Biomedical subjects

Isabelle P Oswald

Publications and source records attributed to Isabelle P Oswald.

16 recordsLinked to original sources

PubMed2006

The inability of Byssochlamys fulva to produce patulin is related to absence of 6-methylsalicylic acid synthase and isoepoxydon dehydrogenase genes.

Byssochlamys species are responsible for spoilage and degradation of fruits and silages. Under specific conditions they are able to produce mycotoxins. The aim of this study was to evaluate the potential of 19 different strains of Byssochlamys nivea and Byssochlamys fulva to produce patulin in relation with the presence of two genes involved in the patulin biosynthesis pathways in the genome of these fungal strains. The strains were characterized by macroscopic, microscopic examinations, internal transcribed spacer (ITS) rRNA and beta-tubulin fragment amplification and sequencing. All of the 8 B. nivea strains tested produced patulin. By contrast, none of the 11 strains of B. fulva produce this toxin. Two genes of the patulin biosynthetic pathway, a polyketide synthase (pks) and the isoepoxydon dehydrogenase (idh) were cloned from B. nivea. The deduced amino acid sequence of the polyketide synthase was 74% identical to the 6-methylsalicylic acid synthase gene of Penicillium griseofulvum and had the five functional domains characteristic of fungal type I polyketide synthases (beta-ketosynthase, acyltransferase, dehydratase, beta-ketoreductase and acyl carrier protein). The complete coding sequence of idh gene displayed after translation 88% of identity with P. griseofulvum IDH and 85% with P. expansum IDH, respectively. Both pks and idh messengers were strongly co-expressed during the production of 6-methylsalicylic acid and patulin. The presence of these genes was then investigated in the genome of B. nivea and B. fulva strains by PCR. All B. nivea strains possess the two genes, by contrast none of the B. fulva strains display these genes. The absence of 6-methylsalicylic acid and isoepoxydon dehydrogenase genes can explain the inability of B. fulva to produce patulin. In conclusion, B. fulva don't seem to be responsible for the occurrence of patulin by lack of genes.

Acyltransferases↗

PubMed2006

Cytokine mRNA profiles in pigs exposed prenatally and postnatally to Schistosoma japonicum.

The pig is a natural host for Schistosoma japonicum and a useful animal model of human infection. The aim of the present study was to assess the differences between the cytokine profiles in prenatally or postnatally S. japonicum exposed pigs. Seven prenatally exposed pigs, 7 postnatally exposed pigs and 4 uninfected control pigs were compared 27 weeks post exposure. Variables included worm burdens, tissue egg counts, liver pathology and mRNA levels of IL-2, IL-4, IL-10, IL-12, TNF-alpha, TGF-beta1 and IFN-gamma in the liver and the caecum, assessed by RT-PCR. Infection intensity and level of septal fibrosis were significantly higher in the postnatal group compared to the prenatal group (P < 0.05). A significant increase of IL-4 (P < 0.01), IL-10 (P < 0.01), IL-12 (P < 0.01) and TNF-alpha (P < 0.05) mRNA level was also observed in the caecum of prenatally infected animals compared to the control group (P < 0.01). The prenatal group showed higher levels of TGF-beta1 in the liver compared with the postnatally infected group (P< 0.05) and the control group (P< 0.01). This suppressive immune response correlated with previously reported low hepatic pathogenesis in prenatally exposed pigs.

Animals↗

PubMed2006

Swine infection with Trichinella spiralis: Comparative analysis of the mucosal intestinal and systemic immune responses.

The immune protective response developed by swine against Trichinella spiralis is not yet fully understood, particularly at the mucosal level. This study aimed to characterise intestinal immunity to T. spiralis by comparison with the systemic response in specifically pathogen-free pigs. For this purpose, the kinetics of cytokine and antibody production were assessed in the intestinal mucosa and serum of swine infected with T. spiralis for up to 60 days post-infection (dpi). An ex vivo model of jejunum mucosa culture was used to collect the supernatant as a source of antibodies (Abs). Mucosal antibodies were observed by Western blot from 15 dpi, while serum antibodies were expressed from 20 dpi. Both sources of antibodies initially recognized a 110 kDa protein, followed by the identification of 35, 43/46 and 55/59 kDa proteins. IgG1 and IgA antibodies were strongly expressed within the mucosa. The expression levels of Type 1 (IFN-gamma, IL-12), Type 2 (IL-4, IL-6), pro-inflammatory (TNF-alpha) and regulatory (IL-10, TGF-beta) cytokines were assessed by RT-PCR in the intestinal mucosa and spleen. Both IL-10 and IFN-gamma mRNA levels were increased in mucosa, whereas IL-6 and IL-12 mRNA were expressed in spleen. Taken together, these results demonstrated a mixed Type 1/Type 2 profile, the Type 2 profile being dominant in the mucosa.

Animals↗

PubMed2006

Mycotoxin fumonisin B1 selectively down-regulates the basal IL-8 expression in pig intestine: in vivo and in vitro studies.

Fumonisin B(1) (FB(1)) is a mycotoxin produced by Fusarium verticillioides and F. proliferatum, common contaminants of maize. FB(1) causes toxicological effects in laboratory and domestic animals including pigs. The gastrointestinal tract represents a barrier encountered by exogenous food compounds. The purpose of our study was to determine FB(1) effects on intestinal immune response. Nine recently weaned piglets orally received 0.5 mg of purified toxin/kg of body weight/day for 7 days, while eight other animals were kept as controls. After necropsy, ileal samples were analyzed for five pro-inflammatory cytokines mRNA expression by RT-PCR. No difference was observed for IL-1beta, IL-6, IL-12 and TNF-beta mRNA levels between control and FB(1)-treated animals. In contrast, FB(1) treatment induced a significant down-regulation of the expression of IL-8 mRNA in the pig ilea. The effect of FB(1) on the IL-8 expression was also examined in the porcine intestinal epithelial cell line IPEC-1. FB(1) decreases the expression of IL-8, both at the mRNA and protein levels, in a dose-dependant manner. Taken together, our data demonstrate that FB(1) alters the intestinal immune response by decreasing the level of IL-8. This may contribute to the increased intestinal colonization by pathogenic Escherichia coli that was observed in FB(1)-treated pigs and may have implications for humans/animals consuming FB(1)-contaminated food/feed.

Animals↗

PubMed2006

Role of intestinal epithelial cells in the innate immune defence of the pig intestine.

The intestinal epithelium serves as a dynamic barrier, which in the course of its normal function, maintains regulated uptake of nutrients and water while excluding potential pathogens. Over the past decade many studies have also revealed the immunological importance of intestinal epithelial cells (IEC). IEC have developed a variety of mechanisms to reduce the risk of infection by invasive pathogens or damage by toxic compounds. The effective maintenance of a physical barrier function is dependent on the establishment of well-organised intercellular junctions and a constant state of regeneration/renewal of the epithelium. IEC also participate in the innate immune responsiveness of the intestine by their ability to secrete mucus and antimicrobial peptides. IEC are also able to secrete cytokines and to respond to exogenous chemokines. This review summarises the current knowledge of the innate immune mechanisms developed by porcine IEC.

Animals↗

PubMed2006

Sex-related differences in the immune response of weanling piglets exposed to low doses of fumonisin extract.

Fumonisin B1 (FB1) is a mycotoxin produced by Fusarium verticillioides, a fungus that commonly contaminates maize. Sex-related effects of FB1 have been observed with respect to carcinogenicity in rodents, to performances in pigs and immunosuppression in mice. In the present study the sex-related effect of FB1 on the pig immune response was determined. Female and castrated male piglets received for 28 d either control feed or feed contaminated with 8 mg FB1/kg feed in the form of F. verticillioides culture material. At day 7 and day 21, animals were immunised subcutaneously with a Mycoplasma agalactiae vaccine. Ingestion of FB1-contaminated feed significantly decreased weight gain in males but had no effect in females. No sex-related difference was observed in biochemical parameters, but a higher level of creatinine was noted in toxin-treated animals. FB1 also altered the pig immune response in a sex-specific manner. In males, ingestion of FB1-contaminated feed significantly decreased specific antibody levels after vaccination as well as the mRNA expression level of IL-10. In females, the toxin has no effect on specific antibodies or on cytokine mRNA levels. The results of the present study indicate that FB1 is immunosuppressive in pigs. The magnitude of this FB1-induced immunosuppression is highly dependent on sex, with males being more susceptible than females.

Animal Feed↗

PubMed2005

The effects of mycotoxins, fungal food contaminants, on the intestinal epithelial cell-derived innate immune response.

Mycotoxins are structurally diverse fungal metabolites that can contaminate a variety of dietary components consumed by animals and humans. It is considered that 25% of the world crop production is contaminated by mycotoxins. The clinical toxicological syndromes caused by ingestion of moderate to high amounts of mycotoxins and their effect on the immune system have been well characterized. However, no particular attention has been focused on the effects of mycotoxins on the local intestinal immune response. Because of their location, intestinal epithelial cells (IECs) could be exposed to high doses of mycotoxins. As a component of the innate local immune response, intestinal epithelial cells have developed a variety of mechanisms which act to reduce the risk of infection by microorganisms or intoxication by toxic compounds. This review summarises the innate immune response developed by intestinal epithelial cells and reports the literature concerning the effects of mycotoxins on them. Particularly, the effects of mycotoxins on the maintenance of a physical barrier by epithelial cells will be discussed together with their effect on extrinsic protective components of the innate intestinal immunity: mucus secretion, antimicrobial peptide generation, IgA and pro-inflammatory cytokine release.

Animals↗

PubMed2005

Oral exposure to culture material extract containing fumonisins predisposes swine to the development of pneumonitis caused by Pasteurellamultocida.

Fumonisin B(1) (FB(1)) is a mycotoxin produced by Fusarium verticillioides and F. proliferatum that commonly occurs in maize. In swine, consumption of contaminated feed induces liver damage and pulmonary edema. Pasteurella multocida is a secondary pathogen, which can generate a respiratory disorder in predisposed pigs. In this study, we examined the effect of oral exposure to fumonisin-containing culture material on lung inflammation caused by P. multocida. Piglets received by gavage a crude extract of fumonisin, 0.5mg FB(1)/kg body weight/day, for 7 days. One day later, the animals were instilled intratracheally with a non toxin producing type A strain of P. multocida and followed up for 13 additional days. Pig weight and cough frequency were measured throughout the experiment. Lung lesions, bronchoalveolar lavage fluid (BALF) cell composition and the expression of inflammatory cytokines were evaluated at the autopsy. Ingestion of fumonisin culture material or infection with P. multocida did not affect weight gain, induced no clinical sign or lung lesion, and only had minimal effect on BALF cell composition. Ingestion of mycotoxin extract increased the expression of IL-8, IL-18 and IFN-gamma mRNA compared with P. multocida infection that increased the expression of TNF-alpha. The combined treatment with fumonisin culture material and P. multocida delayed growth, induced cough, and increased BALF total cells, macrophages and lymphocytes. Lung lesions were significantly enhanced in these animals and consisted of subacute interstitial pneumonia. TNF-alpha, IFN-gamma and IL-18 mRNA expression was also increased. Taken together, our data showed that fumonisin culture material is a predisposing factor to lung inflammation. These results may have implications for humans and animals consuming FB(1) contaminated food or feed.

Animals↗

PubMed2005

Mycotoxin fumonisin B1 alters the cytokine profile and decreases the vaccinal antibody titer in pigs.

Fumonisin B1 (FB1), a mycotoxin produced by Fusarium verticillioides, may contaminate feed and food. In the present study, we investigated the effect of FB1 on the modulation of the cytokine profile and on the establishment of a vaccinal antibody response. In vitro investigations on pig peripheral blood mononuclear cells (PBMC) indicate that FB1 decreased interleukin-4 (IL-4) and increased interferon-gamma (IFN-gamma) synthesis at both the protein and mRNA levels. A short in vivo exposure (7 days) of weanling piglets to 1.5 mg/kg body weight of purified FB1 altered the cytokine balance in mesenteric lymph nodes and spleen similarly to the in vitro PBMC results. We also investigated the effect of FB1 on the antibody response during a vaccination process. A prolonged in vivo exposure (28 days) of weanling piglets to feed contaminated with 8 mg FB1/kg significantly decreased the expression of IL-4 mRNA by porcine whole blood cells and diminished the specific antibody titer after vaccination against Mycoplasma agalactiae. By contrast, ingestion of the contaminated feed had no effect on the serum concentration of the immunoglobulin subset (IgG, IgA, and IgM). Taken together, our data suggest that FB1 alters the cytokine profile and decreases the specific antibody response built during a vaccination protocol. These results may have implications for humans or animals eating contaminated food or feed.

Animals↗

PubMed2005

Byssochlamys nivea as a source of mycophenolic acid.

Byssochlamys species are responsible for spoilage and degradation of fruits and silages and can also produce the mycotoxin patulin. We analyzed secondary metabolite production by Byssochlamys nivea. Mycophenolic acid and its precursors, 5-methylorsellinic acid and 5,7-dihydroxy-4-methylphthalide, were identified in all of the B. nivea strains that we examined.

Ascomycota↗

PubMed2005

Host immune status influences the development of attaching and effacing lesions in weaned pigs.

Attaching and effacing Escherichia coli (AEEC) has been associated with naturally occurring attaching and effacing (A/E) lesions in weaned pigs, and although A/E lesions have been experimentally reproduced in newborn piglets, such lesions have been much more difficult to induce in older conventional pigs. Hence, the aim of this study was to examine the effect of oral administration of dexamethasone on the development of A/E lesions in weaned pigs challenged with a porcine enteropathogenic E. coli (PEPEC) strain and to investigate the involvement of local intestinal cytokine response. Dexamethasone, given orally at a dosage of 3 mg kg of body weight(-1), significantly enhanced both the colonization of the challenge strain and the prevalence of foci of intimately adherent bacteria, resulting in extensive A/E lesions in the ileum, cecum, and colon of challenged pigs. We also confirmed the expression of both intimin and Tir by PEPEC strain ECL1001 in A/E lesions in vivo, which is, to our knowledge, the first report of the involvement of the latter proteins in any AEEC infections in vivo. Moreover, semiquantitative reverse transcription-PCR demonstrated that interleukin 1beta (IL-1beta), IL-6, IL-8, and, to a lesser extent, IL-12p40 are significantly upregulated in the ileum following challenge with strain ECL1001, whereas dexamethasone blocks such upregulation. Taken together, our results strongly suggested that host immune status influences the development of A/E lesions in weaned pigs, and it appears that IL-1beta, IL-6, IL-8, and, to a lesser extent, IL-12p40 are expressed during infection of weaned pigs by PEPEC and may contribute to the natural resistance of the host against PEPEC infection.

Adhesins, Bacterial↗

PubMed2004

Development of a macroarray to specifically analyze immunological gene expression in swine.

DNA arrays are useful tools for simultaneously studying the expressions of a large number of genes. Herein, we describe the construction and the optimization of conditions for a low-density DNA macroarray specific for the porcine immune system. This specific DNA macroarray contains 63 gene products, including 20 cytokines, 11 chemokines, and 12 immunologically relevant receptors. It was constructed by designing gene-specific oligonucleotide primers from porcine sequences available in the EMBL or TIGR expressed sequence tag data bank and using primers from conserved regions of aligned sequences from other species for sequences unavailable for swine. Amplicons produced by reverse transcription-PCR were cloned, sequenced, and spotted onto nylon filters. A trial DNA array was first produced to optimize the intensity, specificity, and variability of signals from amplicons amplified with either gene-specific or universal primers. The DNA macroarray was then validated by comparing the gene expression profile of nonstimulated peripheral blood mononuclear cells (PBMCs) to that of phorbol 12-myristate 13-acetate and ionomycin (PMA-Iono)-stimulated PBMCs from three different animals over a 48-h time period. As already described for more conventional techniques, we showed that certain genes, such as those for CD40, gamma interferon, interleukin 2 (IL-2), the IL-2 receptor, and tumor necrosis factor alpha, were upregulated in PMA-Iono-stimulated PBMCs. A detailed analysis also indicated a downregulation of several genes which are expressed mainly by macrophages (IL-1, IL-8, AMCF-1, natural-resistance-associated macrophage protein, neutrophil chemotactic protein, DAP-12, and monocyte chemoattractant protein) in samples stimulated for 24 h with PMA-Iono compared to their levels of expression in control samples. These results indicate that the DNA macroarray that we constructed can be a useful tool for simultaneously monitoring the mRNA expression of immunologically relevant genes in different porcine samples.

Animals↗

PubMed2003

The mycotoxin fumonisin B1 alters the proliferation and the barrier function of porcine intestinal epithelial cells.

Fumonisin B1 (FB1) is a mycotoxin produced by Fusarium verticillioides (formerly F. moniliforme), a fungus that commonly contaminates maize. FB1 causes toxicological effects in laboratory and domestic animals including pigs. Because the gastrointestinal tract represents the first barrier met by exogenous food compounds, the purpose of this study was to investigate the effects of FB1 on IPEC-1, a porcine intestinal epithelial cell line. We first verified that low concentrations of FB1 did not exert any cytotoxic effect on IPEC-1. Indeed, significant LDH release was only observed for FB1 concentrations greater than 50 and 700 microM on proliferating and nonproliferating cells, respectively. We then demonstrated that FB1 inhibits proliferation of IPEC-1. Fluorescence-activated cell sorting (FACS) analysis of the cell cycle indicated that FB1 blocks the proliferation of intestinal cells in the G0/G1 phase. Similar results were obtained with LLC-PK1, a renal porcine epithelial cell line, which is considered to be a good model for studying FB1 in vitro effects. We have also assessed the effects of FB1 on the integrity of the barrier formed by the intestinal epithelium. We demonstrated that FB1 decreases the transepithelial electrical resistance (TEER) of IPEC-1 in a time- and dose-dependent manner. This effect was only noticed after a long exposure (8-12 days of treatment). FB1 induced the TEER decrease independently of the cell differentiation stage, and this effect was partially reversible. Taken together, our data indicate that FB1 alters the proliferation and the barrier function of intestinal cells. These results may have implications for humans and animals consuming FB1-contaminated food or feed.

Animals↗

PubMed2003

Cytokine mRNA expression profiles in lymphoid tissues of pigs naturally affected by postweaning multisystemic wasting syndrome.

Fifteen 8-week-old conventional pigs were selected from a farm where pigs were suffering from postweaning multisystemic wasting syndrome (PMWS). Ten of the animals were diseased pigs showing typical signs of PMWS (wasting and respiratory disorders) and positive for infection with porcine circovirus type 2 (PCV2), and the other five animals selected as controls were pen-mate, apparently healthy pigs. Blood samples and lymphoid tissues were taken from each animal for haematological, serological and histopathological studies. Also, cytokine mRNA expression of IL-1beta, IL-2, IL-4, IL-8, IL-10, IL-12p40 and IFN-gamma from inguinal and bronchial lymph nodes, tonsils, spleen and thymus was determined by semi-quantitative RT-PCR. Pigs suffering from PMWS showed severe alterations of haematological parameters such as anaemia, lymphopenia with decrease of CD8(+) and IgM(+) cells, monocytosis and neutrophilia. Also, extensive lymphocyte depletion and altered cytokine mRNA expression patterns were seen in most of the examined lymphoid organs. Those cytokine mRNA alterations were characterized by an overexpression of IL-10 mRNA in thymus and IFN-gamma mRNA in tonsils, and by decreases in the mRNA expression of several cytokines as IL-2 and IL-12p40 in the spleen, IL-4 in tonsils, and IFN-gamma, IL-10, IL-12p40 and IL-4 in inguinal lymph nodes. Also, the IL-10 mRNA overexpression was histologically associated with the thymic depletion and atrophy observed in PMWS pigs. In conclusion, the cytokine mRNA imbalance, specially the increased mRNA levels of IL-10 in the thymus, jointly with the histopathological and haematological disorders, are highly indicative of a T-cell immunosuppression, enhancing the notion that the immune system of PMWS-affected pigs is severely impaired.

Animals↗

PubMed2003

Mycotoxin fumonisin B1 increases intestinal colonization by pathogenic Escherichia coli in pigs.

Fumonisin B(1) (FB(1)) is a mycotoxin that commonly occurs in maize. FB(1) causes a variety of toxic effects in different animal species and has been implicated as a contributing factor of esophageal cancers in humans. In the present study, we examined the effect of dietary exposure to FB(1) on intestinal colonization by pathogenic Escherichia coli associated with extraintestinal infection. Three-week-old weaned pigs were given FB(1) by gavage as a crude extract or as a purified toxin at a dose of 0.5 mg/kg of body weight daily for 6 days. On the last day of the toxin treatment, the pigs were orally inoculated with an extraintestinal pathogenic E. coli strain. All animals were euthanized 24 h later, necropsies were performed, and tissues were taken for bacterial counts and light microscopic examination. Ingestion of FB(1) had only a minimal effect on animal weight gain, did not cause any macroscopic or microscopic lesions, and did not change the plasma biochemical profile. However, colonization of the small and large intestines by an extraintestinal pathogenic E. coli strain was significantly increased. Our results show that FB(1) is a predisposing factor to infectious disease and that the pig can be used as a model for the study of the consequences of ingesting mycotoxin-contaminated food.

Administration, Oral↗

PubMedDate not supplied

Pathophysiological changes occurring during Escherichia coli endotoxin and Pasteurella multocida challenge in piglets: relationship with cough and temperature and predicitive value for intensity of lesions.

The aims of this study were (1) to correlate cough and body temperature (BT) with the severity of bronchopneumonia in pigs, (2) to determine whether these clinical signs can be used to early diagnose bronchopneumonia and (3) to assess the predictive values of cough and BT regarding lung lesions. Bronchopneumonia was induced by administering E. coli endotoxin (LPS) combined with Pasteurella multocida type A (PmA) in the trachea of 13 piglets. Saline-instilled negative controls (n = 8), PmA inoculated (n = 6) and LPS instilled (n = 5) groups were also constituted. Cough and BT were recorded daily while the bronchopneumonia severity was assessed using bronchoalveolar lavage fluid (BALF) cytology, cytokines and measurement of lung lesion volume. Changes in expiratory breathing pattern were also measured (Penh). The combination of LPS and PmA induced a subacute bronchopneumonia characterised by macrophage, neutrophil, and lymphocyte infiltration, changes in Penh and an increase in the mRNA level of IFN-gamma while IL8, IL-18 and TNF-alpha mRNA levels remained unchanged. The daily body weight gain of infected animals was significantly reduced. Cough and BT changes were proportional to the intensity of the lung inflammatory process, functional respiratory changes and to the extent of macroscopic lesions. When comparing the individual values of cough and BT to thresholds defined for both parameters, an early diagnosis of pneumonia was possible. Considering the pooled data of each group, it was possible to define thresholds allowing an early segregation between the groups of diseased and healthy piglets. The daily values of cough and BT were predictive for the volume of lung lesions recorded at the end of the trial. In conclusion, cough and BT appear as potential indicators for the intensity and the evolution of the respiratory disease. They also seem to be good predictors for the magnitude of lung lesions and weight gain recorded at the study endpoint.

Animals↗