Viral infection : persistence, host response and pathophysiology
Coordinator : J. Izopet
Our team specializes in the pathophysiology of infections with human immunodeficiency virus (HIV), hepatitis E virus (HEV) and zika virus (ZIKV). The major specific topic is the mechanisms underlying the persistence of virus in immunocompetent hosts (HIV, ZIKV) and immunocompromised patients (HEV). We are also working on how HIV enters host cells via chemokine receptors and the pathophysiology of HIV infection in the intestinal mucosa. Another aspect of our work is the route of transmission and pathogenesis of HEV and ZIKV during pregnancy. We have developed a number of specific model cell systems, including placental explants, extravillous cytotrophoblasts, hepatocytes, enterocytes, peripheral and tissue lymphocytes, together with systems based on clinical samples (intestinal tissue, early and term placenta, blood and biopsies from immunocompromised patients).
AXIS 1: HIV
Our laboratory develops a wide array of approaches in the fields of immunology, virology, molecular pharmacology and structural biology to study important aspects of the pathophysiology of HIV infection and AIDS. We are deeply anchored at the interface between basic and clinical science and benefit from the proximity of the Toulouse University Hospital. Our research comprises two main axes, which are themselves highly interconnected:
Mechanisms of HIV-1 entry and their pathophysiological consequences
PI: B. Lagane; Participants: P. Colin, B. Puissant, S. Raymond, M. Armani
We study the properties of interactions between the HIV-1 envelope glycoproteins (Env) and their cellular receptors, i.e. CD4 and depending on the viral tropism, the coreceptors CCR5 or CXCR4. We investigate how these interactions are regulated by factors of the target cells and the host immune responses and conversely, how the virus alters the cellular functions and immunity of the host. Finally we seek to characterize how the properties of viral entry shape the phenotypic properties of viruses and their role in different processes and stages of HIV-1 infection. These include first the very earliest step of infection, that is transmission of the virus. We seek to identify whether Env determinants lead to virus selection during transmission and favor the first steps in the establishment of infection in the host (WP #1). We also study how the properties of viral entry change over time in infection and by so doing contribute to pathogenesis of infection, in particular depletion of CD4 T-cells. In this regard, we investigate the role that the coreceptor natural ligands, i.e. several CC chemokines for CCR5 and CXCL12 for CXCR4, could play as a driving force of evolution of the properties of CCR5- and CXCR4-using viruses (WP #2). A third project is dealing with how the properties of Env interactions with cellular receptors regulate the cellular tropism of viruses, in particular their capacity to enter into macrophages. These cells play a critical role in the pathophysiology of HIV-1 infection. They form viral reservoirs and contribute to dissemination of the virus in tissues, in particular the central nervous systems, which has been linked to development of neurological disorders in patients. On this topic, we are currently pursuing our recent work (Colin, PLoS Pathog., 2018) on the role of CCR5 conformational heterogeneity in HIV-1 entry into macrophages, both in the context of infection by cell free viruses and through CD4 T-cells/macrophages contacts (WP #3). Lastly, our research deals with the signaling properties of primary Env/CCR5 interactions, which are thought to contribute to many aspects of the pathophysiology of infection. We speculate that signaling of Envs might depend on the CCR5 conformation(s) to which they bind, and that this process contributes to differences in the phenotypic properties between distinct HIV-1 strains. We are currently investigating this using BRET-based methods to monitor in real-time and in living cells the most upstream events of CCR5 signaling, i.e. interactions with G proteins and arrestins (WP #4).
HIV-1 persistence and impaired immune reconstitution in the gut of treated patients.
PI: P. Delobel; Participants: M. Nayrac, C. Vellas, M. Cazabat, M. Requena
Incomplete immune reconstitution in the gut of HIV-1-infected patients, even under sustained effective cART, leads to persistent impairment in epithelium integrity, microbial translocation, and chronic inflammation that drives non-AIDS-defining illnesses such as metabolic and cardio-vascular diseases. We have contributed to a better understanding of the mechanisms that lead to impaired recruitment of CD4 T-cells to the gut, notably of Th17 cells, a T-cell subset critical for mucosal defense against pathogens (Mavigner, J Clin Invest, 2012; Loiseau, Mucosal Immunol, 2016). We have found that this impaired recruitment is due to a downregulation of the production of some chemokines by enterocytes in the gut of HIV-1-infected patients, in particular CCL20 and CCL25. In contrast, other T-cell subsets in the gut remain effectively recruited, such as Th1 cells and effector CD8 T-cells through CXCR3-mediated chemotaxis (Loiseau, J Infect Dis, 2019). They further contribute to the impaired recruitment of Th17 cells through IFN-g and IL-18-mediated mechanisms, while increasing the proportion of Treg cells, thereby perpetuating a Th17/Treg imbalance. We also found that contrary to Th17 cells, Th22 cells can efficiently be recruited to the gut through the CCL28-CCR10 axis as an alternative to the altered CCL20-CCR6 axis in HIV-1-infected patients on cART. We are currently pursuing our work to better decipher the chemokine network that govern T-cell recruitment in the gut mucosa, notably the mechanisms involved in CCL20 and CCL25 down-regulation. We developed an ex-vivo model of human primary enterocyte cultures on transwells to study chemokines production by enterocytes and T-cells/enterocytes interactions in co-cultures (WP #1).
A second part of our work concerns the persistence of HIV-1 in the gut mucosa despite cART. We recently found that residual virus replication persists despite cART and replenishes the reservoirs in the gut mucosa of treated patients. The resulting chronic antigenic stimulation drives the recruitment of HIV-1-specific T-cells in the gut and contributes to impairing CD4 T-cell reconstitution. We aim at better defining the virus reservoirs and HIV-1 target cells in the gut mucosa in gut biopsies from treated patients and by using an ex-vivo model of gut histocultures (WP #2).
Lastly, the third part of our work is dedicated to investigating the mechanisms of Th17/Treg imbalance, as well as of those that account for T-cell exhaustion in the gut of treated patients. We recently collected gut endoscopic biopsies at different levels (duodenum, ileum, and colon) from well-characterized HIV-1-infected patients on cART (n=40) and uninfected controls (n=40) recruited at Toulouse University Hospital in the ANRS EP61 GALT study (PI, P. Delobel). These samples will be used to perform in-depth analyses of the virus reservoirs (cell-associated RNA and DNA, NGS of near full length proviruses) and of the mucosal T-cell response, notably Tregs and exhausted T-cells (WP #3).
AXIS 2: HEV
Pathogenesis of HEV infection
Role of gamma-delta T cells during HEV infections
PI : E. Champagne ; Participants: F. Abravanel, H. El Costa.
Hepatitis E virus (HEV, genotype-3) causes chronic infections in immunosuppressed patients. Viral persistence is linked to the immunological status of the patients but the determinants are largely unknown. We are committed to investigate γδ T cells in the context of human viral infections and we have observed that γδ T cells present activation and mobilization markers in immunosuppressed patients at the acute phase of HEV infection. We aim to clarify their role and if their activation is beneficial or detrimental. Our work is based on the analysis of patient blood samples collected at the acute, resolving or chronic phase of infection. Although rarely symptomatic, acute infections in immunocompetent individuals are sometimes diagnosed and allow investigating antiviral immunity in an immunocompetent context. γδ T cell reactivity against HEV-infected cells is also studied in in vitro models of infection and this has revealed that the virus is able to modulate the cytokine responses of γδ T cells to promote regulatory properties. Our objective is to determine if the immunomodulatory properties of HEV operate in vivo and can be targeted for therapeutic purposes.
HEV life cycle in hepatocytes and enterocytes
Role of autophagy in HEV budding from polarized hepatocytes
PI: S. Chapuy-Regaud ; Participants: J. Izopet, N. Capelli.
The budding of the quasi-enveloped form of the Hepatitis E Virus (eHEV) has been shown to depend on the exocytosis pathway. We developed a system of HEV culture on polarized cells which allows reproducing main features of hepatocytes (including polarized albumin and bile acid secretion and ZO-1 expression). In this system, eHEV is released in an infectious form mainly to the bile side; our preliminary results also show the role of autophagy. Our aim is to understand how exocytosis and autophagy are hijacked by eHEV for its egress and interplay at the molecular level. To this end, we study the characteristics of eHEV particles by proteomics and lipidomics and the intracellular events by shRNA knockdown of target proteins and imaging.
Replication of HEV in enterocytes
PI: J. Izopet ; Participants: O. Marion, M. Migueres, S. Lhomme.
The intestinal epithelium is the first barrier that HEV must cross before it can enter the portal bloodstream and gain access to the liver. The mechanisms by which HEV penetrates the gut epithelium tight-junction barrier are unknown. Animal model data indicate that the gut is an important site of extra-hepatic HEV replication and the human adenocarcinoma Caco-2 cell line is permissive to HEV. Our data from patients for whom ribavirin failed suggest that the gut could be an important virus reservoir. The role of intestinal M cells in HEV replication or transcytosis is unknown. Our preliminary data from cultures of primary small intestine epithelial cells polarized on transwell inserts indicate that enterocytes are permissive to HEV-1 and HEV-3 and release eHEV particles, preferentially from the apical side. Our main objectives are: (1) to study the localization of HEV in the intestinal mucosa after ex vivo infection of intestinal explants (2) to study changes in the permeability of epithelial cells induced by HEV infection (3) to determine the subcellular location of virus proteins (4) to evaluate the role of M cells in HEV replication or transcytosis (5) to study the effect of ribavirin and alpha interferon on virus production (6) to study innate immune signaling pathways following virus entry (HEV-1 vs HEV-3) and cytokine production.
AXIS 3: ZIKV
We are studying the replication of ZIKV in the genital compartment and at the maternofetal interface. We have evidence that ZIKV replicates differentially in a wide range of maternal and fetal cells, including decidual fibroblasts and macrophages, trophoblasts and umbilical cord mesenchymal stem cells.
Our latest results show that the virus persists in the semen of infected patients for a long time and that the spermatozoa bear viral antigens. We are now looking at the mechanisms the virus uses to persist in the genital compartment.
In: Free Radical Biology & Medicine, 2021, ISSN: 1873-4596.
In: Journal of Gynecology Obstetrics and Human Reproduction, vol. 50, no. 1, pp. 101942, 2021, ISSN: 2468-7847.
In: Journal of obstetrics and gynaecology Canada: JOGC = Journal d'obstetrique et gynecologie du Canada: JOGC, vol. 43, no. 1, pp. 43–49, 2021, ISSN: 1701-2163.
In: Hypertension in Pregnancy, pp. 1–7, 2020, ISSN: 1525-6065.
In: Journal of obstetrics and gynaecology Canada: JOGC = Journal d'obstetrique et gynecologie du Canada: JOGC, vol. 42, no. 12, pp. 1498–1504, 2020, ISSN: 1701-2163.
In: Journal of Gynecology Obstetrics and Human Reproduction, pp. 101974, 2020, ISSN: 2468-7847.
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In: JAMA pediatrics, vol. 174, no. 8, pp. 749–750, 2020, ISSN: 2168-6211.
In: American Journal of Obstetrics and Gynecology, vol. 223, no. 2, pp. 299–300, 2020, ISSN: 1097-6868.
In: European Journal of Immunology, vol. 50, no. 6, pp. 763–767, 2020, ISSN: 1521-4141.
COVID19 and Breastfeeding: Not That Simple Journal Article
In: Journal of Human Lactation: Official Journal of International Lactation Consultant Association, vol. 36, no. 2, pp. 369–370, 2020, ISSN: 1552-5732.
In: Scientific Reports, vol. 10, no. 1, pp. 8177, 2020, ISSN: 2045-2322.
In: Prenatal Diagnosis, vol. 40, no. 5, pp. 519–527, 2020, ISSN: 1097-0223.
In: Free Radical Biology & Medicine, vol. 149, pp. 8–22, 2020, ISSN: 1873-4596.
In: Journal for Immunotherapy of Cancer, vol. 8, no. 1, 2020, ISSN: 2051-1426.
In: American Journal of Obstetrics and Gynecology, 2020, ISSN: 1097-6868.
In: American Journal of Perinatology, 2020, ISSN: 1098-8785.
In: Journal of Gynecology Obstetrics and Human Reproduction, vol. 49, no. 1, pp. 101633, 2020, ISSN: 2468-7847.
In: Free Radical Biology & Medicine, vol. 141, pp. 416–425, 2019, ISSN: 1873-4596.
In: Redox Biology, vol. 22, pp. 101126, 2019, ISSN: 2213-2317.
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Transcriptional profiling of Scedosporium apiospermum enzymatic antioxidant gene battery unravels the involvement of thioredoxin reductases against chemical and phagocytic cells oxidative stress Journal Article
In: Medical Mycology, vol. 57, no. 3, pp. 363–373, 2019, ISSN: 1460-2709.
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Laser Adjuvant-Assisted Peptide Vaccine Promotes Skin Mobilization of Dendritic Cells and Enhances Protective CD8(+) TEM and TRM Cell Responses against Herpesvirus Infection and Disease Journal Article
In: J Virol, vol. 92, no. 8, 2018, ISSN: 1098-5514 (Electronic) 0022-538X (Linking).
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CXCL10/CXCR3-Dependent Mobilization of Herpes Simplex Virus-Specific CD8(+) TEM and CD8(+) TRM Cells within Infected Tissues Allows Efficient Protection against Recurrent Herpesvirus Infection and Disease Journal Article
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In: Journal of Thoracic Oncology: Official Publication of the International Association for the Study of Lung Cancer, vol. 11, no. 10, pp. 1765–1773, 2016, ISSN: 1556-1380.
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HIV-1 Tat Protein Induces Production of Proinflammatory Cytokines by Human Dendritic Cells and Monocytes/Macrophages through Engagement of TLR4-MD2-CD14 Complex and Activation of NF-kappaB Pathway Journal Article
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In: Fungal Biology, vol. 119, no. 12, pp. 1322–1333, 2015, ISSN: 1878-6146.
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Knowledge of the biology of RNA viruses and pathophysiological mechanisms.
Our research generates fundamental knowledge about chronic viral infections (HIV and HEV) and emerging infection (ZIKV), and clinical applications to combat these viruses whose pathophysiology remains unclear. Our links with the clinical departments of Toulouse University Hospital, with the technical platform of the CPTP and several international collaborations ensure the optimal development of original themes.
Our team members are committed to the teaching of students in the faculties of Medicine and Pharmacy; we also welcome Master and PhD students from both France and abroad to work and study in our laboratory.
Qian Chen (2016-2019)
Loukas Papargyris (2016-2019)
Jordi Gouilly (2015-2018)
Sènan d’Almeida (2012-2015)
Johan Siewiera (2010-2014)