Moreover, in the absence of infection or intracellular replication, structured antigens such as capsomers or Virus-Like Particles are able to enter both the extracellular and the endogenous processing pathway within antigen presenting cells (APCs), activating also antigen-specific CD8+ cytotoxic T lymphocytes (CTL), a phenomenon known as cross-priming [51], [52]. This evidence concerns the gene CD8A and infection.