Induction of a CD8⁺ cytotoxic T lymphocyte response to soluble antigen given together with a novel muramyl dipeptide adjuvant, N-acetyl-D-glucosaminyl-(β1-4)-N-acetylmuramyl-L-alanyl-Disoglutamine (GMDP)

We have investigated the ability of the novel muramyl dipeptide, GMDP, to act as an adjuvant for the induction of ovalbumin (OVA)-specific, CD8⁺ cytotoxic T lymphocyte (CTL) responses. C57Bl/6 mice were twice immunized s.c. with 50 μg OVA emulsified with a squalane, L121 pluronic containing Tween-80 vehicle either with (STP-GMDP) or without (STP) GMDP. Splenic precursor CD8⁺ CTL activity against E.G7-OVA, but not against EL-4 parental targets was detected in STP-GMDP immunized mice after 5 days of in vitro re-stimulation with irradiated E.G7-OVA cells, while mice immunized with OVA in STP alone or OVA alone failed to demonstrate CTL activity. OVA emulsified in a microfluidized STP vehicle formulation without GMDP also elicited the E.G7-OVA precursor CTL. The ability of GMDP to induce a class I-restricted, CD8⁺ CTL response to a soluble protein antigen may have implications for the development of useful vaccines against viral pathogens or tumours against which CTL responses are desirable.