To solve problems, attentions are focused on the genomic DNA of Lactobacillus gasseri OLL2716 (LG21) strain which has an effect of inhibiting the proliferation of Helicobacter pylori. Then, homology analysis is made on a characteristic core sequence (5'-ATTTTTAC-3': SEQ ID NO:29) consisting of eight bases and having an effect of enhancing immune response, which is contained in a novel nonCpG sequence (AT5AC-L), in the LG21 genomic DNA sequence and consequently 385 sequences containing the AT core sequence are found out from the genomic DNA. As a primary screening, the immunological activities of the above-described AT oligonucleotides having been chemically synthesized are analyzed by using a lymphocyte blastogenic activity test as an indication. In the test, use is made of swine intestinal Peyer's patch cells, swine spleen cells and human peripheral blood monocytes as target cells. As a secondary screening, NF-?B transcriptional activity test is conducted by using a swine cell line with forced expression of Toll-like receptor 9 (TLR9) (a transfectant). As a result, ten novel oligonucleotides having potent TLR9-mediated activities are finally found out.
