Nasal Double-DNA Adjuvant Enhances Mucosal Immunity to Porphyromonas gingivalis FimA

Objectives: We have previously shown that a combination of a plasmid encoding Flt3 Ligand cDNA (pFL) and CpG oligodeoxynucleotide (CpG ODN) as nasal adjuvant elicited prolonged mucosal immune responses and protective secretory-IgA antibody (SIgA) to pathogenic bacteria in aged as well as young mice. In this study, we investigated whether the double-DNA adjuvant for recombinant FimA (rFimA), a major subunit of Porphyromonas gingivalis fimbriae would enhance rFimA-specific mucosal immune responses in young mice.
Methods: BALB/c mice (8-weeks-old) were nasally immunized with 10 µg of rFimA as an antigen plus 50 µg of pFL and 10 µg of CpG ODN as a combined mucosal adjuvant three times at weekly intervals. As controls, mice were nasally given rFimA alone. Saliva, nasal washes (NWs), bronchoalveolar lavage fluid (BALF) and plasma samples were collected one week after the last immunization and Ag-specific Ab responses were determined by ELISA assays. Further, we examined frequencies of CD11c⁺ dendritic cells (DCs) in submandibular glands (SMGs), nasopharyngeal associated lymphoreticular tissues (NALT), nasal passages (NPs), mediastinal lymph nodes (MeLNs).
Results: In saliva, NWs and BALF of mice given nasally rFimA and the double-DNA adjuvant, rFimA-specific SIgA Ab responses were markedly higher than those of mice given nasal Ag alone. Interestingly, increased levels of rFimA-specific IgG and IgA Ab responses were also seen in plasma of mice nasally immunized with rFimA plus the double-DNA adjuvant. In addition, elevated numbers of CD11c⁺ DCs were observed in SMGs, NALT, NPs and MeLNs as compared with those of control mice.
Conclusions: These results show that nasal delivery of the double-DNA adjuvant enhances systemic as well as mucosal immune responses, and the elevated DCs might contribute to induction of immune responses to rFimA antigen. Supported by a Grants-in-Aid (B 17H04424, C17K12034) from Ministry of Education, Science, Sports and Culture of Japan. kataoka-k@cc. osaka-dent. ac.jp.