HTLV-1 propels thymic human T cell development in “human immune system” Rag2-/- gamma c-/- Mice

Alteration of early haematopoietic development is thought to be responsible for the onset of immature leukemias and lymphomas. We have previously demonstrated that TaxHTLV-1 interferes with ß- selection, an important checkpoint of early thymopoiesis, indicating that human T-cell leukemia virus type 1 (HTLV-1) infection has the potential to perturb thymic human αβ T-cell development. To verify that inference and to clarify the impact of HTLV-1 infection on human T-cell development, we investigated the in vivo effects of HTLV-1 infection in a “Human Immune System” (HIS) Rag2-/-γc-/- mouse model. These mice were infected with HTLV-1, at a time when the three main subpopulations of human thymocytes have been detected. In all but two inoculated mice, the HTLV-1 provirus was found integrated in thymocytes; the proviral load increased with the length of the infection period. In the HTLV-1-infected mice we observed alterations in human T-cell development, the extent of which correlated with the proviral load. Thus, in the thymus of HTLV-1-infected HIS Rag2-/-γc-/- mice, mature single-positive (SP) CD4+ and CD8+ cells were most numerous, at the expense of immature and double-positive (DP) thymocytes. These SP cells also accumulated in the spleen. Human lymphocytes from thymus and spleen were activated, as shown by the expression of CD25: this activation was correlated with the presence of tax mRNA and with increased expression of NF-kB dependent genes such as bfl-1, an anti-apoptotic gene, in thymocytes. Finally, hepato-splenomegaly, lymphadenopathy and lymphoma/thymoma, in which Tax was detected, were observed in HTLV-1-infected mice, several months after HTLV-1 infection. These results demonstrate the potential of the HIS Rag2-/-γc-/- animal model to elucidate the initial steps of the leukemogenic process induced by HTLV-1

HTLV-1 propels thymic human T cell development in “human immune system” Rag2-/- IL-2R γc-/- Mice

Alteration of early haematopoietic development is thought to be responsible for the onset of immature leukemias and lymphomas. We have previously demonstrated that TaxHTLV-1 interferes with ß-selection, an important checkpoint of early thymopoiesis, indicating that human T-cell leukemia virus type 1 (HTLV-1) infection has the potential to perturb thymic human αβ T-cell development. To verify that inference and to clarify the impact of HTLV-1 infection on human T-cell development, we investigated the in vivo effects of HTLV-1 infection in a “Human Immune System” (HIS) Rag2-/-γc-/- mouse model. These mice were infected with HTLV-1, at a time when the three main subpopulations of human thymocytes have been detected. In all but two inoculated mice, the HTLV-1 provirus was found integrated in thymocytes; the proviral load increased with the length of the infection period. In the HTLV-1-infected mice we observed alterations in human T-cell development, the extent of which correlated with the proviral load. Thus, in the thymus of HTLV-1-infected HIS Rag2-/-γc-/- mice, mature single-positive (SP) CD4+ and CD8+ cells were most numerous, at the expense of immature and double-positive (DP) thymocytes. These SP cells also accumulated in the spleen. Human lymphocytes from thymus and spleen were activated, as shown by the expression of CD25: this activation was correlated with the presence of tax mRNA and with increased expression of NF-kB dependent genes such as bfl-1, an anti-apoptotic gene, in thymocytes. Finally, hepato-splenomegaly, lymphadenopathy and lymphoma/thymoma, in which Tax was detected, were observed in HTLV-1-infected mice, several months after HTLV-1 infection. These results demonstrate the potential of the HIS Rag2-/-γc-/- animal model to elucidate the initial steps of the leukemogenic process induced by HTLV-1

Evaluation de l activité pro-leucémogène de la protéine TaxHTLV-1 dans les thymocytes immatures humains

Le rétrovirus HTLV-1 est l agent étiologique de la Leucémie T de l Adulte (ATL). La protéine virale Tax participe au processus leucémogène en favorisant la survie et la prolifération des cellules infectées. Cependant, la cellule initiale au sein de laquelle ce processus se met en place reste inconnue. Ces travaux portent sur les effets de Tax dans une population de cellules cibles potentielles, les thymocytes immatures humains au niveau de la sélection b. Ce point de contrôle se caractérise par l expression d un pré-TCR, qui envoie des signaux de survie et de prolifération aux cellules exprimant une chaîne b fonctionnelle. Cette chaîne b est associée à la chaîne invariante pTa et aux molécules du CD3. Nous avons montré que la protéine virale Tax inhibe l activité des protéines E2A sur le promoteur du gène pTa. De plus, Tax inhibe la transcription du gène pTa dans des thymocytes immatures humains fraîchement isolés. Ces résultats suggèrent que les thymocytes ne pourront pas exprimer le pré-TCR requis pour leur survie. Cependant, nous avons également démontré que Tax était capable d activer la transcription des gènes codant pour les sous-unités p50 et p65 du facteur NF- B ainsi que pour les protéines anti-apoptotiques Bfl-1 et BclXL dans les thymocytes immatures. Tax pourrait ainsi pallier l absence du pré-TCR. Par ailleurs, Tax active l expression de l oncogène Tal-1 dans les thymocytes immatures. La perturbation du développement T étant associée au développement de leucémies, l interférence de Tax avec la sélection b pourrait correspondre au premier évènement du processus leucémogène associé à une infection par HTLV-1The HTLV-1 retrovirus is the etiologic agent of Adult T cell Leukaemia (ATL). The viral protein Tax is involved in the leukemic process, favoring the survival and the proliferation of infected T-cells. However, the initial cell that could sustain the leukemic process remains unknown. Herein, we studied the effect of Tax in potential target cells, namely human immature thymocytes undergoing -selection. This checkpoint is characterized by the surface expression of the pre-TCR that allows proliferation and survival of thymocytes expressing a functional beta chain. The pre-TCR is composed of the newly rearranged -chain in association with the pT invariant chain and CD3 molecules. We showed that the viral protein inhibits the transcriptional activity of E2A proteins on the promoter of the pT gene. Furthermore, Tax down-regulates the expression of pT transcripts in freshly isolated human immature thymocytes. These results suggest that Tax prevents the expression of the pre-TCR required for the survival of thymocytes. However, we have also demonstrated in immature thymocytes that Tax triggers the expression of genes coding for the p50 and p65 NF- B subunits, as well as for Bfl-1 and Bcl-Xl anti-apoptotic proteins. Thus, Tax could palliate the absence of pre-TCR signalling. Besides, Tax induces the expression of Tal-1 oncogene in immature thymocytes. Considering that leukemias are induced by disturbances in haematopoietic cells development, the expression of Tax in human immature thymocytes could be a pre-requisite to the emergence of ATL cellsLYON1-BU.Sciences (692662101) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Diagnosis and Management of Severe Asthma in Switzerland: Analysis of Survey Results Conducted with Specialists and General Practitioners

Background: Severe asthma commonly affects 5-10% of the asthmatic population and accounts for approximately 50% of the overall asthma costs.Objective: This analysis investigated how severe asthma is diagnosed, treated, and managed by specialists and general practitioners (GPs) in Switzerland.Methods: Two surveys, one each among specialists (N = 44) and GPs (N = 153), were conducted to understand their self-perception on diagnosis, treatment, and management of severe asthma.Results: Fifty-five percent of the specialists felt very confident and 43% confident in recognizing the symptoms of severe asthma and diagnosing severe asthma. In contrast, 9% of the GPs were very confident and 59% confident in diagnosing severe asthma. More specific diagnostic tests for severe asthma, like total and specific immunoglobulin E levels and measurement of the fraction of exhaled nitric oxide, were run by specialists (χ2 = 171.4; df = 15, p Conclusions: Oral corticosteroids (OCSs) are considered as background therapy for severe asthma by GPs and specialists. In order to reduce the OCS burden, there is a need to improve the awareness for other add-on therapies. A joint collaboration between GPs and specialists is the key to leverage therapeutic strategies together.</p

First Report of Haemoproteus (Haemosporida, Haemoproteidae) Megalomeronts in the Brain of an Avian Host, with Description of Megalomerogony of Haemoproteus Pastoris, the Blood Parasite of the Common Starling

Species of Haemoproteus (Haemoproteidae, Haemosporida) are common bird pathogens. Recent molecular studies combined with histopathology research have reported development of megalomeronts of these parasites in various organs, sometimes resulting in the death of the avian host. Five Common starlings (Sturnus vulgaris) were found naturally infected with Haemoproteus pastoris lineage hLAMPUR01. The parasite was identified using microscopic examination of blood films and DNA sequences. Infected bird organs were investigated histologically for (i) the presence of exo-erythrocytic stages and (ii) the patterns of development (morphology and localization) in different host individuals. For the first time, megalomeronts of Haemoproteus parasites were seen developing in the brain, while numerous others at different stages of maturation were found in the intestine, pancreas, kidneys, lungs, esophagus, spleen, gizzard, and trachea. Megalomeronts were predominantly roundish or oval, up to 800 μm, they were surrounded by a capsular-like wall and developed asynchronously in the same bird individual. After megalomeront maturation and rupture, a massive infiltration of blood cells occurred, indicating the hemorrhagic processes. Review of available data showed that different Haemoproteus species produce markedly different megalomeronts, morphology of which can probably be predicted using phylogenetic analysis based on partial sequences of cytochrome b gene

Massive infection of lungs with exo-erythrocytic meronts in European robin Erithacus rubecula during natural Haemoproteus attenuatus haemoproteosis

Haemoproteus species are widespread avian blood parasites belonging to Haemoproteidae (Haemosporida). Blood stages of these pathogens have been relatively well-investigated, though exo-erythrocytic (tissue) stages remain unidentified for the majority of species. However, recent histopathological studies show that haemoproteins markedly affect bird organs during tissue mero-gony. This study investigated the exo-erythrocytic development of Haemoproteus (Parahaemoproteus) attenuatus (lineage hROBIN1), the common parasite of flycatchers (Muscicapidae). Naturally infected European robins Erithacus rubecula were examined. Parasite species and lineage were identified using microscopic examination of blood stages and DNA sequence analysis. Parasitaemia intensity varied between 0.8 and 26.5% in seven host individuals. Organs of infected birds were collected and processed for histological examination. Tissues stages (meronts) were seen in six birds and were present only in the lungs. The parasites were usually located in groups and were at different stages of maturation, indicating asynchronous exo-erythrocytic development. In most parasitized individuals, 100 meronts were observed in 1 cm2 section of lungs. The largest meronts reached 108 µm in length. Mature meronts contained numerous roundish merozoites of approximately 0.8 µm in diameter. Megalomeronts were not observed. Massive merogony and resulting damage of lungs is a characteristic feature during H. attenuatus infections and might occur in related parasite lineages, causing haemoproteosis

Human T-Cell Leukemia Virus Type 1 Tax Protein Down-Regulates Pre-T-Cell Receptor Alpha Gene Transcription in Human Immature Thymocytes

The human pre-T-cell receptor alpha (TCRα; pTα) gene encodes a polypeptide which associates with the TCRβ chain and CD3 molecules to form the pre-TCR complex. The surface expression of the pre-TCR is pTα dependent, and signaling through this complex triggers an early αβ T-cell developmental checkpoint inside the thymus, known as β-selection. E2A transcription factors, which are involved at multiple stages of T-cell development, regulate the transcription of the pTα gene. Here we show that the regulatory protein Tax of the human T-cell leukemia virus type 1 (HTLV-1) efficiently suppresses the E47-mediated activation of the pTα promoter. Furthermore, we report that in Tax lentivirally transduced human MOLT-4 T cells, which constitutively express the pTα gene, the amount of pTα transcripts decreases. Such a decrease is not observed in MOLT-4 cells transduced by a vector encoding the Tax mutant K88A, which is unable to interact with p300. These data underline that Tax inhibits pTα transcription by recruiting this coactivator. Finally, we show that the expression of Tax in human immature thymocytes results in a decrease of pTα gene transcription but does not modify the level of E47 transcripts. These observations indicate that Tax, by silencing E proteins, down-regulates pTα gene transcription during early thymocyte development. They further provide evidence that Tax can interfere with an important checkpoint during T-cell differentiation in the thymus

Unexpected absence of exo-erythrocytic merogony during high gametocytaemia in two species of Haemoproteus (Haemosporida: Haemoproteidae), including description of Haemoproteus angustus n. sp. (lineage hCWT7) and a report of previously unknown residual bodies during in vitro gametogenesis

Neglected avian blood parasites of the genus Haemoproteus (Haemoproteidae) have recently attracted attention due to the application of molecular diagnostic tools, which unravelled remarkable diversity of their exo-erythrocytic (or tissue) stages both regarding morphology and organ tropism levels. The development of haemoproteids might result in pathologies of internal organs, however the exo-erythrocytic development (EED) of most Haemoproteus species remains unknown. Seven individual birds - Curruca communis (1) and Phylloscopus trochilus (6) – with high gametocytaemia (between 1% and 24%) of Haemoproteus angustus n. sp. (hCWT7) and Haemoproteus palloris (lineage hWW1) were sampled in Lithuania, and their internal organs were examined extensively by parallel application of histology and chromogenic in situ hybridization methods. Tissue stages were apparently absent, suggesting that the parasitaemia was not accompanied by detectable tissue merogony. Haemoproteus angustus n. sp. was described and characterized morphologically and molecularly. Sexual process and ookinete development of the new species readily occurred in vitro, and a unique character for Haemoproteus parasites was discovered – the obligatory development of several tiny residual bodies, which were associated with intracellular transformation of both macrogametocytes and microgametocytes before their escape from the host cells and formation of gametes. A DNA haplotype network was constructed with lineages that cluster in one clade with the lineage hCWT7. This clade consists of lineages mostly found in Curruca birds, indicating specificity for birds of this genus. The lineage hCWT7 is mainly a parasite of C. communis. Most reports of this lineage came from Turkey, with only a few records in Europe, mostly in birds wintering in Africa where transmission probably occurs. This study highlights unexpected difficulties in the research of EED even when using sensitive molecular diagnostic tools and extends information about transformation in early stages of gametogenesis in haemosporidian parasites

Potentiation of Polarized Intestinal Caco-2 Cell Responsiveness to Probiotics Complexed with Secretory IgA*

The precise mechanisms underlying the interaction between intestinal bacteria and the host epithelium lead to multiple consequences that remain poorly understood at the molecular level. Deciphering such events can provide valuable information as to the mode of action of commensal and probiotic microorganisms in the gastrointestinal environment. Potential roles of such microorganisms along the privileged target represented by the mucosal immune system include maturation prior, during and after weaning, and the reduction of inflammatory reactions in pathogenic conditions. Using human intestinal epithelial Caco-2 cell grown as polarized monolayers, we found that association of a Lactobacillus or a Bifidobacterium with nonspecific secretory IgA (SIgA) enhanced probiotic adhesion by a factor of 3.4-fold or more. Bacteria alone or in complex with SIgA reinforced transepithelial electrical resistance, a phenomenon coupled with increased phosphorylation of tight junction proteins zonula occludens-1 and occludin. In contrast, association with SIgA resulted in both enhanced level of nuclear translocation of NF-κB and production of epithelial polymeric Ig receptor as compared with bacteria alone. Moreover, thymic stromal lymphopoietin production was increased upon exposure to bacteria and further enhanced with SIgA-based complexes, whereas the level of pro-inflammatory epithelial cell mediators remained unaffected. Interestingly, SIgA-mediated potentiation of the Caco-2 cell responsiveness to the two probiotics tested involved Fab-independent interaction with the bacteria. These findings add to the multiple functions of SIgA and underscore a novel role of the antibody in interaction with intestinal bacteria