The relative expression levels of CD148 and CD180 on clonal B cells and CD148/CD180 median fluorescence intensity ratios are useful in the characterization of mature B cell lymphoid neoplasms infiltrating blood and bone marrow - Results from a single centre pilot study

INTRODUCTION

The categorization of mature B cell neoplasms (MBN) infiltrating blood and bone marrow are met with difficulties. The inclusion of CD148 and CD180 in the routine flow cytometry/FCM panels has been suggested to refine the diagnosis. We studied the discriminatory ability of CD148 and CD180 median fluorescence intensity(MFI), CD148/CD180 ratio and their expression relative to T cells (CD148^ab/T , CD180^ab/T ), neutrophils (CD148^ab/gr , CD180^ab/gr ) and normal B cells (CD148^ab/n , CD180^ab/n ) in the differentiation of mature B cell neoplasms (MBN) especially non-chronic lymphocytic leukaemia (CLL).

METHODOLOGY

The flow cytometric (FCM) expression of CD148 and CD180 was studied prospectively in 102 patients (non-CLL; n = 72); diagnosed by a comprehensive panel of immunophenotypic and cytogenetic studies. The MFI and ratios were statistically compared across MBNs by Mann-Whitney U test. Cut-off values, sensitivity and specificity were calculated for significant parameters by receiver operator characteristic curve.

RESULTS

CD180MFI > 4.35 showed 100% sensitivity and 90.9% specificity for a diagnosis of marginal zone lymphoma (MZL) while, CD148/180 > 5.15 was 100% specific and 81.8% sensitive for lymphoplasmacytic lymphoma. CD148^ab/T (>4.3; 100% specificity, 83.4% sensitivity) and CD148^ab/gr (>1.1; 100% sensitivity, 90% sensitivity) were useful for differentiating blastoid-mantle cell lymphoma/MCL from diffuse large B cell lymphoma; while CD148MFI (≥20.25), CD148^ab/T (>3.35) and CD148^ab/gr (>0.95) showed >90% specificity and sensitivity for distinguishing MCL from CLL. Pairwise analysis also showed a good discriminant function of various parameters for distinguishing SMZL from other MBNs like FL, MCL as well as CLL.

CONCLUSIONS

The current study shows an excellent utility of CD148MFI, CD180MFI, their ratio and relative expression levels in the subcategorization of immunophenotypically related MBNs.

Flow cytometry expression pattern of CD44 and CD18 markers on feline leukocytes

The paucity of specific feline antibodies for flow cytometry (FC) is an ongoing challenge. Flow cytometrists must extrapolate information from relatively few markers. We evaluated the expression pattern of the panleukocyte markers CD18 and CD44 on leukocyte (white blood cell, WBC) subclasses in the peripheral blood (PB) of 14 healthy cats. The degree of expression of CD18 and CD44 was calculated as the ratio between the median fluorescence intensity (MFI) value of antibody-stained cells and autofluorescence. All samples were acquired with the same cytometer with constant photomultiplier setting and compensation matrices. Both molecules were expressed at higher levels on monocytes, intermediate levels on polymorphonuclear cells (PMNs), and lower levels on lymphocytes. CD18-MFI discriminated well among the 3 populations, whereas CD44-MFI mostly overlapped between monocytes and PMNs. However, CD44-MFI had a lower intra-population variability. Evaluation of CD18 and CD44, together with morphologic parameters, was useful for discriminating among WBC subclasses in healthy cats. This information may be helpful for future studies given that an increase in CD18-MFI may indicate reactive changes, whereas fluctuations in CD44-MFI may suggest neoplasia.

Development of a molecular assay for the general detection of tospoviruses and the distinction between tospoviral species

A Luminex xTAG-based assay for plant-infecting tospoviruses was developed. The test enables the detection of tospoviruses in general and the differentiation of the four important member species of this genus: Tomato spotted wilt virus, Impatiens necrotic spot virus, the proposed 'Capsicum chlorosis virus' and Watermelon silver mottle virus. The generic tospovirus primers used in this method are also applicable for detection of tospoviruses by basic RT-PCR. We also describe an economic alternative method for the distinction of the four tospoviruses mentioned and of additional member viruses, based on a restriction fragment length polymorphism (RFLP). The sophisticated Luminex xTAG technology allows the simultaneous detection of various targets. This study is part of a project that aims to develop a method for the simultaneous detection of various plant pathogens (viral, bacterial and fungal) in plant material.

Changes in immune cell populations in the periphery and liver of GBV-B-infected and convalescent tamarins (Saguinus labiatus)

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GBV-B infection of tamarins is a valuable model for acute HCV infection.

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We observed distinct expression patterns of PD-1, a marker of T-cell activation, on peripheral and hepatic lymphocytes.

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Differential PD-1 expression is coincident with reduction in peripheral GBV-B.

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Liver-associated viral RNA in the absence of peripheral viraemia indicates maintenance of occult infection.

Flaviviruses related to hepatitis C virus (HCV) in suitable animal models may provide further insight into the role that cellular immunity contributes to spontaneous clearance of HCV. We characterised changes in lymphocyte populations in tamarins with an acute GBV-B infection, a hepatitis virus of the flaviviridae. Major immune cell populations were monitored in peripheral and intra-hepatic lymphocytes at high viraemia or following a period when peripheral virus was no longer detected. Limited changes in major lymphocyte populations were apparent during high viraemia; however, the proportions of CD3⁺ lymphocytes decreased and CD20⁺ lymphocytes increased once peripheral viraemia became undetectable. Intrahepatic lymphocyte populations increased at both time points post-infection. Distinct expression patterns of PD-1, a marker of T-cell activation, were observed on peripheral and hepatic lymphocytes; notably there was elevated PD-1 expression on hepatic CD4⁺ T-cells during high viraemia, suggesting an activated phenotype, which decreased following clearance of peripheral viraemia. At times when peripheral vRNA was not detected, suggesting viral clearance, we were able to readily detect GBV-B RNA in the liver, indicative of long-term virus replication. This study is the first description of changes in lymphocyte populations during GBV-B infection of tamarins and provides a foundation for more detailed investigations of the responses that contribute to the control of GBV-B infection.

Jaw bone marrow-derived osteoclast precursors internalize more bisphosphonate than long-bone marrow precursors

Bisphosphonates (BPs) are widely used in the treatment of several bone diseases, such as osteoporosis and cancers that have metastasized to bone, by virtue of their ability to inhibit osteoclastic bone resorption. Previously, it was shown that osteoclasts present at different bone sites have different characteristics. We hypothesized that BPs could have distinct effects on different populations of osteoclasts and their precursors, for example as a result of a different capacity to endocytose the drugs. To investigate this, bone marrow cells were isolated from jaw and long bone from mice and the cells were primed to differentiate into osteoclasts with the cytokines M-CSF and RANKL. Before fusion occurred, cells were incubated with fluorescein-risedronate (FAM-RIS) for 4 or 24h and uptake was determined by flow cytometry. We found that cultures obtained from the jaw internalized 1.7 to 2.5 times more FAM-RIS than long-bone cultures, both after 4 and 24h, and accordingly jaw osteoclasts were more susceptible to inhibition of prenylation of Rap1a after treatment with BPs for 24h. Surprisingly, differences in BP uptake did not differentially affect osteoclastogenesis. This suggests that jaw osteoclast precursors are less sensitive to bisphosphonates after internalization. This was supported by the finding that gene expression of the anti-apoptotic genes Bcl-2 and Bcl-xL was higher in jaw cells than long bone cells, suggesting that the jaw cells might be more resistant to BP-induced apoptosis. Our findings suggest that bisphosphonates have distinct effects on both populations of osteoclast precursors and support previous findings that osteoclasts and precursors are bone-site specific. This study may help to provide more insights into bone-site-specific responses to bisphosphonates.

Differential adhesion-inhibitory patterns of antibodies raised against two major variants of the NTS-DBL2X region of VAR2CSA

BACKGROUND

VAR2CSA is a large polymorphic Plasmodium falciparum protein expressed on infected erythrocytes (IE) that allows their binding in the placenta, thus precipitating placental malaria (PM). The N-terminal part of VAR2CSA that contains the binding site to placental chondroitin sulfate A (CSA) is currently recognized as the most attractive region for vaccine development. An ultimate challenge is to define epitopes in this region that induce a broad cross-reactive adhesion inhibitory antibody response.

METHODS

Based on phylogenetic data that identified a dimorphic sequence motif in the VAR2CSA DBL2X, we raised antibodies against the NTS-DBL2X constructs containing one sequence or the other (3D7 and FCR3) and tested their functional properties on P. falciparum isolates from pregnant women and on laboratory-adapted strains.

RESULTS

The CSA binding inhibitory capacity of the antibodies induced varied from one parasite isolate to another (range, 10%–100%), but the combined analysis of individual activity highlighted a broader functionality that increased the total number of isolates inhibited. Interestingly, the differential inhibitory effect of the antibodies observed on field isolates resulted in significant inhibition of all field isolates tested, suggesting that optimal inhibitory spectrum on field isolates from pregnant women might be achieved with antibodies targeting limited variants of the N-terminal VAR2CSA.

CONCLUSIONS

Our findings indicate that the NTS-DBL2X region of VAR2CSA can elicit strain-transcending anti-adhesion antibodies and suggest that the combination of the two major variants used here could represent the basis for an effective bivalent VAR2CSA-based vaccine.

Use of cross-reactive serological assays for detecting novel pathogens in wildlife: assessing an appropriate cutoff for henipavirus assays in African bats

Reservoir hosts of novel pathogens are often identified or suspected as such on the basis of serological assay results, prior to the isolation of the pathogen itself. Serological assays might therefore be used outside of their original, validated scope in order to infer seroprevalences in reservoir host populations, until such time that specific diagnostic assays can be developed. This is particularly the case in wildlife disease research. The absence of positive and negative control samples and gold standard diagnostic assays presents challenges in determining an appropriate threshold, or 'cutoff', for the assay that enables differentiation between seronegative and seropositive individuals. Here, multiple methods were explored to determine an appropriate cutoff for a multiplexed microsphere assay that is used to detect henipavirus antibody binding in fruit bat plasma. These methods included calculating multiples of 'negative' control assay values, receiver operating characteristic curve analyses, and Bayesian mixture models to assess the distribution of assay outputs for classifying seropositive and seronegative individuals within different age classes. As for any diagnostic assay, the most appropriate cutoff determination method and value selected must be made according to the aims of the study. This study is presented as an example for others where reference samples, and assays that have been characterised previously, are absent.

Proximity ligation assay combined with flow cytometry is a powerful tool for the detection of cytokine receptor dimerization

Many cytokine receptors are cell surface proteins that promiscuously combine to form active signalling homo- or heterodimers. Thus, receptor chain dimerization can be viewed as a direct measure of a high probability of intracellular signalling by specific cytokines. Proximity ligation assay (PLA) is an antibody-based method for selective and highly sensitive detection of protein interactions by microscopy. As proof of concept, the aim of this study was to combine antibodies towards interleukin 7 receptor alpha (IL-7Rα) and the common gamma chain (γc) with PLA and flow cytometry to enable the detection of IL-7 receptor heterodimers. The presence of IL-7 receptor heterodimers on the surface of the HPB-ALL T cell line was detected by PLA and microscopy with a resolution of one complex per cell. Optimisation of the PLA reaction on cell suspensions identified buffer effects with critical importance for the flow cytometric outcome. In addition, blocking, fixation and incubation conditions were optimised to prevent unspecific antibody binding. PLA combined with flow cytometry very sensitively detected receptor heterodimers on the cell surface. Thus, the method is a powerful tool for the investigation of cytokine receptor dimerization.

Profiling post-centrifugation delay of serum and plasma with antibody bead arrays

Several biobanking initiatives have emerged to create extensive collections of specimen for biomedical studies and various analytical platforms. An affinity proteomic analysis with antibody suspension bead arrays was conducted to investigate the influence of the pre-analytical time and temperature conditions on blood derived samples. Serum and EDTA plasma prepared from 16 individuals was centrifuged and aliquots were kept either at 4°C or in ambient temperature for 1h and up to 36h prior to first storage. Multiplexed protein profiles of post-centrifugation delay were generated in 384 biotinylated samples using 373 antibodies that targeted 343 unique proteins. Very few profiles were observed as significantly altered by the studied temperature and time intervals. Single binder and sandwich assays revealed decreasing levels of caldesmon 1 (CALD1) related to EDTA standard tubes and prolonged post-centrifugation delay of 36h. Indications from changes in CALD1 levels require further confirmation in independent material, but the current data suggests that samples should preferentially be frozen during the day of collection when to be profiled with antibody arrays selected for this study.

BIOLOGICAL SIGNIFICANCE

Affinity-based profiling of serum and plasma by microarray assays can provide unique opportunities for the discovery of biomarkers. It is though often not known how differences in sample handling after collection influence the downstream analysis. By profiling three types of blood preparations for alterations in protein profiles with respect to time and temperature post centrifugation, we addressed an important component in the analysis and of such specimen. We believe that this analysis adds valuable information to be considered when biobanking blood derived samples. This article is part of a Special Issue entitled: Standardization and Quality Control in Proteomics.

Effects of transmembrane region variability on cell surface expression and allorecognition of HLA-DP3

The functional relevance of polymorphisms outside the peptide binding groove of HLA molecules is poorly understood. Here we have addressed this issue by studying HLA-DP3, a common antigen relevant for functional matching algorithms of unrelated hematopoietic stem cell transplantation (HSCT) encoded by two transmembrane (TM) region variants, DPB1(*)03:01 and DPB1(*)104:01. The two HLA-DP3 variants were found at a overall allelic frequency of 10.4% in 201 volunteer stem cell donors, at a ratio of 4.2:1. No significant differences were observed in cell surface expression levels of the two variants on B lymphoblastoid cell lines (BLCL), primary B cells or monocytes. Three different alloreactive T cell lines or clones showed similar levels of activation marker CD107a and/or CD137 upregulation in response to HLA-DP3 encoded by DPB1(*)03:01 and DPB1(*)104:01, either endogenously on BLCL or after lentiveral-vector mediated transfer into the same cellular background. These data provide, for the first time, direct evidence for a limited functional role of a TM region polymorphism on expression and allorecognition of HLA-DP3 and are compatible with the notion that the two variants can be considered as a single functional entity for unrelated stem cell donor selection.