Fig. 4

The local and peripheral immune response induced by intranasal-delivered viral vector vaccine. (1) Intranasal delivery of the viral vector vaccine and entry of the recombinant virus. (2) Local secretory immunoglobulin A produced by subepithelial plasma cells. (3) Antigen is recognized and processed by innate immune cells and antigen presenting cells. (4) Immune cell recruitment, including neutrophils, natural killer cells, and monocytes. (5) Activated dendritic cells traffic to draining lymph nodes via afferent lymphatics to prime adaptive responses. In lymph node T cell zones, externally derived antigens are presented on class II MHC, prompting CD4⁺ T cell training, while internally derived antigens are processed and presented on class I MHC to CD8⁺ T cells. (6) APCs promote maturation and expansion of naive CD4⁺ and CD8⁺ T cells. CD8⁺ cytotoxic T cells and subsets of CD4⁺ T helper cells traffic back to the site of infection. (7) Activated B cells undergo expansion and somatic hypermutation of the B cell receptor (BCR), resulting in BCR specificity that strongly binds to peptides maintained on the surface of follicular dendritic cells (FDCs). B cells cycle through iterative rounds of expansion/somatic hypermutation and affinity selection, resulting in the selection of high-affinity BCRs. (8) Interactions with T follicular helper (Tfh) cells lead to B cell differentiation and class-switching to long-lived memory B cells and high-affinity plasma cells, which traffic to sites of infection or maintained as long-lived memory populations. (Created in BioRender)