Enhancement of salivary IgA response to a DNA vaccine against Streptococcus mutans wall-associated protein A in mice by plasmid-based adjuvants.

A specific salivary IgA (sIgA) response was obtained in mice by intranasal immunization with a naked DNA vaccine consisting of the Streptococcus mutans wall-associated protein A gene (wapA) inserted into the mammalian expression vector pcDNA3.1/V5/His-TOPO. In the present study, the vaccine, referred to as pcDNA-wapA, was administered with or without the cationic lipid DMRIE-C. No mucosal response was observed in mice immunized with the vaccine alone, whereas a weak and temporal sIgA response was obtained when the vaccine was mixed with DMRIE-C. To investigate the use of pcDNA containing the interleukin 5 (IL-5) gene (pcDNA-il-5) or the cholera toxin B gene (pcDNA-ctb) as genetic adjuvants, these constructs were used in co-immunization studies. The enhancement effect was transient with pcDNA-il-5, but longer lasting with pcDNA-ctb, thus supporting the use of the latter as a genetic adjuvant to DNA vaccine.