The Type VI Secretion System Encoded in Salmonella Pathogenicity Island 19 Is Required for Salmonella enterica Serotype Gallinarum Survival within Infected Macrophages

Salmonella enterica serotype Gallinarum is the causative agent of fowl typhoid, a disease characterized by high morbidity and mortality that causes major economic losses in poultry production. We have reported that S. Gallinarum harbors a type VI secretion system (T6SS) encoded in Salmonella pathogenicity island 19 (SPI-19) that is required for efficient colonization of chicks. In the present study, we aimed to characterize the SPI-19 T6SS functionality and to investigate the mechanisms behind the phenotypes previously observed in vivo. Expression analyses revealed that SPI-19 T6SS core components are expressed and produced under in vitro bacterial growth conditions. However, secretion of the structural/secreted components Hcp1, Hcp2, and VgrG to the culture medium could not be determined, suggesting that additional signals are required for T6SS-dependent secretion of these proteins. In vitro bacterial competition assays failed to demonstrate a role for SPI-19 T6SS in interbacterial killing. In contrast, cell culture experiments with murine and avian macrophages (RAW264.7 and HD11, respectively) revealed production of a green fluorescent protein-tagged version of VgrG soon after Salmonella uptake. Furthermore, infection of RAW264.7 and HD11 macrophages with deletion mutants of SPI-19 or strains with genes encoding specific T6SS core components (clpV and vgrG) revealed that SPI-19 T6SS contributes to S. Gallinarum survival within macrophages at 20 h postuptake. SPI-19 T6SS function was not linked to Salmonella-induced cytotoxicity or cell death of infected macrophages, as has been described for other T6SS. Our data indicate that SPI-19 T6SS corresponds to a novel tool used by Salmonella to survive within host cells.     

Average spectral power changes at the hippocampal electroencephalogram in schizophrenia model induced by ketamine

The use of ketamine (Ket) as a pharmacological model of schizophrenia is an important tool for understanding the main mechanisms of glutamatergic regulated neural oscillations. Thus, the aim of the current study was to evaluate Ket‐induced changes in the average spectral power using the hippocampal quantitative electroencephalography (QEEG). To this end, male Wistar rats were submitted to a stereotactic surgery for the implantation of an electrode in the right hippocampus. After three days, the animals were divided into four groups that were treated for 10 consecutive days with Ket (10, 50, or 100 mg/kg). Brainwaves were captured on the 1st or 10th day, respectively, to acute or repeated treatments. The administration of Ket (10, 50, or 100 mg/kg), compared with controls, induced changes in the hippocampal average spectral power of delta, theta, alpha, gamma low or high waves, after acute or repeated treatments. Therefore, based on the alterations in the average spectral power of hippocampal waves induced by Ket, our findings might provide a basis for the use of hippocampal QEEG in animal models of schizophrenia.     

HLA-DR antibodies in transfusion-related acute lung injury (TRALI): a case report.

Transfusion-related acute lung injury (TRALI) is a serious adverse consequence of blood product transfusion. Cases of TRALI have gone unrecognized or misdiagnosed, since the symptoms can be confused with other transfusion-related events or with non-transfusion related comorbidities. Suspected cases of TRALI may be insufficiently investigated, and mild or moderate cases may not be investigated or reported at all. We report here the case of a 73-year man who developed TRALI following a transfusion of packed red blood cells (pRBCs) mediated by HLA class II antibodies (HLA-DR) detected by luminex technology. A very few cases of TRALI have been described being caused by HLA class II antibodies without the simultaneous presence of anti-HLA class I antibodies. Technology for antibody detection has increased the power and the specificity, especially with the use of flow cytometry with a better definition of the antigen/antibody pairs that have resulted in TRALI episodes. In this sense, HLA class II antibodies can exactly be detected with these methods and have surely been underestimated until now.     

Inhibition of dendritic cell maturation by malaria is dose dependent and does not require Plasmodium falciparum erythrocyte membrane protein 1

Red blood cells infected with Plasmodium falciparum (iRBCs) have been shown to modulate maturation of human monocyte-derived dendritic cells (DCs), interfering with their ability to activate T cells. Interaction between Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) and CD36 expressed by DCs is the proposed mechanism, but we show here that DC modulation does not require CD36 binding, PfEMP1, or contact between DCs and infected RBCs and depends on the iRBC dose. iRBCs expressing a PfEMP1 variant that binds chondroitin sulfate A (CSA) but not CD36 were phagocytosed, inhibited lipopolysaccharide (LPS)-induced phenotypic maturation and cytokine secretion, and abrogated the ability of DCs to stimulate allogeneic T-cell proliferation. CD36- and CSA-binding iRBCs showed comparable inhibition. P. falciparum lines rendered deficient in PfEMP1 expression by targeted gene knockout or knockdown also inhibited LPS-induced phenotypic maturation, and separation of DCs and iRBCs in transwells showed that inhibition was not contact dependent. Inhibition was observed at an iRBC:DC ratio of 100:1 but not at a ratio of 10:1. High doses of iRBCs were associated with apoptosis of DCs, which was not activation induced. Lower doses of iRBCs stimulated DC maturation sufficient to activate autologous T-cell proliferation. In conclusion, modulation of DC maturation by P. falciparum is dose dependent and does not require interaction between PfEMP1 and CD36. Inhibition and apoptosis of DCs by high-dose iRBCs may or may not be physiological. However, our observation that low-dose iRBCs initiate functional DC maturation warrants reevaluation and further investigation of DC interactions with blood-stage P. falciparum.     

CagA antibodies as a marker of virulence in chilean patients with Helicobacter pylori infection

BACKGROUND: The bacterial and host factors that influence the clinical outcomes of the Helicobacter pylori infection have not been fully identified. Cytotoxin-associated gene product (CagA), one of the virulence factors, has been associated with a more aggressive form of infection. The authors studied the relationship between CagA status and clinical outcome in Chilean children and adults with H. pylori infection. METHODS: One hundred eighty consecutive patients undergoing upper gastrointestinal endoscopic analysis were enrolled after informed consent was obtained. Rapid urease test and histologic analysis were used to detect H. pylori infection. IgA and IgG antibodies to H. pylori whole cell antigen preparation and IgG antibodies to CagA were measured by enzyme-linked immunosorbent assay (ELISA). RESULTS: H. pylori infection was detected in 42% of the patients by biopsy or urease test and in 38% and 20% of patients by IgG and IgA antibodies, respectively. The prevalence of H. pylori either by the invasive or the serologic tests was directly related to patient age. Among patients with H. pylori, there was no significant association between age and prevalence of CagA. Nearly 70% of the patients with H. pylori and peptic ulcer disease had CagA-positive strains. In contrast, only 49% of the patients with chronic gastritis alone had CagA-positive strains (P < 0.05). CONCLUSIONS: In Chile, patients infected with H. pylori have a proportion of CagA-positive strains similar to that reported in developed countries. CagA prevalence was not significantly different in adults and children infected with H. pylori, suggesting that variations in clinical outcome may be related to host immune or environmental factors.