Antibody-dependent enhancement of infection: bacteria do it too

Antibodies should defend us from microbial infection, however, new research suggests that bacteria can use antibodies against us. An ingenious strategy by pneumococcus uses specific antibacterial IgA antibodies to enhance colonisation on respiratory cells. After degradation by a bacterial protease, IgA–Fab fragments induce the selective unmasking of a bacterial ligand used in interactions with host cells, providing a means for enhanced attachment. This finding challenges conventional views on vaccine design for mucosal pathogens.