Immunoproteomic identification of 11 novel immunoreactive proteins ofRiemerella anatipestiferserotype 2

OmpC, a novel factor H-binding surface protein, is dispensable for the adherence and virulence of Salmonella enterica serovar Typhimurium

Salmonella enterica serovar Typhimurium utilizes a series of strategies to evade host innate immune defenses, including the serum complement system. Many microbial pathogens have evolved the ability to bind the complement regulatory protein factor H (FH) through their surface factor H-binding proteins (FHBPs) to circumvent the complement-mediated bactericidal effect. However, the roles of FHBPs in Salmonella pathogenesis are not well understood. In this study, we demonstrated that the survival of S. Typhimurium in human serum was decreased in a time and concentration dependent manner. Pre-incubation with FH attenuated the sensitivity of S. Typhimurium strain χ3761 to complement-mediated serum killing, suggesting FH binding enhance survival in serum. We aimed to identify novel S. Typhimurium FHBPs and characterize their biological functions. Here, six potential FHBPs were identified by two-dimensional (2D)-Far-western blot, and three of them were further confirmed to bind FH by Far-western blot and dot blot. We found that deletion of ompC (ΔompC) significantly inhibited the survival of S. Typhimurium strain χ3761 in human serum. Our results indicated that the ompC mutation does not affect χ3761 adhesion to HeLa cells. Furthermore, a mice infection model showed that deletion of ompC had no significant effect on the histopathological lesions or viability compared with the wild-type strain χ3761. In summary, these results suggested that OmpC is an important FHBP, but not a critical virulence factor of S. Typhimurium.

IL-17A treatment influences murine susceptibility to experimental Riemerella anatipestifer infection

Riemerella anatipestifer causes infectious disease and considerable economic loss in the duck industry worldwide. Our previous studies demonstrated an association between proinflammatory cytokine interleukin (IL)-17A and R. anatipestifer infection. Here, we provide evidence for IL-17A involvement in R. anatipestifer infection using a mouse model. Mice showed higher resistance to R. anatipestifer infection than ducks, with median lethal doses (LD₅₀) of 3.5 × 10¹⁰ and 5 × 10⁷ colony-forming units (CFU), respectively. Twenty-four hours after infection, mice with a sub-lethal dose (3.5 × 10⁹ CFU) exhibited levels of IL-17A and IL-23 expression similar to uninfected mice. Thus, we hypothesized that exogenous IL-17A or IL-23 administration affects susceptibility of mice to R. anatipestifer. Mice pretreated with IL-17A or IL-23 prior to sub-lethal dose infection of R. anatipestifer exhibited increased bacterial burden and spleen weights compared to untreated infected mice, confirming the involvement of IL-17A in susceptibility to R. anatipestifer infection in vivo.

Production of anti-Trichophyton rubrum egg yolk immunoglobulin and its therapeutic potential for treating dermatophytosis

The aim of this study was to estimate the therapeutic potential of specific egg yolk immunoglobulin (IgY) on dermatophytosis caused by Trichophyton rubrum. The IgY was produced by immunizing hens with cell wall proteins of T. rubrum, extracted from eggs by PEG precipitation and then purified by ammonium sulfate precipitation. The cross-reactivity (CR) with other fungi, growth inhibition on T. rubrum in vitro and therapeutic effect on T. rubrum infection in BALB/C mice of the specific IgY were then evaluated. Anti- T. rubrum cell wall proteins IgY (anti-trCWP IgY) presented a certain degree of cross-reactivity with different fungi. In the in vitro and in vivo activity researches, Anti-trCWP IgY showed a significant dose-dependent growth inhibitory effect on T. rubrum in vitro and a significant dose-dependent therapeutic effect on T. rubrum infection in BALB/C mice.

Riemerella anatipestifer infection in ducks induces IL-17A production, but not IL-23p19

R. anatipestifer (RA) is one of the most harmful bacterial pathogens affecting the duck industry, and infection is associated with the production of proinflammatory cytokines, including IL-17A. Another proinflammatory cytokine, IL-23, is critical for the development of Th17 cells, which produce IL-17. However, IL-23 roles have not been studied in this infection. Here, we describe the identification and mRNA expression analysis of duck IL-23p19 (duIL-23p19) in splenic lymphocytes and macrophages stimulated with killed RA and in spleens of RA-infected ducks. Expression of duIL-23p19 transcript identified in this study was relatively high in livers of healthy ducks and was upregulated in mitogen-activated splenic lymphocytes as well as in splenic lymphocytes and macrophages stimulated with killed RA. In spleens of RA-infected ducks, expression levels of duIL-23p19 transcript were unchanged at all time points except on days 4 and 7 post-infection; however, duIL-17A and IL-17F expression levels were upregulated in both spleens of RA-infected ducks and splenic lymphocytes and macrophages stimulated with killed RA. In sera collected at 24 h after this infection, duIL-23p19 expression levels were unchanged, whereas IL-17A significantly upregulated. These results suggest that IL-23p19 does not play a critical role in the IL-17A response in early stages of RA-infected ducks.

Downregulation of common cytokine receptor γ chain inhibits inflammatory responses in macrophages stimulated with Riemerella anatipestifer

Th17-cell-mediated inflammation is affected by the soluble form of common cytokine receptor γ chain (γ_c). We previously suggested that inflammatory cytokines including interleukin (IL)-17A are associated with Riemerella anatipestifer infection, which a harmful bacterial pathogen in ducks. Here, the expression profiles of membrane-associated γ_c (duγ_c-a) and soluble γ_c (duγ_c-b) in R. anatipestifer-stimulated splenic lymphocytes and macrophages, and in the spleens and livers of R. anatipestifer-infected ducks, were investigated. In vitro and in vivo results indicated that the expression levels of both forms of γ_c were increased, showing that marked increases were detected in the expression of the duγ_c-b form rather than the duγ_c-a form. Treatment with γ_c-specific siRNA downregulated mRNA expression of Th17-related cytokines, including IL-17A and IL-17F, in duck splenic macrophages stimulated with R. anatipestifer, whereas the expressions of interferon (IFN)-γ and IL-2 were enhanced. The results showed that the upregulation of γ_c, especially the duγ_c-b form, was associated with expression of Th17-related cytokines during R. anatipestifer infection.

Development of a subunit vaccine containing recombinant Riemerella anatipestifer outer membrane protein A and CpG ODN adjuvant

Riemerella anatipestifer, a Gram-negative bacillus, causes septicemia that can result in high mortality for ducklings. In this study, we evaluated the immune response and protective efficacy provided by a subunit vaccine containing recombinant outer membrane protein A (rOmpA) and plasmid constructs containing CpG oligodeoxynucleotides (ODN). Results showed that CpG ODN enhanced both humoral and cell-mediated immunity elicited by rOmpA as early as two weeks after primary immunization. When compared to ducks immunized with rOmpA, ducks immunized with rOmpA+CpG ODN showed higher levels (p<0.05) of antibody titer, T cell proliferation, and percentages of CD4(+) and CD8(+) T cell in peripheral blood mononuclear cells (PBMCs). The relative fold inductions of mRNA expression of Th1-type (IFN-γ and IL-12), and Th2-type (IL-6) cytokines in PBMCs isolated from ducks immunized with rOmpA+CpG ODN were significantly higher than those of the rOmpA group. Homologous challenge result showed that the rOmpA+CpG ODN vaccine reduced the pathological score by 90% in comparison with the saline control. In conclusion, our study found that CpG ODN can enhance both humoral and cellular immunity elicited by a rOmpA vaccine. The rOmpA+CpG ODN vaccine can be further developed as a subunit vaccine against R. anatipestifer.

Fifteen novel immunoreactive proteins of Chinese virulent Haemophilus parasuis serotype 5 verified by an immunoproteomic assay

Haemophilus parasuis (H. parasuis) is associated with meningitis, polyserositis, polyarthritis and bacterial pneumonia. At present, its prevention and control is difficult because of the lack of suitable subunit vaccines. Nowadays, high-throughput methods, immunoproteomics, are available to screen for more vaccine candidates. A protein extraction method for H. parasuis and two-dimensional electrophoresis (2-DE) were optimized to provide high-resolution profiles covering pH 3 to 10. Twenty immunoreactive spots were excised from gels after strict comparison between 2-DE Western blot membranes and the relevant gels. Matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS) and MALDI-TOF-TOF-MS successfully identified 16 different proteins. Fifteen of them were reported as immunoreactive proteins in H. parasuis for the first time. In addition, recombinant HP5-7 (ABC transporter, periplasmic-binding protein) showed immunoreactivity both with hyperimmune rabbit serum and convalescent swine serum. Four recombinants of the 14 successfully expressed genes showed immunoreactivity with hyperimmune rabbit serum.