Case Study:
New adjuvant drives unprecedented cytotoxic T cell response providing a potent vaccine development platform

Wells, J. (pictured left) et al. (2008). Combined Triggering of Dendritic Cell Receptors Results in Synergistic Activation and Potent Cytotoxic Immunity. J. Immunology. 181(5): 3422-3431.
[PubMedID: 18714014]

Wells et al. investigated novel combinations of vaccine adjuvants and using Pro5® MHC Class I Pentamers, showed that optimal antigen-specific responses can be achieved using well-tolerated compounds that result in dendritic cell activation through the activation of toll-like receptors.

Initially using the ovalbumin H-2Kb/SIINFEKL epitope as a model, Pentamer staining indicated that a vaccine adjuvant referred to as a ‘combined adjuvant for synergistic activation of cellular immunity’ (CASAC) provided the greatest antigen-specific response as indicated by H-2Kb/SIINFEKL Pentamer+/CD8+ T cell staining. The vaccination also induced a strong memory response upon re-injection of SIINFEKL peptide as measured by Pentamer staining. The CASAC adjuvant contained several key components including two toll-like receptor agonists (e.g. CpG DNA+monophosphoryl lipid A), IFN-gamma and CD40 antibody or a class II MHC peptide to induce IL-12 production from dendritic cells. This was combined with SIINFEKL peptide in an emulsion.

The efficacy of the CASAC adjuvant was further tested on a mouse melanoma model using the TRP-2 tumour epitope (H-2Kb/SVYDFFVWL), which is known to bind with a low affinity to the H-2Kb allele. Mice were injected with B16 melanoma cells and then immunized with TRP-2 peptide suspended in either CASAC or the most potent adjuvant combination previously described (anti-CD40 and a single TLR agonist). Pentamer-binding CD8+ cells were only detected in mice that had received the CASAC adjuvant. Protection from tumours was maintained after further challenge with B16 melanoma cells.

Flow cytometry data showing staining of TRP-2 specific CD8 T cells CASC induces potent tumor protection in a melanoma treatment model mediated partly but not entirely by tumor-Ag specific T cells. The figure shows staining of TRP-2 specific CD8 T cells in blood of mice using TRP-2(180-188) H-2Kb Pentamer. SIINFEKL Pentamer was used for the negative control stain. Mean percentage + SEM from 6-8 mice is shown. 

Copyright 2008 The American Association of Immunologists Inc.

**p<0.005 as determined by unpaired Student’s t tests on the mean values.

The use of Pro5® MHC Pentamers to measure antigen-specific T cell responses accurately enabled the investigators to demonstrate that a combinatorial adjuvant approach may provide more effective protection than current anti-cancer vaccine strategies.