Search

An effective delivery platform is crucial for the development of mRNA vaccines and therapeutics. Here, a versatile platform utilizing cholesterol-modified oligonucleotides (L-oligo) that bind to the mRNA within lipid nanoparticles (LNP), and enables the effective delivery of the mRNA into target cells is introduced. mRNA incorporated into LNPs via linkage with L-oligo, termed oligonucleotide-linked LNP (lnLNP), is superior in cellular uptake and transfection efficiency in target cells in vitro and in vivo, compared to the conventional LNP formulations. It is further applied lnLNP as an mRNA vaccine platform for SARS-CoV-2, demonstrating robust induction of neutralizing activity as well as polyfunctional SARS-CoV-2-specific T-cell response in vivo. The current strategy can be versatilely applied to different LNP platforms, for vaccine and therapeutic applications against various diseases, such as infections and cancers., (© 2024 Wiley‐VCH GmbH.)

Although CD4+CD25+FOXP3+ regulatory T (TREG) cells have been studied in patients with COVID-19, changes in the TREG cell population have not been longitudinally examined during the course of COVID-19. In this study, we longitudinally investigated the quantitative and qualitative changes in the TREG cell population in patients with COVID-19. We found that the frequencies of total TREG cells and CD45RA-FOXP3hi activated TREG cells were significantly increased 15-28 d postsymptom onset in severe patients, but not in mild patients. TREG cells from severe patients exhibited not only increased proliferation but also enhanced apoptosis, suggesting functional derangement of the TREG cell population during severe COVID-19. The suppressive functions of the TREG cell population did not differ between patients with severe versus mild COVID-19. The frequency of TREG cells inversely correlated with SARS-CoV-2-specific cytokine production by CD4+ T cells and their polyfunctionality in patients with mild disease, suggesting that TREG cells are major regulators of virus-specific CD4+ T cell responses during mild COVID-19. However, such correlations were not observed in patients with severe disease. Thus, in this study, we describe distinctive changes in the TREG cell population in patients with severe and mild COVID-19. Our study provides a deep understanding of host immune responses upon SARS-CoV-2 infection in regard to TREG cells., (Copyright © 2023 by The American Association of Immunologists, Inc.)

COVID-19 vaccines elicit humoral and cellular immune responses. Durable maintenance of vaccine-induced immunity is required for long-term protection of the host. Here, we examine activation and differentiation of vaccine-induced CD8 + T cells using MHC class I (MHC-I) multimers and correlations between early differentiation and the durability of CD8 + T cell responses among healthcare workers immunized with two doses of BNT162b2. The frequency of MHC-I multimer + cells is robustly increased by BNT162b2 but decreases 6 months post-second vaccination to 2.4%-65.6% (23.0% on average) of the peak. MHC-I multimer + cells dominantly exhibit phenotypes of activated effector cells 1-2 weeks post-second vaccination and gradually acquire phenotypes of long-term memory cells, including stem cell-like memory T (T SCM ) cells. Importantly, the frequency of T SCM cells 1-2 weeks post-second vaccination significantly correlates with the 6-month durability of CD8 + T cells, indicating that early generation of T SCM cells determines the longevity of vaccine-induced memory CD8 + T cell responses., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2022 The Author(s). Published by Elsevier Inc. All rights reserved.)

The Omicron variant (B.1.1.529) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) extensively escapes neutralizing antibodies elicited by SARS-CoV-2 infection or vaccination. In the present study, we investigated whether BNT162b2 messenger RNA vaccine-induced memory T cells functionally respond to the Omicron spike protein. Experiments were performed using samples from healthcare workers who were immunized with two or three doses of the BNT162b2 mRNA vaccine and individuals with prior SARS-CoV-2 infection who were immunized with two doses of the BNT162b2 vaccine. Vaccine-induced memory T cells exhibited substantial responses to the Omicron spike protein, with no difference between healthcare workers with two versus three vaccine doses. In individuals with prior infection, two-dose vaccination robustly boosted memory T cells that responded to the Omicron spike protein and the SARS-CoV-2 wild-type (lineage B) spike protein. Importantly, polyfunctionality was preserved in vaccine-induced memory T cells responding to the Omicron spike protein. The present findings indicate that BNT162b2-induced memory T cells substantially respond to the Omicron variant with preserved polyfunctionality., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

Background: We assessed the safety and immunogenicity of two recombinant DNA vaccines for COVID-19: GX-19 containing plasmid DNA encoding the SARS-CoV-2 spike protein, and GX-19N containing plasmid DNA encoding the SARS-CoV-2 receptor-binding domain (RBD) foldon, nucleocapsid protein, and plasmid DNA encoding the spike protein., Methods: Two open-label non-randomised phase 1 trials, one of GX-19 and the other of GX-19N were done at two hospitals in South Korea. We enrolled healthy adults aged 19-49 years for the GX-19 trial and healthy adults aged 19-54 years for the GX-19N trial. Participants who tested positive by serological testing for SARS-CoV-2 were excluded. At 4-week intervals, the GX-19 trial participants received two vaccine doses (either 1·5 mg or 3·0 mg), and the GX-19N trial participants received two 3·0 mg doses. The vaccines were delivered intramuscularly using an electroporator. The participants were followed up for 52 weeks after first vaccination. Data collected up to day 57 after first vaccination were analysed in this interim analysis. The primary outcome was safety within 28 days after each vaccination measured in the intention-to-treat population. The secondary outcome was vaccine immunogenicity using blood samples collected on day 43 or 57 after first vaccination measured in the intention-to-treat population. The GX-19 (NCT044445389) and GX-19N (NCT04715997) trials are registered with ClinicalTrials.gov., Findings: Between June 17 and July 30, 2020, we screened 97 individuals, of whom 40 (41%) participants were enrolled in the GX-19 trial (20 [50%] in the 1·5 mg group and 20 [50%] in the 3·0 mg group). Between Dec 28 and 31, 2020, we screened 23 participants, of whom 21 (91%) participants were enrolled on the GX-19N trial. 32 (52%) of 61 participants reported 80 treatment-emergent adverse events after vaccination. All solicited adverse events were mild except one (2%) case of moderate fatigue in the 1·5 mg GX-19 group; no serious vaccine-related adverse events were detected. Binding antibody responses increased after second dose of vaccination in all groups (p=0·0002 in the 1·5 mg GX-19 group; p<0·0001 in the 3·0 mg GX-19; and p=0·0004 for the spike protein and p=0·0001 for the RBD in the 3·0 mg GX-19N group)., Interpretation: GX-19 and GX-19N are safe and well tolerated. GX-19N induces humoral and broad SARS-CoV-2-specific T-cell responses. GX-19N shows lower neutralising antibody responses and needs improvement to enhance immunogenicity., Funding: The Korea Drug Development Fund, funded by the Ministry of Science and ICT, Ministry of Trade, Industry, and Energy, and Ministry of Health and Welfare., Competing Interests: YSS, Y-JC, JWY, JWW, and YCS are employees and stakeholders of Genexine. All other authors declare no competing interests. YSS, Y-JC, JWY, JWW, and YCS report grants from Korea Drug Development Fund during the conduct of the study. YCS has a patent (10-2020-0176874) issued for a novel vaccine composition for preventing and treating coronavirus., (© 2022 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY-NC-ND 4.0 license.)

While the seroprevalence of SARS-CoV-2 in healthy people does not differ significantly among age groups, those aged 65 years or older exhibit strikingly higher COVID-19 mortality compared to younger individuals. To further understand differing COVID-19 manifestations in patients of different ages, three age groups of ferrets are infected with SARS-CoV-2. Although SARS-CoV-2 is isolated from all ferrets regardless of age, aged ferrets (≥3 years old) show higher viral loads, longer nasal virus shedding, and more severe lung inflammatory cell infiltration, and clinical symptoms compared to juvenile (≤6 months) and young adult (1-2 years) groups. Furthermore, direct contact ferrets co-housed with the virus-infected aged group shed more virus than direct-contact ferrets co-housed with virus-infected juvenile or young adult ferrets. Transcriptome analysis of aged ferret lungs reveals strong enrichment of gene sets related to type I interferon, activated T cells, and M1 macrophage responses, mimicking the gene expression profile of severe COVID-19 patients. Thus, SARS-CoV-2-infected aged ferrets highly recapitulate COVID-19 patients with severe symptoms and are useful for understanding age-associated infection, transmission, and pathogenesis of SARS-CoV-2., (© 2022. The Author(s).)

Background: Our understanding of adaptive immune responses in patients with coronavirus disease 2019 (COVID-19) is rapidly evolving, but information on the innate immune responses by natural killer (NK) cells is still insufficient., Objective: We aimed to examine the phenotypic and functional status of NK cells and their changes during the course of mild and severe COVID-19., Methods: We performed RNA sequencing and flow cytometric analysis of NK cells from patients with mild and severe COVID-19 at multiple time points in the course of the disease using cryopreserved PBMCs., Results: In RNA-sequencing analysis, the NK cells exhibited distinctive features compared with healthy donors, with significant enrichment of proinflammatory cytokine-mediated signaling pathways. Intriguingly, we found that the unconventional CD56 dim CD16 neg NK-cell population expanded in cryopreserved PBMCs from patients with COVID-19 regardless of disease severity, accompanied by decreased NK-cell cytotoxicity. The NK-cell population was rapidly normalized alongside the disappearance of unconventional CD56 dim CD16 neg NK cells and the recovery of NK-cell cytotoxicity in patients with mild COVID-19, but this occurred slowly in patients with severe COVID-19., Conclusions: The current longitudinal study provides a deep understanding of the NK-cell biology in COVID-19., (Copyright © 2021 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

Background: There is insufficient data on the longevity of immunity acquired after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection., Methods: We aimed to evaluate the duration of SARS-CoV-2-specific humoral and cellular immunity according to the clinical severity of coronavirus disease 2019 (COVID-19). The study population comprised asymptomatic (n = 14), symptomatic/nonpneumonic (n = 42), and pneumonic (n = 41) patients., Results: The anti-SARS-CoV-2 immunoglobulin class G and neutralizing antibody (NAb) titers lasted until 6 months after diagnosis, with positivity rates of 66.7% and 86.9%, respectively. Older age, prolonged viral shedding, and accompanying pneumonia were more frequently found in patients with sustained humoral immunity. Severe acute respiratory syndrome coronavirus 2-specific T-cell response was strongly observed in pneumonic patients and prominent in individuals with sustained humoral immunity., Conclusions: In conclusion, most (>85%) patients carry NAb until 6 months after diagnosis of SARS-CoV-2 infection, providing insights for establishing vaccination strategies against COVID-19., (© The Author(s) 2021. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.)

Few studies have used a longitudinal approach to describe the immune response to SARS-CoV-2 infection. Here, we perform single-cell RNA sequencing of bronchoalveolar lavage fluid cells longitudinally obtained from SARS-CoV-2-infected ferrets. Landscape analysis of the lung immune microenvironment shows distinct changes in cell proportions and characteristics compared to uninfected control, at 2 and 5 days post-infection (dpi). Macrophages are classified into 10 distinct subpopulations with transcriptome changes among monocyte-derived infiltrating macrophages and differentiated M1/M2 macrophages, notably at 2 dpi. Moreover, trajectory analysis reveals gene expression changes from monocyte-derived infiltrating macrophages toward M1 or M2 macrophages and identifies a macrophage subpopulation that has rapidly undergone SARS-CoV-2-mediated activation of inflammatory responses. Finally, we find that M1 or M2 macrophages show distinct patterns of gene modules downregulated by immune-modulatory drugs. Overall, these results elucidate fundamental aspects of the immune response dynamics provoked by SARS-CoV-2 infection., (© 2021. The Author(s).)

Memory T cells contribute to rapid viral clearance during re-infection, but the longevity and differentiation of SARS-CoV-2-specific memory T cells remain unclear. Here we conduct ex vivo assays to evaluate SARS-CoV-2-specific CD4 + and CD8 + T cell responses in COVID-19 convalescent patients up to 317 days post-symptom onset (DPSO), and find that memory T cell responses are maintained during the study period regardless of the severity of COVID-19. In particular, we observe sustained polyfunctionality and proliferation capacity of SARS-CoV-2-specific T cells. Among SARS-CoV-2-specific CD4 + and CD8 + T cells detected by activation-induced markers, the proportion of stem cell-like memory T (T SCM ) cells is increased, peaking at approximately 120 DPSO. Development of T SCM cells is confirmed by SARS-CoV-2-specific MHC-I multimer staining. Considering the self-renewal capacity and multipotency of T SCM cells, our data suggest that SARS-CoV-2-specific T cells are long-lasting after recovery from COVID-19, thus support the feasibility of effective vaccination programs as a measure for COVID-19 control.

Memory T cell responses have been demonstrated in COVID-19 convalescents, but ex vivo phenotypes of SARS-CoV-2-specific T cells have been unclear. We detected SARS-CoV-2-specific CD8 + T cells by MHC class I multimer staining and examined their phenotypes and functions in acute and convalescent COVID-19. Multimer + cells exhibited early differentiated effector-memory phenotypes in the early convalescent phase. The frequency of stem-like memory cells was increased among multimer + cells in the late convalescent phase. Cytokine secretion assays combined with MHC class I multimer staining revealed that the proportion of interferon-γ (IFN-γ)-producing cells was significantly lower among SARS-CoV-2-specific CD8 + T cells than those specific to influenza A virus. Importantly, the proportion of IFN-γ-producing cells was higher in PD-1 + cells than PD-1 - cells among multimer + cells, indicating that PD-1-expressing, SARS-CoV-2-specific CD8 + T cells are not exhausted, but functional. Our current findings provide information for understanding of SARS-CoV-2-specific CD8 + T cells elicited by infection or vaccination., Competing Interests: Declaration of Interests The authors have no conflicts of interest., (Copyright © 2020 Elsevier Inc. All rights reserved.)

There is insufficient data on the longevity of immunity acquired following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. We aimed to evaluate the duration of SARS-CoV-2-specific humoral and cellular immunity according to the clinical severity of coronavirus disease 2019 (COVID-19). The study population comprised asymptomatic (n=14), symptomatic/non-pneumonic (n=42), and pneumonic (n=41) patients. The anti-SARS-CoV-2 IgG and neutralizing antibody (NAb) titers lasted until six months after diagnosis, with positivity rates of 66.7% and 86.9%, respectively. Older age, prolonged viral shedding and accompanying pneumonia were more frequently found in patients with sustained humoral immunity. SARS-CoV-2 specific T-cell response was strongly observed in pneumonic patients and prominent in individuals with sustained humoral immunity. In conclusion, most (> 85%) patients carries NAb until six months after diagnosis of SARS-CoV-2 infection, providing insights for establishing vaccination strategies against COVID-19. [ABSTRACT FROM AUTHOR]

COVID-19 vaccines elicit humoral and cellular immune responses. Durable maintenance of vaccine-induced immunity is required for long-term protection of the host. Here, we examine activation and differentiation of vaccine-induced CD8+ T cells using MHC class I (MHC-I) multimers and correlations between early differentiation and the durability of CD8+ T cell responses among healthcare workers immunized with two doses of BNT162b2. The frequency of MHC-I multimer+ cells is robustly increased by BNT162b2 but decreases 6 months post-second vaccination to 2.4%–65.6% (23.0% on average) of the peak. MHC-I multimer+ cells dominantly exhibit phenotypes of activated effector cells 1–2 weeks post-second vaccination and gradually acquire phenotypes of long-term memory cells, including stem cell-like memory T (T SCM) cells. Importantly, the frequency of T SCM cells 1–2 weeks post-second vaccination significantly correlates with the 6-month durability of CD8+ T cells, indicating that early generation of T SCM cells determines the longevity of vaccine-induced memory CD8+ T cell responses. [Display omitted] • Spike-specific CD8+ T cells quantitatively decrease 6 months after BNT162b2 vaccination • CD8+ T SCM cells are successfully generated by BNT162b2 vaccination • T SCM cell generation significantly correlates with the durability of CD8+ T cells • T SCM cell generation inversely correlates with the age of vaccinated individuals The longevity of SARS-CoV-2-specific CD8+ T cells elicited by BNT162b2 has yet to be fully understood. Jung et al. demonstrate that early generation of T SCM cells after vaccination determines the durability of spike-specific memory CD8+ T cells. This early generation of T SCM cells negatively correlates with age. [ABSTRACT FROM AUTHOR]