SEVI Fibrils are Induced by Bacterial Surface Molecules and Exert Antimicrobial Activity Against ESKAPE Pathogens

The semen-derived enhancer of viral infection (SEVI) is an amyloid fibril formed by the self-assembly of the PAP248-286 peptide, a cleavage product of prostatic acid phosphatase, which is naturally present in human seminal plasma. Beyond its previously described role in HIV transmission, findings highlight a physiological function for SEVI in innate immunity. As many amyloids display antimicrobial effects, we tested SEVI fibrils for antibacterial activity against microbial ESKAPE pathogens and urogenital bacteria, including Pseudomonas aeruginosa, Klebsiella quasipneumoniae, Escherichia coli, Acinetobacter baumannii, Staphylococcus aureus, Streptococcus agalactiae and Listeria monocytogenes. SEVI exhibited direct dose-dependent antibacterial effects in radial diffusion and survival assays, with activity observed at physiologically relevant concentrations. Bacterial surface molecules such as lipopolysaccharides and lipoteichoic acid induced the formation of SEVI fibrils, as confirmed by kinetic assays. Preincubation with epigallocatechin gallate, a fibril disruptor, abolished SEVIs antibacterial activity, pointing to the importance of its fibrillar structure. Mechanistic studies and electron microscopy revealed limited bacterial membrane disruption and the intracellular accumulation of polyphosphate granules in P. aeruginosa, indicating a stress response. In conclusion, SEVI exerts a potent antibacterial activity against pathogens found in the urogenital tract, indicating a potential physiological role in vaginal mucosal immunity.