Matteo Conti

Dynamics of the interaction between a fibronectin molecule and a living bacterium under mechanical force

Fibronectin (Fn) is an important mediator of bacterial invasions and of persistent infections like that of Staphylococcus epidermis. Similar to many other types of cell-protein adhesion, the binding between Fn and S. epidermidis takes place under physiological shear rates. We investigated the dynamics of the interaction between individual living S. epidermidis cells and single Fn molecules under mechanical force by using the scanning force microscope. The mechanical strength of this interaction and the binding site in the Fn molecule were determined. The energy landscape of the binding/unbinding process was mapped, and the force spectrum and the association and dissociation rate constants of the binding pair were measured. The interaction between S. epidermidis cells and Fn molecules is compared with those of two other protein/ligand pairs known to mediate different dynamic states of adhesion of cells under a hydrodynamic flow: the firm adhesion mediated by biotin/avidin interactions, and the rolling adhesion, mediated by L-selectin/P-selectin glycoprotein ligand-1 interactions. The inner barrier in the energy landscape of the Fn case characterizes a high-energy binding mode that can sustain larger deformations and for significantly longer times than the correspondent high-strength L-selectin/P-selectin glycoprotein ligand-1 binding mode. The association kinetics of the former interaction is much slower to settle than the latter. On this basis, the observations made at the macroscopic scale by other authors of a strong lability of the bacterial adhesions mediated by Fn under high turbulent flow are rationalized at the molecular level.

Staphylococcus epidermidis–fibronectin binding and its inhibition by heparin

Staphylococcus epidermidis is able to adhere onto biomaterials and to cause implant infections. Recently, host matrix proteins, which in vivo cover the implants, have been indicated as substrates for adhesion by specific bacterial adhesins. Here, the binding of S. epidermidis to fibronectin, a main protein of the extracellular matrix, and the effect of heparin on this interaction were studied by dynamic force spectroscopy (DFS). Novelties are that S. epidermidis strains analysed by DFS were clinical isolates from prosthesis-associated infections, genotyped and phenotyped for their adhesion properties to fibronectin and examined as living cells. Thus, fibronectin-binding staphylococci adhered to the fibronectin-coated substratum and formed a continuous layer assuring their contact with the fibronectin-coated cantilever tip during the approach-retraction cycles of the DFS measurements. Results show that only a single molecular binding site of fibronectin is involved in the interaction with S. epidermidis, that it takes place at the domain near the C-terminus and that it is specifically inhibited by heparin.

Changes in Serum Markers of Inflammation and Endothelial Activation in HIV-Infected Antiretroviral Naive Patients Starting A Treatment with Abacavir-Lamivudine or Tenofovir-Emtricitabine Plus Efavirenz

BACKGROUND The association between abacavir use and increased risk of myocardial infarction has been heavily debated, but cohort studies and randomized trials have provided conflicting results. Aim of our study is to compare the effect of abacavir and tenofovir on the inflammation and endothelial activation markers. METHODS We performed an observational study of HIV-infected naïve patients starting tenofovir/emtricitabine (group A) or abacavir/lamivudine (group B) plus efavirenz. In the present analysis, we measured serum levels of high-sensitivity C-reactive protein (hsCRP), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), soluble vascular adhesion molecule-1 (VCAM-1), soluble intercellular adhesion molecule-1 (ICAM-1), E-selectin and P-selectin at baseline and during a 48-week follow-up. RESULTS As a whole, 118 patients (93 males; mean age ± SD of 42.8 ± 10.1 years) were enrolled: 61 in group A and 57 in group B. In group A at weeks 24 and 48 the mean concentrations of IL-6, TNF-α, ICAM-1, VCAM-1, E-selectin and Pselectin decreased significantly in comparison with respective baseline values. In group B at week 24 a significant increase in mean values of these markers was reported in comparison with group A, but after 48 weeks they significantly decreased in group B too and no significant differences between groups A and B were found. CONCLUSION In our study, naïve patients starting tenofovir/emtricitabine or abacavir/lamivudine plus efavirenz showed after 48 weeks a significant and comparable decrease in serum concentrations of IL-6, TNF-α, ICAM-1, VCAM-1, Eselectin and P-selectin, while the mean level of hs-CRP did not change significantly in any group.

Improvement in renal function and bone mineral density after a switch from tenofovir/emtricitabine plus ritonavir-boosted protease inhibitor to raltegravir plus nevirapine: a pilot study.

BACKGROUND The antiretroviral regimens including tenofovir and a ritonavir-boosted protease inhibitor (r/PI) have been associated with a reduced bone mineral density (BMD), increased bone turnover markers and renal tubular dysfunction. METHODS An observational, prospective study was performed including HIV-1-infected, virologically suppressed patients treated with tenofovir/emtricitabine plus an r/PI for at least 12 months who switched to raltegravir plus nevirapine. The primary end point was changes after 48 weeks in estimated glomerular filtration rate (eGFR), prevalence of tubular dysfunction, BMD and concentration of two serum markers of bone turnover: collagen type-1 cross-linked C-telopeptide (CTX) and bone-specific alkaline phosphatase (BAP). RESULTS A total of 46 patients were enrolled: 78% were male, 96% were Caucasian, the mean age was 45 years and the mean CD4(+) T-lymphocyte count was 681 cells/mm(3). A renal impairment was present in 72% of patients and was the main reason for the switch. After 48 weeks, prevalence of proximal tubular dysfunction decreased significantly (-72%; P<0.001), whereas the mean value of eGFR did not change significantly. At the same time, after 48 weeks a significant increase in both lumbar spine and total hip BMD, T-score and Z-score was reported (+11.5% in lumbar spine T-score; P<0.001), and there was a significant reduction in both CTX and BAP mean serum concentrations (-15% and -13%, respectively; P<0.001). Two (4.3%) patients had virological failure due to suboptimal adherence and one (2.2%) subject discontinued treatment due to a skin rash. CONCLUSIONS Switching virologically suppressed patients from tenofovir/emtricitabine plus one r/PI to raltegravir plus nevirapine after 48 weeks significantly improved proximal tubular function, increased BMD and reduced serum markers of bone turnover.

Use of Daptomycin in Critically Ill Children With Bloodstream Infections and Complicated Skin and Soft-tissue Infections.

We report our clinical experience with the use of daptomycin, administered in the dosage of 8 mg/kg/d in 3 minutes, in treating 12 critically ill children younger than 12 years, with bloodstream infections (n = 9) and complicated skin and soft-tissue infections (n = 3). Mean treatment duration was 14 ± 5 days; microbiologic eradication was achieved in all patients, and no drug related adverse events occurred.

Dual Raltegravir-Darunavir/Ritonavir Combination in Virologically Suppressed HIV-1-Infected Patients on Antiretroviral Therapy Including a Ritonavir-Boosted Protease Inhibitor Plus Two Nucleoside/ Nucleotide Reverse Transcriptase Inhibitors

Background: Nucleoside reverse transcriptase inhibitor (NRTI)-sparing antiretroviral therapies may be useful in HIV-infected patients with resistance or intolerance to this class. Methods: We performed an observational study of patients on suppressive antiretroviral therapy containing two NRTIs plus one ritonavir-boosted protease inhibitor who switched to a dual regimen containing raltegravir (400 mg twice daily) and darunavir/ritonavir (800/100 mg once daily) and were followed-up for 48 weeks. Results: As a whole, 82 patients were enrolled. Mean duration of current regimen was 4.6 years and mean duration of plasma HIV RNA < 50 copies/mL before the switch was 46.2 months. Reason for simplification was toxicity in 76 patients and resistance to NRTIs in 13. After switching, the percentage of patients with HIV RNA < 50 copies/mL at week 48 was 92.7% in the intent-to-treat-exposed analysis and 97.6% in the per-protocol analysis. The switch led to a significant reduction in the mean triglyceride value (−85.2 mg/dL), in the prevalence of tubular proteinuria (−56%) and in the mean level of interleukin-6 (−0.94 pg/mL), with a significant increase in the mean phosphoremia (+0.58 mg/dL). Mean trough concentrations of both raltegravir and darunavir were within the therapeutic range. Two patients (2.4%) had virological failure due to suboptimal adherence and 4 subjects (4.9%) discontinued treatment due to adverse events, but no patients experienced Grade 3 or 4 adverse events. Conclusion: In our study, simplification to a dual therapy containing raltegravir plus darunavir/ritonavir after 48 weeks maintained viral suppression in more than 90% of patients and showed a good tolerability with a favourable effect on proteinuria, ipophosphoremia, and lipid metabolism.

Plasma concentrations of efavirenz, darunavir/ritonavir and raltegravir in HIV-HCV-coinfected patients without liver cirrhosis in comparison with HIV-monoinfected patients

Abstract Background: The objective of the study was to assess plasma concentrations of efavirenz, darunavir/ritonavir and raltegravir in patients with human immunodeficiency virus-hepatitis C virus (HIV-HCV)-coinfection without liver cirrhosis. Methods: In this observational, open-label study, adult HIV-infected outpatients treated with tenofovir/emtricitabine plus efavirenz (600 mg daily), darunavir/ritonavir (800/100 mg daily) or raltegravir (400 mg twice daily) for at least 4 weeks were asked to participate. Subjects with liver cirrhosis were excluded. The trough concentration (Ctrough) of darunavir/ritonavir and raltegravir and the mid-dose concentration (C12h) of efavirenz were assessed at steady state by a validated high-performance liquid chromatography (HPLC)-tandem mass spectrometry method. Results: A total of 96 HIV-positive patients were enrolled into the study. Thirty-four patients were treated with efavirenz, 33 with darunavir/ritonavir and 29 with raltegravir. The geometric mean plasma Ctrough [coefficient of variation (%)] of darunavir was comparable between HIV+/HCV+ and HIV+/HCV– subjects: 2644 ng/ml (155%) and 2491 ng/ml (139%), respectively (geometric mean ratio (GMR) = 0.81; 95% confidence interval (CI) = 0.79–1.56; p = 0.69). These values were comparable for raltegravir: 108 ng/ml (149%) in the HIV+/HCV+ group and 96 ng/ml (161%) in the HIV+/HCV– group (GMR = 0.84; 95% CI = 0.61–1.44; p = 0.72). On the contrary, the geometric mean plasma C12h of efavirenz was significantly higher among the 15 HIV+/HCV+ patients (1915 ng/ml, 159%) than among the 19 HIV+/HCV– patients (1505 ng/ml, 167%; GMR = 1.41; 95% CI = 1.19–1.71; p = 0.009). Conclusions: The mean plasma concentration of efavirenz was significantly higher in HCV-positive than in HCV-negative patients without liver cirrhosis, while the mean plasma levels of darunavir/ritonavir and raltegravir were comparable in both groups.

DUAL RALTEGRAVIR-ETRAVIRINE COMBINATION AS MAINTENANCE REGIMEN IN VIROLOGICALLY SUPPRESSED HIV-1-INFECTED PATIENTS.

Nucleoside reverse transcriptase inhibitor (NRTI)- and protease inhibitor (PI)-sparing antiretroviral regimens may be useful in selected human immune deficiency virus (HIV)-infected patients with resistance or intolerance to these drug classes. This was an observational prospective study of patients on suppressive antiretroviral therapy containing two NRTIs plus one ritonavir-boosted PI who switched to a dual regimen containing raltegravir plus etravirine. Patients were required not to have prior virological failure to raltegravir and to have efficacy of etravirine shown through the genotypic resistance assay in case of prior non-nucleoside reverse transcriptase inhibitor (NNRTI) virological failure. As a whole, 38 patients were enrolled. The mean duration of current regimen was 4.3 years, and the reason for simplification was toxicity in 29 patients and resistance to NRTIs in 9 patients. After switching, the percentage of patients with HIV RNA <20 copies/ml at week 48 was 81.6% in the intent-to-treat-exposed analysis. The switch led to a significant reduction in the mean serum triglyceride levels (-81.2 mg/dl), in the mean total cholesterol levels (-44.3 mg/dl), and in the prevalence of tubular proteinuria (-30.2%), with a significant increase in the mean phosphoremia (+0.52 mg/dl) and in both mean lumbar and femoral neck bone mineral density (+6.5% and +4.7%, respectively). Two patients (5.2%) had virological failure due to suboptimal adherence, and five subjects (13.1%) discontinued treatment due to adverse events. In our study, simplification to the dual-therapy raltegravir plus etravirine was associated with a good efficacy and tolerability, in addition to a favorable effect on kidney, bone, and serum lipids.

SANIST: a rapid mass spectrometric SACI/ESI data acquisition and elaboration platform for verifying potential candidate biomarkers.

Rationale Surface‐Activated Chemical Ionization/Electrospray Ionization mass spectrometry (SACI/ESI‐MS) is a technique with high sensitivity and low noise that allows accurate biomarker discovery studies. We developed a dedicated SACI/ESI software, named SANIST, for both biomarker fingerprint data acquisition and as a diagnostic tool, using prostate cancer (PCa) as the disease of interest. Methods Liquid chromatography (LC)/SACI/ESI‐MS technology was employed to detect a potential biomarker panel for PCa disease prediction. Serum from patients with histologically confirmed or negative prostate biopsies for PCa was employed. The biomarker data (m/z or Thompson value, retention time and extraction mass chromatogram peak area) were stored in an ascii database. SANIST software allowed identification of potential biomarkers. A Bayesian scoring algorithm developed in house allowed sample separation based on comparison with samples in the database. Results Biomarker candidates from the carnitine family were detected at significantly lower levels in patients showing histologically confirmed PCa. Using these biomarkers, the SANIST scoring algorithm allowed separation of patients with PCa from biopsy negative subjects with high accuracy and sensitivity. Conclusions SANIST was able to rapidly identify and perform a preliminary evaluation of the potential diagnostic efficiency of potential biomarkers for PCa.

SANIST: optimization of a technology for compound identification based on the European Union directive with applications in forensic, pharmaceutical and food analyses

Electrospray Ionization and collision induced dissociation tandem mass spectrometry are usually employed to obtain compound identification through a mass spectra match. Different algorithms have been developed for this purpose (for example the nist match algorithm). These approaches compare the tandem mass spectra of the unknown analyte with the tandem mass spectra spectra of known compounds inserted in a database. The compounds are usually identified on the basis of spectral match value associated with a probability of recognition. However, this approach is not usually applied to multiple reaction monitoring transition spectra achieved by means of triple quadrupole apparatus, mainly due to the lack of a transition spectra database. The Surface Activated Chemical Ionization-Electrospray-NIST Bayesian model database search (SANIST) platform has been recently developed for new potential metabolite biomarker discovery, to confirm their identity and to use them for clinical and diagnostic applications. Here, we present an improved version of the SANIST platform that extends its application to forensic, pharmaceutical, and food analysis studies, where the compound identification rules are strict. The European Union (EU) has set directives for compound identification (EU directive 2002/657/EC). We have applied the SANIST method to identification of 11-nor-9-carboxytetrahydro-cannabinol in urine samples (an example of a forensic application), circulating levels of the immunosuppressive drug tacrolimus in blood (an example of a pharmaceutical application) and glyphosate in fruit juice (an example of a food analysis application) that meet the EU directive requirements. Copyright