[Advances in Research on the Role of Bacterial c-di-AMP in Host Immunity].

Cyclic dimeric adenosine 3',5'-monophosphate (c-di-AMP) is a newly-discovered second messenger in bacteria and archaea. By directly binding to or affecting the expression of target proteins, c-di-AMP regulates the physiological functions of bacteria, including maintaining osmotic pressure, balancing central metabolism, monitoring DNA damage, and controlling biofilm and spore formation. As a new pathogen-associated molecular pattern (PAMP), it binds to the host pattern recognition receptor (PRR), induces cyclic GMP-AMP synthase (cGAS)-STING signal axis to produce type Ⅰ interferon by activating the stimulator of interferon genes (STING), and promotes the secretion of inflammatory factors through nuclear factor κB (NF-κB) signaling pathway, thereby playing an important role in host immunity to bacterial infection and tumorigenesis. Due to its immunogenicity, c-di-AMP could be used as an immune adjuvant to provide new targets for the development of vaccines. However, the specific mechanism of action of c-di-AMP in host immunity awaits further exploration. Herein, we presented the structure and biological characteristics of c-di-AMP, and summarized the possible mechanism of c-di-AMP's regulation of host immune response. In addition, we also reported the latest findings on using c-di-AMP as an immune adjuvant in clinical treatment. Research on the function of c-di-AMP and its mechanism of action on host immune response provides new ideas for finding clinical solutions to bacterial resistance, infection control, tumor prevention, and vaccine development in the future.

Norovirus outbreaks in Fengtai District, Beijing, China, 2014.

Norovirus (NoV) is the most common cause of non-bacterial acute gastroenteritis (AGE) outbreaks worldwide. Eight NoV outbreaks in the Fengtai District of Beijing City, China, were identified in 2014. Samples were collected from the eight outbreaks, and 73 out of 119 samples from cases and 10 out of 59 samples from the close contacts were positive for NoVs. The genotypes were determined by sequencing analysis. Six different GII genotypes, including GII.2, 4, 6, 7, 8, 14, and 17 were found, and GII.4 was not the local major epidemic genotype in the present study. Enhanced strain surveillance is necessary for future NoV epidemics.