Persistence of porcine reproductive and respiratory syndrome virus and porcine circovirus type 2 in bacterial biofilms

The aim of this pilot project was to investigate association of viruses with bacterial biofilms. Our preliminary data indicate that important viral pathogens of swine, namely, porcine reproductive and respiratory syndrome virus and porcine circovirus type 2, can associate with and persist within bacterial biofilms for several days

The use of personalized medicine for patient selection for renal transplantation: Physicians' views on the clinical and ethical implications

<p>Abstract</p> <p>Background</p> <p>The overwhelming scarcity of organs within renal transplantation forces researchers and transplantation teams to seek new ways to increase efficacy. One of the possibilities is the use of personalized medicine, an approach based on quantifiable and scientific factors that determine the global immunological risk of rejection for each patient. Although this approach can improve the efficacy of transplantations, it also poses a number of ethical questions.</p> <p>Methods</p> <p>The qualitative research involved 22 semi-structured interviews with nephrologists involved in renal transplantation, with the goal of determining the professionals' views about calculating the global immunological risk and the attendant ethical issues.</p> <p>Results</p> <p>The results demonstrate a general acceptance of this approach amongst the participants in the study. Knowledge of each patient's immunological risk could improve treatment and the post-graft follow-up. On the other hand, the possibility that patients might be excluded from transplantation poses a significant ethical issue. This approach is not seen as something entirely new, given the fact that medicine is increasingly scientific and evidence-based. Although renal transplantation incorporates scientific data, these physicians believe that there should always be a place for clinical judgment and the physician-patient relationship.</p> <p>Conclusions</p> <p>The participants see the benefits of including the calculation of the global immunological risk within transplantation. Such data, being more precise and rigorous, could be of help in their clinical work. However, in spite of the use of such scientific data, a place must be retained for the clinical judgment that allows a physician to make decisions based on medical data, professional expertise and knowledge of the patient. To act in the best interests of the patient is key to whether the calculation of the global immunological risk is employed.</p

Actinobacillus pleuropneumoniae induces SJPL cell cycle arrest in G2/M-phase and inhibits porcine reproductive and respiratory syndrome virus replication

Background: Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most important pathogens in the swine industry and causes important economic losses. No effective antiviral drugs against it are commercially available. We recently reported that the culture supernatant of Actinobacillus pleuropneumoniae, the porcine pleuropneumonia causative agent, has an antiviral activity in vitro against PRRSV in SJPL cells. Objectives of this study were (i) to identify the mechanism behind the antiviral activity displayed by A. pleuropneumoniae and (ii) to characterize the active molecules present in the bacterial culture supernatant. Methods: Antibody microarray analysis was used in order to point out cellular pathways modulated by the A. pleuropneumoniae supernatant. Subsequent, flow cytometry analysis and cell cycle inhibitors were used to confirm antibody microarray data and to link them to the antiviral activity of the A. pleuropneumoniae supernatant. Finally, A. pleuropneumoniae supernatant characterization was partially achieved using mass spectrometry. Results: Using antibody microarray, we observed modulations in G2/M-phase cell cycle regulation pathway when SJPL cells were treated with A. pleuropneumoniae culture supernatant. These modulations were confirmed by a cell cycle arrest at the G2/M-phase when cells were treated with the A. pleuropneumoniae culture supernatant. Furthermore, two G2/M-phase cell cycle inhibitors demonstrated the ability to inhibit PRRSV infection, indicating a potential key role for PRRSV infection. Finally, mass spectrometry lead to identify two molecules (m/z 515.2 and m/z 663.6) present only in the culture supernatant. Conclusions: We demonstrated for the first time that A. pleuropneumoniae is able to disrupt SJPL cell cycle resulting in inhibitory activity against PRRSV. Furthermore, two putative molecules were identified from the culture supernatant. This study highlighted the cell cycle importance for PRRSV and will allow the development of new prophylactic or therapeutic approaches against PRRSV

Effects of growth conditions on biofilm formation by Actinobacillus pleuropneumoniae

Biofilm formation is an important virulence trait of many bacterial pathogens. It has been reported in the literature that only two of the reference strains of the swine pathogen Actinobacillus pleuropneumoniae, representing serotypes 5b and 11, were able to form biofilm in vitro. In this study, we compared biofilm formation by the serotype 1 reference strain S4074 of A. pleuropneumoniae grown in five different culture media. We observed that strain S4074 of A. pleuropneumoniae is able to form biofilms after growth in one of the culture conditions tested brain heart infusion (BHI medium, supplier B). Confocal laser scanning microscopy using a fluorescent probe specific to the poly-N-acetylglucosamine (PGA) polysaccharide further confirmed biofilm formation. In accordance, biofilm formation was susceptible to dispersin B, a PGA hydrolase. Transcriptional profiles of A. pleuropneumoniae S4074 following growth in BHI-B, which allowed a robust biofilm formation, and in BHI-A, in which only a slight biofilm formation was observed, were compared. Genes such as tadC, tadD, genes with homology to autotransporter adhesins as well as genes pgaABC involved in PGA biosynthesis and genes involved in zinc transport were up-regulated after growth in BHI-B. Interestingly, biofilm formation was inhibited by zinc, which was found to be more present in BHI-A (no or slight biofilm) than in BHI-B. We also observed biofilm formation in reference strains representing serotypes 3, 4, 5a, 12 and 14 as well as in 20 of the 37 fresh field isolates tested. Our data indicate that A. pleuropneumoniae has the ability to form biofilms under appropriate growth conditions and transition from a biofilm-positive to a biofilm-negative phenotype was reversible

Actinobacillus pleuropneumoniae Possesses an Antiviral Activity against Porcine Reproductive and Respiratory Syndrome Virus

Pigs are often colonized by more than one bacterial and/or viral species during respiratory tract infections. This phenomenon is known as the porcine respiratory disease complex (PRDC). Actinobacillus pleuropneumoniae (App) and porcine reproductive and respiratory syndrome virus (PRRSV) are pathogens that are frequently involved in PRDC. The main objective of this project was to study the in vitro interactions between these two pathogens and the host cells in the context of mixed infections. To fulfill this objective, PRRSV permissive cell lines such as MARC-145, SJPL, and porcine alveolar macrophages (PAM) were used. A pre-infection with PRRSV was performed at 0.5 multiplicity of infection (MOI) followed by an infection with App at 10 MOI. Bacterial adherence and cell death were compared. Results showed that PRRSV preinfection did not affect bacterial adherence to the cells. PRRSV and App co-infection produced an additive cytotoxicity effect. Interestingly, a pre-infection of SJPL and PAM cells with App blocked completely PRRSV infection. Incubation of SJPL and PAM cells with an App cell-free culture supernatant is also sufficient to significantly block PRRSV infection. This antiviral activity is not due to LPS but rather by small molecular weight, heat-resistant App metabolites (,1 kDa). The antiviral activity was also observed in SJPL cells infected with swine influenza virus but to a much lower extent compared to PRRSV. More importantly, the PRRSV antiviral activity of App was also seen with PAM, the cells targeted by the virus in vivo during infection in pigs. The antiviral activity might be due, at least in part, to the production of interferon c. The use of in vitro experimental models to study viral and bacterial co-infections will lead to a better understanding of the interactions between pathogens and their host cells, and could allow the development of novel prophylactic and therapeutic tools

Escherichia coli heat-stable enterotoxin b (STb) in vivo internalization within rat intestinal epithelial cells

Heat-stable enterotoxin b (STb) is a low molecular weight toxin known to bind sulfatide, its receptor. The fate of STb bound to rat intestinal epithelium cells was followed using an anti-toxin gold labeled assay and transmission electron microscopy. The data suggest that STb toxin and the fusion protein maltose binding protein (MBP)-STb were internalized whereas its mutant I41E-M42R with reduced hydrophobicity did not show internalization. There was a significant difference in the mean of gold particles per field between rat intestine incubated with STb or the fusion protein MBP-STb and the negative control consisting of intestine incubated with PBS alone. No subcellular compartment seems to be particularly aimed by the toxin as gold particles were randomly distributed within the cell.Internalisation in vivo de l'entérotoxine b (STb) d'Escherichia coli dans les cellules épithéliales d'intestin de rat. L'entérotoxine b thermostable (STb) est une toxine de faible masse moléculaire qui se lie au sulfatide, son récepteur. À l'aide d'un essai avec un anticorps anti-STb marqué à l'or suivi d'une visualisation en microscopie électronique, nous avons observé les évènements suivant l'attachement de STb aux cellules épithéliales d'intestin de rat. La toxine STb et la protéine de fusion Maltose Binding Protein-STb (MBP-STb) ont été internalisées tandis que le mutant I41E-M42R avec une hydrophobicité réduite ne présentait pas d'internalisation. Nous avons observé une différence significative de la moyenne de particules d'or par champ entre l'intestin de rat incubé avec STb ou la protéine de fusion MBP-STb et le contrôle négatif, soit le tampon PBS seul. Aucun organelle cellulaire ne semble particulièrement visé par la toxine puisque les particules d'or étaient distribuées aléatoirement dans la cellule