An implantable carotid sinus baroreflex activating system: surgical technique and short-term outcome from a multi-center feasibility trial for the treatment of resistant hypertension

OBJECTIVES: To assess perioperative outcomes and blood pressure (BP) responses to an implantable carotid sinus baroreflex activating system being investigated for the treatment of resistant hypertension. METHODS: We report on the first seventeen patients enrolled in a multicenter study. Bilateral perivascular carotid sinus electrodes (CSL) and a pulse generator (IPG) are permanently implanted. Optimal placement of the CSL is determined by intraoperative BP responses to test activations. Acute BP responses were tested postoperatively and during the first four months of follow-up. RESULTS: Prior to implant, BP was 189.6+/-27.5/110.7+/-15.3 mmHg despite stable therapy (5.2+/-1.8 antihypertensive drugs). The mean procedure time was 202+/-43 minutes. No perioperative strokes or deaths occurred. System tests performed 1 or up to 3 days postoperatively resulted in significant (all p < or = 0.0001) mean maximum reduction, with standard deviations and 95% confidence limits for systolic BP, diastolic BP and heart rate of 28+/-22 (17, 39) mmHg, 16+/-11 (10, 22) mmHg and 8+/-4 (6, 11) BPM, respectively. Repeated testing during 3 months of therapeutic electrical activation demonstrated a durable response. CONCLUSIONS: These preliminary data suggest an acceptable safety of the procedure with a low rate of adverse events and support further clinical development of baroreflex activation as a new concept to treat resistant hypertension.

Viral Escape in the Central Nervous System with Multidrug-Resistant Human Immunodeficiency Virus-1

In this study, we report the case of a patient infected with human immunodeficiency virus (HIV)-1 who developed ataxia and neurocognitive impairment due to viral escape within the central nervous system (CNS) with a multidrug-resistant HIV-1 despite long-term viral suppression in plasma. Antiretroviral therapy optimization with drugs with high CNS penetration led to viral suppression in the CSF, regression of ataxia, and improvement of neurocognitive symptoms.

Fic domain-catalyzed adenylylation: insight provided by the structural analysis of the type IV secretion system effector BepA

Numerous bacterial pathogens subvert cellular functions of eukaryotic host cells by the injection of effector proteins via dedicated secretion systems. The type IV secretion system (T4SS) effector protein BepA from Bartonella henselae is composed of an N-terminal Fic domain and a C-terminal Bartonella intracellular delivery domain, the latter being responsible for T4SS-mediated translocation into host cells. A proteolysis resistant fragment (residues 10-302) that includes the Fic domain shows autoadenylylation activity and adenylyl transfer onto Hela cell extract proteins as demonstrated by autoradiography on incubation with α-[(32)P]-ATP. Its crystal structure, determined to 2.9-Å resolution by the SeMet-SAD method, exhibits the canonical Fic fold including the HPFxxGNGRxxR signature motif with several elaborations in loop regions and an additional β-rich domain at the C-terminus. On crystal soaking with ATP/Mg(2+), additional electron density indicated the presence of a PP(i) /Mg(2+) moiety, the side product of the adenylylation reaction, in the anion binding nest of the signature motif. On the basis of this information and that of the recent structure of IbpA(Fic2) in complex with the eukaryotic target protein Cdc42, we present a detailed model for the ternary complex of Fic with the two substrates, ATP/Mg(2+) and target tyrosine. The model is consistent with an in-line nucleophilic attack of the deprotonated side-chain hydroxyl group onto the α-phosphorus of the nucleotide to accomplish AMP transfer. Furthermore, a general, sequence-independent mechanism of target positioning through antiparallel β-strand interactions between enzyme and target is suggested.

A metalloproteinase karilysin present in the majority of Tannerella forsythia isolates inhibits all pathways of the complement system

Tannerella forsythia is a poorly studied pathogen despite being one of the main causes of periodontitis, which is an inflammatory disease of the supporting structures of the teeth. We found that despite being recognized by all complement pathways, T. forsythia is resistant to killing by human complement, which is present at up to 70% of serum concentration in gingival crevicular fluid. Incubation of human serum with karilysin, a metalloproteinase of T. forsythia, resulted in a decrease in bactericidal activity of the serum. T. forsythia strains expressing karilysin at higher levels were more resistant than low-expressing strains. Furthermore, the low-expressing strain was significantly more opsonized with activated complement factor 3 and membrane attack complex from serum compared with the other strains. The high-expressing strain was more resistant to killing in human blood. The protective effect of karilysin against serum bactericidal activity was attributable to its ability to inhibit complement at several stages. The classical and lectin complement pathways were inhibited because of the efficient degradation of mannose-binding lectin, ficolin-2, ficolin-3, and C4 by karilysin, whereas inhibition of the terminal pathway was caused by degradation of C5. Interestingly, karilysin was able to release biologically active C5a peptide in human plasma and induce migration of neutrophils. Importantly, we detected the karilysin gene in >90% of gingival crevicular fluid samples containing T. forsythia obtained from patients with periodontitis. Taken together, the newly characterized karilysin appears to be an important virulence factor of T. forsythia and might have several important implications for immune evasion.

Emergence of linezolid-resistant Staphylococcus aureus after prolonged treatment of cystic fibrosis patients in Cleveland, Ohio

Linezolid (LZD)-resistant Staphylococcus aureus (LRSA) isolates were monitored from 2000 to 2009 in Cleveland, OH. LRSA first emerged in 2004 only in cystic fibrosis (CF) patients, with 11 LRSA-infected CF patients being identified by 2009. LRSA was isolated from 8 of 77 CF patients with S. aureus respiratory tract infection treated with LZD from 2000 to 2006. Analysis of clinical data showed that the 8 CF patients with LRSA received more LZD courses (18.8 versus 5.9; P = 0.001) for a longer duration (546.5 versus 211.9 days; P < 0.001) and had extended periods of exposure to LZD (83.1 versus 30.1 days/year; P < 0.001) than the 69 with LZD-susceptible isolates. Five LRSA isolates included in the clinical analysis (2000 to 2006) and three collected in 2009 were available for molecular studies. Genotyping by repetitive extrapalindromic PCR and pulsed-field gel electrophoresis revealed that seven of these eight LRSA strains from unique patients were genetically similar. By multilocus sequence typing, all LRSA isolates were included in clonal complex 5 (seven of sequence type 5 [ST5] and one of ST1788, a new single-locus variant of ST5). However, seven different variants were identified by spa typing. According to the Escherichia coli numbering system, seven LRSA isolates contained a G2576T mutation (G2603T, S. aureus numbering) in one to four of the five copies of domain V of the 23S rRNA genes. One strain also contained a mutation (C2461T, E. coli numbering) not previously reported. Two strains, including one without domain V mutations, possessed single amino acid substitutions (Gly152Asp or Gly139Arg) in the ribosomal protein L3 of the peptidyltransferase center, substitutions not previously reported in clinical isolates. Emergence of LRSA is a serious concern for CF patients who undergo prolonged courses of LZD therapy.

Sustained acute voltage-dependent blood pressure decrease with prolonged carotid baroreflex activation in therapy-resistant hypertension

Chronic carotid baroreflex stimulation (Rheos system) has been shown to effectively reduce blood pressure in patients with resistant hypertension. Upon acute stimulation blood pressure also falls as a function of voltage. the aim of this study is to evaluate whether this voltage-dependent blood pressure decrease is preserved after long-term carotid baroreflex stimulation.

[How the bovine viral diarrhea virus outwits the immune system]

The interaction of bovine viral diarrhea virus (BVD virus) with its host has several unique features, most notably the capacity to infect its host either transiently or persistently. The transient infection stimulates an antiviral immune reaction similar to that seen in other transient viral infections. In contrast, being associated with immunotolerance specific for the infecting BVD viral strain, the persistent infection differs fundamentally from other persistent infections like those caused by lentiviruses. Whereas the latter are characterized by complex viral evasion of the host's adaptive immune response by mechanisms such as antigenic drift and interference with presentation of T cell epitopes, BVD virus avoids the immune response altogether by inducing both humoral and cellular immune tolerance. This is made possible by invasion of the fetus at an early stage of development. In addition to adaptive immunity, BVD virus also manipulates key elements of the host's innate immune response. The non-cytopathic biotype of BVD virus, which is capable of persistently infecting its host, fails to induce type I interferon. In addition, persistently infected cells are resistant to the induction of apoptosis by double-stranded RNA and do not produce interferon when treated with this pathogen-associated molecular pattern (PAMP) that signals viral infection. Moreover, when treated with interferon, cells persistently infected with non-cytopathic BVD virus do not clear the virus. Surprisingly, however, despite this lack of effect on persistent infection, interferon readily induces an antiviral state in these cells, as shown by the protection against infection by unrelated viruses. Overall, BVD virus manipulates the host's interferon defense in a manner that optimises its chances of maintaining the persistent infection as well as decreasing the risks that heterologous viral infections may carry for the host. Thus, since not all potential host cells are infected in animals persistently infected with BVD virus, heterologous viruses replicating in cells uninfected with BVD virus will still trigger production of interferon. Interferon produced by such cells will curtail the replication of heterologous viruses only, be that in cells already infected with BVD virus, or in cells in which the heterologous virus may replicate alone. From an evolutionary viewpoint, this strategy clearly enhances the chances of transmission of BVD virus to new hosts, as it attenuates the negative effects that a global immunosuppression would have on the survival of persistently infected animals.

Vancomycin acts synergistically with gentamicin against penicillin-resistant pneumococci by increasing the intracellular penetration of gentamicin

Vancomycin and gentamicin act synergistically against penicillin-resistant pneumococci in vitro and in experimental rabbit meningitis. The aim of the present study was to investigate the underlying mechanism of this synergism. The intracellular concentration of gentamicin was measured by using the following experimental setting. Bacterial cultures were incubated with either gentamicin alone or gentamicin plus vancomycin for a short period (15 min). The gentamicin concentration was determined before and after grinding of the cultures by using the COBAS INTEGRA fluorescence polarization system (Roche). The grinding efficacies ranged between 44 and 54%, as determined by viable cell counts. In the combination regimen the intracellular concentration of gentamicin increased to 186% compared to that achieved with gentamicin monotherapy. These data suggest that the synergy observed in vivo and in vitro is based on an increased intracellular penetration of the aminoglycoside, probably due to the effect of vancomycin on the permeability of the cell wall.

L-Selectin-deficient SJL and C57BL/6 mice are not resistant to experimental autoimmune encephalomyelitis

L-selectin has been suggested to play a role in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis. Here we demonstrate that L-selectin(-/-) SJL mice are susceptible to proteolipid protein (PLP)-induced EAE because the compromised antigen-specific T cell proliferation in peripheral lymph nodes is fully compensated by the T cell response raised in their spleen. Transfer of PLP-specific T cells into syngeneic recipients induced EAE independent of the presence or absence of L-selectin on PLP-specific T cells or in the recipient. Leukocyte infiltration into the central nervous system parenchyma was detectable independent of the mode of disease induction and the presence or absence of L-selectin. In addition, we found L-selectin(-/-) C57BL/6 mice to be susceptible to myelin oligodendrocyte glycoprotein-induced EAE. Taken together, we demonstrate that in SJL and C57BL/6 mice L-selectin is not required for EAE pathogenesis. The apparent discrepancy of our present observation to previous findings, demonstrating a role of L-selectin in EAE pathogenesis in C57BL/6 mice or myelin-basic protein (MBP)-specific TCR-transgenic B10.PL mice, may be attributed to background genes rather than L-selectin and to a unique role of L-selectin in EAE pathogenesis in MBP-TCR-transgenic mice.

Analysis of key molecules of the innate immune system in mammary epithelial cells isolated from marker-assisted and conventionally selected cattle

Mastitis is the most prevalent infectious disease in dairy herds. Breeding programs considering mastitis susceptibility were adopted as approaches to improve udder health status. In recent decades, conventional selection criteria based on phenotypic characteristics such as somatic cell score in milk have been widely used to select animals. Recently, approaches to incorporate molecular information have become feasible because of the detection of quantitative trait loci (QTL) affecting mastitis resistance. The aims of the study were to explore molecular mechanisms underlying mastitis resistance and the genetic mechanisms underlying a QTL on Bos taurus chromosome 18 found to influence udder health. Primary cell cultures of mammary epithelial cells from heifers that were selected for high or low susceptibility to mastitis were established. Selection based on estimated pedigree breeding value or on the basis of marker-assisted selection using QTL information was implemented. The mRNA expression of 10 key molecules of the innate immune system was measured using quantitative real-time PCR after 1, 6, and 24 h of challenge with heat-inactivated mastitis pathogens (Escherichia coli and Staphylococcus aureus) and expression levels in the high and low susceptibility groups were compared according to selection criteria. In the marker-assisted selection groups, mRNA expression in cells isolated from less-susceptible animals was significantly elevated for toll-like receptor 2, tumor necrosis factor-alpha, IL-1beta, IL-6, IL-8, RANTES (regulated upon activation, normal t-cell expressed and secreted), complement factor C3, and lactoferrin. In the estimated pedigree breeding value groups, mRNA expression was significantly elevated only for V-rel reticuloendotheliosis viral oncogene homolog A, IL-1 beta, and RANTES. These observations provide first insights into genetically determined divergent reactions to pathogens in the bovine mammary gland and indicate that the application of QTL information could be a successful tool for the selection of animals resistant to mastitis.

Temporal trends of extended-spectrum cephalosporin-resistant Escherichia coli and Klebsiella pneumoniae isolates in in- and outpatients in Switzerland, 2004 to 2011

Increasing trends for invasive infections with extended-spectrum cephalosporin-resistant (ESC-R) Enterobacteriaceae have been described in many countries worldwide. However, data on the rates of ESC-R isolates in non-invasive infections and in the outpatient setting are scarce. We used a laboratory-based nationwide surveillance system to compare temporal trends of ESC-R rates in Escherichia coli and Klebsiella pneumoniae for in- and outpatients in Switzerland. Our data showed a significant increase in ESC-R rates from 1% to 5.8% in E. coli (p<0.001) and from 1.1% to 4.4% in K. pneumoniae (p=0.002) during an eight-year period (2004–2011). For E. coli, the increase was significantly higher in inpatients (from 1.2% to 6.6%), in patients residing in eastern Switzerland (from 1.0% to 6.2%), in patients older than 45 years (from 1.2% to 6.7%), and in male patients (from 1.2% to 8.1%). While the increase in inpatients was linear (p<0.001) for E. coli, the increase of ESC R K. pneumoniae isolates was the result of multiple outbreaks in several institutions. Notably, an increasing proportion of ESC-R E. coli was co-resistant to both trimethoprim-sulfamethoxazole and quinolones (42% in 2004 to 49.1% in 2011, p=0.009), further limiting the available oral therapeutic options.

Ecosystem functions are resistant to extreme changes to rainfall regimes in a mesotrophic grassland

Major changes to rainfall regimes are predicted for the future but the effect of such changes on terrestrial ecosystem function is largely unknown. We created a rainfall manipulation experiment to investigate the effects of extreme changes in rainfall regimes on ecosystem functioning in a grassland system. We applied two rainfall regimes; a prolonged drought treatment (30 % reduction over spring and summer) and drought/downpour treatment (long periods of no rainfall interspersed with downpours), with an ambient control. Both rainfall manipulations included increased winter rainfall. We measured plant community composition, CO2 fluxes and soil nutrient availability. Plant species richness and cover were lower in the drought/downpour treatment, and showed little recovery after the treatment ceased. Ecosystem processes were less affected, possibly due to winter rainfall additions buffering reduced summer rainfall, which saw relatively small soil moisture changes. However, soil extractable P and ecosystem respiration were significantly higher in rainfall change treatments than in the control. This grassland appears fairly resistant, in the short term, to even the more extreme rainfall changes that are predicted for the region, although prolonged study is needed to measure longer-term impacts. Differences in ecosystem responses between the two treatments emphasise the variety of ecosystem responses to changes in both the size and frequency of rainfall events. Given that model predictions are inconsistent there is therefore a need to assess ecosystem function under a range of potential climate change scenarios.

Regulation of hematopoietic and leukemic stem cells by the immune system.

Hematopoietic stem cells (HSCs) are rare, multipotent cells that generate via progenitor and precursor cells of all blood lineages. Similar to normal hematopoiesis, leukemia is also hierarchically organized and a subpopulation of leukemic cells, the leukemic stem cells (LSCs), is responsible for disease initiation and maintenance and gives rise to more differentiated malignant cells. Although genetically abnormal, LSCs share many characteristics with normal HSCs, including quiescence, multipotency and self-renewal. Normal HSCs reside in a specialized microenvironment in the bone marrow (BM), the so-called HSC niche that crucially regulates HSC survival and function. Many cell types including osteoblastic, perivascular, endothelial and mesenchymal cells contribute to the HSC niche. In addition, the BM functions as primary and secondary lymphoid organ and hosts various mature immune cell types, including T and B cells, dendritic cells and macrophages that contribute to the HSC niche. Signals derived from the HSC niche are necessary to regulate demand-adapted responses of HSCs and progenitor cells after BM stress or during infection. LSCs occupy similar niches and depend on signals from the BM microenvironment. However, in addition to the cell types that constitute the HSC niche during homeostasis, in leukemia the BM is infiltrated by activated leukemia-specific immune cells. Leukemic cells express different antigens that are able to activate CD4(+) and CD8(+) T cells. It is well documented that activated T cells can contribute to the control of leukemic cells and it was hoped that these cells may be able to target and eliminate the therapy-resistant LSCs. However, the actual interaction of leukemia-specific T cells with LSCs remains ill-defined. Paradoxically, many immune mechanisms that evolved to activate emergency hematopoiesis during infection may actually contribute to the expansion and differentiation of LSCs, promoting leukemia progression. In this review, we summarize mechanisms by which the immune system regulates HSCs and LSCs.

Colonization with resistant microorganisms in patients transferred from abroad: who needs to be screened?

BACKGROUND While multi-drug resistant organisms (MDRO) are a global phenomenon, there are significant regional differences in terms of prevalence. Traveling to countries with a high MDRO prevalence increases the risk of acquiring such an organism. In this study we determined risk factors for MDRO colonization among patients who returned from a healthcare system in a high-prevalence area (so-called transfer patients). Factors predicting colonization could serve as screening criteria to better target those at highest risk. METHODS This screening study included adult patients who had been exposed to a healthcare system abroad or in a high-prevalence region in Switzerland over the past six months and presented to our 950-bed tertiary care hospital between January 1, 2012 and December 31, 2013, a 24-month period. Laboratory screening tests focused on Gram-negative MDROs and methicillin-resistant Staphylococcus aureus (MRSA). RESULTS A total of 235 transfer patients were screened and analyzed, of which 43 (18 %) were positive for an MDRO. Most of them yielded Gram-negative bacteria (42; 98 %), with only a single screening revealing MRSA (2 %); three screenings showed a combination of Gram-negative bacteria and MRSA. For the risk factor analysis we focused on the 42 Gram-negative MDROs. Most of them were ESBL-producing Escherichia coli and Klebsiella pneumoniae while only two were carbapenemase producers. In univariate analysis, factors associated with screening positivity were hospitalization outside of Europe (p < 0.001), surgical procedure in a hospital abroad (p = 0.007), and - on admission to our hospital - active infection (p = 0.002), antibiotic treatment (p = 0.014) and presence of skin lesions (p = 0.001). Only hospitalization outside of Europe (Odds Ratio, OR 3.2 (95 % CI 1.5- 6.8)) and active infection on admission (OR 2.7 (95 % CI 1.07- 6.6)) remained as independent predictors of Gram-negative MDRO colonization. CONCLUSION Our data suggest that a large proportion of patients (i.e., 82 %) transferred to Switzerland from hospitals in high MDRO prevalence areas are unnecessarily screened for MDRO colonization. Basing our screening strategy on certain criteria (such as presence of skin lesions, active infection, antibiotic treatment, history of a surgical procedure abroad and hospitalization outside of Europe) promises to be a better targeted and more cost-effective strategy.