Characterization of genomic DNA of lactic acid bacteria for activation of plasmacytoid dendritic cells .

Lactococcus lactis strain Plasma (LC-Plasma) possesses strong activity of stimulating plasmacytoid dendritic cells (pDCs) via the TLR9-Myd88 pathway. To reveal the effective genome structure for pDCs stimulatory activity, we performed an in vitro screening, using randomly selected DNA fragments from the LC-Plasma genome. The results showed that CpG motifs are necessary factor for active DNA fragment, but the copy number of CpG motifs did not show strong correlation to the pDCs stimulatory activity of DNA fragment. We also found that the G+C contents of DNA fragments have significant negative effects on pDCs stimulatory activity. We also performed bioinformatics analysis of genome of lactic acid bacteria (LAB) and investigated the relation between CpG copy number in the genome and pDCs stimulatory activity. We found that strains of lactic acid bacteria (LAB) with high copy number of CpG motifs in the low-G+C region of the genome had higher probability of having high pDCs stimulatory activity. Three species, L.lactis subsp. lactis, Leuconostoc mesenteroides, and Pediococcus pentosaceus were the typical examples of high pDCs stimulatory activity LAB.\n\nImportanceThis study provides a new perspective on the structure of DNA fragments that are able to activate pDCs via the TLR9-Myd88 pathway. The information from this study should be useful for designing new DNA fragments, including phosphodiesterbond-DNA oligomers containing CpG motifs and DNA-containing vaccines. This work also presented an in silico screening method for identifying bacterial species that are able to activate pDCs. Therefore, this study should be useful for providing data for the development of vaccine adjuvants and therapeutics for infectious and allergic diseases.