Figure 2.

Recombinant CyaA proteins can deliver antigens into antigen presenting cells. Recombinant CyaA carrying an antigen genetically inserted into the catalytic domain, dCyaA-Ag, binds to dendritic cells (DC) as a result of its selective interaction with the CD11b/CD18 integrin receptor (ϕ). After translocation across the plasma membrane of the DC (left); the antigen is degraded by the proteasome into peptides that can reach the classical cytosolic MHC class I presentation pathway, to elicit specific CD8⁺ CTL responses. Alternatively, the recombinant CyaA can be endocytosed (right). After proteolysis in endosomes/lysosomes, the released peptides, including antigen-derived CD4⁺ epitopes, can enter the MHC class II presentation pathway, to elicit specific Th1 type CD4⁺ helper T-cell responses.