的潜伏特别相关。然而,关于感染动物模型中DSB修复缺陷型结核分枝杆菌的表型,目前所知甚少。在这里,我们在C57BL/6J小鼠、C3HeB/FeJ小鼠、豚鼠以及小鼠中空纤维感染模型中测试了缺乏NHEJ的结核分枝杆菌菌株(Δku ΔligD菌株)、缺乏HR的菌株(ΔrecA菌株)或两者都缺乏的菌株(ΔrecA Δku菌株)。我们发现在任何感染模型中,野生型和DSB修复突变菌株之间在细菌载量、组织病理学或宿主死亡率方面均无差异。这些结果表明,所测试的动物模型不会对分枝杆菌染色体造成DSB,其他修复途径可以弥补NHEJ和HR的缺失,或者DSB修复对于结核分枝杆菌的发病机制并非必需。