Ag85B with c-di-AMP as mucosal adjuvant showed immunotherapeutic effects on persistent Mycobacterium tuberculosis infection in mice

Tuberculosis (TB), caused by Mycobacterium tuberculosis, remains the leading cause of mortality by a single infectious agent in the world. M. tuberculosis infection could also result in clinical chronic infection, known as latent TB infection (LTBI). Compared to the current limited treatment, several subunit vaccines showed immunotherapeutic effects and were included in clinical trials. In this study, a subunit vaccine of Ag85B with a novel mucosal adjuvant c-di-AMP (Ag85B:c-di-AMP) was delivered intranasally to a persistent M. tuberculosis H37Ra infection mouse model, which also presented the asymptomatic characteristics of LTBI. Compared with Ag85B immunization, Ag85B:c-di-AMP vaccination induced stronger humoral immune responses, significantly higher CD4+ T cells recruitment, enhanced Th1/Th2/Th17 profile response in the lung, decreased pathological lesions of the lung, and reduced M. tuberculosis load in mice. Taken together, Ag85B:c-di-AMP mucosal route immunization provided an immunotherapeutic effect on persistent M. tuberculosis H37Ra infection, and c-di-AMP, as a promising potential mucosal adjuvant, could be further used in therapeutic or prophylactic vaccine strategies for persistent M. tuberculosis infection as well as LTBI.

Leptospiral c-di-AMP-binding protein regulates potassium ion transport / 中华微生物学和免疫学杂志

Objective:To investigate whether KtrA was a binding protein of c-di-AMP, the second messenger in Leptospira, and to explore the function and regulatory mechanism of the c-di-AMP-KtrA/B system. Methods:KtrA gene was amplified by PCR and cloned into pET42a plasmid to construct the pET42a ktrA prokaryotic expression vector. Then the vector was transferred into E. coli BL21DE3 to construct an engineering bacterium E. coli BL21DE3 pET42a-ktrA for the expression of recombinant KtrA (rKtrA). The expressed rKtrA was purified by affinity chromatography. BIAcore technology was used to detect the binding ability of rKtrA to c-di-AMP. Bacterial two-hybrid analysis was used to analyze the interaction between KtrA and KtrB in the leptospiral Ktr system with or without exogenetic c-di-AMP. The above genes were then complemented into the potassium transport-deficient E. coli mutants to analyze the function of the c-di-AMP-KtrA/B pathway. Results:An prokaryotic engineering bacterium for the expression of ktrA gene of Leptospira was constructed successfully. The purified rKtrA could specifically bind to c-di-AMP. There was interaction between KtrA and KtrB, but the interaction could be dissociated by c-di-AMP. The KtrA/B system was involved in potassium ion uptake and it was negatively regulated by c-di-AMP. Conclusions:Leptospiral KtrA was a c-di-AMP-binding protein and the c-di-AMP-KtrA/B system was involved in potassium ion transport.

CdaR-DAC signaling systems regulating the synthesis of a second messenger c-di-AMP in Leptospira interrogans / 中华微生物学和免疫学杂志

Objective To analyze the activity of diadenylate cyclase ( DAC) encoded by LA3304 gene of Leptospira interrogans ( L. interrogans) and to investigate the influence of CdaR encoded by LA3303 gene on DAC activity. Methods The LA3304 gene in L. interrogans serogroup Icterohaemorrhagiae serovar Lai strain Lai was amplified by PCR and inserted into a prokaryotic expression system for expressing DAC. The expressed recombinant protein, rDAC, was purified by Ni-NTA affinity chromatography. High Perform-ance Liquid Chromatography ( HPLC) was used to measure the synthesis of c-di-AMP from ATP by rDAC in vitro. Bacterial two-hybrid analysis was used to detect the interaction between CdaR and DAC. Prokaryotic co-expression system was constructed and used in combination with HPLC to analyze the role of CdaR in acti-vating DAC. Results The constructed prokaryotic expression system for LA3304 gene of L. interrogans strain Lai could highly express the rDAC upon the induction of IPTG. The purified rDAC showed high purity with a single protein band in gel as indicated by SDS-PAGE. rDAC could synthesize c-di-AMP from ATP in vitro. CdaR interacted with DAC and enhanced the activity of DAC (P<0. 05). Conclusion DAC encoded by LA3304 gene was a diadenylate cyclase that could convert ATP into c-di-AMP. CdaR promoted the acti-vation of DAC and formed a CdaR-DAC system with DAC. The system was involved in the synthesis of c-di-AMP in L. interrogans.

c-di-AMP regulates bacterial biofilm formation / 生物工程学报

Bacterial biofilm plays an important role in persistent microbial infection. Delineation of the formation and development of bacterial biofilm would provide a promising strategy to treat recalcitrant infection. c-di-AMP (Cyclic diadenosine monophosphate) is a recently identified second messenger of bacteria and involved in plethora of bacterial activities, including cell growth, cell wall homeostasis, biofilm formation and microbial pathogenicity. Here we review the recent literature pertinent to the role and molecular mechanisms of c-di-AMP in regulating biofilm formation of bacteria. The potential application of c-di-AMP and its related proteins in the development of novel antimicrobial therapeutics has also been discussed.