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.Fil: Sekine, Takuya. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Perez Potti, André. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Rivera Ballesteros, Olga. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Strålin, Kristoffer. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Gorin, Jean Baptiste. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Olsson, Annika. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Llewellyn Lacey, Sian. University Hospital of Wales; Reino UnidoFil: Kamal, Habiba. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Bogdanovic, Gordana. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Muschiol, Sandra. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Wullimann, David J.. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Kammann, Tobias. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Emgård, Johanna. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Parrot, Tiphaine. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Folkesson, Elin. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Rooyackers, Olav. Karolinska Huddinge Hospital. Karolinska Institutet; Suecia. Karolinska University Hospital; SueciaFil: Eriksson, Lars I.. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Henter, Jan Inge. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Sönnerborg, Anders. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Allander, Tobias. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Albert, Jan. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Nielsen, Morten. Technical University of Denmark; Dinamarca. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas; ArgentinaFil: Klingstrom, Jonas. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Gredmark Russ, Sara. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Björkström, Niklas K.. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Sandberg, Johan K.. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Price, David A.. Cardiff University School of Medicine; Reino UnidoFil: Ljunggren, Hans Gustaf. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Aleman, Soo. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Buggert, Marcus. Karolinska Huddinge Hospital. Karolinska Institutet; Sueci

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

Alpha Particles Induce Autophagy in Multiple Myeloma Cells

International audienceOBJECTIVES: Radiation emitted by the radionuclides in radioimmunotherapy (RIT) approaches induce direct killing of the targeted cells as well as indirect killing through the bystander effect. Our research group is dedicated to the development of α-RIT, i.e., RIT using α-particles especially for the treatment of multiple myeloma (MM). γ-irradiation and β-irradiation have been shown to trigger apoptosis in tumor cells. Cell death mode induced by (213)Bi α-irradiation appears more controversial. We therefore decided to investigate the effects of (213)Bi on MM cell radiobiology, notably cell death mechanisms as well as tumor cell immunogenicity after irradiation.METHODS: Murine 5T33 and human LP-1 MM cell lines were used to study the effects of such α-particles. We first examined the effects of (213)Bi on proliferation rate, double-strand DNA breaks, cell cycle, and cell death. Then, we investigated autophagy after (213)Bi irradiation. Finally, a coculture of dendritic cells (DCs) with irradiated tumor cells or their culture media was performed to test whether it would induce DC activation.RESULTS: We showed that (213)Bi induces DNA double-strand breaks, cell cycle arrest, and autophagy in both cell lines, but we detected only slight levels of early apoptosis within the 120 h following irradiation in 5T33 and LP-1. Inhibition of autophagy prevented (213)Bi-induced inhibition of proliferation in LP-1 suggesting that this mechanism is involved in cell death after irradiation. We then assessed the immunogenicity of irradiated cells and found that irradiated LP-1 can activate DC through the secretion of soluble factor(s); however, no increase in membrane or extracellular expression of danger-associated molecular patterns was observed after irradiation.CONCLUSION: This study demonstrates that (213)Bi induces mainly necrosis in MM cells, low levels of apoptosis, and autophagy that might be involved in tumor cell death

Radio- immunothérapie alpha : Principes et intérêts en immunité antitumorale

International audience> La radioimmunothérapie alpha (RITα) est une thérapie anticancéreuse vectorisée utilisant généralement un anticorps monoclonal spécifique d'un antigène tumoral couplé à un émetteur de particules α. Les émetteurs α représentent un outil idéal pour éradiquer les tumeurs disséminées ou les métastases. De récentes données démontrent que les rayonnements ionisants, en plus de leur cytotoxicité directe, peuvent aussi induire une immunité antitumorale efficace. Les effets biologiques de l'irradiation pourraient donc être utilisés pour potentialiser la réponse à différents types d'immunothérapie, et ainsi ouvrir la voie au développement de nouvelles thérapies combinant RITα et immunothérapies. < radionucléide. Le choix du radionu-cléide repose sur des considérations pratiques (le coût, la disponibilité, le type de techniques de radiomar-quage et la facilité d'utilisation), le type d'émission du radioélément, le transfert d'énergie linéique (TEL : quantité d'énergie transférée au milieu par la particule incidente, par unité de longueur de la trajectoire en keV 1 /µm) et la demi-vie physique du radioisotope (durée nécessaire pour que la moitié des noyaux radioactifs d'une source se soient désintégrés) [2]. Cette dernière doit être, autant que possible, en adéquation avec la pharmacocinétique du vecteur utilisé, afin de délivrer la plus grande dose possible de radioactivité à la tumeur après l'injection. Une demi-vie trop courte entraînera un nombre élevé de désintégrations avant d'atteindre la cible. À l'inverse, une demi-vie trop longue engendrera un grand nombre de désintégrations du radionucléide pendant la phase d'éli-mination du vecteur, rendant le radioimmunoconjugué plus toxique. La demi-vie doit également être compatible avec les applications cliniques et la prise en charge du patient. Ainsi, le temps nécessaire au transfert du radionucléide du site de production jusqu'à l'hôpital, 1 1 keV (kiloélectronvolts) = 10 3 eV ; 1 MeV (megaélectonvolts) = 10 6 eV

Antitumor Immunity Induced after α Irradiation

Radioimmunotherapy (RIT) is a therapeutic modality that allows delivering of ionizing radiation directly to targeted cancer cells. Conventional RIT uses β-emitting radioisotopes, but recently, a growing interest has emerged for the clinical development of α particles. α emitters are ideal for killing isolated or small clusters of tumor cells, thanks to their specific characteristics (high linear energy transfer and short path in the tissue), and their effect is less dependent on dose rate, tissue oxygenation, or cell cycle status than γ and X rays. Several studies have been performed to describe α emitter radiobiology and cell death mechanisms induced after α irradiation. But so far, no investigation has been undertaken to analyze the impact of α particles on the immune system, when several studies have shown that external irradiation, using γ and X rays, can foster an antitumor immune response. Therefore, we decided to evaluate the immunogenicity of murine adenocarcinoma MC-38 after bismuth-213 (213Bi) irradiation using a vaccination approach. In vivo studies performed in immunocompetent C57Bl/6 mice induced a protective antitumor response that is mediated by tumor-specific T cells. The molecular mechanisms potentially involved in the activation of adaptative immunity were also investigated by in vitro studies. We observed that 213Bi-treated MC-38 cells release “danger signals” and activate dendritic cells. Our results demonstrate that α irradiation can stimulate adaptive immunity, elicits an efficient antitumor protection, and therefore is an immunogenic cell death inducer, which provides an attractive complement to its direct cytolytic effect on tumor cells

Combining α-Radioimmunotherapy and Adoptive T Cell Therapy to Potentiate Tumor Destruction.

Ionizing radiation induces direct and indirect killing of cancer cells and for long has been considered as immunosuppressive. However, this concept has evolved over the past few years with the demonstration that irradiation can increase tumor immunogenicity and can actually favor the implementation of an immune response against tumor cells. Adoptive T-cell transfer (ACT) is also used to treat cancer and several studies have shown that the efficacy of this immunotherapy was enhanced when combined with radiation therapy. α-Radioimmunotherapy (α-RIT) is a type of internal radiotherapy which is currently under development to treat disseminated tumors. α-particles are indeed highly efficient to destroy small cluster of cancer cells with minimal impact on surrounding healthy tissues. We thus hypothesized that, in the setting of α-RIT, an immunotherapy like ACT, could benefit from the immune context induced by irradiation. Hence, we decided to further investigate the possibilities to promote an efficient and long-lasting anti-tumor response by combining α-RIT and ACT. To perform such study we set up a multiple myeloma murine model which express the tumor antigen CD138 and ovalbumine (OVA). Then we evaluated the therapeutic efficacy in the mice treated with α-RIT, using an anti-CD138 antibody coupled to bismuth-213, followed by an adoptive transfer of OVA-specific CD8+ T cells (OT-I CD8+ T cells). We observed a significant tumor growth control and an improved survival in the animals treated with the combined treatment. These results demonstrate the efficacy of combining α-RIT and ACT in the MM model we established

Factors Influencing Functional Heterogeneity in Human Mucosa-Associated Invariant T Cells

Mucosa-associated invariant T (MAIT) cells are unconventional innate-like T cells that recognize microbial riboflavin metabolites presented by the monomorphic MHC class I-related (MR1) molecule. Despite the high level of evolutionary conservation of MR1 and the limited diversity of known antigens, human MAIT cells and their responses may not be as homogeneous as previously thought. Here, we review recent findings indicating that MAIT cells display microbe-specific response patterns with multiple layers of heterogeneity. The natural killer cell receptor CD56 marks a MAIT cell subset with distinct response profile, and the T cell receptor β-chain diversity influences responsiveness at the single cell level. The MAIT cell tissue localization also influences their response profiles with higher IL-17 in tissue-resident MAIT cells. Furthermore, there is emerging evidence that the type of antigen-presenting cells, and innate cytokines produced by such cells, influence the quality of the ensuing MAIT cell response. On the microbial side, the expression patterns of MR1-presented antigenic and non-antigenic compounds, expression of other bioactive microbial products, and of innate pattern recognition ligands all influence downstream MAIT cell responses. These recent findings deepen our understanding of MAIT cell functional diversity and adaptation to the type and location of microbial challenge

OT-I CD8⁺ T cells persist within the tumor but also in the lymphoid organs and the periphery.

<p>After the different treatment as indicated on the graph (n = 8 to 10 per group), when tumour reached a volume of 2500 mm³, the mice were sacrificed and spleen (A), lymph nodes (B), tumor (C) and blood (D) were harvested. Then, cells were stained with monoclonal anti-CD8b PE and anti-CD45.1 FITC. Histograms represent the percentage of CD45.1⁺ in CD8⁺ cells. Statistical analysis were performed using non-parametric Mann-Whitney test.</p

5T33-OVA phenotypic analysis after transduction by a lentiviral vector encoding cytoplasmic <i>ovalbumin</i> (A) 5T33 and 5T33-OVA staining with PE-conjugated antibody 25-D1.16, which specifically recognizes the OVA peptide ‘SIINFEKL’ bound to the MHC class I molecule H-2K^b and (B) staining of 5T33 and 5T33-OVA with APC-conjugated anti-mouse CD138 mAb.

<p>Flow cytometry was performed on a BD FACSCalibur Flow Cytometry System.</p

Adoptive OT-I T cell transfer.

<p>(A), Dose response of 5T33-OVA tumor cells to adoptive transfer of OT-I CD8+ T cells treatment. Animals were injected subcutaneously with 2x10⁶ tumor cells and received the indicated doses of OT-I CD8⁺ T cells (n = 10 mice per group). Tumor volume was determined by using a caliper. Data points represent mean ± SD of 10 measures. *** p<0,001 as determined by two-way ANOVA and Bonferonni post-tests. (B), Tumors were explanted and single cell suspensions were prepared by grinding tumors in a tissu grinder. Cells were stained with monoclonal anti-CD8b PE and anti-CD45.1 FITC. Histograms represent the percentage of CD45.1⁺ in CD8⁺ cells.</p