Human signal-regulatory protein is expressed on normal, but not on subsets of leukemic myeloid cells and mediates cellular adhesion involving its counterreceptor CD47

Signal-regulatory proteins (SIRPs) comprise a novel transmembrane glycoprotein family involved in the negative regulation of receptor tyrosine kinase-coupled signaling pathways. To analyze the expression and function of SIRPs, we prepared soluble recombinant fusion proteins of the extracellular regions of SIRPalpha1 and SIRPalpha2, as well as a variety of monoclonal antibodies (MoAbs) against these domains. The antibodies reacted predominantly with monocytes, granulocytes, dendritic cells, and their precursors, as well as with bone marrow CD34(+), AC133(+), CD90(+) hematopoietic stem/progenitor cells. In contrast, SIRP expression was absent or significantly reduced on the majority of myeloid blasts from patients with acute myeloid leukemia (AML) or chronic myeloid leukemia (CML). Functional studies showed that the extracellular domains of SIRPalpha1 and SIRPalpha2 support adhesion of a number of primary hematopoietic cells and cell lines. This interaction could be blocked by 4 of 7 SIRPalpha1-reactive MoAbs. In addition, SIRPalpha1 and SIRPalpha2 competed for the same cell binding site, suggesting a common widely expressed SIRP ligand. In an approach to identify this molecule, MoAbs were generated against the SIRP-binding cell line CCRF-CEM, and MoAb CC2C6 was selected because of its capacity to inhibit cell binding to SIRPalpha1. Further analysis showed that this antibody recognized CD47, a ubiquitously expressed plasma membrane protein previously implicated in integrin function, host defense action, and neutrophil migration. In this study, we identify CD47 as the extracellular ligand for human SIRP and show that these two counterreceptors are involved in cellular adhesion.     

Successful Treatment of Carbapenemase-Producing Pandrug-Resistant Klebsiella pneumoniae Bacteremia

New antibiotic options are urgently needed for the treatment of carbapenem-resistant Enterobacteriaceae infections. We report a 64-year-old female with prolonged hospitalization following an intestinal transplant who developed refractory bacteremia due to a serine carbapenemase-producing pandrug-resistant isolate of Klebsiella pneumoniae. After failing multiple antimicrobial regimens, the patient was successfully treated.     

Pathogenicity of Nc-Bahia and Nc-1 strains of Neospora caninum in experimentally infected cows and buffaloes in early pregnancy

Neospora caninum is a protozoan parasite known as an important cause of bovine abortion worldwide. Little is currently known about how different strains of N. caninum vary in their pathogenicity. In this study, we compared a Brazilian strain, Nc-Bahia, with the first isolate of this coccidian, Nc-1. Eight cows and seven buffaloes were submitted to fixed-time artificial insemination protocols for a better control of pregnancy. Group 1 was inoculated with Nc-Bahia (n?=?8; five cows and three buffaloes), and Group 2 was inoculated with Nc-1 (n?=?5; two cows and three buffaloes). One nonpregnant female of each species was left uninfected as sentinel controls for potential environmental infection. All inoculated animals received 5?×?10⁸ tachyzoites of N. caninum, by intravenous route, on the 70th day of gestation. Uninfected animals remained seronegative throughout the experiment, indicating no exogenous infection, whereas all inoculated animals became seropositive to N. caninum. In Group 1, abortion was found in only one cow on 42 days postinfection (dpi; frequency of abortion?=?12.5 %), whilst all animals from Group 2 aborted on 35 dpi (frequency of abortion?=?100 %). Parasite DNA was detected by seminested PCR in maternal, foetal and placental tissues, confirming vertical transmission in Groups 1 and 2, although histological lesions had different frequencies and degrees of severity between the groups. There was evidence of lower pathogenicity of Nc-Bahia compared to Nc-1 when used in experimental infection, as it caused fewer abortions, as well as less frequent and milder histological lesions. This was the first time Nc-Bahia has been used for experimental infection.     

MALDI-TOF mass spectrometry as a tool for the discrimination of high-risk Escherichia coli clones from phylogenetic groups B2 (ST131) and D (ST69, ST405, ST393)

Reliable, quick and low-cost methods are needed for the early detection of multidrug-resistant and highly virulent high-risk B2 and D Escherichia coli clones or clonal complexes (HiRCC). Matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) seems to have a good discriminatory potential at different subspecies levels, but it was never evaluated for the discrimination of E. coli clones. We assessed the potential of MALDI-TOF MS coupled to multivariate data analysis to discriminate representative E. coli B2 and D HiRCC. Seventy-three E. coli isolates from B2 (including ST131 and B2 non-ST131 clones) and D (ST69, ST393, ST405) with variable pulsed-field gel electrophoresis (PFGE) patterns, origins and dates (1980–2010) were tested. MS spectra were acquired from independent extracts obtained from different plate cultures in two different Microflex LT MALDI-TOF devices (Bruker) after a standard extraction procedure. MALDI-TOF MS fingerprinting analysis revealed a good discriminatory ability between the four HiRCC analysed (ST131, ST69, ST405, ST393) and between B2 ST131 and other B2 non-ST131 isolates. Clusters defined by MALDI-TOF MS were consistent with the clonal complexes assigned by multilocus sequence typing (MLST), although differences were detected regarding the composition of clusters obtained by the comparison of PFGE profiles. We demonstrate, for the first time, that characteristic mass fingerprints of different E. coli HiRCC are sufficiently discriminatory and robust to enable their differentiation by MALDI-TOF MS, which might represent a promising tool for the optimisation of infection control, individual patient management and large-scale epidemiological studies of public health relevance. The good correlation between phenotypic and genotypic features further corroborates phylogenetic relationships delineated by MLST.     

Serum amyloid A induces interleukin‐6 in dermal fibroblasts via Toll‐like receptor 2, interleukin‐1 receptor‐associated kinase 4 and nuclear factor‐κB

Systemic sclerosis is an autoimmune idiopathic connective tissue disease, characterized by vasculopathy, inflammation and fibrosis. There appears to be a link between inflammation and fibrosis, although the exact nature of the relationship is unknown. Serum amyloid A (SAA) is an acute‐phase protein that is elevated up to 1000‐fold in times of infection or inflammation. This acute‐phase reactant, as well as being a marker of inflammation, may initiate signals in a cytokine‐like manner, possibly through toll‐like receptors (TLRs) promoting inflammation. This study addressed the role of SAA in initiating interleukin‐6 (IL‐6) production in dermal fibroblasts and the role of TLR2 in this system. We show that SAA induces IL‐6 secretion in healthy dermal fibroblasts and that blockade of TLR2 with a neutralizing antibody to TLR2 or specific small interfering RNA attenuated the SAA‐induced IL‐6 secretion and that this was also mediated through the TLR adaptor protein IL‐1 receptor‐associated kinase 4. The effect is nuclear factor‐κB‐mediated because blockade of nuclear factor‐κB reduced the induction. We also demonstrate that dermal fibroblasts express TLR2; this is functional and over‐expressed in the fibroblasts of patients with systemic sclerosis. Taken together these data suggest that SAA is a danger signal that initiates IL‐6 signalling in systemic sclerosis via enhanced TLR2 signalling.