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ARS Home » Northeast Area » Leetown, West Virginia » Cool and Cold Water Aquaculture Research » Research » Publications at this Location » Publication #410740

Research Project: Improving Salmonid Health through Breeding, Vaccination and Microbiome Modulation

Location: Cool and Cold Water Aquaculture Research

Title: Structural and genetic basis for binding of a mouse monoclonal antibody to Flavobacterium psychrophilum lipopolysaccharide

Author
item CISAR, JOHN - Collaborator
item WANG, XIACONG - University Of Georgia
item WOODS, ROBERT - University Of Georgia
item CAIN, KENNETH - University Of Idaho
item Wiens, Gregory - Greg

Submitted to: Journal of Fish Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/8/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Flavobacterium psychrophilum is a bacterial pathogen of rainbow trout that causes significant losses. Methods and reagents to distinguish different strains of F. psychrophilum are needed to improve disease surveillance and allow rapid identification and tracking of virulent strains. Scientists have previously reported rabbit antibodies that differentiate particular strains; however, the precise genetic and biochemical differences have not been clear. In this manuscript, we report the analysis of a mouse monoclonal antibody, FL100A, that we show binds strongly to the o-polysaccharide from strain CSF259-93 but only weakly or not at all to o-polysaccharide from strain 950106-1/1. Modeling the conformation explains the differences in binding as the CSF259-93 o-polysaccharide forms a compact helix while the 950106-1/1 o-polysaccharide forms a linear structure. Monoclonal antibody FL100A is thus a specific probe for strain CSF259-93 lipopolysaccharide and closely related strains.

Technical Abstract: A mouse monoclonal antibody (mAb FL100A) previously prepared against Flavobacterium psychrophilum (Fp) CSF259-93 has now been examined for binding to lipopolysaccharides (LPS) of this strain and Fp 950106-1/1. The corresponding O-polysaccharides (O-PS) of these strains are formed by identical trisaccharide repeats composed of L-Rhamnose (L-Rha), 2-acetamido-2-deoxy-L-fucose (L-FucNAc) and 2-acetamido-4-R1-2,4-dideoxy-D-quinovose (D-Qui2NAc4NR1) where R1 represents a dihydroxyhexanamido moiety. The O-PS loci of these strains are also identical except for the gene (wzy1 or wzy2) that encodes the polysaccharide polymerase. Accordingly, adjacent O-PS repeats are joined through D-Qui2NAc4NR1 and L-Rha by wzy2-dependent alpha (1-2) linkages in Fp CSF259-93 versus wzy1-dependent beta (1-3) linkages in Fp 950106-1/1. mAb FL100A reacted strongly with Fp CSF259-93 O-PS and LPS but weakly or not at all with Fp 950106-1/1 LPS and O-PS. Importantly, it also labeled cell surface blebs on the former but not the latter strain. Additionally, mAb binding was approximately 5-times stronger to homologous Fp CSF259-93 LPS than to LPS from a strain with a different R-group gene. A conformational epitope for mAb FL100A binding was suggested from molecular dynamic simulations of each O-PS. Thus, Fp CSF259-93 O-PS formed a stable well-defined compact helix in which the R1 groups were displayed in a regular pattern on the helix exterior while unreactive Fp 950106-1/1 O-PS adopted a flexible extended linear conformation. Taken together, the findings establish the specificity of mAb FL100A for Wzy2-linked F. psychrophilum O-PS and LPS.