Robust T cell immunity in convalescent individuals with asymptomatic or mild COVID-19

SARS-CoV-2-specific memory T cells will likely prove critical for long-term immune protection against COVID-19. Here, we systematically mapped the functional and phenotypic landscape of SARS-CoV-2-specific T cell responses in unexposed individuals, exposed family members, and individuals with acute or convalescent COVID-19. Acute-phase SARS-CoV-2-specific T cells displayed a highly activated cytotoxic phenotype that correlated with various clinical markers of disease severity, whereas convalescent-phase SARS-CoV-2-specific T cells were polyfunctional and displayed a stem-like memory phenotype. Importantly, SARS-CoV-2-specific T cells were detectable in antibody-seronegative exposed family members and convalescent individuals with a history of asymptomatic and mild COVID-19. Our collective dataset shows that SARS-CoV-2 elicits broadly directed and functionally replete memory T cell responses, suggesting that natural exposure or infection may prevent recurrent episodes of severe COVID-19

Characterization of the decoupling of natural killer cell functions during infections with dengue, zika and chikungunya viruses

L'histoire récente à été marquée par des épidémies récentes de dengue (Denv), Chikungunya (CHIKV) et Zika (ZIKV). Bien que ces maladies soient largement asymptomatiques, elles peuvent générer de sérieuses complications comme des formes chroniques d'arthralgies et peuvent causer des hémorragies pouvant conduire au décès (Majoritairement DENV), des microcéphalies (Maj. ZIKV) et des Syndromes de Guillain-Barré (Zikv et Chikv). Ces épidémies récentes ont poussé l'OMS à classer ces maladies comme maladies à déclaration obligatoire. A ce jour aucun traitement spécifique existe contre ces maladies rendant prioritaire la compréhension de l'immunité dirigée contre ces virus. Bien que peu de choses soient connues sur l'immunité dirigée contre ces virus, certaines études ont montré le rôle de l'immunité innée dans la clairance de ces infections. Parmi les cellules de l'immunité innée on trouve les cellules Natural Killer qui ont la capacité de s'activer sans immunisation préalable via la reconnaissance de molécules de stresse. Une fois activées, ces cellules ont la capacité de produire des cytokines afin d'induire l'activation de l'immunité adaptatives et de tuer les cellules infectées. Les premiers travaux menés au laboratoire ont montré un découplage des fonctions NK au cours de ces infections : Cytoxicité uniquement au cours des infections par CHIKV, production de cytokines au cours des infections par DENV. Nous nous sommes intéressé à créer des modèles d'étude des interactions entre les cellules NK et des cibles infectées par ces virus afin de caractériser les couples ligands/récepteurs mis en jeu ainsi que les voies de signalisation impliquées dans ce découplage fonctionnel.Recent history has been marked by recent epidemics of dengue fever (Denv), Chikungunya (CHIKV) and Zika (ZIKV). Although these diseases are largely asymptomatic, they can generate serious complications such as chronic forms of arthralgia and can cause hemorrhages that can lead to death (mainly DENV), microcephalies (Mainly ZIKV) and Guillain-Barré Syndromes (Zikv and Chikv). These recent epidemics have prompted WHO to classify these diseases as notifiable diseases. To date, no specific treatment exists against these diseases, making it a priority to understand the immunity directed against these viruses. Although little is known about immunity against these viruses, some studies have shown the role of innate immunity in the clearance of these infections. Among the innate immunity cells : Natural Killer cells have the ability to be activated without prior immunization via the recognition of stress molecules. Once activated, these cells have the ability to produce cytokines to induce the activation of adaptive immunity and can kill infected cells. Initial work in the laboratory showed a decoupling of NK functions during these infections: Cytoxicity only during CHIKV infections, cytokine production during DENV infections. We have been interested in creating models to study interactions between NK cells and targets infected with these viruses in order to characterize the ligand/receptor pairs involved and in order to characterize the signalling pathways involved in this functional decoupling

Caractérisation du découplage des fonctions des cellules natural killer au cours des infections par les virus de la dengue, du zika et du chikungunya

Recent history has been marked by recent epidemics of dengue fever (Denv), Chikungunya (CHIKV) and Zika (ZIKV). Although these diseases are largely asymptomatic, they can generate serious complications such as chronic forms of arthralgia and can cause hemorrhages that can lead to death (mainly DENV), microcephalies (Mainly ZIKV) and Guillain-Barré Syndromes (Zikv and Chikv). These recent epidemics have prompted WHO to classify these diseases as notifiable diseases. To date, no specific treatment exists against these diseases, making it a priority to understand the immunity directed against these viruses. Although little is known about immunity against these viruses, some studies have shown the role of innate immunity in the clearance of these infections. Among the innate immunity cells : Natural Killer cells have the ability to be activated without prior immunization via the recognition of stress molecules. Once activated, these cells have the ability to produce cytokines to induce the activation of adaptive immunity and can kill infected cells. Initial work in the laboratory showed a decoupling of NK functions during these infections: Cytoxicity only during CHIKV infections, cytokine production during DENV infections. We have been interested in creating models to study interactions between NK cells and targets infected with these viruses in order to characterize the ligand/receptor pairs involved and in order to characterize the signalling pathways involved in this functional decoupling.L'histoire récente à été marquée par des épidémies récentes de dengue (Denv), Chikungunya (CHIKV) et Zika (ZIKV). Bien que ces maladies soient largement asymptomatiques, elles peuvent générer de sérieuses complications comme des formes chroniques d'arthralgies et peuvent causer des hémorragies pouvant conduire au décès (Majoritairement DENV), des microcéphalies (Maj. ZIKV) et des Syndromes de Guillain-Barré (Zikv et Chikv). Ces épidémies récentes ont poussé l'OMS à classer ces maladies comme maladies à déclaration obligatoire. A ce jour aucun traitement spécifique existe contre ces maladies rendant prioritaire la compréhension de l'immunité dirigée contre ces virus. Bien que peu de choses soient connues sur l'immunité dirigée contre ces virus, certaines études ont montré le rôle de l'immunité innée dans la clairance de ces infections. Parmi les cellules de l'immunité innée on trouve les cellules Natural Killer qui ont la capacité de s'activer sans immunisation préalable via la reconnaissance de molécules de stresse. Une fois activées, ces cellules ont la capacité de produire des cytokines afin d'induire l'activation de l'immunité adaptatives et de tuer les cellules infectées. Les premiers travaux menés au laboratoire ont montré un découplage des fonctions NK au cours de ces infections : Cytoxicité uniquement au cours des infections par CHIKV, production de cytokines au cours des infections par DENV. Nous nous sommes intéressé à créer des modèles d'étude des interactions entre les cellules NK et des cibles infectées par ces virus afin de caractériser les couples ligands/récepteurs mis en jeu ainsi que les voies de signalisation impliquées dans ce découplage fonctionnel

Control of Acute Arboviral Infection by Natural Killer Cells

The recent explosive pandemic of chikungunya virus (CHIKV) followed by Zika (ZIKV) virus infections occurring throughout many countries represents the most unexpected arrival of arthropod-borne viral diseases in the past 20 years. Transmitted through the bite of Aedes mosquitoes, the clinical picture associated with these acute arbovirus infections, including Dengue (DENV), CHIKV and ZIKV, ranges from classical febrile illness to life-threatening disease. Whereas ZIKV and CHIKV-mediated infections have previously been recognized as relatively benign diseases, in contrast to Dengue fever, recent epidemic events have brought waves of increased morbidity and mortality leading to a serious public health problem. Although the host immune response plays a crucial role in controlling infections, it may also promote viral spread and immunopathology. Here, we review recent developments in our understanding of the immune response, with an emphasis on the early antiviral immune response mediated by natural killer cells and emphasize their Janus-faced effects in the control of arbovirus infection and pathogenesis. Improving our understanding knowledge on of the mechanisms that control viral infection is crucial in the current race against the globalization of arbovirus epidemics

Zika virus in the eye of the cytokine storm

International audienc

HLA-C-restricted viral epitopes are associated with an escape mechanism from KIR2DL2+ NK cells in Lassa virus infectionResearch in context

Background: Lassa virus (LASV) is the etiologic agent of an acute hemorrhagic fever endemic in West Africa. Natural killer (NK) cells control viral infections in part through the interaction between killer cell immunoglobulin-like receptors (KIRs) and their ligands. LASV infection is associated with defective immune responses, including inhibition of NK cell activity in the presence of MHC-class 1+-infected target cells. Methods: We compared individual KIR and HLA-class 1 genotypes of 68 healthy volunteers to 51 patients infected with LASV in Sierra Leone, including 37 survivors and 14 fatalities. Next, potential HLA-C1, HLA-C2, and HLA-Bw4 binding epitopes were in silico screened among LASV nucleoprotein (NP) and envelope glycoprotein (GP). Selected 10-mer peptides were then tested in peptide-HLA stabilization, KIR binding and polyfunction assays. Findings: LASV-infected patients were similar to healthy controls, except for the inhibitory KIR2DL2 gene. We found a specific increase in the HLA-C1:KIR2DL2 interaction in fatalities (10/11) as compared to survivors (12/19) and controls (19/29). We also identified that strong of NP and GP viral epitopes was only observed with HLA-C molecules, and associated with strong inhibition of degranulation in the presence of KIR2DL+ NK cells. This inhibitory effect significantly increased in the presence of the vGP420 variant, detected in 28.1% of LASV sequences. Interpretation: Our finding suggests that presentation of specific LASV epitopes by HLA-C alleles to the inhibitory KIR2DL2 receptor on NK cells could potentially prevent the killing of infected cells and provides insights into the mechanisms by which LASV can escape NK-cell-mediated immune pressure. Keywords: Lassa virus, NK cells, KIR-L, HLA-C, Viral escap

Tagging of NS5A expressed from a functional hepatitis C virus replicon

Knowledge of how hepatitis C virus (HCV) proteins associate with components of the host cell to form a functional replication complex is still limited. To address this issue, HCV replicon constructs were generated where either green fluorescent protein (GFP) or the Propionibacterium shermanii transcarboxylase domain (PSTCD) was introduced into the NS5A coding region. Insertion of both GFP and PSTCD was tolerated well, allowing formation of stable replicon-containing cell lines that contained viral protein and transcript levels that were comparable to those of an unmodified parental replicon. Cell lines generated from the GFP-tagged NS5A replicon allowed live-cell visualization of the location of NS5A. Cell lines generated from the PSTCD-tagged replicons allowed rapid and efficient precipitation of the PSTCD-tagged NS5A, as well as other HCV non-structural proteins, using streptavidin-coated magnetic beads. Both replicons represent useful tools that offer different but complementary ways of examining replication-complex formation in cells

Comprehensive analysis of early T cell responses to acute Zika Virus infection during the first epidemic in Bahia, Brazil.

BackgroundIn most cases, Zika virus (ZIKV) causes a self-limited acute illness in adults, characterized by mild clinical symptoms that resolve within a few days. Immune responses, both innate and adaptive, play a central role in controlling and eliminating virus-infected cells during the early stages of infection.AimTo test the hypothesis that circulating T cells exhibit phenotypic and functional activation characteristics during the viremic phase of ZIKV infection.MethodsA comprehensive analysis using mass cytometry was performed on peripheral blood mononuclear cells obtained from patients with acute ZIKV infection (as confirmed by RT-PCR) and compared with that from healthy donors (HD). The frequency of IFN-γ-producing T cells in response to peptide pools covering immunogenic regions of structural and nonstructural ZIKV proteins was quantified using an ELISpot assay.ResultsCirculating CD4+ and CD8+ T lymphocytes from ZIKV-infected patients expressed higher levels of IFN-γ and pSTAT-5, as well as cell surface markers associated with proliferation (Ki-67), activation ((HLA-DR, CD38) or exhaustion (PD1 and CTLA-4), compared to those from HD. Activation of CD4+ and CD8+ memory T cell subsets, including Transitional Memory T Cells (TTM), Effector Memory T cells (TEM), and Effector Memory T cells Re-expressing CD45RA (TEMRA), was prominent among CD4+ T cell subset of ZIKV-infected patients and was associated with increased levels of IFN-γ, pSTAT-5, Ki-67, CTLA-4, and PD1, as compared to HD. Additionally, approximately 30% of ZIKV-infected patients exhibited a T cell response primarily directed against the ZIKV NS5 protein.ConclusionCirculating T lymphocytes spontaneously produce IFN-γ and express elevated levels of pSTAT-5 during the early phase of ZIKV infection whereas recognition of ZIKV antigen results in the generation of virus-specific IFN-γ-producing T cells