Antibody Binding to the O-Specific Antigen of Pseudomonas aeruginosa O6 Inhibits Cell Growth

Abstract

Pseudomonas aeruginosa is an opportunistic pathogen that is inherently resistant to many antibiotics and represents an increasing threat due to the emergence of drug-resistant strains. There is a pressing need to develop innovative antimicrobials against this pathogen. In this study, we identified the O-specific antigen (OSA) of P. aeruginosa serotype O6 as a novel target for therapeutic intervention. Binding of monoclonal antibodies and antigen-binding fragments therefrom to O6 OSA leads to rapid outer membrane destabilization and inhibition of cell growth. The antimicrobial effect correlated directly with antibody affinity. Antibody binding to the O antigen of a second lipopolysaccharide (LPS) type present in P. aeruginosa or to the LPS core did not affect cell viability. Atomic force microscopy showed that antibody binding to OSA resulted in early flagellum loss, formation of membrane blebs, and eventually complete outer membrane loss. We hypothesize that antibody binding to OSA disrupts a key interaction in the P. aeruginosa outer membrane.

Bactericidal fully human single‐chain fragment variable antibodies protect mice against methicillin‐resistant Staphylococcusaureus bacteraemia

“…35 In another study, Richard et al confirmed that the S20 scFv exerted its antibacterial activity through binding to the Ospecific antigen of P. aeruginosa (serotype O6), leading to the outer membrane disruption, followed by bacterial death. 34 The direct bactericidal activity of scFv fragments can be explained by their function as AMPs 35,37,38 or catalysis of some chemical reactions (e.g. abzymes), 35 besides interference with the biological function of the bacterium as mentioned above.…”

“…[28][29][30] A group of scFvs has been generated against pathogen targets, 32 some of which showed direct bactericidal activities. [33][34][35][36] These antibacterial scFvs seem to exert their bactericidal effects by disrupting the bacterium's biological activity, compromising the cell wall integrity or functioning as abzymes. 35,[37][38][39] In this regard, Wang et al isolated eight high-affinity anti-S. aureus scFvs from a phage-display library, which was constructed from the peripheral blood lymphocytes of cows with mastitis caused by S. aureus.…”

“…The inhibitory effect of MEH63, MEH158 and MEH183 on the growth of S. aureus was assessed using the microtitre plate and agar plate assays as described previously with some modifications. 34,35,38 Using the microtitre plate technique, 50 µL of bacterial suspensions (S. aureus S.a.48, S.a.61, S.a.124 and ATCC 6538,~10 8 CFU mL −1 ) was initially incubated with an equal volume of vancomycin (0.0625-32 µg mL −1 ) for 20 h at 37°C, and the OD 600 was read every hour for 10 h and once after 20 h. After assessing the growth curves of four strains treated with vancomycin (positive control), 50 µL of bacterial suspensions of S. aureus S.a.48, S.a.61, S.a.124 and ATCC 6538 was individually incubated with an equal volume of MEH63, MEH158 and MEH183 (at a final concentration of 200 µg mL −1 ), as described for vancomycin, and their growth curves were compared with the growth curves of untreated bacteria (incubated with PBS), bacteria incubated with the denatured MEH158 (scFv heated at 100°C for 30 min) and bacteria incubated with vancomycin (1 µg mL −1 for S. aureus ATCC 6538 and 2 µg mL −1 for S. aureus S.a.48, S.a.61 and S.a.124 strains).…”

“…Moreover, the scFv fragment can be expressed in various hosts, making it possible to produce large quantities easily and cost‐effectively 28–30 . A group of scFvs has been generated against pathogen targets, 32 some of which showed direct bactericidal activities 33–36 . These antibacterial scFvs seem to exert their bactericidal effects by disrupting the bacterium’s biological activity, compromising the cell wall integrity or functioning as abzymes 35,37–39 .…”

Hematological Picture of Rabbits Immunized with Pseudomonas aeruginosa

“…candidates and immunization trials targeted many compartments of P. aeruginosa such as external proteins, like flagella (8,9) and pili (10), cytosolic protein (11), outer membrane proteins (12,13), alginate which is an extracellular polysaccharide (14), lipopolysaccharide (15), capsular antigen (16), somatic antigen known as "O antigen" (17,18), and biofilm (19).…”