Hart Bryan E, Hale Laura P, Lee Sunhee
Human Vaccine Institute and Department of Medicine, Duke University Medical Center, Durham, North Carolina, United States of America.
Human Vaccine Institute and Department of Medicine, Duke University Medical Center, Durham, North Carolina, United States of America; Department of Pathology, Duke University, Durham, North Carolina, United States of America.
PLoS Negl Trop Dis. 2015 Sep 22;9(9):e0004046. doi: 10.1371/journal.pntd.0004046. eCollection 2015 Sep.
Buruli ulcer, an emerging tropical disease caused by Mycobacterium ulcerans (MU), is characterized by disfiguring skin necrosis and high morbidity. Relatively little is understood about the mode of transmission, pathogenesis, or host immune responses to MU infection. Due to significant reduction in quality of life for patients with extensive tissue scarring, and that a disproportionately high percentage of those affected are disadvantaged children, a Buruli ulcer vaccine would be greatly beneficial to the worldwide community. Previous studies have shown that mice inoculated with either M. bovis bacille Calmette-Guérin (BCG) or a DNA vaccine encoding the M. ulcerans mycolyl transferase, Ag85A (MU-Ag85A), are transiently protected against pathology caused by intradermal challenge with MU. Building upon this principle, we have generated quality-controlled, live-recombinant strains of BCG and M. smegmatis which express the immunodominant MU Ag85A. Priming with rBCG MU-Ag85A followed by an M. smegmatis MU-Ag85A boost strongly induced murine antigen-specific CD4+ T cells and elicited functional IFNγ-producing splenocytes which recognized MU-Ag85A peptide and whole M. ulcerans better than a BCG prime-boost vaccination. Strikingly, mice vaccinated with a single subcutaneous dose of BCG MU-Ag85A or prime-boost displayed significantly enhanced survival, reduced tissue pathology, and lower bacterial load compared to mice vaccinated with BCG. Importantly, this level of superior protection against experimental Buruli ulcer compared to BCG has not previously been achieved. These results suggest that use of BCG as a recombinant vehicle expressing MU antigens represents an effective Buruli ulcer vaccine strategy and warrants further antigen discovery to improve vaccine efficacy.
布氏杆菌溃疡是由溃疡分枝杆菌(MU)引起的一种新出现的热带疾病,其特征为毁容性皮肤坏死和高发病率。关于MU感染的传播方式、发病机制或宿主免疫反应,人们了解相对较少。由于广泛组织瘢痕化患者的生活质量显著下降,且受影响人群中处于不利地位的儿童比例过高,布氏杆菌溃疡疫苗将对全球社会大有裨益。先前的研究表明,接种卡介苗(BCG)或编码溃疡分枝杆菌分枝菌酸转移酶Ag85A(MU-Ag85A)的DNA疫苗的小鼠,可短暂抵御由皮内注射MU引起的病理变化。基于这一原理,我们构建了表达免疫显性MU Ag85A的质量可控的卡介苗和耻垢分枝杆菌的活重组菌株。用重组卡介苗MU-Ag85A进行初免,随后用耻垢分枝杆菌MU-Ag85A进行加强免疫,强烈诱导了小鼠抗原特异性CD4+T细胞,并引发了产生功能性IFNγ的脾细胞,这些脾细胞比卡介苗初免-加强免疫接种更好地识别MU-Ag85A肽和完整的溃疡分枝杆菌。令人惊讶的是,与接种卡介苗的小鼠相比,单次皮下注射卡介苗MU-Ag85A或初免-加强免疫的小鼠存活率显著提高,组织病理学改变减轻,细菌载量降低。重要的是,此前尚未达到这种比卡介苗对实验性布氏杆菌溃疡更优的保护水平。这些结果表明,将卡介苗用作表达MU抗原的重组载体代表了一种有效的布氏杆菌溃疡疫苗策略,值得进一步探索抗原以提高疫苗效力。