Enhanced immunogenicity of Renibacterium salmoninarum in chinook salmon after removal of the bacterial cell surface-associated 57 kDa protein

A study was conducted to determine the effect of endogenous serine protease activity on the immunogenicity of Renibacterium salmoninarum cells in chinook salmon Oncorhynchus tshawytscha. Salmon were immunized with either R. salmoninarum cells possessing p57 (p57(+)) or substantially depleted of p57 (p57(-)). The resultant antisera were examined by whole cell ELISA and immunoblot procedures using p57(+), p57(-), proteinase-K-treated, and periodate-treated whole cells. These analyses revealed that the removal of p57 by the endogenous serine protease significantly enhanced the immunogenicity of the cell, resulting in a 20-fold increase in detectable antibody titers. The bulk of this antibody activity was directed at sites blocked by the presence of the p57 molecule. Furthermore, proteinase-K and periodate treatment of R. salmoninarum cells revealed that the increased antibody activity almost exclusively reacted with carbohydrate moieties on the p57(-) cell

Teleost antibody structure: Simple prototype or elegant alternative?

Teleosts possess mechanism(s) by which they can generate considerable structural diversity within their tetrameric antibody molecules. In salmonids, this diversity is generated through a process of random polymerisation of the constituent monomeric subunits rather than dependency upon isotypic gene diversity. Thus, one gene product can give rise to as many as six different structural forms of immunoglobulin. In contrast to mammals, evidence suggests that this polymerisation process occurs late in the secretory process and not within the endoplasmic reticulum. This assembly process is likely to be important in the generation of teleost antibody functional diversity, thereby potentially simulating isotypy

The Strength of B Cell Interaction with Antigen Determines the Degree of IgM Polymerization

The induction of variable disulfide polymerization of IgM in the trout (Oncorhynchus mykiss) and its effect on its half-life were examined. An association between greater Ab affinity and increased disulfide polymerization was first indicated by the observation of this increased IgM disulfide polymerization during the process of affinity maturation. A direct association between Ab affinity and disulfide polymerization was then established by the fractionation of individual sera into high- and low-affinity subpopulations, which also resulted in the partitioning of high and low degrees of disulfide polymerization. The ability of high-affinity B cells to produce more highly polymerized Abs upon Ag induction was demonstrated by in vitro Ag-driven selection. Low Ag concentrations, which elicited only high-affinity Abs, also possessed the highest degree of polymerization, whereas higher concentrations of Ag elicited a broader array of Ab affinities, yielding a lower average affinity and degree of polymerization. Half-life studies revealed that the high-affinity, highly polymerized Abs possessed longer half-lives than the lower-affinity, lightly polymerized Abs. Finally, although the affinity for Ag is associated with elevated levels of polymerization, analysis of naive Ig revealed that the degree of polymerization alone, not affinity, appears sufficient to prolong Ig half-life. The Journal of Immunology, 2010,184: 844-850

Effect Of Homogenate From Different Oyster Species On Perkinsus Marinus Proliferation And Subtilisin Gene Transcription

The modulation of Perkinsus marinus proliferation and subtilisin gene transcription by host (oyster) tissue was examined. Perkinsus rnarinus cells were cultured for 4 weeks in media supplemented with extract from either one of four different Crassostrea virginica stocks or with extract from one of two other Crassostrea species, C. ariakensis and C. gigas. After 4 weeks in culture, we determined cell counts and relative subtilisin gene transcription levels using quantitative real-time polymerise chain reaction (qRTPCR). Cell proliferation and subtilisin gene transcription were significantly lower when P. marinus\u27 cells were grown in the presence of homogenate from any of the three oyster species than in unsupplemented media. Perkinstrs marinas subtilisin gene transcription was also significantly lower in cells cultured in media supplemented with homogenate from either C. ariakensis or C. gigas, than in media containing extract from the native oyster host, C. virginica. Gene transcription levels among cells grown in media supplemented with homogenate from the different stocks of C. virginica were not significantly different from one another

Antigenic and functional characterization of p57 produced by Renibacterium salmoninarum

Renibacterium salmoninarum, the causative agent of bacterial kidney disease, produces large quantities of a 57-58 kDa protein (p57) during growth in broth culture and during infection of salmonid fish. Biological activities of secreted p57 include agglutination of salmonid leucocytes and rabbit erythrocytes. We define the location of epitopes on p57 recognized by agglutination-blocking monoclonal antibodies (MAbs) 4C11, 4H8 and 4D3, and demonstrate that the majority of secreted p57 is a monomer that retains salmonid leucocyte agglutinating activity. The 3 MAbs bound a recombinant, amino-terminal fragment of p57 (211 aa) but not a carboxy-terminal fragment (315 aa) demonstrating that the neutralizing epitopes are located within the amino-terminal portion of p57. When combinations of the MAbs were used in an antigen capture ELISA, the epitopes recognized by the 3 MAbs were shown to be sterically separate. However, when the same MAb was used as both the coating and detection MAb, binding of the biotinylated detection MAb was not observed. These data indicate that the epitopes recognized by the 3 agglutination-blocking antibodies are functionally available only once per molecule and that native p57 exists as a monomer. Similar ELISA results were obtained when kidney tissues from 3 naturally infected chinook salmon were assayed. Finally, a p57 monomer was purified using anion exchange and size exclusion chromatography that retained in vitro agglutinating activity. A model in which p57 is released from R. salmoninarum as a biologically active monomer during infection of salmonid fish is proposed

Histopathology of the thymus of coho salmon Oncorhynchus kisutch experimentally infected with Renibacterium salmoninarum

We report on the histopathological changes occurring in the thymus of coho salmon Oncorhynchus kisutch experimentally infected with Renibacterium salmoninarum. Coho salmon were intraperitoneally infected, and the thymi were collected weekly from 1 to 7 wk post-infection, and processed for ultrastructural study. The thymus appeared to be infected only in fish collected at 6 and 7 wk post-infection. The first stage of the infection was characterized by the presence of a low number of bacteria scattered in the connective tissue of the capsule. Further progression of the thymic infection was characterized by the rupture of the capsular-thymic barrier, and by the bacterial colonization of the subcapsular and inner zones of the parenchyma, where the bacteria were located mainly in macrophages, but also apparently in pale reticular-epithelial cells and in thymocytes. Other reticular-epithelial cells, and the vascular trabeculae, remained free of R. salmoninarun during the initial stages of the infection. In severely infected thymi, necrosis of the parenchyma of the subcapsular and inner zones, and bacterial invasion of the trabeculae occurred. The integrity of the pharyngeal epithelium covering the thymus was not affected during the infection

CXCL8 Chemokines in Teleost Fish: Two Lineages with Distinct Expression Profiles during Early Phases of Inflammation

Contains fulltext : 126584.pdf (publisher's version ) (Open Access

Comparative analysis of mycobacterial infections in wild striped bass Morone saxatilis from Chesapeake Bay

During an ongoing epizootic of mycobacteriosis, wild striped bass Morone saxatilis from Chesapeake Bay were analyzed using 3 methods for detection of either mycobacterial infection or associated granulomatous pathology. The specific detection techniques, which utilized aseptically collected splenic tissue, were histology, quantitative culture and nested PCR. Based on analysis of 118 samples, detection of infection differed significantly between the 3 methods (chi-square, p = 0.0007). Quantitative culture and nested PCR detected similar, higher rates of infection (69 and 75%, respectively) than the histological method (52%). Although primary PCR assays for a 924 to 940 bp segment of the mycobacterial 16S rRNA gene were positive for genomic DNA from mycobacterial cultures, a secondary, nested PCR reaction for an internal 300 bp gene segment was required in order to detect mycobacteria within splenic tissue. A similar rate of mycobacterial infection was present in fish collected from all sites tested. Although all detection methods found that striped bass age 4.0 to 4.9 yr had the highest positive incidence, nested PCR detected a higher frequency of mycobacterial infection in fish \u3e= 6.0 yr of age than the other 2 methods. Quantitative bacteriology was a more sensitive detection technique when the fish tissue contained \u3c= 10(3) mycobacteria g(-1)

Teleost fish mount complex clonal IgM and IgT responses in spleen upon systemic viral infection

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