Amine-reactive dyes for dead cell discrimination in fixed samples

SNAP-Tag-Based Recombinant Photoimmunotherapeutic Agents for the Selective Detection and Killing of Light-Accessible Melanotransferrin-Expressing Melanoma and Triple-Negative Breast Cancer

BACKGROUND

Melanoma and triple negative breast cancer (TNBC) represent the most aggressive skin and breast cancer subtypes and are associated with poor diagnostic and limited therapeutic options leading to poor prognosis. Melanotransferrin/p97 (MTf), initially identified as a tumor-associated antigen (TAA) in melanoma, is overexpressed in various solid tumors, including TNBC. Beyond its high differential expression and dreadful tumorigenic impact, MTf is also associated with chemoresistance development, and its inhibition significantly hampers tumor progression, making MTf a promising target for effective targeted therapies. Near-infrared photoimmunotherapy (NIR-PIT) is an approach that combines the precision of antibodies directed against specific TAA with the phototoxic effects of a light-sensitive photosensitizer (IR700), activated by near-infrared (NIR) light irradiation. This study aimed to generate a novel photoimmunoconjugate to specifically destroy MTf-positive melanoma and TNBC cells in vitro following NIR light irradiation.

METHODS

A single-chain variable fragment (scFv) assembled from anti-MTf antibody L49 was recombinantly fused with the SNAP-tag protein (L49(scFv)-SNAP), capable of irreversible and autocatalytic conjugation to any O(6)-benzylguanine (BG) substrate in a 1:1 stoichiometry. Purified full-length SNAP-tag-based fusion protein (L49(scFv)-SNAP-tag) was either conjugated to a BG-modified fluorescent imaging agent (Alexa 488) to specifically assess its selective binding to MTf-expressing cell lines via confocal imaging and flow cytometry or to a BG-modified light-sensitive photosensitizer (IR700) to evaluate its phototoxic properties using an XTT cell viability assay.

RESULTS

The selective binding and internalization of L49(scFv)-SNAP-Alexa 488 towards MTf-positive melanoma and TNBC cell lines were successfully demonstrated with MTF expression percentages ranging from 52.8 to 83.1. Once confirmed, dose-dependent phototoxicity of L49(scFv)-SNAP-IR700 was achieved on illuminated MTf-positive cell lines showing IC50 values in the nanomolar range (2.20-5.24 nM).

CONCLUSION

This study highlights the therapeutic potential of MTf as a promising target for the diagnosis as well as selective and efficient elimination of NIR-light-accessible melanoma and TNBC by NIR-PIT.

TRIAL REGISTRATION

NCT03769506.

Fluorescent Cell Barcoding of Peripheral Blood Mononuclear Cells for High-Throughput Assessment of Vaccine-Induced T Cell Responses in Low-Volume Research Samples

T cell responses are rarely measured in large-scale human vaccine studies due to the sample volumes required, as well as the logistical, technical, and financial challenges associated with available assays. Fluorescent cell barcoding has been proposed in other contexts to allow for more high-throughput flow cytometry-based assays. Here, we aimed to expand on existing barcoding approaches to develop a reagent and sample-sparing assay for in-depth assessment of T cell responses to vaccine antigens. By using various concentrations of two fixable viability dyes in a matrix format, up to 25 samples that were pooled and acquired together could be successfully deconvoluted based on their unique fluorescent signature. This fluorescent cell barcoding approach was then combined with extracellular and intracellular staining to identify functional (i.e., producing at least one cytokine) and polyfunctional (i.e., producing multiple cytokines) T cells in response to vaccine antigen stimulation. As a proof-of-concept, we plated just 200,000 peripheral blood mononuclear cells (PBMC) per condition, and by staining and acquiring only two pooled samples, we were able to detect rare antigen-specific T cell responses in eight donors to four stimulants each. The frequencies of antigen-induced cytokine-positive cells detected in barcoded samples with 200,000 input PBMC were strongly correlated with those detected in non-barcoded samples from the same donors with 1 million input PBMC, demonstrating the validity of this approach. In conclusion, by reducing the number of PBMC needed by five-fold, and the volume of staining reagents needed by 25-fold, this assay has widespread potential applications to human vaccine studies.

Investigating pulmonary neutrophil responses to inflammation in mice via flow cytometry

Neutrophils play a crucial role in maintaining lung health by defending against infections and participating in inflammation processes. Here we describe a detailed protocol for evaluating pulmonary neutrophil phenotype using a murine model of sterile inflammation induced by the fungal cell wall particle zymosan. We provide step-by-step instructions for the isolation of single cells from both lung tissues and airspaces, followed by comprehensive staining techniques for both cell surface markers and intracellular components. This protocol facilitates the sorting and detailed characterization of lung neutrophils via flow cytometry, making it suitable for downstream applications such as mRNA extraction, single-cell sequencing, and analysis of neutrophil heterogeneity. We also identify and discuss essential considerations for conducting successful neutrophil flow cytometry experiments. This work is aimed at researchers exploring the intricate functions of neutrophils in the lung under physiological and pathological conditions with the aid of flow cytometry.

Tamm-Horsfall protein augments neutrophil NETosis during urinary tract infection

Urinary neutrophils are a hallmark of urinary tract infection (UTI), yet the mechanisms governing their activation, function, and efficacy in controlling infection remain incompletely understood. Tamm-Horsfall glycoprotein (THP), the most abundant protein in urine, uses terminal sialic acids to bind an inhibitory receptor and dampen neutrophil inflammatory responses. We hypothesized that neutrophil modulation is an integral part of THP-mediated host protection. In a UTI model, THP-deficient mice showed elevated urinary tract bacterial burdens, increased neutrophil recruitment, and more severe tissue histopathological changes compared with WT mice. Furthermore, THP-deficient mice displayed impaired urinary NETosis during UTI. To investigate the effect of THP on NETosis, we coupled in vitro fluorescence-based NET assays, proteomic analyses, and standard and imaging flow cytometry with peripheral human neutrophils. We found that THP increases proteins involved in respiratory chain, neutrophil granules, and chromatin remodeling pathways; enhances NETosis in an ROS-dependent manner; and drives NET-associated morphologic features including nuclear decondensation. These effects were observed only in the presence of a NETosis stimulus and could not be solely replicated with equivalent levels of sialic acid alone. We conclude that THP is a critical regulator of NETosis in the urinary tract, playing a key role in host defense against UTI.

Efficacy of Chitosan-N-Arginine Chitosomes in mRNA Delivery and Cell Viability Enhancement

Cationic lipid-based carriers are recognized for their ability to complex with mRNA and effectively deliver the mRNA for vaccination and therapeutic purposes. However, the significant cytotoxicity of these carriers often restricts their practical application. In the present study, polymer-lipid hybrid nanoparticles, termed chitosomes, incorporating chitosan-N-arginine (CSA) with the DOTAP cationic lipid and the DOPE helper lipid, were synthesized and evaluated. The addition of CSA to the lipid formulations improved their physicochemical stability and enhanced mRNA complexation, resulting in high transfection rates in the HeLa and HEK293T cell lines. However, the transfection efficiency was low in the NIH-3T3 cell line, indicating a cell type-specific response to chitosomes. Importantly, CSA significantly reduced the cytotoxicity typically associated with DOTAP. Overall, the present study indicated that optimizing the ratio of CSA to DOTAP is crucial for developing mRNA nanocarriers to achieve high transfection efficiency and reduce cytotoxicity across different cell lines.

Tamm-Horsfall protein augments neutrophil NETosis during urinary tract infection

Urinary neutrophils are a hallmark of urinary tract infection (UTI), yet the mechanisms governing their activation, function, and efficacy in controlling infection remain incompletely understood. Tamm-Horsfall glycoprotein (THP), the most abundant protein in urine, uses terminal sialic acids to bind an inhibitory receptor and dampen neutrophil inflammatory responses. We hypothesized that neutrophil modulation is an integral part of THP-mediated host protection. In a UTI model, THP-deficient mice showed elevated urinary tract bacterial burdens, increased neutrophil recruitment, and more severe tissue histopathological changes compared to WT mice. Furthermore, THP-deficient mice displayed impaired urinary NETosis during UTI. To investigate the impact of THP on NETosis, we coupled in vitro fluorescence-based NET assays, proteomic analyses, and standard and imaging flow cytometry with peripheral human neutrophils. We found that THP increases proteins involved in respiratory chain, neutrophil granules, and chromatin remodeling pathways, enhances NETosis in an ROS-dependent manner, and drives NET-associated morphologic features including nuclear decondensation. These effects were observed only in the presence of a NETosis stimulus and could not be solely replicated with equivalent levels of sialic acid alone. We conclude that THP is a critical regulator of NETosis in the urinary tract, playing a key role in host defense against UTI.

Animal board invited review: An update on the methods for semen quality evaluation in swine - from farm to the lab

Pig breeding is mainly conducted through artificial insemination with liquid-stored semen. It is, therefore, crucial to ensure that sperm quality is over the standard thresholds, as reduced sperm motility, morphology or plasma membrane integrity are associated with reduced farrowing rates and litter sizes. This work aims to summarise the methods utilised in farms and research laboratories to evaluate sperm quality in pigs. The conventional spermiogram consists in the assessment of sperm concentration, motility and morphology, which are the most estimated variables in farms. Yet, while the determination of these sperm parameters is enough for farms to prepare seminal doses, other tests, usually carried out in specialised laboratories, may be required when boar studs exhibit a decreased reproductive performance. These methods include the evaluation of functional sperm parameters, such as plasma membrane integrity and fluidity, intracellular levels of calcium and reactive oxygen species, mitochondrial activity, and acrosome integrity, using fluorescent probes and flow cytometry. Furthermore, sperm chromatin condensation and DNA integrity, despite not being routinely assessed, may also help determine the causes of reduced fertilising capacity. Sperm DNA integrity can be evaluated through direct (Comet, transferase deoxynucleotide nick end labelling (TUNEL) and its in situ nick variant) or indirect tests (Sperm Chromatin Structure Assay, Sperm Chromatin Dispersion Test), whereas chromatin condensation can be determined with Chromomycin A3. Considering the high degree of chromatin packaging in pig sperm, which only have protamine 1, growing evidence suggests that complete decondensation of that chromatin is needed before DNA fragmentation through TUNEL or Comet can be examined.

A Guide to Flow Cytometry: Components, Basic Principles, Experimental Design, and Cancer Research Applications

Flow cytometry (FCM) is a state-of-the-art technique for the qualitative and quantitative assessment of cells and other particles' physical and biological properties. These cells are suspended within a high-velocity fluid stream and pass through a laser beam in single file. The main principle of the FCM instrument is the light scattering and fluorescence emission upon the interaction of the fluorescent particle with the laser beam. It also allows for the physical sorting of particles depending on different parameters. A flow cytometer comprises different components, including fluidic, optics, and electronics systems. This article briefly explains the mechanism of all components of a flow cytometer to clarify the FCM technique's general principles, provides some useful guidelines for the proper design of FCM panels, and highlights some general applications and important applications in cancer research. © 2023 Wiley Periodicals LLC.

Cell Viability Multiplexing: Quantification of Cellular Viability by Barcode Flow Cytometry and Computational Analysis

Fluorescent cell barcoding (FCB) is a useful flow cytometric technique for high-throughput multiplexed analyses and can minimize technical variations after preliminary optimization and validation of protocols. To date, FCB is widely used for measurement of phosphorylation status of certain proteins, while it can be also employed for cellular viability assessment. In this chapter, we describe the protocol to perform FCB combined with viability assessment on lymphocytes and monocytes using manual and computational analysis. We also provide recommendations for FCB protocol optimization and validation for clinical sample analysis.

Probing cell membrane integrity using a histone-targeting protein nanocage displaying precisely positioned fluorophores

Cell membrane integrity is fundamental to the normal activities of cells and is involved in both acute and chronic pathologies. Here, we report a probe for analyzing cell membrane integrity developed from a 9 nm-sized protein nanocage named Dps via fluorophore conjugation with high spatial precision to avoid self-quenching. The probe cannot enter normal live cells but can accumulate in dead or live cells with damaged membranes, which, interestingly, leads to weak cytoplasmic and strong nuclear staining. This differential staining is found attributed to the high affinity of Dps for histones rather than DNA, providing a staining mechanism different from those of known membrane exclusion probes (MEPs). Moreover, the Dps nanoprobe is larger in size and thus applies a more stringent criterion for identifying severe membrane damage than currently available MEPs. This study shows the potential of Dps as a new bioimaging platform for biological and medical analyses.

ELECTRONIC SUPPLEMENTARY MATERIAL

Supplementary material (Figs. S1-S12 including distance information between neighboring fluorophores on Dps, TEM images, MALDI-TOF analysis, fluorescence spectra, confocal images, gel retardation analysis, tissue staining, and additional data) is available in the online version of this article at 10.1007/s12274-022-4785-5.

A flow-through microfluidic chip for continuous dielectrophoretic separation of viable and non-viable human T-cells

Effective methods for rapid sorting of cells according to their viability are critical in T cells based therapies to prevent any risk to patients. In this context, we present a novel microfluidic device that continuously separates viable and non-viable T-cells according to their dielectric properties. A dielectrophoresis (DEP) force is generated by an array of castellated microelectrodes embedded into a microfluidic channel with a single inlet and two outlets; cells subjected to positive DEP forces are drawn toward the electrodes array and leave from the top outlet, those subjected to negative DEP forces are repelled away from the electrodes and leave from the bottom outlet. Computational fluid dynamics is used to predict the device separation efficacy, according to the applied alternative current (AC) frequency, at which the cells move from/to a negative/positive DEP region and the ionic strength of the suspension medium. The model is used to support the design of the operational conditions, confirming a separation efficiency, in terms of purity, of 96% under an applied AC frequency of 1.5 × 10⁶  Hz and a flow rate of 20 μl/h. This work represents the first example of effective continuous sorting of viable and non-viable human T-cells in a single-inlet microfluidic chip, paving the way for lab-on-a-chip applications at the point of need.

A Radioactive-Free Method for the Thorough Analysis of the Kinetics of Cell Cytotoxicity

The cytotoxic activity of T cells and Natural Killer cells is usually measured with the chromium release assay (CRA), which involves the use of 51Chromium (⁵¹Cr), a radioactive substance dangerous to the operator and expensive to handle and dismiss. The accuracy of the measurements depends on how well the target cells incorporate ⁵¹Cr during labelling which, in turn, depends on cellular division. Due to bystander metabolism, the target cells spontaneously release ⁵¹Cr, producing a high background noise. Alternative radioactive-free methods have been developed. Here, we compare a bioluminescence (BLI)-based and a carboxyfluorescein succinimidyl ester (CFSE)-based cytotoxicity assay to the standard radioactive CRA. In the first assay, the target cells stably express the enzyme luciferase, and vitality is measured by photon emission upon the addition of the substrate d-luciferin. In the second one, the target cells are labelled with CFSE, and the signal is detected by Flow Cytometry. We used these two protocols to measure cytotoxicity induced by treatment with NK cells. The cytotoxicity of NK cells was determined by adding increasing doses of human NK cells. The results obtained with the BLI method were consistent with those obtained with the CRA- or CFSE-based assays 4 hours after adding the NK cells. Most importantly, with the BLI assay, the kinetic of NK cells’ killing was thoroughly traced with multiple time point measurements, in contrast with the single time point measurement the other two methods allow, which unveiled additional information on NK cell killing pathways.

Flow-cytometric analysis of membrane integrity of stallion sperm in the face of agglutination: the "zombie sperm" dilemma

PURPOSE

To define the effect of sperm agglutination, associated with incubation under capacitating conditions, on accuracy of membrane assessment via flow cytometry and to develop methods to mitigate that effect.

METHODS

Sperm motility was measured by CASA. Sperm were stained with PI-PSA or a novel method, LD-PSA, using fixable live/dead stain and cell dissociation treatment, before flow-cytometric analysis. Using LD-PSA, acrosome reaction and plasma membrane status were determined in equine sperm treated with 10 μm A23187 for 10 min, followed by 0, 1, or 2 h incubation in capacitating conditions.

RESULTS

Using PI-PSA, measured membrane integrity (MI; live sperm) was dramatically lower than was total motility (TMOT), indicating spurious results ("zombie sperm"). Sperm aggregates were largely of motile sperm. Loss of motility after A23187 treatment was associated with disaggregation and increased MI. On disaggregation using LD-PSA, MI rose, and MI then corresponded with TMOT. In equine sperm incubated after A23187 treatment, as the percentage of live acrosome-reacted sperm increased, TMOT decreased to near 0.

CONCLUSION

Flow cytometry assesses only individualized sperm; thus, agglutination of viable sperm alters recorded membrane integrity. As viable sperm become immotile, they individualize; therefore, factors that decrease motility, such as A23187, result in increased measured MI. Disaggregation before assessment allows more accurate determination of sperm membrane status; in this case we documented a mismatch between motility and live acrosome-reacted equine sperm that may relate to the poor repeatability of A23187 treatment for equine IVF. These findings are of profound value to future studies on sperm capacitation.

Generation and Culture of Lingual Organoids Derived from Adult Mouse Taste Stem Cells

The sense of taste is mediated by taste buds on the tongue, which are composed of rapidly renewing taste receptor cells (TRCs). This continual turnover is powered by local progenitor cells and renders taste function prone to disruption by a multitude of medical treatments, which in turn severely impacts the quality of life. Thus, studying this process in the context of drug treatment is vital to understanding if and how taste progenitor function and TRC production are affected. Given the ethical concerns and limited availability of human taste tissue, mouse models, which have a taste system similar to humans, are commonly used. Compared to in vivo methods, which are time-consuming, expensive, and not amenable to high throughput studies, murine lingual organoids can enable experiments to be run rapidly with many replicates and fewer mice. Here, previously published protocols have been adapted and a standardized method for generating taste organoids from taste progenitor cells isolated from the circumvallate papilla (CVP) of adult mice is presented. Taste progenitor cells in the CVP express LGR5 and can be isolated via EGFP fluorescence-activated cell sorting (FACS) from mice carrying an Lgr5^{EGFP-IRES-CreERT2} allele. Sorted cells are plated onto a matrix gel-based 3D culture system and cultured for 12 days. Organoids expand for the first 6 days of the culture period via proliferation and then enter a differentiation phase, during which they generate all three taste cell types along with non-taste epithelial cells. Organoids can be harvested upon maturation at day 12 or at any time during the growth process for RNA expression and immunohistochemical analysis. Standardizing culture methods for production of lingual organoids from adult stem cells will improve reproducibility and advance lingual organoids as a powerful drug screening tool in the fight to help patients experiencing taste dysfunction.

Recapitulation of HIV-1 Env-antibody coevolution in macaques leading to neutralization breadth

Neutralizing antibodies elicited by HIV-1 coevolve with viral envelope proteins (Env) in distinctive patterns, in some cases acquiring substantial breadth. We report that primary HIV-1 envelope proteins-when expressed by simian-human immunodeficiency viruses in rhesus macaques-elicited patterns of Env-antibody coevolution very similar to those in humans, including conserved immunogenetic, structural, and chemical solutions to epitope recognition and precise Env-amino acid substitutions, insertions, and deletions leading to virus persistence. The structure of one rhesus antibody, capable of neutralizing 49% of a 208-strain panel, revealed a V2 apex mode of recognition like that of human broadly neutralizing antibodies (bNAbs) PGT145 and PCT64-35S. Another rhesus antibody bound the CD4 binding site by CD4 mimicry, mirroring human bNAbs 8ANC131, CH235, and VRC01. Virus-antibody coevolution in macaques can thus recapitulate developmental features of human bNAbs, thereby guiding HIV-1 immunogen design.

Introduction to Multiparametric Flow Cytometry and Analysis of High-Dimensional Data

Multiparametric flow cytometry is a technique utilized in translational experiments that utilizes fluorescently tagged antibodies and functional fluorescent dyes to measure proteins on the surface or in the cytoplasm of cells and to measure processes occurring within cells themselves. These fluorescent molecules, or fluorophores, can be tagged to antibodies to measure specific biological molecules such as proteins inside or on the surface of cells. Small organic compounds such as the nucleic acid binding dye propidium iodide (PI) can permeate compromised cell membranes when cells are no longer viable or used to measure DNA content of cycling cells. Successful completion of flow cytometry experiments requires expertise in both the preparation of the samples, acquisition of the samples on instruments, and analyses of the results. This chapter describes the principles needed to conduct a successful multiparameter flow cytometry experiment needed for drug development with references to well established internet resources that are useful to those less experienced in the field. In addition, we provide a brief introduction to data analysis including complex analysis of 10+ parameters simultaneously. These high-dimensional datasets require novel methods for analysis due to the volume of data collected, which are also introduced in this chapter.

An Overview of Flow Cytometry: Its Principles and Applications in Allergic Disease Research

Flow cytometry is a popular technique used for both clinical and research purposes. It involves laser-based technology to characterize cells based on size, shape, and complexity. Additionally, flow cytometers are equipped with the ability to take fluorescence measurements at multiple wavelengths. This capability makes the flow cytometer a practical resource in the utilization of fluorescently conjugated antibodies, fluorescent proteins, DNA binding dyes, viability dyes, and ion indicator dyes. As the technology advances, the number of parameters a flow cytometer can measure has increased tremendously, and now some has the capacity to analyze 30-50 or more parameters on a single cell. Here, we describe the basic principles involved in the mechanics and procedures of flow cytometry along with an insight into applications of flow cytometry techniques for biomedical and allergic disease research.

Ram semen quality can be assessed by flow cytometry several hours after post-fixation

Ram spermatozoa are very sensitive to any cold shock or oxidative damage, therefore making them unsuitable for prolonged storage or distant transport to specialized laboratories for flow-cytometric analysis. The aim of this study was to stain ram semen samples with several fluorescent markers and analyse their stability during formaldehyde fixation. Briefly, freshly collected semen samples were stained for apoptosis (annexin V-FITC, YO-PRO™-1 and FLICA), acrosomal damage (PNA-AF488 and FITC-conjugated antibody against GAPDHS), mitochondrial activity (Mitotracker probes), oxidative damage [dihydroethidium (DHE) and CellROX™ Green] and cell viability (live/dead fixable viability dyes). Next, samples were fixed in buffer containing formaldehyde and then washed. Stained sample were analyzed using flow cytometer before fixation, immediately after fixation, and at 5 h and 20 h post-fixation. Fluorescent signals and the proportion of positively stained spermatozoa were compared statistically in fresh and post-fixed samples. All examined markers, except YO-PRO-1 (decreased significantly, P < 0.05), retained their fluorescence intensities after fixation. In conclusion, several tested markers were able to withstand formaldehyde fixation of ram semen samples as follows: annexin V and FLICA for apoptosis; PNA for acrosomal status; MitoTracker Red CMXRos for mitochondrial activity; and CellROX Green for oxidative status in combination with a suitable live/dead fixable viability dye. This optimized methodology could help to comprehensively analyse the quality of ram semen from local farms countrywide.

Betamethasone induces potent immunosuppression and reduces HIV infection in a PBMC in vitro model

Genital inflammation is an established risk factor for increased HIV acquisition risk. Certain HIV-exposed seronegative populations, who are naturally resistant to HIV infection, have an immune quiescent phenotype defined by reduced immune activation and inflammatory cytokines at the genital tract. Therefore, the aim of this study was to create an immune quiescent environment using immunomodulatory drugs to mitigate HIV infection. Using an in vitro peripheral blood mononuclear cell (PBMC) model, we found that inflammation was induced using phytohemagglutinin and Toll-like receptor (TLR) agonists Pam3CSK4 (TLR1/2), lipopolysaccharide (LPS) (TLR4) and R848 (TLR7/8). After treatment with anti-inflammatory drugs, ibuprofen (IBF) and betamethasone (BMS), PBMCs were exposed to HIV NL4-3 AD8. Multiplexed ELISA was used to measure 28 cytokines to assess inflammation. Flow cytometry was used to measure immune activation (CD38, HLA-DR and CCR5) and HIV infection (p24 production) of CD4+ T cells. BMS potently suppressed inflammation (soluble cytokines, p<0.05) and immune activation (CD4+ T cells, p<0.05). BMS significantly reduced HIV infection of CD4+ T cells only in the LPS (0.98%) and unstimulated (1.7%) conditions (p<0.02). In contrast, IBF had minimal anti-inflammatory and immunosuppressive but no anti-HIV effects. BMS demonstrated potent anti-inflammatory effects, regardless of stimulation condition. Despite uniform immunosuppression, BMS differentially affected HIV infection according to the stimulation conditions, highlighting the complex nature of these interactions. Together, these data underscore the importance of interrogating inflammatory signaling pathways to identify novel drug targets to mitigate HIV infection.

Fragile neutrophils in surgical patients: A phenomenon associated with critical illness

Leukocyte viability (determined by e.g. propidium iodide [PI] staining) is automatically measured by hematology analyzers to check for delayed bench time. Incidental findings in fresh blood samples revealed the existence of leukocytes with decreased viability in critically ill surgical patients. Not much is known about these cells and their functional and/or clinical implications. Therefore, we investigated the incidence of decreased leukocyte viability, the implications for leukocyte functioning and its relation with clinical outcomes. An automated alarm was set in a routine hematology analyzer (Cell-Dyn Sapphire) for the presence of non-viable leukocytes characterized by increased fluorescence in the PI-channel (FL3:630±30nm). Patients with non-viable leukocytes were prospectively included and blood samples were drawn to investigate leukocyte viability in detail and to investigate leukocyte functioning (phagocytosis and responsiveness to a bacterial stimulus). Then, a retrospective analysis was conducted to investigate the incidence of fragile neutrophils in the circulation and clinical outcomes of surgical patients with fragile neutrophils hospitalized between 2013–2017. A high FL3 signal was either caused by 1) neutrophil autofluorescence which was considered false positive, or by 2) actual non-viable PI-positive neutrophils in the blood sample. These two causes could be distinguished using automatically generated data from the hematology analyzer. The non-viable (PI-positive) neutrophils proved to be viable (PI-negative) in non-lysed blood samples, and were therefore referred to as ‘fragile neutrophils’. Overall leukocyte functioning was not impaired in patients with fragile neutrophils. Of the 11 872 retrospectively included surgical patients, 75 (0.63%) were identified to have fragile neutrophils during hospitalization. Of all patients with fragile neutrophils, 75.7% developed an infection, 70.3% were admitted to the ICU and 31.3% died during hospitalization. In conclusion, fragile neutrophils occur in the circulation of critically ill surgical patients. These cells can be automatically detected during routine blood analyses and are an indicator of critical illness.

The palette of techniques for cell cycle analysis

The cell division cycle is the generational period of cellular growth and propagation. Cell cycle progression needs to be highly regulated to preserve genomic fidelity while increasing cell number. In multicellular organisms, the cell cycle must also coordinate with cell fate specification during development and tissue homeostasis. Altered cell cycle dynamics play a central role also in a number of pathophysiological processes. Thus, extensive effort has been made to define the biochemical machineries that execute the cell cycle and their regulation, as well as implementing more sensitive and accurate cell cycle measurements. Here, we review the available techniques for cell cycle analysis, revisiting the assumptions behind conventional population-based measurements and discussing new tools to better address cell cycle heterogeneity in the single-cell era. We weigh the strengths, weaknesses, and trade-offs of methods designed to measure temporal aspects of the cell cycle. Finally, we discuss emerging techniques for capturing cell cycle speed at single-cell resolution in live animals.

The Impact of Lidocaine on Adipose-Derived Stem Cells in Human Adipose Tissue Harvested by Liposuction and Used for Lipotransfer

The local anesthetic lidocaine, which has been used extensively during liposuction, has been reported to have cytotoxic effects and therefore would be unsuitable for use in autologous lipotransfer. We evaluated the effect of lidocaine on the distribution, number, and viability of adipose-derived stem cells (ASCs), preadipocytes, mature adipocytes, and leukocytes in the fatty and fluid portion of the lipoaspirate using antibody staining and flow cytometry analyses. Adipose tissue was harvested from 11 female patients who underwent liposuction. Abdominal subcutaneous fat tissue was infiltrated with tumescent local anesthesia, containing lidocaine on the left and lacking lidocaine on the right side of the abdomen, and harvested subsequently. Lidocaine had no influence on the relative distribution, cell number, or viability of ASCs, preadipocytes, mature adipocytes, or leukocytes in the stromal-vascular fraction. Assessing the fatty and fluid portions of the lipoaspirate, the fatty portions contained significantly more ASCs (p < 0.05), stem cells expressing the preadipocyte marker Pref-1 (p < 0.01 w/lidocaine, p < 0.05 w/o lidocaine), and mature adipocytes (p < 0.05 w/lidocaine, p < 0.01 w/o lidocaine) than the fluid portions. Only the fatty portion should be used for transplantation. This study found no evidence that would contraindicate the use of lidocaine in lipotransfer. Limitations of the study include the small sample size and the inclusion of only female patients.

New insights into the pathogenesis of leprosy: contribution of subversion of host cell metabolism to bacterial persistence, disease progression, and transmission

Chronic infection by the obligate intracellular pathogen Mycobacterium leprae may lead to the development of leprosy. Of note, in the lepromatous clinical form of the disease, failure of the immune system to constrain infection allows the pathogen to reproduce to very high numbers with minimal clinical signs, favoring transmission. The bacillus can modulate cellular metabolism to support its survival, and these changes directly influence immune responses, leading to host tolerance, permanent disease, and dissemination. Among the metabolic changes, upregulation of cholesterol, phospholipids, and fatty acid biosynthesis is particularly important, as it leads to lipid accumulation in the host cells (macrophages and Schwann cells) in the form of lipid droplets, which are sites of polyunsaturated fatty acid-derived lipid mediator biosynthesis that modulate the inflammatory and immune responses. In Schwann cells, energy metabolism is also subverted to support a lipogenic environment. Furthermore, effects on tryptophan and iron metabolisms favor pathogen survival with moderate tissue damage. This review discusses the implications of metabolic changes on the course of M. leprae infection and host immune response and emphasizes the induction of regulatory T cells, which may play a pivotal role in immune modulation in leprosy.

Genome-wide profiling of nucleosome position and chromatin accessibility in single cells using scMNase-seq

Nucleosome organization is important for chromatin compaction and accessibility. Profiling nucleosome positioning genome-wide in single cells provides critical information to understand the cell-to-cell heterogeneity of chromatin states within a cell population. This protocol describes single-cell micrococcal nuclease sequencing (scMNase-seq), a method for detecting genome-wide nucleosome positioning and chromatin accessibility simultaneously from a small number of cells or single cells. To generate scMNase-seq libraries, single cells are isolated by FACS sorting, lysed and digested by MNase. DNA is purified, end-repaired and ligated to Y-shaped adaptors. Following PCR amplification with indexing primers, the subnucleosome-sized (fragments with a length of ≤80 bp) and mononucleosome-sized (fragments with a length between 140 and 180 bp) DNA fragments are recovered and sequenced on Illumina HiSeq platforms. On average, 0.5-1 million unique mapped reads are obtained for each single cell. The mononucleosome-sized DNA fragments precisely define genome-wide nucleosome positions in single cells, while the subnucleosome-sized DNA fragments provide information on chromatin accessibility. Library preparation of scMNase-seq takes only 2 d, requires only standard molecular biology techniques and does not require sophisticated laboratory equipment. Processing of high-throughput sequencing data requires basic bioinformatics skills and uses publicly available bioinformatics software.

Analysis of Immunological Treatment Effects of Virotherapy in Tumor Tissue

In addition of being directly tumoricidal, oncolytic viruses have emerged as potent partners for established and investigational immunotherapies due to their immune-stimulatory effects. The shifting focus on virus-mediated immune modulation calls for a comprehensive analysis of the tumor microenvironment (TME) and the factors orchestrating the antiviral and antitumor immune response. The oncolytic VSV-GP studied in our lab is a safe and potent antitumor agent with a fast replication cycle and killing of a broad range of different cancer types. It induces a robust local inflammatory conversion of the TME and drives a strong adaptive immune response toward the tumor. Here we present our multidisciplinary approach to study VSV-GP treatment effects in tumors by assessing both immune cells (tumor-infiltrating lymphocytes and tumor-associated macrophages) and immune-regulatory factors (cytokines) as well as characterizing immune signatures using an immune-targeted NanoString gene expression system.

Heat and Chemical Treatments Affect the Viability, Morphology, and Physiology of Staphylococcus aureus and Its Subsequent Antibody Labeling for Flow Cytometric Analysis

The effects of heat and chemical treatments on Staphylococcus aureus viability and physiology and their subsequent effects on antibody binding ability and cell morphology were measured. Treatments included lethal and sublethal heat; exposure to organic acids, salt, and sodium hydroxide; and freeze-thawing. Strain-related differences in viability were noted depending on treatment and were reflected in changes in physiology as monitored by flow cytometry (FCM) using three different staining protocols: SYTO 9/propidium iodide (PI), DiOC₂(3), or calcein acetoxymethyl ester (calcein-AM)/PI. Treatments that resulted in significant losses in viability as measured by plate counting were reflected better by the first two staining combinations, as intracellular calcein-AM uptake may have been impaired by certain treatments. FCM analysis using labeling by commercial anti-S. aureus antibodies indicated that differences in cell physiology as a result of treatments influenced immunofluorescence detection. The ratio of the mean fluorescence intensities of stained cells to those of unstained cells [MFI/MFI_(us)] varied with treatment, five of these treatments, including freeze-thaw, citric acid, oxalic acid, NaCl, and NaOH treatments, resulted in significantly lower fluorescence values compared to controls.IMPORTANCE FCM data indicated that cells conventionally considered to be dead and which would not give rise to CFU in a plate count assay, e.g., cells heated to 80°C, were labeled by antibody staining. This finding suggests that without the inclusion of a live/dead discriminating dye, these cells would be erroneously detected as viable within an FCM assay. Reductions in antibody staining due to physicochemical treatment were strain related, reflecting the complexity of the phenomenon under study and illustrating that substantial validation of any new antibody detection-based method, including physiological staining and cell sorting, should be undertaken. Researchers should be aware of physicochemical treatments causing false-negative results: in this study, freeze-thawing severely reduced antibody binding without affecting the viability of a substantial percentage of cells. Scanning electron microscopy carried out on treated cells revealed a range of morphological changes resulting from physicochemical treatments which may have hindered antibody binding.

A Nucleus-Targeting DNA Aptamer for Dead Cell Indication

Dead cells always accompany with live cells in vivo and in cell culture. It is important to distinguish dead cells from live cells in various biological studies. Currently, the probes for dead cells are mainly nucleic acid-intercalators, most of which have low affinity and potential toxicity to live cells. In this work, we report a novel aptameric probe (Ch4-1) for the first time, which binds cell nuclei with high affinity (apparent K_d = 6.65 ± 3.40 nM). Ch4-1 was generated by Cell-SELEX process, it was identified to target nucleoproteins in cell nuclei. As an oligonucleotide, Ch4-1 cannot penetrate the integrated cell membrane; therefore, it only binds to dead cells rather than live cells. Compared with traditional DNA-targeting nuclear dyes, Ch4-1 possesses a high affinity to the nucleus, no toxicity to live cells, and can be easily labeled with different fluorescent dyes. It was demonstrated to serve as a probe for distinguishing dead cells from live cells in apoptosis assay, as well as for the nuclear staining of tissue sections.

Nanoparticle-mediated magnetic hyperthermia is an effective method for killing the human-infective protozoan parasite Leishmania mexicana in vitro

Cutaneous leishmaniasis is a neglected tropical disease characterized by disfiguring skin lesions. Current chemotherapeutic options depend on toxic, expensive drugs that are both difficult to administer and becoming less effective due to increasing levels of resistance. In comparison, thermotherapy displays greater patient compliance and less adverse systemic effects, but there are still significant issues associated with this. The procedure is painful, requiring local anaesthetic, and is less effective against large lesions. Using nanoparticles to controllably generate heat in a localized manner may provide an alternative solution. Here we evaluate magnetic hyperthermia, using iron oxide magnetic nanoparticles, as a localized, heat-based method to kill the human-infective parasite in vitro. We assessed the effectiveness of this method against the differentiated, amastigote form of the parasite using three distinct viability assays: PrestoBlue, Live/Dead stain and a novel luciferase-based assay. Changes in amastigote morphology and ultrastructure were assessed by immunofluorescence, scanning and transmission electron microscopy. Our findings show that magnetic hyperthermia is an effective method to kill host-infective amastigotes, with morphological changes consistent with heat treatment. This method has the potential to be a step-change for research into new therapeutic options that moves away from the expensive chemotherapeutics currently dominating the research climate.

Manipulation of Salmonella Typhi Gene Expression Impacts Innate Cell Responses in the Human Intestinal Mucosa

Although immunity induced by typhoid fever is moderated and short-lived, typhoid vaccination with the attenuated Ty21a oral vaccine generates long-lasting protection rates reaching up to 92%. Thus, there are important differences on how wild-type Salmonella and typhoid vaccine strains stimulate host immunity. We hypothesize that vaccine strains with different mutations might affect gut inflammation and intestinal permeability by different mechanisms. To test this hypothesis, we used an in vitro organotypic model of the human intestinal mucosa composed of human intestinal epithelial cells, lymphocytes/monocytes, endothelial cells, and fibroblasts. We also used six Salmonella enterica serovar Typhi (S. Typhi) strains: the licensed Ty21a oral vaccine, four typhoid vaccine candidates (i.e., CVD 908, CVD 909, CVD 910, and CVD 915) and the wild-type Ty2 strain. We found that genetically engineered S. Typhi vaccine strains elicit differential host changes not only in the intestinal permeability and secretion of inflammatory cytokines, but also in the phenotype and activation pathways of innate cells. These changes were distinct from those elicited by the parent wild-type S. Typhi and depended on the genetic manipulation. In sum, these results emphasize the importance of carefully selecting specific manipulations of the Salmonella genome in the development of typhoid vaccines.

Quantitation of IRF3 Nuclear Translocation in Heterogeneous Cellular Populations from Cervical Tissue Using Imaging Flow Cytometry

Imaging flow cytometry (IFC) has become a powerful tool for studying the activation of transcriptional factors in heterogeneous cell populations in high-content imaging mode. With considerable interest to the clinical development of IFC, the question becomes how we can accelerate its application to solid tissues. We developed the first IFC-based procedure to quantify the nuclear translocation of interferon regulatory factor (IRF) 3, an important measure of induction of type I interferon antiviral response, in primary human immune cells including in solid tissues. After tissue digestion and protocol optimization by spectral flow cytometry, cell suspension is stained for intracellular IRF3 and acquired by IFC. Image analysis is performed using an optimized nuclear mask and similarity score parameter to correlate the location of IRF3 staining and a nuclear dye. The technique measures IRF3 activation at a single cell level and can detect small changes in the percent of activated cells providing objective quantitative data for statistical analysis.

Neutrophil and T-Cell Homeostasis in the Closed Eye

Purpose

This study sought to examine the changes and phenotype of the tear neutrophil and T-cell populations between early eyelid closure and after a full night of sleep.

Methods

Fourteen healthy participants were recruited and trained to wash the ocular surface with PBS for at-home self-collection of ocular surface and tear leukocytes following up to 1 hour of sleep and a full night of sleep (average 7 hours), on separate days. Cells were isolated, counted, and incubated with fluorescently labeled antibodies to identify neutrophils, monocytes, and T cells. For neutrophil analysis, samples were stimulated with lipopolysaccharide (LPS) or calcium ionophore (CaI) before antibody incubation. Flow cytometry was performed.

Results

Following up to 1 hour of sleep, numerous leukocytes were collected (2.6 × 105 ± 3.0 × 105 cells), although significantly (P < 0.005) more accumulated with 7 hours of sleep (9.9 × 105 ± 1.2× 106 cells). Neutrophils (65%), T cells (3%), and monocytes (1%) were identified as part of the closed eye leukocyte infiltration following 7 hours of sleep. Th17 cells represented 22% of the total CD4+ population at the 7-hour time point. Neutrophil phenotype changed with increasing sleep, with a downregulation of membrane receptors CD16, CD11b, CD14, and CD15, indicating a loss in the phagocytic capability of neutrophils.

Conclusions

Neutrophils begin accumulating in the closed eye conjunctival sac much earlier than previously demonstrated. The closed eye tears are also populated with T cells, including a subset of Th17 cells. The closed eye environment is more inflammatory than previously thought and is relevant to understanding ocular homeostasis.

High-Dimensional Fluorescence Cytometry

The immune system consists of a complex network of cells, all expressing a wide range of surface and/or intracellular proteins. Using flow cytometry, these cells can be analyzed by labeling with fluorophore-conjugated antibodies. The recent expansion of fluorescence flow cytometry technology, in conjunction with the ever-expanding understanding of the complexity of the immune system, has led to the generation of larger high-dimensional fluorescence flow cytometry panels. However, as panel size and complexity increases, so too does the difficulty involved in constructing high-quality panels, in addition to the challenges of analyzing such high-dimensional datasets. As such, this unit seeks to review the key principles involved in building high-dimensional panels, as well as to guide users through the process of building and analyzing quality panels. Here, cytometer configuration, fluorophore brightness, spreading error, antigen density, choosing the best conjugates, titration, optimization, and data analysis will all be addressed. © 2017 by John Wiley & Sons, Inc.

Optimization and standardization of fluorescent cell barcoding for multiplexed flow cytometric phenotyping

Fluorescent cell barcoding (FCB) is a cell-based multiplexing technique for high-throughput flow cytometry. Barcoded samples can be stained and acquired collectively, minimizing staining variability and antibody consumption, and decreasing required sample volumes. Combined with functional measurements, FCB can be used for drug screening, signaling profiling, and cytokine detection, but technical issues are present. We optimized the FCB technique for routine utilization using DyLight 350, DyLight 800, Pacific Orange, and CBD500 for barcoding six, nine, or 36 human peripheral blood specimens. Working concentrations of FCB dyes ranging from 0 to 500 μg/ml were tested, and viability dye staining was optimized to increase robustness of data. A five-color staining with surface markers for Vβ usage analysis in CD4⁺ and CD8⁺ T cells was achieved in combination with nine sample barcoding. We provide improvements of the FCB technique that should be useful for multiplex drug screening and for lymphocyte characterization and perturbations in the diagnosis and during the course of disease. Published 2017 by Wiley Periodicals, Inc., on behalf of International Society for Advancement of Cytometry. This article is a US government work and as such, is in the public domain in the United States of America.

FISH-Flow, a protocol for the concurrent detection of mRNA and protein in single cells using fluorescence in situ hybridization and flow cytometry

We describe a flow-cytometry-based protocol for intracellular mRNA measurements in nonadherent mammalian cells using fluorescence in situ hybridization (FISH) probes. The method, which we call FISH-Flow, allows for high-throughput multiparametric measurements of gene expression, a task that was not feasible with earlier, microscopy-based approaches. The FISH-Flow protocol involves cell fixation, permeabilization and hybridization with a set of fluorescently labeled oligonucleotide probes. In this protocol, surface and intracellular protein markers can also be stained with fluorescently labeled antibodies for simultaneous protein and mRNA measurement. Moreover, a semiautomated, single-tube version of the protocol can be performed with a commercially available cell-wash device that reduces cell loss, operator time and interoperator variability. It takes ∼30 h to perform this protocol. An example of FISH-Flow measurements of cytokine mRNA induction by ex vivo stimulation of primed T cells with specific antigens is described.

Targeting and Internalization of Liposomes by Bladder Tumor Cells Using a Fibronectin Attachment Protein-Derived Peptide-Lipopolymer Conjugate

A synthetic peptidolipopolymer conjugate, incorporated into liposomes to promote specific binding to the fibronectin (FBN) matrix surrounding bladder tumor cells and promote cellular internalization of FBN-integrin complexes, is reported. The peptide promotes association with MB49 mouse model bladder tumor cells in a sequence-specific and concentration-dependent manner, with the maximum cell association occurring at 2 mol % RWFV-PEG2000-DSPE. Double PEGylation of the liposome membrane (i.e., 4 mol % mPEG1000-DSPE + 2 mol % RWFV-PEG2000-DSPE) enhanced binding by >1.6-fold, by improving ligand presentation on the liposome surface. The sequence specificity of the peptide-lipopolymer construct was confirmed by comparing liposomes containing RWFV-PEG2000-DSPE with scrambled and nonpeptidic lipopolymer liposomal formulations. MB49 tumor-bearing mice showed greater mean radiance values for FAP peptide-targeted liposomes in tumor-associated regions of interest than for nontargeted and scrambled peptide liposome formulations. These findings suggest that peptide-modified liposomes may be an attractive vehicle for targeted delivery to bladder tumors in vivo.

A New Method for Evaluating Stallion Sperm Viability and Mitochondrial Membrane Potential in Fixed Semen Samples

Multiparametric assessment of stallion sperm quality using flow cytometry can be a useful adjunct in semen evaluation; however, the availability of flow cytometers in veterinary practice is limited. The ability to preserve and transport sperm samples for later flow cytometric analysis using fixable probes would potentially facilitate this process. In the current study, we validated the combination of live/dead Zombie Green^® (a fixable dye used to assess live and dead sperm) and MitoTracker Deep Red^® (used to assess mitochondrial membrane potential). The assay was validated against classic, non-fixable, membrane assays (SYBR-14/PI). Our results demonstrated the feasibility of the assay. In conclusion, stained and fixed semen samples stored for 72 h obtained equivalent results to the exam on the same day; this new protocol shall facilitate the wider use of flow cytometry in stallion andrology in the future. © 2017 International Clinical Cytometry Society.

Effect of cryopreservation on delineation of immune cell subpopulations in tumor specimens as determinated by multiparametric single cell mass cytometry analysis

Background

Comprehensive understanding of cellular immune subsets involved in regulation of tumor progression is central to the development of cancer immunotherapies. Single cell immunophenotyping has historically been accomplished by flow cytometry (FC) analysis, enabling the analysis of up to 18 markers. Recent advancements in mass cytometry (MC) have facilitated detection of over 50 markers, utilizing high resolving power of mass spectrometry (MS). This study examined an analytical and operational feasibility of MC for an in-depth immunophenotyping analysis of the tumor microenvironment, using the commercial CyTOF™ instrument, and further interrogated challenges in managing the integrity of tumor specimens.

Results

Initial longitudinal studies with frozen peripheral blood mononuclear cells (PBMCs) showed minimal MC inter-assay variability over nine independent runs. In addition, detection of common leukocyte lineage markers using MC and FC detection confirmed that these methodologies are comparable in cell subset identification. An advanced multiparametric MC analysis of 39 total markers enabled a comprehensive evaluation of cell surface marker expression in fresh and cryopreserved tumor samples. This comparative analysis revealed significant reduction of expression levels of multiple markers upon cryopreservation. Most notably myeloid derived suppressor cells (MDSC), defined by co-expression of CD66b⁺ and CD15⁺, HLA-DR^dim and CD14⁻ phenotype, were undetectable in frozen samples.

Conclusion

These results suggest that optimization and evaluation of cryopreservation protocols is necessary for accurate biomarker discovery in frozen tumor specimens.

Electronic supplementary material

The online version of this article (doi:10.1186/s12865-017-0192-1) contains supplementary material, which is available to authorized users.

FACS Analysis of Memory T Lymphocytes

Flow cytometry is a powerful and robust technology for detecting and monitoring multiple markers at the level of single cells. Since its early development, flow cytometry has been used to assess heterogeneity in a cell suspension. Over the years, the increasing number of parameters that could be included in a single assay combined with physical separation by fluorescence-activated cell sorting (FACS) revealed that the T cell compartment is extremely heterogenous in terms of phenotypic diversity, functional capacity, and transcriptional regulation. While naïve T cells are fairly homogenous, diversity becomes extreme in the antigen-experienced memory compartment. The precise identification of memory subsets by the simultaneous analysis of multiple markers by flow cytometry is key not only to basic science but also for the correct immunomonitoring of patients undergoing immunotherapy or for T cell-based therapeutic approaches. In this chapter, we provide guidelines to optimize complex flow cytometry panels, to achieve correct fluorescence compensation and determine positivity for a given antigen. Correct selection of reagents and their validation is essential to the success of the assay. Despite having been developed for the identification of human naïve and memory T cell subsets, the concepts illustrated here can be applied to any experiment aiming to investigate n parameters by flow cytometry.

Necrosis avid near infrared fluorescent cyanines for imaging cell death and their use to monitor therapeutic efficacy in mouse tumor models

Quantification of tumor necrosis in cancer patients is of diagnostic value as the amount of necrosis is correlated with disease prognosis and it could also be used to predict early efficacy of anti-cancer treatments. In the present study, we identified two near infrared fluorescent (NIRF) carboxylated cyanines, HQ5 and IRDye 800CW (800CW), which possess strong necrosis avidity. In vitro studies showed that both dyes selectively bind to cytoplasmic proteins of dead cells that have lost membrane integrity. Affinity for cytoplasmic proteins was confirmed using quantitative structure activity relations modeling. In vivo results, using NIRF and optoacoustic imaging, confirmed the necrosis avid properties of HQ5 and 800CW in a mouse 4T1 breast cancer tumor model of spontaneous necrosis. Finally, in a mouse EL4 lymphoma tumor model, already 24 h post chemotherapy, a significant increase in 800CW fluorescence intensity was observed in treated compared to untreated tumors. In conclusion, we show, for the first time, that the NIRF carboxylated cyanines HQ5 and 800CW possess strong necrosis avid properties in vitro and in vivo. When translated to the clinic, these dyes may be used for diagnostic or prognostic purposes and for monitoring in vivo tumor response early after the start of treatment.

Amine reactive dyes: an alternative to estimate membrane integrity in fish sperm cells

Fluorescent dyes that binds irreversibly to cellular amines, come in several available emission spectra, and do not poses health concerns were used to evaluate membrane integrity in fish sperm cells. The objectives of the present study were to determine: (1) a working dye concentration for fish sperm samples, and (2) if the traditional propidium iodide/SYBR-14 staining combination was comparable with the amine reactive dye (ARD) methods at identifying cell populations with intact and compromised membranes after sperm activation, refrigerated storage, and exposure to cryoprotectant and surfactant. Zebrafish (Danio rerio) sperm were obtained by stripping, and pooled samples (in triplicate) were used in all tests. Six dilutions of the amine dye (ranging from 0.625 to 0.02 μL/mL) were evaluated, and compared with the traditional staining protocol. A concentration of 0.5 μL/mL ARD was selected to be used in subsequent assays. Sperm suspensions were activated with deionized water to simulate urine contamination. After 10 sec, osmolality was increased to stop activation, and the procedure was repeated in 10-sec intervals until the sperm remained activated for 120 consecutive sec; membrane integrity was analyzed at each time interval. For the storage assay, sperm suspensions were prepared in Hanks' balanced salt solution at 302 mOsm/kg osmolality (HBSS302), HBSS354 and HBSS402, and evaluated every 2 hr for 8 hr, and every 24 hr for 72 hr. Cryoprotectant toxicity was tested by diluting sperm suspensions in HBSS340 with methanol at 5, 10 and 15% final concentrations. Surfactant toxicity was tested by diluting sperm suspensions in HBSS354 with Triton X-100 at 0.2, 0.15 and 0.1 mM final concentrations. In each toxicity assay, membrane integrity was tested every 20 min for 80 min. The number of membrane-intact cells significantly decreased across time in all treatments (p < 0.05). Significant differences between staining protocols were observed after activation and after exposure to methanol at 10 and 15%, and to Triton X-100 (p < 0.05). The average difference, however, was minor (between 1 and 6% in average) in relation to the typical values used for decision making based on this assay. Results showed that this method has the potential to contribute greatly to the standardization of cryopreservation in aquatic species.

Targeted Isolation of Antibodies Directed against Major Sites of SIV Env Vulnerability

The simian immunodeficiency virus (SIV) challenge model of lentiviral infection is often used as a model to human immunodeficiency virus type 1 (HIV-1) for studying vaccine mediated and immune correlates of protection. However, knowledge of the structure of the SIV envelope (Env) glycoprotein is limited, as is knowledge of binding specificity, function and potential efficacy of SIV antibody responses. In this study we describe the use of a competitive probe binding sort strategy as well as scaffolded probes for targeted isolation of SIV Env-specific monoclonal antibodies (mAbs). We isolated nearly 70 SIV-specific mAbs directed against major sites of SIV Env vulnerability analogous to broadly neutralizing antibody (bnAb) targets of HIV-1, namely, the CD4 binding site (CD4bs), CD4-induced (CD4i)-site, peptide epitopes in variable loops 1, 2 and 3 (V1, V2, V3) and potentially glycan targets of SIV Env. The range of SIV mAbs isolated includes those exhibiting varying degrees of neutralization breadth and potency as well as others that demonstrated binding but not neutralization. Several SIV mAbs displayed broad and potent neutralization of a diverse panel of 20 SIV viral isolates with some also neutralizing HIV-2_7312A. This extensive panel of SIV mAbs will facilitate more effective use of the SIV non-human primate (NHP) model for understanding the variables in development of a HIV vaccine or immunotherapy.

An antibody-based approach targeting human immunodeficiency virus (HIV) envelope (Env) protein may eventually prove to be effective in treating or preventing HIV infection. However, before any candidate HIV treatment or vaccine can be tested in humans, it must first be evaluated in nonhuman primates (NHPs)–the closest living relatives to humans. Simian immunodeficiency virus (SIV) is the closest available non-chimeric virus—NHP model for studying and testing HIV vaccines or therapies. The SIV model complements the simian-human immunodeficiency virus (SHIV) model in distinctive ways, although less is known about SIV Env-specific antibody responses in NHPs. There are several sites on HIV Env that are vulnerable to antibody-mediated protection, and here we isolated and analyzed monoclonal antibodies (mAbs) from NHPs targeting analogous sites on SIV Env. In particular, we studied mAbs for their ability to bind the viral Env protein and to block infection of cells by widely divergent strains of SIV. These well-characterized SIV Env-specific antibodies will allow for more thorough NHP pre-clinical testing of various antibody-based SIV/HIV vaccine and immunotherapeutic strategies before proceeding to human clinical trials and may yield unanticipated findings relating to molecular mechanisms underlying the unusual breadth of neutralization observed in HIV-2 infection.

Cryopreservation in fish: current status and pathways to quality assurance and quality control in repository development

Cryopreservation in aquatic species in general has been constrained to research activities for more than 60 years. Although the need for application and commercialisation pathways has become clear, the lack of comprehensive quality assurance and quality control programs has impeded the progress of the field, delaying the establishment of germplasm repositories and commercial-scale applications. In this review we focus on the opportunities for standardisation in the practices involved in the four main stages of the cryopreservation process: (1) source, housing and conditioning of fish; (2) sample collection and preparation; (3) freezing and cryogenic storage of samples; and (4) egg collection and use of thawed sperm samples. In addition, we introduce some key factors that would assist the transition to commercial-scale, high-throughput application.

Approaches for monitoring of non virus-specific and virus-specific T-cell response in solid organ transplantation and their clinical applications

Opportunistic viral infections are still a major complication following solid organ transplantation. Immune monitoring may allow the identification of patients at risk of infection and, eventually, the modulation of immunosuppressive strategies. Immune monitoring can be performed using virus-specific and non virus-specific assays. This article describes and summarizes the pros and cons of the different technical approaches. Among the assays based on non virus-specific antigens, the enumeration of T-cell subsets, the quantification of cytokines and chemokines and the quantification of intracellular adenosine triphosphate following mitogen stimulation are described and their clinical applications to determine the risk for viral infection are discussed. In addition, current specific methods available for monitoring viral-specific T-cell responses are summarized, such as peptide-MHC multimer staining, intracellular cytokine staining, enzyme-linked immunospot and virus-specific IFN-γ ELISA assays, and their clinical applications to determine the individual risk for opportunistic viral infections with human cytomegalovirus, Epstein-Barr virus and polyoma BK virus are discussed. The standardization of the procedure, the choice of the antigen(s) and the criteria to define cut-off values for positive responses are needed for some of these approaches before their implementation in the clinic. Nevertheless, immune monitoring combined with virological monitoring in transplant recipients is increasingly regarded as a helpful tool to identify patients at risk of infection as well as to assess treatment efficacy.

Pseudomonas aeruginosa exotoxin T induces potent cytotoxicity against a variety of murine and human cancer cell lines

In patients with malignancy, the major barrier to achieving complete response is emergence of resistance to current chemotherapeutic agents. One of the major mechanisms by which tumour cells become resistant to therapies is by altering cellular drug targets through mutations and/or deletions. Resistance by this mechanism is achieved more easily if the drug has limited cellular targets and/or processes. We hypothesized that as Pseudomonas aeruginosa exotoxin T (ExoT) targets six proteins that are required for cancer cell survival and proliferation, it is highly unlikely for cancer cells to develop resistance to this toxin. We assessed ExoT's cytotoxicity against multiple invasive and highly resistant tumour cell lines in order to evaluate its potential as a chemotherapeutic agent. Our data demonstrated that ExoT induced potent cytotoxicity in all tumour cell lines that we examined. Collectively, our data highlighted the potential of ExoT as a possible chemotherapeutic candidate for the treatment of cancer.

Characteristics of memory B cells elicited by a highly efficacious HPV vaccine in subjects with no pre-existing immunity

Licensed human papillomavirus (HPV) vaccines provide near complete protection against the types of HPV that most commonly cause anogenital and oropharyngeal cancers (HPV 16 and 18) when administered to individuals naive to these types. These vaccines, like most other prophylactic vaccines, appear to protect by generating antibodies. However, almost nothing is known about the immunological memory that forms following HPV vaccination, which is required for long-term immunity. Here, we have identified and isolated HPV 16-specific memory B cells from female adolescents and young women who received the quadrivalent HPV vaccine in the absence of pre-existing immunity, using fluorescently conjugated HPV 16 pseudoviruses to label antigen receptors on the surface of memory B cells. Antibodies cloned and expressed from these singly sorted HPV 16-pseudovirus labeled memory B cells were predominantly IgG (>IgA>IgM), utilized diverse variable genes, and potently neutralized HPV 16 pseudoviruses in vitro despite possessing only average levels of somatic mutation. These findings suggest that the quadrivalent HPV vaccine provides an excellent model for studying the development of B cell memory; and, in the context of what is known about memory B cells elicited by influenza vaccination/infection, HIV-1 infection, or tetanus toxoid vaccination, indicates that extensive somatic hypermutation is not required to achieve potent vaccine-specific neutralizing antibody responses.

There is an urgent need to better understand how to reliably generate effective vaccines, particularly subunit vaccines, as certain pathogens are considered to pose too great of a safety risk to be developed as live, attenuated or killed vaccines (e.g., HIV-1). The human papillomavirus (HPV) vaccines are two of the most effective subunit vaccines ever developed and have continued to show protection against HPV associated disease up to and beyond five years post-vaccination. Moreover, the target population for these vaccines have essentially no pre-existing immunity to the HPV types covered by the vaccine; therefore, these vaccines provide an excellent model for studying the immunity elicited by a highly effective subunit vaccine. As the HPV vaccines, like most vaccines, protect by generating antibodies, we are interested in characterizing the memory B cells elicited by the HPV vaccine. Memory B cells help to sustain antibody levels over time by rapidly differentiating into antibody secreting cells upon pathogen re-exposure. Although previous studies have provided evidence that the HPV vaccines elicit memory B cells, they did not characterize these cells. Here, we have isolated HPV-specific memory B cells from adolescent females and women who received the quadrivalent HPV vaccine and have cloned antibodies from these cells. Importantly, we find that these antibodies potently inhibit HPV and that the memory B cells from which they derive exhibit hallmarks of long-lived memory B cells.

Immunological tools: engaging students in the use and analysis of flow cytometry and enzyme-linked immunosorbent assay (ELISA)

Flow cytometry and enzyme-linked immunosorbent assay (ELISA) are commonly used techniques associated with clinical and research applications within the immunology and medical fields. The use of these techniques is becoming increasingly valuable in many life science and engineering disciplines as well. Herein, we report the development and evaluation of a novel half-semester course that focused on introducing undergraduate and graduate students to advance conceptual and technical skills associated with flow cytometry and ELISA, with emphasis on applications, experimental design, and data analysis. This course was offered in the North Carolina State University Biotechnology Program over three semesters and consisted of weekly lectures and laboratories. Students performed and/or analyzed flow cytometry and ELISA in three separate laboratory exercises: (1) identification of transgenic zebrafish hematopoietic cells, (2) analysis of transfection efficiency, and (3) analysis of cytokine production upon lipopolysaccharide stimulation. Student learning outcomes were achieved as demonstrated by multiple means of assessment, including three laboratory reports, a data analysis laboratory practicum, and a cumulative final exam. Further, anonymous student self-assessment revealed increased student confidence in the knowledge and skill sets defined in the learning outcomes.