Vaccination against Salmonella
To defend a host against infectious agents, the immune system
has evolved a variety of components. Innate immunity is characterized
by the recognition of invading micro-organisms, the subsequent
production of cytokines and soluble factors and the
activation of phagocytic cells (Dougan et al., 2011). The innate response
lacks any form of memory and, although often successful in
controlling the initial growth of Salmonella, is insufficient to ensure
resistance to infection (Dougan et al., 2011). The acquired immune
system includes the humoral (mostly against extracellular invaders)
and cell-mediated (mainly against intracellular invaders) immune
response, allowing the clearance of Salmonella and the
establishment of a long-lasting immunity to re-infection (Mastroeni
et al., 2000).
Where killed Salmonella whole-cell vaccines lack the ability to
induce proper cell-mediated immunity (Xu et al., 1993; Yamane