Invasion plasmid antigen B (IpaB)

Invasion plasmid antigen B (IpaB) is a 62 kDa effector protein encoded on the virulence plasmid of *Shigella* spp. and is essential for the ability of these bacteria to invade host epithelial cells and escape from intracellular phagosomes[1][6][5]. IpaB is a core component of the type III secretion system (T3SS), functioning both as a translocator inserted into host membranes and as an effector that, upon translocation, triggers rearrangement of the actin cytoskeleton, membrane ruffling, and uptake of the bacterium through macropinocytosis[1][5]. It is homologous to SipB in *Salmonella* and YopB in *Yersinia*, and is required for both the invasion process and the induction of host cell death—sometimes by binding host Caspase-1 to trigger apoptosis[1]. IpaB is a major antigen recognized by the immune system after infection or vaccination, and antibodies against IpaB (especially certain epitopes at the N-terminus) can inhibit invasion and are protective in animal challenge models, making it a prime candidate for inclusion in vaccines against shigellosis[3][4][7]. While no drugs directly target IpaB for therapeutic use, its antibody epitopes are in development for multivalent *Shigella* vaccines[3][4][7]. As a bacterial virulence factor, IpaB is not present in humans or other eukaryotes. The primary therapeutic concern is its central role in infectious pathogenesis and potential (but unproven) risk of autoimmune responses due to its structural similarity to some host proteins[6].

Other names

IpaBShigella IpaBShigella invasion plasmid antigen BS. flexneri IpaB

Neutralizing antibodies block IpaB function, thereby preventing Shigella invasion of epithelial cells[3][4][7] Vaccine-induced immunity aims to elicit anti-IpaB antibodies (protective mechanism via immune neutralization)[3][4]