Etienne Joly

IPBS - Institut de Pharmacologie et de Biologie Structurale · Department of Structural Biology and Biophysics

The HAT-field protocol described here is an optimization of the recently published HAT hemagglutination test, for the detection of antibodies directed against the receptor binding domain (RBD) of the SARS-Cov-2 virus (Townsend et al. 2021). HAT and HAT-field are both based on hemagglutination triggered by a single reagent, the IH4-RBD recombinant p...

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), responsible for COVID-19 in people, has been detected in companion animals on rare occasions. A limited number of large-scale studies have investigated the exposure of companion animals to SARS-CoV-2. The objective of this prospective study was to estimate seroprevalence in privately own...

Hundreds of cytotoxic natural or synthetic lipidic compounds contain chiral alkynylcarbinol motifs, but the mechanism of action of those potential therapeutic agents remains unknown. Using a genetic screen in haploid human cells, we discovered that the enantiospecific cytotoxicity of numerous terminal alkynylcarbinols, including the highly cytotoxi...

We have recently described a very simple and cheap serological test called HAT to detect antibodies directed against the RBD of the SARS-Cov-2 virus. HAT is based on hemagglutination, triggered by a single reagent (IH4-RBD) comprised of the viral RBD domain fused to a nanobody specific for glycophorin, which is expressed at very high levels at the...

Hundreds of cytotoxic natural or synthetic lipidic compounds contain chiral alkynylcarbinol motifs, but the mechanism of action of those potential therapeutic agents remains unknown. Using a genetic screen in haploid human cells, we discovered that the enantiospecific cytotoxicity of numerous terminal alkynylcarbinols, including the highly cytotoxi...

Serological tests are important for understanding the physiopathology and following the evolution of the Covid-19 pandemic. Assays based on flow cytometry (FACS) of tissue culture cells expressing the spike (S) protein of SARS-CoV-2 have repeatedly proven to perform slightly better than the plate-based assays ELISA and CLIA (chemiluminescent immuno...

Serological detection of antibodies to SARS-CoV-2 is essential for establishing rates of seroconversion in populations, and for seeking evidence for a level of antibody that may be protective against COVID-19 disease. Several high-performance commercial tests have been described, but these require centralised laboratory facilities that are comparat...

Serological detection of antibodies to SARS-CoV-2 is essential for establishing rates ofseroconversion in populations, and for seeking evidence for a level of antibody that may beprotective against COVID-19 disease. Several high-performance commercial tests have beendescribed, but these require centralised laboratory facilities that are comparative...

Serological detection of antibodies to SARS-CoV-2 is essential for establishing rates of seroconversion in populations, detection of seroconversion after vaccination, and for seeking evidence for a level of antibody that may be protective against COVID-19 disease. Several high-performance commercial tests have been described, but these require cent...

Serological detection of antibodies to SARS-CoV-2 is essential for establishing rates of seroconversion in populations, detection of seroconversion after vaccination, and for seeking evidence for a level of antibody that may be protective against COVID-19 disease. Several high-performance commercial tests have been described, but these require cent...

Serological detection of antibodies to SARS-CoV-2 is essential for establishing rates of seroconversion in populations, detection of seroconversion after vaccination, and for seeking evidence for a level of antibody that may be protective against COVID-19 disease. Several high-performance commercial tests have been described, but these require cent...

This article proposes that one should explore whether the pulmonary complications of Covid-19 can be reduced or avoided by bypassing the airway entry of the SARS-CoV-2 virus. This could possibly be achieved by injecting live SARS-CoV-2 virus intradermal (ID), subcutaneous, intra-muscular (IM) or intra-peritoneal (IP), or by targeting the virus to t...

Lipidic alkynylcarbinols (LACs) have been identified as potential antitumor compounds, and a thorough understanding of their pharmacophoric environment is now required to elucidate their biological mode of action. In the dialkynylcarbinol (DAC) series, a specific study of the pharmacophore potential has been undertaken by focusing on the synthesis...

Among acetylenic natural products, chiral lipidic alkynylcarbinol (LAC) metabolites, mostly extracted from marine sponges, have revealed a broad spectrum of biological activities, in particular, remarkable antitumor cytotoxicity. With reference to one of the simplest natural representatives, [(S)-eicos-(4E)-en-1-yn-3-ol], and a given cancer cell li...

In line with our study of the pharmacological potential of bio‐inspired synthetic acetylenic lipids, this work specifically addresses the issue of the carbon backbone length. Focusing on two representative chiral alkynylcarbinol pharmacophores, a systematic variation of the aliphatic chain was carried out. The critical impact of the length of the l...

Background: We wanted to investigate the physical state of biological membranes in live cells under the most physiological conditions possible. Methods: For this we have been using laurdan, C-laurdan or M-laurdan to label a variety of cells, and a biphoton microscope equipped with both a thermostatic chamber and a spectral analyser. We also used a...

Background: We wanted to investigate the physical state of biological membranes in live cells under the most physiological conditions possible. Methods: For this we have been using laurdan, C-laurdan or M-laurdan to label a variety of cells, and a biphoton microscope equipped with both a thermostatic chamber and a spectral analyser. We also used a...

Intermediary flow cytometry data for Figure 8: Using flow cytometry (FACS) to quantify staining intensities at 450 and 530 nm, as well as the ratio between the two

A recently proposed "ethynylogation" pharmacochemical approach, first envisaged in the series of anticancer lipidic dialkynylcarbinols (DACs) H–C≡C–CH(OH)–C≡C–R at the levels of the H–C⋮ and ⋮C–R bonds for R = n-C 12H 25, is completed here at the level of the (HO)C–H bond. The so-devised mono-lipidic trialkynylcarbinol (TAC) target (HC≡C) 2C(OH)–C≡...

Ethynylogation of a chiral lipidic dialkynylcarbinol (DAC), identified as a lead for cytotoxicity against HCT116 cancer cells, is shown to typify the butadiynyl-alkynylcarbinol (BAC) unit as a new pharmacophore. The enantiomers of the internal BAC have been synthesized with 72–75% yield and 85% ee through the use of a modified Carreira reaction sho...

Chiral lipidic dialkynylcarbinols (DACs), recently highlighted as antitumoral pharmacophores, have been conjugated to difluoroboron-dipyrromethene (bodipy), 7-hydroxy-coumarine, and 7-nitro-benzoxadiazole (NBD) fluorophore motifs through triazole clips. The labeled lipids preserve cytotoxic activity against HCT116 cells, and fluorescence microscopy...

The chiral alkynylcarbinol motif typically found in natural marine products, has been the subject of intense research activity for its pharmacophoric properties, in particular cytotoxicity against tumor cell lines. In a chemical synthesis-driven four-parameter structure-activity relationship (SAR) study from the (S,E)-eicos-4-en-1-yl-3-ol natural r...

Microdomains corresponding to localized partition of lipids between ordered and less ordered environments are the subject of intensive investigations, because of their putative participation in modulating cellular responses. One popular approach in the field consists in labelling membranes with solvatochromic fluorescent probes such as laurdan and...

Microdomains corresponding to localized partition of lipids between ordered and less ordered environments are the subject of intensive investigations, because of their putative participation in modulating cellular responses. One popular approach in the field consists in labelling membranes with solvatochromic fluorescent probes such as laurdan and...

To date, it is widely accepted that microdomains do form in the biological membranes of all eukaryotic cells, and quite possibly also in prokaryotes. Those sub-micrometric domains play crucial roles in signaling, in intracellular transport, and even in inter-cellular communications. Despite their ubiquitous distribution, and the broad and lasting i...

Rett syndrome is a neurological disorder caused by mutations in the MECP2 gene. MeCP2 transcripts are alternatively spliced to generate two protein isoforms (MeCP2_e1 and MeCP2_e2) that differ at their N-termini. Whilst mRNAs for both forms are expressed ubiquitously, the one for MeCP2_e1 is more abundant than for MeCP2_e2 in the central nervous sy...

The latest version, in the originally intended format (i.e. before the manuscript was modified to conform with the journal's style), is provided as an additional file to this manuscript. Previous versions are also available as formatted pdfs from http://precedings.nature.com/documents/5003, or http://arxiv4.library.cornell.edu/abs/1011.0825, or htt...

Background Speciation corresponds to the progressive establishment of reproductive barriers between groups of individuals derived from an ancestral stock. Since Darwin did not believe that reproductive barriers could be selected for, he proposed that most events of speciation would occur through a process of separation and divergence, and this poin...

The existence of species rests on a metastable equilibrium between inbreeding and outbreeding

During the orchestrated process leading to mature erythrocytes, reticulocytes must synthesize large amounts of hemoglobin, while eliminating numerous cellular components. Exosomes are small secreted vesicles that play an important role in this process of specific elimination. To understand the mechanisms of proteolipidic sorting leading to their bi...

Whilst the principle of adaptive evolution is unanimously recognised as being caused by the process of natural selection favouring the survival and/or reproduction of individuals having acquired new advantageous traits, a consensus has proven much harder to find regarding the actual origin of species. Indeed, since speciation corresponds to the est...

Background Speciation corresponds to the progressive establishment of reproductive barriers between groups of individuals derived from an ancestral stock. Since Darwin did not believe that reproductive barriers could be selected for, he proposed that most events of speciation would occur through a process of separation and divergence, and this poin...

Essay: On the close relationship between speciation, inbreeding and recessive mutations.

Whilst the principle of adaptive evolution is unanimously recognised as being caused by the process of natural selection favouring the survival and/or reproduction of individuals having acquired new advantageous traits, a consensus has proven much harder to find regarding the actual origin of species. Indeed, since speciation corresponds to the est...

Although epitope tags are useful to detect intracellular proteins and follow their localization with antibodies, background and nonspecific staining often remain problematic. We describe a simple assay based on the split GFP complementation system. Proteins tagged with the 15-amino acid GFP 11 fragment are detected with a solution of the recombinan...

During chronic inflammation, immune effectors progressively organize themselves into a functional tertiary lymphoid tissue (TLT) within the targeted organ. TLT has been observed in a wide range of chronic inflammatory conditions but its pathophysiological significance remains unknown. We used the rat aortic interposition model in which a TLT has be...

Exchange of plasma membrane fragments, including cell-surface proteins and lipids, in conjugates formed between lymphocytes and their cellular partners is a field of intense investigation. Apart from its natural occurrence during Ag recognition, the process of membrane transfer can be triggered in experimental or therapeutic settings when lymphocyt...

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Differences in the transfer efficiency of various GFP proteins on T or B cells are not correlated to their expression levels at the PM. A) A mask (middle panel) delimitating the PM of HEK-FcRγGFP was constructed using the Metamorph software based on extra-cellular anti-MHC class I staining (left panel) and was applied on FcRγ-GFP staining in order...

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Examples of the levels of expression attained after transient transfection with plasmids coding for various proteins fused to GFP. Typical examples of flow cytometry analyses 48 hours after transient transfection in HEK-FcγRII of 9 different proteins fused to GFP. This type of analysis was performed systematically for all proteins used in this stud...

The transfer efficiency of a given protein by trogocytosis is not directly related to its level of expression by target cells. A) Expression by HEK-FcγRII cell of the FcRγ-GFP protein expressed after transient transfection with increasing amounts of vector encoding FcRγ-GFP is shown in the top panels. Capture of the FcRγ-GFP by gated OT-I cells exp...

T and B cells capture antigens via membrane fragments of antigen presenting cells (APC) in a process termed trogocytosis. Whether (and how) a preferential transfer of some APC components occurs during trogocytosis is still largely unknown. We analyzed the transfer onto murine T and B cells of a large panel of fluorescent proteins with different int...

CD8(+) T cells have been shown to capture plasma membrane fragments from target cells expressing their cognate antigen, a process termed "trogocytosis". Here, we report that human CD4, the Human Immunodeficiency Virus (HIV) receptor, can be found among the proteins transferred by trogocytosis. CD4 is expressed in a correct orientation after its cap...

Vaccination with recombinant adenylate cyclase of Bordetella pertussis (CyaA) carrying antigen is a promising approach to target antigen-presenting cells. We have used Trogocytosis Analysis Protocol (TRAP) assays to monitor immune responses raised by different vaccination regimens with recombinant CyaA carrying the ovalbumin antigen. We find that t...

Trogocytosis is a recently discovered phenomenon whereby lymphocytes capture fragments of the plasma membrane from antigen presenting cells (APCs). Using APCs labeled with widely used fluorescent lipophilic probes, we previously described a trogocytosis analysis protocol (TRAP) useful to understand the mechanisms and biological consequences of this...

Upon recognition of their respective cellular partners, T and B cells acquire their antigens by a process of membrane capture called trogocytosis. Here, we report that various inhibitors of actin polymerization or of kinases involved in intracellular signaling partially or fully inhibited trogocytosis by CD8(+) and CD4(+) T cells, whereas they had...

To obtain an optimised form of BFP for use as a reporter gene in mammalian cells, the brightest available GFP form, EGFP, was mutated at 5 different positions, yielding 8 different mutagenised forms of BFP. The intensity of the fluorescent signals attained in mammalian cells with all these various versions of BFP was analysed by flow cytometry of t...

Key events of T and B cell biology are regulated through direct interaction with APC or target cells. Trogocytosis is a process whereby CD4(+) T, CD8(+) T, and B cells capture their specific membrane-bound Ag through the acquisition of plasma membrane fragments from their cellular targets. With the aim of investigating whether the ability to trigge...

Studies of the quantitative and qualitative aspects of anti-microbial, anti-tumoral or autoreactive immune responses have been greatly facilitated by the possibility to stain antigen-specific CD8(+) T cells using fluorescently labeled multimeric major histocompatibility complex (MHC) class I/peptide complexes. So far, this technology has been devel...

The expression of MHC class I genes is repressed in mature neurons. The molecular basis of this regulation is poorly understood, but the genes are particularly rich in CpG islands. MeCP2 is a transcriptional repressor that binds to methylated CpG dinucleotides; mutations in this protein also cause the neurodevelopmental disease called Rett syndrome...

The strain of MeCP2tm1.1Bird mice is a broadly used model for Rett syndrome. Because males carrying the invalidated MeCP2 locus are sterile, this strain has to be maintained in a heterozygous state. All animals therefore have to be genotyped at every generation to discriminate those carrying the invalidated allele (+/- females and y/- males) from t...

Chronic vascular rejection, the main cause of allograft failure, is characterized by the destruction of smooth muscle cells (SMCs) in the media concomitantly with the proliferation of SMCs in the adjacent neointima. We hypothesized that alloantibodies might be responsible for these 2 opposite but coordinated events. We used the rat aortic interposi...

I am in complete agreement with the suggestion by Matthew Falagas [1] that a unique author identification number (UAIN) would represent a major improvement for the use of databases of scientific publications. In this regard, I perceive that he has not mentioned several other important advantages that a UAIN system would provide, and that are worth...

The prompt rejection of transplanted allogeneic lymphocytes by rat NK cells in non-sensitized recipients (allogeneic lymphocyte cyto-toxicity or ALC) is determined by MHC genes as well as by genes located in the NK complex. The same genetic control is found when NK alloreactivity is measured by an in vitro assay, and we have employed this assay to...

Detection, quantification, separation and characterization of T and B cells reactive to specific antigens are important tasks in both basic and clinical immunology. Here, we describe an approach allowing the performance of all four tasks on a functional basis by flow cytometry. The assay is based on the property of lymphocytes to capture membrane c...

We have developed a method exploiting the phenomenon of trogocytosis to detect lymphocytes reacting specifically with target cells by flow cytometry. Trogocytosis is a process by which lymphocytes capture fragments of the plasma membrane from the antigen-presenting cells (APCs) expressing their cognate antigen. For this method, a label (such as a f...

Whether MHC molecules undergo concerted evolution or not has been the subject of a long-standing debate. By comparing sequences of eight functional homologues of HLA-E from primates and rodents with those of MHC class Ia molecules from the same eight species, we find that different portions of MHC class I molecules undergo different patterns of evo...

Background In the accompanying paper by Virginie Rouillon and myself, our demonstration that homogenisation by gene conversion occurs readily among MHC class I genes was made possible because of the exceptional conservation of the CD94L locus between divergent species of separate taxa, suggesting that the molecules of this family are endowed with v...

We coined the word trogocyto-sis from the ancient greek trogo which means nibble (1). It refers to a cellular process whereby a recipient cell rapidly and actively 'nibbles' sizeable quantities of plasma membrane fragments from a donor cell following spe-cific receptor-ligand interactions. This mechanism explains how some recipient cells can captur...

Recent advances indicate that, in various chronic inflammatory disorders, the activation of the immune system is triggered locally rather than in lymphoid organs. In this study, we have evaluated whether the humoral alloimmune response involved in chronic rejection is elicited within the graft. We used the rat aortic interposition model and microdi...

We have investigated the density of peptides required to elicit different biological responses in cytotoxic T lymphocytes (CTL), including trogocytosis (i.e., the phenomenon whereby the lymphocytes actively capture fragments of plasma membrane from those cells with which they establish an immune synapse). We have used two separate mouse models of C...

Over the past decade, it has become apparent that specialised membrane microdomains, commonly called rafts, where lipids like sphingolipids and cholesterol are arranged compactly in a liquid ordered phase are involved in cell signalling. The core of the hypothesis presented here is that resting cells may actively maintain their plasma membrane in l...

Several reports have documented that lymphocytes can extract surface molecules through the 'immunological synapse' from the antigen-presenting cells to which they are conjugated1. This phenomenon, which we have called 'trogocytosis'1 (from the ancient Greek trogo, meaning 'gnaw'), involves the transfer of plasma membrane fragments from the presenti...

For the benefit of the scientific community, complete Open Access to all primary scientific articles is clear- ly the only way to go. But to ensure the quality of the papers published, it is hard to conceive that scientific publishing could be carried out except by paid professionals. The only viable solution is therefore for publishing charges to...