Nasal double DNA adjuvant induces salivary FimA-specific secretory IgA antibodies in young and aging mice and blocks Porphyromonas gingivalis binding to a salivary protein

We previously showed that nasal administration of a combination of dendritic cell (DC) targeted DNA plasmid expressing Flt3 ligand and CpG oligodeoxynucleotides 1826 as a mucosal adjuvant (double adjuvant, DA) provoked protective immunity in the upper respiratory tract of young adult and aging mice. Here, we investigated whether the nasal DA system induces secretory (S)IgA antibodies (Abs) toward recombinant fimbrillin (rFimA) of Porphyromonas gingivalis (P. gingivalis) in the saliva of young adult and aging mice. Further, we examined the functional applicability of rFimA-specific salivary SIgA Abs. BALB/c mice (8- or 48-week-old) were nasally immunized with rFimA plus DA three times at weekly intervals. Control mice were nasally administered rFimA alone. Saliva samples were collected 1 week after the final immunization, and were subjected to rFimA-specific ELISA. To examine the functional applicability of rFimA-specific SIgA Abs, IgA-enriched saliva samples were subjected to an inhibition assay in order to assess the numbers of P. gingivalis cells bound to the salivary protein statherin. The 8- and 48-week-old mice administered nasal rFimA plus DA showed significantly increased levels of rFimA-specific SIgA Abs in saliva and elevated numbers of CD11c DCs in sublingual glands (SLGs), periglandular lymph nodes (PGLNs) and submandibular glands (SMGs) as well as nasopharyngeal-associated lymphoid tissues (NALT) compared to mice administered rFimA alone. Further, rFimA-specific SIgA Abs-containing saliva, in which IgG Abs of 8- and 48-week-old mice administered nasal rFimA plus DA were removed, significantly inhibited binding of P. gingivalis to the salivary protein. These findings show that this DA system could be an effective nasal vaccine strategy for the enhancement of P. gingivalis-specific protective immunity in the oral cavity of adolescents and older individuals.