Generation of nanobodies acting as silent and positive allosteric modulators of the α7 nicotinic acetylcholine receptor.

The α7 nicotinic acetylcholine receptor (nAChR), a potential drug target for treating cognitive disorders, mediates communication between neuronal and non-neuronal cells. Although many competitive antagonists, agonists, and partial-agonists have been found and synthesized, they have not led to effective therapeutic treatments. In this context, small molecules acting as positive allosteric modulators binding outside the orthosteric, acetylcholine, site have attracted considerable interest. Two single-domain antibody fragments, C4 and E3, against the extracellular domain of the human α7-nAChR were generated through alpaca immunization with cells expressing a human α7-nAChR/mouse 5-HT3A chimera, and are herein described. They bind to the α7-nAChR but not to the other major nAChR subtypes, α4ß2 and α3ß4. E3 acts as a slowly associating positive allosteric modulator, strongly potentiating the acetylcholine-elicited currents, while not precluding the desensitization of the receptor. An E3-E3 bivalent construct shows similar potentiating properties but displays very slow dissociation kinetics conferring quasi-irreversible properties. Whereas, C4 does not alter the receptor function, but fully inhibits the E3-evoked potentiation, showing it is a silent allosteric modulator competing with E3 binding. Both nanobodies do not compete with α-bungarotoxin, localizing at an allosteric extracellular binding site away from the orthosteric site. The functional differences of each nanobody, as well as the alteration of functional properties through nanobody modifications indicate the importance of this extracellular site. The nanobodies will be useful for pharmacological and structural investigations; moreover, they, along with the extracellular site, have a direct potential for clinical applications.

FLO1 is a variable green beard gene that drives biofilm-like cooperation in budding yeast.

The budding yeast, Saccharomyces cerevisiae, has emerged as an archetype of eukaryotic cell biology. Here we show that S. cerevisiae is also a model for the evolution of cooperative behavior by revisiting flocculation, a self-adherence phenotype lacking in most laboratory strains. Expression of the gene FLO1 in the laboratory strain S288C restores flocculation, an altered physiological state, reminiscent of bacterial biofilms. Flocculation protects the FLO1 expressing cells from multiple stresses, including antimicrobials and ethanol. Furthermore, FLO1(+) cells avoid exploitation by nonexpressing flo1 cells by self/non-self recognition: FLO1(+) cells preferentially stick to one another, regardless of genetic relatedness across the rest of the genome. Flocculation, therefore, is driven by one of a few known "green beard genes," which direct cooperation toward other carriers of the same gene. Moreover, FLO1 is highly variable among strains both in expression and in sequence, suggesting that flocculation in S. cerevisiae is a dynamic, rapidly evolving social trait.

Concatemers to re-investigate the role of α5 in α4ß2 nicotinic receptors.

Nicotinic acetylcholine receptors (nAChRs) are pentameric ion channels expressed in the central nervous systems. nAChRs containing the α4, ß2 and α5 subunits are specifically involved in addictive processes, but their functional architecture is poorly understood due to the intricacy of assembly of these subunits. Here we constrained the subunit assembly by designing fully concatenated human α4ß2 and α4ß2α5 receptors and characterized their properties by two-electrodes voltage-clamp electrophysiology in Xenopus oocytes. We found that α5-containing nAChRs are irreversibly blocked by methanethiosulfonate (MTS) reagents through a covalent reaction with a cysteine present only in α5. MTS-block experiments establish that the concatemers are expressed in intact form at the oocyte surface, but that reconstitution of nAChRs from loose subunits show inefficient and highly variable assembly of α5 with α4 and ß2. Mutational analysis shows that the concatemers assemble both in clockwise and anticlockwise orientations, and that α5 does not contribute to ACh binding from its principal (+) site. Reinvestigation of suspected α5-ligands such as galantamine show no specific effect on α5-containing concatemers. Analysis of the α5-D398N mutation that is linked to smoking and lung cancer shows no significant effect on the electrophysiological function, suggesting that its effect might arise from alteration of other cellular processes. The concatemeric strategy provides a well-characterized platform for mechanistic analysis and screening of human α5-specific ligands.

Listeria monocytogenes switches from dissemination to persistence by adopting a vacuolar lifestyle in epithelial cells.

Listeria monocytogenes causes listeriosis, a foodborne disease that poses serious risks to fetuses, newborns and immunocompromised adults. This intracellular bacterial pathogen proliferates in the host cytosol and exploits the host actin polymerization machinery to spread from cell-to-cell and disseminate in the host. Here, we report that during several days of infection in human hepatocytes or trophoblast cells, L. monocytogenes switches from this active motile lifestyle to a stage of persistence in vacuoles. Upon intercellular spread, bacteria gradually stopped producing the actin-nucleating protein ActA and became trapped in lysosome-like vacuoles termed Listeria-Containing Vacuoles (LisCVs). Subpopulations of bacteria resisted degradation in LisCVs and entered a slow/non-replicative state. During the subculture of host cells harboring LisCVs, bacteria showed a capacity to cycle between the vacuolar and the actin-based motility stages. When ActA was absent, such as in ΔactA mutants, vacuolar bacteria parasitized host cells in the so-called "viable but non-culturable" state (VBNC), preventing their detection by conventional colony counting methods. The exposure of infected cells to high doses of gentamicin did not trigger the formation of LisCVs, but selected for vacuolar and VBNC bacteria. Together, these results reveal the ability of L. monocytogenes to enter a persistent state in a subset of epithelial cells, which may favor the asymptomatic carriage of this pathogen, lengthen the incubation period of listeriosis, and promote bacterial survival during antibiotic therapy.

MybA, a transcription factor involved in conidiation and conidial viability of the human pathogen Aspergillus fumigatus.

Aspergillus fumigatus, a ubiquitous human fungal pathogen, produces asexual spores (conidia), which are the main mode of propagation, survival and infection of this human pathogen. In this study, we present the molecular characterization of a novel regulator of conidiogenesis and conidial survival called MybA because the predicted protein contains a Myb DNA binding motif. Cellular localization of the MybA::Gfp fusion and immunoprecipitation of the MybA::Gfp or MybA::3xHa protein showed that MybA is localized to the nucleus. RNA sequencing data and a uidA reporter assay indicated that the MybA protein functions upstream of wetA, vosA and velB, the key regulators involved in conidial maturation. The deletion of mybA resulted in a very significant reduction in the number and viability of conidia. As a consequence, the ΔmybA strain has a reduced virulence in an experimental murine model of aspergillosis. RNA-sequencing and biochemical studies of the ΔmybA strain suggested that MybA protein controls the expression of enzymes involved in trehalose biosynthesis as well as other cell wall and membrane-associated proteins and ROS scavenging enzymes. In summary, MybA protein is a new key regulator of conidiogenesis and conidial maturation and survival, and plays a crucial role in propagation and virulence of A. fumigatus.

A Large Collection of Novel Nematode-Infecting Microsporidia and Their Diverse Interactions with Caenorhabditis elegans and Other Related Nematodes.

Microsporidia are fungi-related intracellular pathogens that may infect virtually all animals, but are poorly understood. The nematode Caenorhabditis elegans has recently become a model host for studying microsporidia through the identification of its natural microsporidian pathogen Nematocida parisii. However, it was unclear how widespread and diverse microsporidia infections are in C. elegans or other related nematodes in the wild. Here we describe the isolation and culture of 47 nematodes with microsporidian infections. N. parisii is found to be the most common microsporidia infecting C. elegans in the wild. In addition, we further describe and name six new species in the Nematocida genus. Our sampling and phylogenetic analysis further identify two subclades that are genetically distinct from Nematocida, and we name them Enteropsectra and Pancytospora. Interestingly, unlike Nematocida, these two genera belong to the main clade of microsporidia that includes human pathogens. All of these microsporidia are horizontally transmitted and most specifically infect intestinal cells, except Pancytospora epiphaga that replicates mostly in the epidermis of its Caenorhabditis host. At the subcellular level in the infected host cell, spores of the novel genus Enteropsectra show a characteristic apical distribution and exit via budding off of the plasma membrane, instead of exiting via exocytosis as spores of Nematocida. Host specificity is broad for some microsporidia, narrow for others: indeed, some microsporidia can infect Oscheius tipulae but not its sister species Oscheius sp. 3, and conversely some microsporidia found infecting Oscheius sp. 3 do not infect O. tipulae. We also show that N. ausubeli fails to strongly induce in C. elegans the transcription of genes that are induced by other Nematocida species, suggesting it has evolved mechanisms to prevent induction of this host response. Altogether, these newly isolated species illustrate the diversity and ubiquity of microsporidian infections in nematodes, and provide a rich resource to investigate host-parasite coevolution in tractable nematode hosts.

Anoxia and glucose supplementation preserve neutrophil viability and function.

Functional studies of human neutrophils and their transfusion for clinical purposes have been hampered by their short life span after isolation. Here, we demonstrate that neutrophil viability is maintained for 20 hours in culture media at 37°C under anoxic conditions with 3 mM glucose and 32 µg/mL dimethyloxalylglycine supplementation, as evidenced by stabilization of Mcl-1, proliferating cell nuclear antigen (PCNA), and pro-caspase-3. Notably, neutrophil morphology (nucleus shape and cell-surface markers) and functions (phagocytosis, degranulation, calcium release, chemotaxis, and reactive oxygen species production) were comparable to blood circulating neutrophils. The observed extension in neutrophil viability was reversed upon exposure to oxygen. Extending neutrophil life span allowed efficient transfection of plasmids (40% transfection efficiency) and short interfering RNA (interleukin-8, PCNA, and Bax), as a validation of effective and functional genetic manipulation of neutrophils both in vitro and in vivo. In vivo, transfusion of conditioned neutrophils in a neutropenic guinea pig model increased bacterial clearance of Shigella flexneri upon colonic infection, strongly suggesting that these conditioned neutrophils might be suitable for transfusion purposes. In summary, such conditioning of neutrophils in vitro should facilitate their study and offer new opportunities for genetic manipulation and therapeutic use.

Impact of wearing a helmet on the risk of hospitalization and intracranial haemorrhage after a sports injury.

BACKGROUND: Despite their reported protective effect against the occurrence of head injuries, helmets are still used inconsistently in sports in which they are optional. We aimed to assess the impact of helmet use on the risk of hospitalization and intracranial haemorrhage for trauma occurring during sport activities. METHODS: Retrospective cohort of all patients who presented themselves, over an 18-month period, at the emergency department of a tertiary trauma centre for an injury sustained in a sport or leisure activity where the use of a helmet is optional. Impact of helmet use was assessed using multivariable regression analyses (relative risks, RR). RESULTS: Among the 1,022 patients included in the study, half were cyclists and 40% were skiers or snowboarders. A total of 40 % of patients wore a helmet at the time of injury, 18% had a head injury, 16% were hospitalized and 13% of patients with a head injury had an intracranial haemorrhage. Among all patients, no association was observed between hospital admission and helmet use. However, helmet use in patients with a head injury was associated with significant reductions in the risks of hospitalization (RR 0.41 [95% CI: 0.22-0.76]) and intracranial haemorrhage (RR 0.28 [95% CI: 0.11-0.71]). CONCLUSIONS: Results suggest that, in recreational athletes who sustain a head injury, helmet use is associated with a reduced risk of hospitalization (all sports) and intracranial haemorrhage (cyclists).

Identification and Analysis of Factors Contributing to the Reduction in Seclusion and Restraint for a Population with Intellectual Disability.

BACKGROUND: A cohort of 11 patients with an intellectual disability and a psychiatric diagnosis present severe behavioural disorders in psychiatric hospital of Quebec in 2009. Control-measure use for this clientele has now been reduced. How do management personnel, families and care teams explain the changes? What clinical interventions did management and care providers implement that contributed to the reduction? METHOD: A retrospective case study was conducted. Five focus groups were held with people involved in their care, and the patient files were examined. RESULTS: The factors contributing to this change were the cohesion of the care providers, the involvement of the families and the efforts to determine the function of the behaviour. IMPLICATIONS: This study may inspire other care teams to try new approaches in dealing with patients with severe behavioural disorders. Also, the model of factors and interventions supporting a reduction in seclusion and restraint measures may inspire future studies.

GH16 and GH81 family ß-(1,3)-glucanases in Aspergillus fumigatus are essential for conidial cell wall morphogenesis.

The fungal cell wall is a rigid structure because of fibrillar and branched ß-(1,3)-glucan linked to chitin. Softening of the cell wall is an essential phenomenon during fungal morphogenesis, wherein rigid cell wall structures are cleaved by glycosylhydrolases. During the search for glycosylhydrolases acting on ß-(1,3)-glucan, we identified seven genes in the Aspergillus fumigatus genome coding for potential endo-ß-(1,3)-glucanase. ENG1 (previously characterized and named ENGL1, Mouyna et al., ), belongs to the Glycoside-Hydrolase 81 (GH81) family, while ENG2 to ENG7, to GH16 family. ENG1 and four GH16 genes (ENG2-5) were expressed in the resting conidia as well as during germination, suggesting an essential role during A. fumigatus morphogenesis. Here, we report the effect of sequential deletion of AfENG2-5 (GH16) followed by AfENG1 (GH81) deletion in the Δeng2,3,4,5 mutant. The Δeng1,2,3,4,5 mutant showed conidial defects, with linear chains of conidia unable to separate while the germination rate was not affected. These results show, for the first time in a filamentous fungus, that endo ß-(1,3)-glucanases are essential for proper conidial cell wall assembly and thus segregation of conidia during conidiation.

Biosynthesis of cell wall mannan in the conidium and the mycelium of Aspergillus fumigatus.

The galactomannan is a major cell wall molecule of Aspergillus fumigatus. This molecule is composed of a linear mannan with a repeating unit composed of four α1,6 and α1,2 linked mannose with side chains of galactofuran. To obtain a better understanding of the mannan biosynthesis in A. fumigatus, it was decided to undertake the successive deletion of the 11 genes which are putative orthologs of the mannosyltransferases responsible for establishing α1,6 and α1,2 mannose linkages in yeast. These deletions did not lead to a reduction of the mannan content of the cell wall of the mycelium of A. fumigatus. In contrast, the mannan content of the conidial cell wall was reduced and this reduction was associated with a partial disorganization of the cell wall leading to defects in conidial survival both in vitro and in vivo.

Aspergillus fumigatus devoid of cell wall ß-1,3-glucan is viable, massively sheds galactomannan and is killed by septum formation inhibitors.

Echinocandins inhibit ß-1,3-glucan synthesis and are one of the few antimycotic drug classes effective against Aspergillus spp. In this study, we characterized the ß-1,3-glucan synthase Fks1 of Aspergillus fumigatus, the putative target of echinocandins. Data obtained with a conditional mutant suggest that fks1 is not essential. In agreement, we successfully constructed a viable Δfks1 deletion mutant. Lack of Fks1 results in characteristic growth phenotypes similar to wild type treated with echinocandins and an increased susceptibility to calcofluor white and sodium dodecyl sulfate. In agreement with Fks1 being the only ß-1,3-glucan synthase in A. fumigatus, the cell wall is devoid of ß-1,3-glucan. This is accompanied by a compensatory increase of chitin and galactosaminogalactan and a significant decrease in cell wall galactomannan due to a massively enhanced galactomannan shedding. Our data furthermore suggest that inhibition of hyphal septation can overcome the limitations of echinocandin therapy. Compounds inhibiting septum formation boosted the antifungal activity of caspofungin. Thus, development of clinically applicable inhibitors of septum formation is a promising strategy to improve existing antifungal therapy.

Modulation of Shigella virulence in response to available oxygen in vivo.

Bacteria coordinate expression of virulence determinants in response to localized microenvironments in their hosts. Here we show that Shigella flexneri, which causes dysentery, encounters varying oxygen concentrations in the gastrointestinal tract, which govern activity of its type three secretion system (T3SS). The T3SS is essential for cell invasion and virulence. In anaerobic environments (for example, the gastrointestinal tract lumen), Shigella is primed for invasion and expresses extended T3SS needles while reducing Ipa (invasion plasmid antigen) effector secretion. This is mediated by FNR (fumarate and nitrate reduction), a regulator of anaerobic metabolism that represses transcription of spa32 and spa33, virulence genes that regulate secretion through the T3SS. We demonstrate there is a zone of relative oxygenation adjacent to the gastrointestinal tract mucosa, caused by diffusion from the capillary network at the tips of villi. This would reverse the anaerobic block of Ipa secretion, allowing T3SS activation at its precise site of action, enhancing invasion and virulence.

Intermediate closed state for glycine receptor function revealed by cysteine cross-linking.

Pentameric ligand-gated ion channels (pLGICs) mediate signal transmission by coupling the binding of extracellular ligands to the opening of their ion channel. Agonist binding elicits activation and desensitization of pLGICs, through several conformational states, that are, thus far, incompletely characterized at the structural level. We previously reported for GLIC, a prokaryotic pLGIC, that cross-linking of a pair of cysteines at both sides of the extracellular and transmembrane domain interface stabilizes a locally closed (LC) X-ray structure. Here, we introduced the homologous pair of cysteines on the human α1 glycine receptor. We show by electrophysiology that cysteine cross-linking produces a gain-of-function phenotype characterized by concomitant constitutive openings, increased agonist potency, and equalization of efficacies of full and partial agonists. However, it also produces a reduction of maximal currents at saturating agonist concentrations without change of the unitary channel conductance, an effect reversed by the positive allosteric modulator propofol. The cross-linking thus favors a unique closed state distinct from the resting and longest-lived desensitized states. Fitting the data according to a three-state allosteric model suggests that it could correspond to a LC conformation. Its plausible assignment to a gating intermediate or a fast-desensitized state is discussed. Overall, our data show that relative movement of two loops at the extracellular-transmembrane interface accompanies orthosteric agonist-mediated gating.

Deciphering the role of the chitin synthase families 1 and 2 in the in vivo and in vitro growth of Aspergillus fumigatus by multiple gene targeting deletion.

Although chitin is an essential component of the fungal cell wall (CW), its biosynthesis and role in virulence is poorly understood. In Aspergillus fumigatus, there are eight chitin synthase (CHS) genes belonging to two families CHSA-C, CHSG in family 1 and CHSF, CHSD, CSMA, CSMB in family 2). To understand the function of these CHS genes, their single and multiple deletions were performed using ß-rec/six system to be able to delete all genes within each family (up to a quadruple ΔchsA/C/B/G mutant in family 1 and a quadruple ΔcsmA/csmB/F/D mutant in family 2). Radial growth, conidiation, mycelial/conidial morphology, CW polysaccharide content, Chs-activity, susceptibility to antifungal molecules and pathogenicity in experimental animal aspergillosis were analysed for all the mutants. Among the family 1 CHS, ΔchsA, ΔchsB and ΔchsC mutants showed limited impact on chitin synthesis. In contrast, there was reduced conidiation, altered mycelial morphotype and reduced growth and Chs-activity in the ΔchsG and ΔchsA/C/B/G mutants. In spite of this altered phenotype, these two mutants were as virulent as the parental strain in the experimental aspergillosis models. Among family 2 CHS, phenotypic defects mainly resulted from the CSMA deletion. Despite significant morphological mycelial and conidial growth phenotypes in the quadruple ΔcsmA/csmB/F/D mutant, the chitin content was poorly affected by gene deletions in this family. However, the entire mycelial cell wall structure was disorganized in the family 2 mutants that may be related to the reduced pathogenicity of the quadruple ΔcsmA/csmB/F/D mutant strain compared to the parental strain, in vivo. Deletion of the genes encompassing the two families (ΔcsmA/csmB/F/G) showed that in spite of being originated from an ancient divergence of fungi, these two families work cooperatively to synthesize chitin in A. fumigatus and demonstrate the essentiality of chitin biosynthesis for vegetative growth, resistance to antifungal drugs, and virulence of this filamentous fungus.

Species-specific impact of the autophagy machinery on Chikungunya virus infection.

Chikungunya virus (CHIKV) is a recently re-emerged arbovirus that triggers autophagy. Here, we show that CHIKV interacts with components of the autophagy machinery during its replication cycle, inducing a cytoprotective effect. The autophagy receptor p62 protects cells from death by binding ubiquitinated capsid and targeting it to autophagolysosomes. By contrast, the human autophagy receptor NDP52--but not its mouse orthologue--interacts with the non-structural protein nsP2, thereby promoting viral replication. These results highlight the distinct roles of p62 and NDP52 in viral infection, and identify NDP52 as a cellular factor that accounts for CHIKV species specificity.

A natural system of chromosome transfer in Yersinia pseudotuberculosis.

The High Pathogenicity Island of Yersinia pseudotuberculosis IP32637 was previously shown to be horizontally transferable as part of a large chromosomal segment. We demonstrate here that at low temperature other chromosomal loci, as well as a non-mobilizable plasmid (pUC4K), are also transferable. This transfer, designated GDT4 (Generalized DNA Transfer at 4°C), required the presence of an IP32637 endogenous plasmid (pGDT4) that carries several mobile genetic elements and a conjugation machinery. We established that cure of this plasmid or inactivation of its sex pilus fully abrogates this process. Analysis of the mobilized pUC4K recovered from transconjugants revealed the insertion of one of the pGDT4-borne ISs, designated ISYps1, at different sites on the transferred plasmid molecules. This IS belongs to the IS6 family, which moves by replicative transposition, and thus could drive the formation of cointegrates between pGDT4 and the host chromosome and could mediate the transfer of chromosomal regions in an Hfr-like manner. In support of this model, we show that a suicide plasmid carrying ISYps1 is able to integrate itself, flanked by ISYps1 copies, at multiple locations into the Escherichia coli chromosome. Furthermore, we demonstrate the formation of RecA-independent cointegrates between the ISYps1-harboring plasmid and an ISYps1-free replicon, leading to the passive transfer of the non-conjugative plasmid. We thus demonstrate here a natural mechanism of horizontal gene exchange, which is less constrained and more powerful than the classical Hfr mechanism, as it only requires the presence of an IS6-type element on a conjugative replicon to drive the horizontal transfer of any large block of plasmid or chromosomal DNA. This natural mechanism of chromosome transfer, which occurs under conditions mimicking those found in the environment, may thus play a significant role in bacterial evolution, pathogenesis, and adaptation to new ecological niches.

SUN proteins belong to a novel family of ß-(1,3)-glucan-modifying enzymes involved in fungal morphogenesis.

BACKGROUND: SUN proteins are involved in yeast morphogenesis, but their function is unknown. RESULTS: SUN protein plays a role in the Aspergillus fumigatus morphogenesis. Biochemical properties of recombinant SUN proteins were elucidated. CONCLUSION: Both Candida albicans and Aspergillus fumigatus sun proteins show a ß-(1,3)-glucanase activity. SIGNIFICANCE: The mode of action of SUN proteins on ß-(1,3)-glucan is unique, new, and original. In yeasts, the family of SUN proteins has been involved in cell wall biogenesis. Here, we report the characterization of SUN proteins in a filamentous fungus, Aspergillus fumigatus. The function of the two A. fumigatus SUN genes was investigated by combining reverse genetics and biochemistry. During conidial swelling and mycelial growth, the expression of AfSUN1 was strongly induced, whereas the expression of AfSUN2 was not detectable. Deletion of AfSUN1 negatively affected hyphal growth and conidiation. A closer examination of the morphological defects revealed swollen hyphae, leaky tips, intrahyphal growth, and double cell wall, suggesting that, like in yeast, AfSun1p is associated with cell wall biogenesis. In contrast to AfSUN1, deletion of AfSUN2 either in the parental strain or in the AfSUN1 single mutant strain did not affect colony and hyphal morphology. Biochemical characterization of the recombinant AfSun1p and Candida albicans Sun41p showed that both proteins had a unique hydrolysis pattern: acting on ß-(1,3)-oligomers from dimer up to insoluble ß-(1,3)-glucan. Referring to the CAZy database, it is clear that fungal SUN proteins represent a new family of glucan hydrolases (GH132) and play an important morphogenetic role in fungal cell wall biogenesis and septation.

Transcytosis of HTLV-1 across a tight human epithelial barrier and infection of subepithelial dendritic cells.

Human T-cell leukemia virus type 1 (HTLV-1) is the causative agent of adult T-cell leukemia/lymphoma and HTLV-1-associated myelopathy/tropical spastic paraparesis. In addition to blood transfusion and sexual transmission, HTLV-1 is transmitted mainly through prolonged breastfeeding, and such infection represents a major risk for the development of adult T-cell leukemia/lymphoma. Although HTLV-1-infected lymphocytes can be retrieved from maternal milk, the mechanisms of HTLV-1 transmission through the digestive tract remain unknown. In the present study, we assessed HTLV-1 transport across the epithelial barrier using an in vitro model. Our results show that the integrity of the epithelial barrier was maintained during coculture with HTLV-1-infected lymphocytes, because neither morphological nor functional alterations of the cell monolayer were observed. Enterocytes were not susceptible to HTLV-1 infection, but free infectious HTLV-1 virions could cross the epithelial barrier via a transcytosis mechanism. Such virions were able to infect productively human dendritic cells located beneath the epithelial barrier. Our data indicate that HTLV-1 crosses the tight epithelial barrier without disruption or infection of the epithelium to further infect target cells such as dendritic cells. The present study provides the first data pertaining to the mode of HTLV-1 transport across a tight epithelial barrier, as can occur during mother-to-child HTLV-1 transmission during breastfeeding.

The Reading the Mind in the Eyes test: validation of a French version and exploration of cultural variations in a multi-ethnic city.

INTRODUCTION: The first aim of our study was to validate the French version of the Reading the Mind in the Eyes test, a theory of mind test. The second aim was to test whether cultural differences modulate performance on this test. METHODS: A total of 109 participants completed the original English version and 97 participants completed the French version. Another group of 30 participants completed the French version twice, one week apart. RESULTS: We report a similar overall distribution of scores in both versions and no differences in the mean scores between them. However, 2 items in the French version did not collect a majority of responses, which differed from the results of the English version. Test-retest showed good stability of the French version. As expected, participants who do not speak French or English at home, and those born in Asia, performed worse than North American participants, and those who speak English or French at home. CONCLUSIONS: We report a French version with acceptable validity and good stability. The cultural differences observed support the idea that Asian culture does not use theory of mind to explain people's behaviours as much as North American people do.