Designing CD8+ T cell vaccines: It`s not rocket science (yet) Jonathan W Yewdell Current Opinion in Immunology But the review is....

CD8+ vaccines Function of CD8+ T cells: - clearance of viral infections - tumor immunity BUT tumors have good Immune- Escape strategies Therapeutic cervical cancer vaccination CD8+ response 13 diff. HPV peptides + Freud`s adjuvants HPV induced cervical tumor Data from: Welters et al., Clin Cacer Res. 2008; Kenter et al., N Engl J Med., 2009 Yewdell et al., Nat Rev Imm, 2003

Activation of CD8+ T cells Aim: Induction of tumor-specific Tmem for therapeutic cancer vaccination MHC II Extracellular antigen APC CD4+ T cell APC MHC I Intracellular antigen CD8+ T cell e.g. bacteria e.g. viruses MHC I Cross-presentation APC e.g. dying cells, proteins, peptides CD8+ T cell

Cross-Presentation MHC I endolysosome Vacuolar pathway Phagosome - to cytosol - pathway Cat S TAP MHC I ER Proteasome

Vaccine Strategies What is the desired response? -What peptides? - response should be as minimal as possible to avoid side-effects and induction of tolerance - What Types of CD8+ T cells? - What anatomic locations should be focused of the response? How should this response be generated? - What immunogens should be used - What dose and - Which route? - How many boosts? Mouse models BUT mice are still not human

How can we learn from cross-priming? Yewdell et al., Nat Rev Imm, 2003 (1) MHC I Trafficking - mod. Cytoplasmic domain no travelling to endolysosome (2) APC modification loss of cross-priming via: - CD8  - /CD103 - DCs - injection of proapopt. CytochromeC - DC preactivation CD8  CD103 (4) Genetic modulation of antigen processing - KO of endosomal protease IRAP (3) Drug modulation of antigen processing - Bortezomib inhibits Proteasome - Chloroquine enhances cytosolic delivery Endolysosome

- Proteins favoured - antigen stability important - peptides have to metabolically stable (law of mass action) -BUT: chaperoned pepetides might work - Immnunogenicity highly dependant on cargo - e.g adjuvant effect of secreted gp96 Antigen for cross-priming: Proteins vs. peptides gp96 High immunogenicity Yewdell et al., Nat Rev Imm, 2003

Antigen acquisition in cross-priming - Cell-delivered antigens - Nibbling from alive cells - Phagocytosis of dead cells - Trogocytosis / „cross-dressing“ -Acquire preformed C1PCs from other APCs during cellular interactions (e.g. from monocytes which phagocytosed dead cell antigens) - even TCRs can be exchanges between naive T cells and CD8+ T cells - Peptide transfer via gap junctions (but more in direct priming) - Expression of cell death signals enhances cross-presenation - CLEC9A a necrotic cell detector - selectively expressed by CD8  + and plasmacytoid DCs

Who is priming? - Cross-priming appears to be dependant on CD8  + CD103+ DCs - CD8  features: optimizing endolysosome pH, CLEC9A regulated cross-priming - CD103+ DCs: migrating subset, transport antigen from periphery to LN - But in humans? - maybe BDCA3+ DC similar to CD8  + DC in mouse -pAPC „Wannabes“ capable of cross-priming: -pDCs, IFN producing killer DCs, neutrophils (but not in significant quantities?)

Some “practical advice” - Cross-priming is optimized by expressing long-lived antiges - extended peptide have increased immunogenicity because of resistance to protease destruction - advances in material science offer great promise for polypeptide-based vaccines: Immunigenicity is increased when delivering antigen and TLR- activating substances in the same particle

Conclusion Still a lot to do in science before we really understand cross-priming based vaccine strategies Thank you for your attention! Questions ??? Questions ???