Porcine differential gene expression in response to Salmonella enterica serovars Choleraesuis and Typhimurium.

An investigation of the porcine response to gastrointestinal infection with Salmonella enterica serovars Choleraesuis (narrow host range) and Typhimurium (broad host range) revealed markedly different transcriptional profiles. Seven genes identified by suppression subtractive hybridization as up-regulated in the mesenteric lymph nodes at 24h (h) post-inoculation (p.i.) in serovar Choleraesuis-infected pigs (ARPC2, CCT7, HSPH1, LCP1, PTMA, SDCBP, VCP) and three genes in serovar Typhimurium-infected pigs (CD47/IAP, CXCL10, SCARB2) were analyzed by real-time PCR at 8h, 24 h, 48 h, 7 days (d) and 21 d p.i. A comparison between the two Salmonella infections revealed significant differences in transcriptional induction early in the infection (8-24h) for the serovar Typhimurium-infected pigs, whereas the serovar Choleraesuis-infected pigs exhibited significantly higher levels of gene expression at the later time points (48h-21 d), except for HSPH1. A similar gene expression trend was observed for immune-related genes involved in innate immunity and the inflammatory T helper 1 (Th1) response. Initial repression of gene expression in the serovar Choleraesuis-infected pigs from 8 to 48h p.i. (IFNG, IL12A, IL4, IL8, CSF2) coincided with extended transcriptional activation throughout the 21 d infection (IFNG, INDO, SOCS1, STAT1, IL1B, IL6, IL8, SLC11A1). The serovar Typhimurium-infected swine presented a more transient induction of immune-related genes (IFNG, INDO, IRF1, SOCS1, STAT1, IL1B, IL8, SLC11A1) early in the infection (24-48 h) followed by a significant repression of IL12A, IL12B, IL4, IL8 and CSF2. Collectively, these data reveal specific porcine genes with differences in gene expression kinetics that may be responsible for the variation in disease progression observed in swine infected with Typhimurium compared to Choleraesuis.

Analysis of porcine differential gene expression following challenge with Salmonella enterica serovar Choleraesuis using suppression subtractive hybridization.

Swine-adapted Salmonella enterica subsp. enterica serovar Choleraesuis (S. Choleraesuis) is the pathogen most frequently isolated from diseased pigs and may affect host gene expression in a species-specific manner. To characterize the porcine transcriptional response to S. Choleraesuis infection, the mRNA profiles from the mesenteric lymph nodes of three non-infected and three experimentally infected pigs at 24 h post-inoculation were analyzed by suppression subtractive hybridization (SSH). Forty-four up-regulated and 44 down-regulated genes were revealed by differential cDNA screening of 384 forward and 288 reverse subtracted cDNA clones. The DNA sequence of the cDNA clones identified genes with a role in a variety of cellular functions as well as gene products of unknown function. Seven up-regulated genes (CXCL10, CXCR4, SDCBP, DNAJA1, HSPH1, HSP90 and ANXA5) and two functionally related genes (HSP70 and DNAJA4:pDJA1) were selected for further analysis based on their predicted roles in infection and immunity. Real-time RT-PCR was performed using RNA collected from a time course of infection spanning from the acute phase (8 h) to the chronic phase (21 days) to confirm and quantitate the up-regulation of the SSH-enriched genes. Correlating with the clinical signs of infection (fever, diarrhea and lethargy), the most dramatic induction of gene expression for all nine genes occurred at 48 h post-inoculation. This investigation further defines the porcine response to a host-adapted strain of Salmonella by revealing the differential expression of genes with a role in a variety of host cellular functions including innate immunity and cytoskeleton regulation.

Development of a baculovirus expression system for soluble porcine tumor necrosis factor receptor type I and soluble porcine tumor necrosis factor receptor type I-IgG fusion protein.

Tumor necrosis factor-alpha (TNF-alpha) is a key mediator of inflammatory responses and gram-negative bacterial sepsis, but the role that it plays during Salmonella enterica species bacterial infections in swine has not yet been elucidated. To facilitate studies on the role of TNF-alpha on the pathology associated with Salmonella infections in pigs, recombinant soluble porcine TNF receptor type I (rspTNF-RI) and soluble TNF receptor type I fused to the Fc region of porcine IgG1 (rspTNF-RI-IgG) were expressed in insect cells using a baculovirus expression system. The proteins were secreted into the cell culture media and purified by anti-soluble porcine TNF-RI antibody and protein G affinity chromatography, respectively. The yield of protein using this method was approximately 1.5mg rspTNF-RI and 4mg rspTNF-RI-IgG/L of cell culture medium. In in vitro assays, rspTNF-RI-IgG was approximately 10-fold (0.97 vs. 10.00pmol/ml) more effective than rspTNF-RI at completely inhibiting the cytotoxic activity of 500U of recombinant porcine TNF-alpha on 3 x 10(4) WEHI 164 murine fibrosarcoma, clone 13, cells. Compared to previously described methods, this method yields significantly more biologically active rspTNF-RI.

Segmented filamentous bacteria interact with intraepithelial mononuclear cells.

Segmented filamentous bacteria (SFB) are found in multiple species and play an important role in the development of mucosal immunity. The mechanism by which the bacteria interact with the immune system has not been well defined. We provide morphologic evidence of direct interaction between SFB and intraepithelial mononuclear cells.