Intranasal DNA Vaccine for Protection against Respiratory Infectious Diseases: The Delivery Perspectives

Xu, Yingying; Yuen, Pak-Wai; Lam, Jenny Ka-Wing

APCs are a heterogeneous group of immunocompetent cells that mediate immune response by processing and presenting antigens to the T cells. T cells recognize only antigenic peptide fragments on the surface of APCs through the T cell receptors. Helper T cells recognize antigen in association with class II MHC proteins, whereas cytotoxic T cells recognize antigen in association with class I MHC proteins. An additional co-stimulatory signal is then produced by the APCs, leading to the activation of T cells. Non-professional APCs lack the co-stimulatory signaling, and therefore do not simulate T cells sufficiently. There are three types of professional APCs, namely DCs, macrophages and B cells. Among them, DCs have the broadest range of antigen presentation and are considered as the most efficient cells for induction and regulation of immune responses. They play a central role in bridging the innate immune system with the adaptive immune system [116] [117] [118] . To achieve efficient DNA vaccination, it is logical to target the plasmid DNA to DCs where the encoded antigen could be expressed endogenously.