Molecular Characterization, Phylogenetic, Expression, and Protective Immunity Analysis of OmpF, a Promising Candidate Immunogen Against Yersinia ruckeri Infection in Channel Catfish

Abstract

Outer membrane porins, as the major components of Gram-negative bacterial membrane proteins, have been proven to be involved in interactions with the host immune system and potent protective antigen candidates against bacterial infection in fish. Outer membrane porin F (OmpF) is one of the major porins of Yersinia ruckeri (Y. ruckeri), the causative agent of enteric red mouth disease of salmonid and non-salmonid fish. In the present study, the molecular characterization and phylogenetic analysis of OmpF gene was studied, heterogenous expression, immunogenicity and protective immunity of OmpF were systemically evaluated as a subunit vaccine for channel catfish against Y. ruckeri infection. The results showed that OmpF gene was highly conserved among 15 known Yersinia species based on the analysis of conserved motifs, sequences alignment and phylogenetic tree, and was subjected to negative/purifying selection with global dN/dS ratios value of 0.649 throughout the evolution. Besides, OmpF was also identified to have immunogenicity by western blotting and was verified to be located on the surface of Y. ruckeri using cell surface staining and indirect immunofluorescence assays. Moreover, recombinant OmpF (rtOmpF) as a subunit vaccine was injected with commercial adjuvant ISA763, significantly enhanced the immune response by increasing serum antibody levels, lysozyme activity, complement C3 activity, total protein content, SOD activity, immune-related genes expression in the head kidney and spleen, and survival percent of channel catfish against Y. ruckeri infection. Thus, our present results not only enriched the information of molecular characterization and phylogenetics of OmpF, but also demonstrated that OmpF holds promise to be used as a potential antigen against Y. ruckeri infection in fish.

Overcoming Fish Defences: The Virulence Factors of Yersinia ruckeri

“…In recent years, however, OMPs have been discussed as promising vaccine candidates in fish. A recent study explored the protective capabilities of outer membrane porin F (OmpF) in Y. ruckeri [145]. OmpF is one of the major Y. ruckeri OMPs.…”

“…Phylogenetic and multiple alignment analysis of OmpF demonstrated high sequence identity of OmpF within the Yersiniae (80.8–86.8%), compared to other Enterobacterales (58.8–76.4%), indicating that OmpF is a promising vaccine candidate. Indeed, recombinant OmpF injected into channel catfish ( I. punctatus ) enhanced the immune response by increasing, among others, lysozyme activity, complement C3 activity and serum antibody levels [145].…”

Diversification of OmpA and OmpF of Yersinia ruckeri is independent of the underlying species phylogeny and evidence of virulence-related selection

“…Additionally, OmpF has been reported to be a protective antigen against some bacterial infections 51 , 64 , 65 . The loops of OmpF contain putative antigenic epitopes 51 , 52 and indeed, a recombinant OmpF subunit vaccine provides protective immunity against Y. ruckeri infection in catfish 53 . The identification of a 13-amino acid insertion at the tip of loop 5 in biotype 2, serotype O1 isolates of Y. ruckeri could be important if this segment of the loop represents a highly immunogenic and protective epitope.…”

“… 48 , E. coli 49 and Salmonella Typhi 50 . The loops of OmpF are known to have putative antigenic epitopes 51 , 52 and indeed, a recombinant OmpF subunit vaccine has been shown to provide protective immunity against Y. ruckeri infection in catfish 53 .…”

Development of IMBs–qPCR detection method for Yersinia enterocolitica based on the foxA gene

“…Ail protein can promote the ability of Y. enterocolitica to attach and invade cells and help to improve the resistance of bacteria to serum (Bliska and Falkow 1992). Outer membrane protein F (OmpF) plays an important role in controlling the selective penetration of cell membranes (Shaban et al 2017) and is also considered as a candidate antigen for inhibiting Y. enterocolitica infection (Wang et al 2018a). Both outer membrane proteins Ail and OmpF have strain-speci city and good conservation (Huang et al 2010;Stenkova et al 2011), therefore we chose their antibodies as coupling proteins of immunomagnetic beads.…”