Riemerella anatipestifer T9SS Effector SspA Functions in Bacterial Virulence and Defending Natural Host Immunity

Abstract

In recent years, Riemerella anatipestifer T9SS has been reported to act as a virulence factor. However, the functions of the proteins secreted by R. anatipestifer T9SS are not entirely clear.

Purification, crystallization and crystallographic analysis of the PorX response regulator associated with the type IX secretion system

“…Each of the three major oral pathogens (P. gingivalis, Tannerella forsythia and Prevotella intermedia) associated with periodontitis and other human systemic diseases employs a T9SS (Lasica et al, 2017). Other T9SS-utilizing pathogens, including Riemerella anatipestifer, Flavobacterium coulminris, F. psychrophilum and F. branchiophilum, are responsible for major bacterial infections in birds and farmed fish, such as rainbow trout fry syndrome and cold-water disease (Li et al, 2017;Barbier et al, 2020;Good et al, 2015;Chen et al, 2022). PorX is a conserved protein that is common to all these pathogens as well as to nonpathogenic gliding bacteria (Fig.…”

Occludin and collagen IV degradation mediated by the T9SS effector SspA contributes to blood–brain barrier damage in ducks during Riemerella anatipestifer infection

“…SspA is a metalloproteinase secreted via the R. anatipestifer T9SS. In our previous study, R. anatipestifer SspA was verified to be involved in bacterial virulence and the degradation of host gelatine, fibrinogen, and bacitracin LL-37 [ 21 ]. Bacteria-secreted metalloproteases can disrupt host BBB integrity, e.g., Bacillus anthracis InhA contributes to BBB disruption associated with anthrax meningitis through proteolytic attack of the endothelial tight junctional protein zonula occludens (ZO)-1 [ 47 ].…”

“…Wild-type R. anatipestifer Yb2 is a serotype 2 virulent strain [ 23 ]. The sspA gene mutant strain Yb2ΔsspA and the complementation strain cYb2ΔsspA were constructed in our previous study [ 21 ]. The R. anatipestifer strains were grown at 37 °C in tryptic soy broth (TSB; Difco, Franklin Lakes, NJ, USA) or on solid tryptic soy agar (TSA) plates, and TSB was supplemented with 25% glycerol for storage at −80 °C.…”

“…After transfection of pcMV -sspA-flag into 293 T cells, the cell lysate was analysed by gelatine zymography as we described previously [ 21 , 30 ]. In brief, equal amounts of (50 μg) of protein in cell lysates were separated via SDS‒PAGE at 4 °C on a 10% polyacrylamide gel copolymerized with gelatine (1%) as the substrate.…”

“…The gel was stained with 0.05% Coomassie Brilliant Blue R-250 and then destained with 30% methanol and 10% acetic acid. Gelatinolytic activity was detected as unstained bands against the background of Coomassie-stained gelatine, and the recombinant protein rSspA, which was confirmed to exhibit hydrolytic activity towards gelatine, was used as the gelatinase control [ 21 ]. The lysates of untransfected 293 T cells and 293 T cells transfected with the pcMV -flag plasmid were used as negative controls.…”