Figure 1.

Human papilloma virus (HPV) vaccination. HPV vaccination is achieved from either preventive or therapeutic vaccines. The goal of preventive HPV vaccines is to prevent HPV infections by targeting humoral immunity through delivering virus-like particles (VLPs) encoding late HPV viral capsid proteins L1 and/or L2. Once VLPs are delivered, T-helper 2 (T_H2) cells activate B-cells to bind to the particles to become plasma cells, allowing antibodies to be generated. The neutralizing antibodies produced via preventive vaccines will block the HPV infection and induce protection from HPV. On the other hand, therapeutic HPV vaccines target cell-mediated immunity through professional antigen-presenting cells (APCs). APCs such as dendritic cells (DCs) present major histocompatibility complex (MHC)-peptide complexes to T-cells to allow for T-cell priming into effector cells. Helper CD4+ T-cells are presented via MHC class II molecules, whereas cytotoxic CD8+ T-cells, or cytotoxic T lymphocytes (CTLs), are presented via MHC class I molecules. CD4+ T-cells further differentiate into T_H cells to amplify CTL responses as well as activating humoral B-cells to produce more neutralizing antibodies. CTLs mediate the antigen-specific killing of tumor cells.