Listeriolysin (LLO)

Listeria monocyto-genes (LM) is a kind of food-borne zoonotic pathogen that is Gram-positive and facultative intracellular parasitism. It can cause gastroenteritis, meningitis, sepsis and abortion in humans and animals. The pathogenicity of LM depends on a variety of virulence factors produced by bacteria, of which the main virulence factor is listeriolysin O (LLO). LLO encoded by the hly gene is a secreted protein with a relative molecular mass of 56,000 and consisting of 505 amino acids. The protein has the characteristics of forming pores, which causes LM to escape from phagosome and enter into cytoplasm by dissolving intracellular endocytosis, and promotes the proliferation of bacteria in cells. The pore-forming properties of LLO give it the properties of breaking the red cell membrane and causing hemolysis, so it is called hemolysin. In addition, LLO can also induce cellular inflammatory reactions and immune response, so it is often used as a biological adjuvant in the development of vaccines. It is known that under natural conditions, LLO is synthesized by LM and secreted outside the cell to exert its pathogenic effect.