FIG. 5.
Adjuvant effects of a plasmid for soluble GITRL. (A) CTL assay and (B) IFN-γ ELISPOT assay. Compared to pScGag alone, pSP-D-GITRL significantly augmented CTL and cellular IFN-γ production (P < 0.01 for pScGag plus pSP-D-GITRL versus pScGag alone). However, pSP-D-CD40L was a more effective CD8+ T-cell stimulant than pSP-D-GITRL (P < 0.05 for pScGag plus pSP-D-CD40L versus pScGag plus pSP-D-GITRL). SFC, ELISPOT-forming cells. (C) Splenocyte proliferation assay. Spleen cells were incubated with Gag protein, and [3H]thymidine incorporation was measured. Results are expressed as the stimulation index. pScGag did not induce proliferation responses, nor were responses significantly augmented when pSP-D-CD40L was added to the immunization. This was a consistent result in 10 experiments. However, pSP-D-GITRL significantly augmented the proliferative response to antigen. (D) Anti-Gag antibody responses. Immunization with pScGag elicited modest levels of anti-Gag antibodies. The addition of pSP-D-CD40L did not significantly increase antibody titer and even appeared to suppress it in some experiments. In contrast, pSP-D-GITRL significantly augmented antibody production (P < 0.05). O.D., optical density.