Early Laboratory Diagnosis of COVID-19 by Antigen Detection in Blood Samples of the SARS-CoV-2 Nucleocapsid Protein.

The purpose of this study was to characterize the diagnostic performance of a newly developed enzyme-linked immunosorbent assay (ELISA) for detection of SARS-CoV-2 nucleocapsid protein (NP) in blood. Blood samples were collected during hospitalization of 165 inpatients with PCR-confirmed SARS-CoV-2 infection and from 505 outpatients predominantly with relevant symptoms of COVID-19 simultaneously with PCR testing. For the 143 inpatients who had their first blood sample collected within 2 weeks after PCR-confirmed infection, the diagnostic sensitivity of the ELISA was 91.6%. The mean NP concentration of the 131 ELISA-positive blood samples was 1,734 pg/ml (range, 10 to 3,840 pg/ml). An exponential decline in NP concentration was observed for 368 blood samples collected over the first 4 weeks after PCR-confirmed SARS-CoV-2 infection, and all blood samples taken later had an NP concentration below the 10-pg/ml diagnostic cutoff. The diagnostic sensitivity of the ELISA was 81.4% for the 43 blood samples collected from outpatients with a simultaneous positive PCR test, and the mean NP concentration of the 35 ELISA-positive samples was 157 pg/ml (range, 10 to 1,377 pg/ml). For the 462 outpatients with a simultaneous negative PCR test, the diagnostic specificity of the ELISA was 99.8%. In conclusion, the SARS-CoV-2 NP ELISA is a suitable laboratory diagnostic test for COVID-19, particularly for hospitals, where blood samples are readily available and screening of serum or plasma by ELISA can facilitate prevention of nosocomial infections and reduce the requirement for laborious swab sampling and subsequent PCR analysis to confirmatory tests only.

The HER2 CISH pharmDx(™) Kit in the assessment of breast cancer patients for anti-HER2 treatment.

Testing for amplification of the human EGF receptor 2 (HER2) gene by in situ hybridization is a central principle for the identification of breast cancer patients likely to respond to treatments directed toward HER2. However, its application in clinical routine has been somewhat restricted by the typical use of a visualization system based on fluorescence (FISH), which requires skilled, work-intensive, high-magnification quantitative microscopy. The US FDA has recently approved the HER2 CISH pharmDx™ Kit, which is characterized by employing a chromogenic visualization system that allows quantification of the HER2 gene and centromere 17 reference signals by relatively low-magnification brightfield microscopy. It is indicated as an aid in the assessment of patients for whom Herceptin(®) (trastuzumab) treatment is being considered.

Digital image analysis of membrane connectivity is a robust measure of HER2 immunostains.

The purpose of this study was to develop and validate a new software, HER2-CONNECT(TM), for digital image analysis of the human epidermal growth factor receptor 2 (HER2) in breast cancer specimens. The software assesses immunohistochemical (IHC) staining reactions of HER2 based on an algorithm evaluating the cell membrane connectivity. The HER2-CONNECT algorithm was aligned to match digital image scorings of HER2 performed by 5 experienced assessors in a training set and confirmed in a separate validation set. The training set consisted of 167 breast carcinoma tissue core images in which the assessors individually and blinded outlined regions of interest and gave their HER2 score 0/1+/2+/3+ to the specific tumor region. The validation set consisted of 86 core images where the result of the automated image analysis software was correlated to the scores provided by the 5 assessors. HER2 fluorescence in situ hybridization (FISH) was performed on all cores and used as a reference standard. The overall agreement between the image analysis software and the digital scorings of the 5 assessors was 92.1% (Cohen's Kappa: 0.859) in the training set and 92.3% (Cohen's Kappa: 0.864) in the validation set. The image analysis sensitivity was 99.2% and specificity 100% when correlated to FISH. In conclusion, the Visiopharm HER2 IHC algorithm HER2-CONNECT(TM) can discriminate between amplified and non-amplified cases with high accuracy and diminish the equivocal category and thereby provides a promising supplementary diagnostic tool to increase consistency in HER2 assessment.

Practical considerations of image analysis and quantification of signal transduction IHC staining.

The dramatic increase in computer processing power in combination with the availability of high-quality digital cameras during the last 10 years has fertilized the grounds for quantitative microscopy based on digital image analysis. With the present introduction of robust scanners for whole slide imaging in both research and routine, the benefits of automation and objectivity in the analysis of tissue sections will be even more obvious. For in situ studies of signal transduction, the combination of tissue microarrays, immunohistochemistry, digital imaging, and quantitative image analysis will be central operations. However, immunohistochemistry is a multistep procedure including a lot of technical pitfalls leading to intra- and interlaboratory variability of its outcome. The resulting variations in staining intensity and disruption of original morphology are an extra challenge for the image analysis software, which therefore preferably should be dedicated to the detection and quantification of histomorphometrical end points.

Characterization of anti-TIMP-1 monoclonal antibodies for immunohistochemical localization in formalin-fixed, paraffin-embedded tissue.

The aim of this study was to evaluate seven anti-TIMP-1 (tissue inhibitor of metalloproteinase-1) monoclonal antibodies by immunohistochemical (IHC) staining of formalin-fixed, paraffin-embedded (FFPE) tissue. Detection of the TIMP-1 protein was studied by IHC in FFPE human archival normal and neoplastic samples. Indirect IHC technique was used, and the seven antibodies (clones VT1, VT2, VT4, VT5, VT6, VT7, and VT8) were tested in various concentrations using different pretreatment protocols. All seven VT antibodies specifically immunostained the cytoplasm of islets of Langerhans cells in normal pancreas, epithelial cells of hyperplastic prostate, tumor cells of medullary thyroid carcinoma, and fibroblast-like cells of malignant melanoma. Specificity of the anti-TIMP-1 antibodies was confirmed by several controls, e.g., Western blotting on proteins extracted from FFPE tissue showed that the VT7 antibody reacted specifically with a protein band of approximately 28 kDa, corresponding to the molecular mass of TIMP-1. However, sensitivity varied with the different antibodies. Use of heat-induced epitope retrieval (HIER) and the VT7 clone applied at low concentrations demonstrated more intense immunoreactivity with the TIMP-1-positive cell types compared to the other six clones. Furthermore, when tested on a range of normal and neoplastic endocrine tissues, the VT7 clone demonstrated immunoreactivity with all neuroendocrine cell types. In conclusion, all seven antibodies detected TIMP-1 protein in various normal and neoplastic FFPE tissues, but one clone, VT7, was superior for IHC staining of TIMP-1 in FFPE tissue sections when using HIER.

A scrutiny of matrix metalloproteinases in osteoclasts: evidence for heterogeneity and for the presence of MMPs synthesized by other cells.

Genetic diseases and knockout mice stress the importance of matrix metalloproteinases (MMPs) in skeletal turnover. Our study aims at clarifying which MMPs are expressed by osteoclasts. Previous analyses of this basic question led to conflicting reports in the literature. In the present study, we used a variety of approaches: PCR, Northern blots, Slot blots, in situ hybridization, and immunohistochemistry. We analyzed osteoclasts in culture as well as osteoclasts in native bone at different locations and compared mouse and rabbit osteoclasts. Osteoclasts express MMP-9 and -14 in all conditions, although to a variable extent, and they are able to synthesize MMP-3, -10, and -12, at least under some circumstances. The induction of a given MMP in osteoclasts is influenced by its environment (e.g., osteoclast culture vs. native bone, and various sites within the same bone) and depends on the species (e.g., mouse vs. rabbit). Osteoclasts show high amounts of MMP-2 and -13 protein presumably made to a large extent by other cells, thereby documenting how proteinases of nonosteoclastic origin may contribute to osteoclast activities and giving insight in why the resorptive activity of purified osteoclasts appears insensitive to MMP inhibitors. Our study shows that the confusion about osteoclastic MMPs in the literature reflects the remarkable ability of osteoclasts to adapt to their environment, as required by the structural or functional diversity of bone tissue. Our observations provide basic information needed for understanding the emerging role of MMPs in controlling cell signaling and bone resorption.

The chloride channel inhibitor NS3736 [corrected] prevents bone resorption in ovariectomized rats without changing bone formation.

UNLABELLED: Chloride channel activity is essential for osteoclast function. Consequently, inhibition of the osteoclastic chloride channel should prevent bone resorption. Accordingly, we tested a chloride channel inhibitor on bone turnover and found that it inhibits bone resorption without affecting bone formation. This study indicates that chloride channel inhibitors are highly promising for treatment of osteoporosis. INTRODUCTION: The chloride channel inhibitor, NS3736, blocked osteoclastic acidification and resorption in vitro with an IC50 value of 30 microM. When tested in the rat ovariectomy model for osteoporosis, daily treatment with 30 mg/kg orally protected bone strength and BMD by approximately 50% 6 weeks after surgery. Most interestingly, bone formation assessed by osteocalcin, mineral apposition rate, and mineralized surface index was not inhibited. MATERIALS AND METHODS: Analysis of chloride channels in human osteoclasts revealed that ClC-7 and CLIC1 were highly expressed. Furthermore, by electrophysiology, we detected a volume-activated anion channel on human osteoclasts. Screening 50 different human tissues showed a broad expression for CLIC1 and a restricted immunoreactivity for ClC-7, appearing mainly in osteoclasts, ovaries, appendix, and Purkinje cells. This highly selective distribution predicts that inhibition of ClC-7 should specifically target osteoclasts in vivo. We suggest that NS3736 is inhibiting ClC-7, leading to a bone-specific effect in vivo. RESULTS AND CONCLUSION: In conclusion, we show for the first time that chloride channel inhibitors can be used for prevention of ovariectomy-induced bone loss without impeding bone formation. We speculate that the coupling of bone resorption to bone formation is linked to the acidification of the resorption lacunae, thereby enabling compounds that directly interfere with this process to be able to positive uncouple this process resulting in a net bone gain.

Matrix metalloproteinase-12 (MMP-12) in osteoclasts: new lesson on the involvement of MMPs in bone resorption.

Osteoclasts require matrix metalloproteinase (MMP) activity and cathepsin K to resorb bone, but the critical MMP has not been identified. Osteoclasts express MMP-9 and MMP-14, which do not appear limiting for resorption, and the expression of additional MMPs is not clear. MMP-12, also called metalloelastase, is reported only in a few cells, including tissue macrophages and hypertrophic chondrocytes. MMP-12 is critical for invasion and destruction in pathologies such as aneurysm and emphysema. In the present study, we demonstrate that osteoclasts express MMP-12, although only in some situations. Northern blots show that highly purified rabbit osteoclasts in culture express MMP-12 at the same level as macrophages, whereas in situ hybridizations performed on rabbit bone do not show any MMP-12 expression in osteoclasts whatever the bone type. In contrast, in situ hybridizations performed on mouse bone show MMP-12 expression in osteoclasts in calvariae and long bones. We also demonstrate that recombinant MMP-12 cleaves the putative functional domains of osteopontin and bone sialoprotein, two bone matrix proteins that strongly influence osteoclast activities, such as attachment, spreading and resorption. Furthermore, we investigated the role of MMP-12 in bone resorption and osteoclast recruitment by comparing MMP-12 knockout and wild-type mice in specialized culture models known to depend on MMP activity, as well as in the ovariectomy model, and we did not find any indication for a limiting role of MMP-12 in these processes. In conclusion, we found that osteoclasts are able to express MMP-12, but MMP-12 did not appear critical for osteoclast recruitment or resorption. The fact that none of the MMPs identified so far in osteoclasts appears limiting for resorption, gives strength to the hypothesis that the critical MMP for bone solubilization is produced by non-osteoclastic cells.

Transforming growth factor-beta controls human osteoclastogenesis through the p38 MAPK and regulation of RANK expression.

Although RANK-L is essential for osteoclast formation, factors such as transforming growth factor-beta (TGF-beta) are potent modulators of osteoclastogenic stimuli. To systematically investigate the role of TGF-beta in human osteoclastogenesis, monocytes were isolated from peripheral blood by three distinct approaches, resulting in either a lymphocyte-rich, a lymphocyte-poor, or a pure osteoclast precursor (CD14-positive) cell population. In each of these osteoclast precursor populations, the effect of TGF-beta on proliferation, TRAP activity, and bone resorption was investigated with respect to time and length of exposure. When using the highly pure CD14 osteoclast precursor cell population, the effect of TGF-beta was strongly dependent on the stage of osteoclast maturation. When monocytes were exposed to TGF-beta during the initial culture period (days 1-7), TRAP activity and bone resorption were increased by 40%, whereas the cell number was reduced by 25%. A similar decrease in cell number was observed when TGF-beta was present during the entire culture period (days 1-21), but in direct contrast, TRAP activity, cell fusion, cathepsin K, and matrix metalloproteinase (MMP)-9 expression as well as bone resorption were almost completely abrogated. Moreover, we found that latent TGF-beta was strongly activated by incubation with MMP-9 and suggest this to be a highly relevant mechanism for regulating osteoclast activity. To further investigate the molecular mechanism responsible for the divergent effects of continuous versus discontinuous exposure to TGF-beta, we examined RANK expression and p38 MAPK activation. We found the TGF-beta strongly induced p38 MAPK in monocytes, but not in mature osteoclasts, and that continuous exposure of TGF-beta to monocytes down-regulated RANK expression. The current results suggest that TGF-beta promotes human osteoclastogenesis in monocytes through stimulation of the p38 MAPK, whereas continuous exposure to TGF-beta abrogates osteoclastogenesis through down-regulation of RANK expression and therefore attenuation of RANK-RANK-L signaling.

Matrix metalloproteinase-dependent activation of latent transforming growth factor-beta controls the conversion of osteoblasts into osteocytes by blocking osteoblast apoptosis.

Upon termination of bone matrix synthesis, osteoblasts either undergo apoptosis or differentiate into osteocytes or bone lining cells. In this study, we investigated the role of matrix metalloproteinases (MMPs) and growth factors in the differentiation of osteoblasts into osteocytes and in osteoblast apoptosis. The mouse osteoblast cell line MC3T3-E1 and primary mouse calvarial osteoblasts were either grown on two-dimensional (2-D) collagen-coated surfaces, where they morphologically resemble flattened, cuboidal bone lining cells, or embedded in three-dimensional (3-D) collagen gels, where they resemble dendritic osteocytes constituting a network of cells. When MC3T3-E1 osteoblasts were grown in a 3-D matrix in the presence of an MMP inhibitor (GM6001), the cell number was dose-dependently reduced by approximately 50%, whereas no effect was observed on a 2-D substratum. In contrast, the murine mature osteocyte cell line, MLO-Y4, was unaffected by GM6001 under all culture conditions. According to TUNEL assay, the osteoblast apoptosis was increased 2.5-fold by 10 microm GM6001. To investigate the mechanism by which MMPs mediate the survival of osteoblasts, we examined the effect of GM6001 on MC3T3-E1 osteoblasts in the presence of extracellular matrix components and growth factors, including tenascin, fibronectin, laminin, collagenase-cleaved collagen, gelatin, parathyroid hormone, basic fibroblast growth factor, vascular epidermal growth factor, insulin-like growth factor, interleukin-1, and latent and active transforming growth factor-beta (TGF-beta). Only active TGF-beta, but not latent TGF-beta or other agents tested, restored cell number and apoptosis to control levels. Furthermore, we found that the membrane type MMP, MT1-MMP, which is produced by osteoblasts, could activate latent TGF-beta and that antibodies neutralizing endogenous TGF-beta led to a similar decrease in cell number as GM6001. Whereas inhibitors of other protease families did not induce osteoblast apoptosis, an inhibitor of the p44/42 mitogen-activated protein kinase showed the same but non-synergetic effect as GM6001. These findings suggest that MMP-activated TGF-beta maintains osteoblast survival during trans-differentiation into osteocytes by a p44/42-dependent pathway.