invasins

Invasins are virulence factors produced by various bacterial pathogens that promote invasion of host tissues. They are typically proteins that enable bacteria to enter non-phagocytic cells by engaging host receptors and triggering uptake. Invasins can be surface-exposed adhesins that bind receptors such as integrins, or secreted effector proteins delivered by secretion systems that remodel the actin cytoskeleton or disrupt intercellular junctions. By promoting uptake into epithelial or endothelial cells, invasins help pathogens cross mucosal barriers and disseminate within the host.

A well-studied example is invasin (Inv) from Yersinia species, which binds beta1 integrins on M cells and enterocytes to induce bacterial entry. Other pathogens use related invasion factors, including internalins in Listeria monocytogenes, and various Type III secretion system effectors in organisms such as Shigella and Salmonella that trigger cytoskeletal remodeling to promote uptake. Although these proteins share the general goal of enabling invasion, they differ in structure, receptors targeted, and the exact signaling pathways involved.

Invasins are often encoded on virulence plasmids or pathogenicity islands and are regulated by environmental cues such as temperature, calcium levels, and host contact. Their activity contributes to the ability of pathogens to breach epithelial barriers, invade underlying tissues, and spread within the host, with implications for disease severity and transmission.

Further study of invasins informs approaches to prevent invasive infection, including the development of vaccines or therapies that block host-pathogen interactions.