Virulence factors in brucellosis: implications for aetiopathogenesis and treatment

Brucella species are responsible for the global zoonotic disease brucellosis. These intracellular pathogens express a set of factors – including lipopolysaccharides, virulence regulator proteins and phosphatidylcholine – to ensure their full virulence. Some virulence factors are essential for invasion of the host cell, whereas others are crucial to avoid elimination by the host. They allow Brucella spp. to survive and proliferate within its replicative vacuole and enable the bacteria to escape detection by the host immune system. Several strategies have been used to develop animal vaccines against brucellosis, but no adequate vaccine yet exists to cure the disease in humans. This is probably due to the complicated pathophysiology of human Brucella spp. infection, which is different than in animal models. Here we review Brucella spp. virulence factors and how they control bacterial trafficking within the host cell.