High Frequencies of Functional Virus-Specific CD4+ T Cells in SARS-CoV-2 Subjects With Olfactory and Taste Disorders

Nervous system-related tropism of SARS-CoV-2 and autoimmunity in COVID-19 infection

The effects of SARS-CoV-2 in COVID-19 on the nervous system are incompletely understood. SARS-CoV-2 can infect endothelial cells, neurons, astrocytes, and oligodendrocytes with consequences for the host. There are indications that infection of these CNS-resident cells may result in long-term effects, including emergence of neurodegenerative diseases. Indirect effects of infection with SARS-CoV-2 relate to the induction of autoimmune disease involving molecular mimicry or/and bystander activation of T- and B cells and emergence of autoantibodies against various self-antigens. Data obtained in preclinical models of coronavirus-induced disease gives important clues for the understanding of nervous system-related assault of SARS-CoV-2. The pathophysiology of long-COVID syndrome and post-COVID syndrome in which autoimmunity and immune dysregulation might be the driving forces are still incompletely understood. A better understanding of nervous-system-related immunity in COVID-19 might support the development of therapeutic approaches. In this review, the current understanding of SARS-CoV-2 tropism for the nervous system, the associated immune responses, and diseases are summarized. The data indicates that there is viral tropism of SARS-CoV-2 in the nervous system resulting in various disease conditions. Prevention of SARS-CoV-2 infection by means of vaccination is currently the best strategy for the prevention of subsequent tissue damage involving the nervous system.

The MegaPool Approach to Characterize Adaptive CD4+ and CD8+ T Cell Responses

Epitopes recognized by T cells are a collection of short peptide fragments derived from specific antigens or proteins. Immunological research to study T cell responses is hindered by the extreme degree of heterogeneity of epitope targets, which are usually derived from multiple antigens; within a given antigen, hundreds of different T cell epitopes can be recognized, differing from one individual to the next because T cell epitope recognition is restricted by the epitopes' ability to bind to MHC molecules, which are extremely polymorphic in different individuals. Testing large pools encompassing hundreds of peptides is technically challenging because of logistical considerations regarding solvent-induced toxicity. To address this issue, we developed the MegaPool (MP) approach based on sequential lyophilization of large numbers of peptides that can be used in a variety of assays to measure T cell responses, including ELISPOT, intracellular cytokine staining, and activation-induced marker assays, and that has been validated in the study of infectious diseases, allergies, and autoimmunity. Here, we describe the procedures for generating and testing MPs, starting with peptide synthesis and lyophilization, as well as a step-by-step guide and recommendations for their handling and experimental usage. Overall, the MP approach is a powerful strategy for studying T cell responses and understanding the immune system's role in health and disease. © 2023 Wiley Periodicals LLC. Basic Protocol 1: Generation of peptide pools ("MegaPools") Basic Protocol 2: MegaPool testing and quantitation of antigen-specific T cell responses.

Comparable cytokine release ex-vivo by whole blood from COVID-19 patients with and without non-invasive ventilation

T cells are key players in the resolution of the infection by SARS-CoV-2. A delay in their activation can lead to severe COVID-19. The present work aimed to identify differences in cytokine release by T cells ex-vivo between COVID-19 patients in the acute phase, showing diverse disease severity. Concentrations of IFNγ, Granzyme B, IL-6, IL-10, IL-17A, IL-18, IP-10, MCP-1, and TNFα were evaluated after stimulation ex-vivo of whole blood samples with peptides from SARS-CoV-2 spike protein and a mitogen as well as without stimulation. Samples derived from hospitalized COVID-19 patients and SARS-CoV-2 vaccinated controls (CTR). Patients were classified on disease severity considering the necessity of non-invasive ventilation (NIV). Samples from patients requiring NIV revealed a similar release of cytokines compared with patients without NIV. COVID-19 patients showed higher spontaneous production of IFNγ and IP-10, lower production of MCP-1 after SARS-CoV-2 peptide stimulation and lower production of IFNγ, IL-10, IL-17A, Granzyme B, IP-10 after mitogenic stimulus compared with CTR. In conclusion, differences in T cell responses evaluated ex-vivo by a whole blood-based cytokine release assay do not appear to explain the need for non-invasive ventilation in COVID-19 patients.

Long-Term Dysfunction of Taste Papillae in SARS-CoV-2

BACKGROUND

We sought to determine whether ongoing taste disturbance in the postacute sequelae of coronavirus disease 2019 period is associated with persistent virus in primary taste tissue.

METHODS

We performed fungiform papillae biopsies on 16 patients who reported taste disturbance lasting more than 6 weeks after molecularly determined severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Then, on multiple occasions, we rebiopsied 10 of those patients who still had taste complaints for at least 6 months postinfection. Fungiform papillae obtained from other patients before March 2020 served as negative controls. We performed hematoxylin and eosin staining to examine fungiform papillae morphology and immunofluorescence and fluorescence in situ hybridization to look for evidence of persistent viral infection and immune response.

RESULTS

In all patients, we found evidence of SARS-CoV-2, accompanying immune response and misshapen or absent taste buds with loss of intergemmal neurite fibers. Six patients reported normal taste perception by 6 months postinfection and were not further biopsied. In the remaining 10, the virus was eliminated in a seemingly random fashion from their fungiform papillae, but four patients still, by history, reported incomplete return to preinfection taste perception by the time we wrote this report.

CONCLUSIONS

Our data show a temporal association in patients between functional taste, taste papillae morphology, and the presence of SARS-CoV-2 and its associated immunological changes. (Funded by Intramural Research Program/National Institute on Aging/National Institute of Allergy and Infectious Diseases/National Institutes of Health; ClinicalTrials.gov numbers NCT03366168 and NCT04565067.).

TLRs: Innate Immune Sentries against SARS-CoV-2 Infection

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been responsible for a devastating pandemic since March 2020. Toll-like receptors (TLRs), crucial components in the initiation of innate immune responses to different pathogens, trigger the downstream production of pro-inflammatory cytokines, interferons, and other mediators. It has been demonstrated that they contribute to the dysregulated immune response observed in patients with severe COVID-19. TLR2, TLR3, TLR4 and TLR7 have been associated with COVID-19 severity. Here, we review the role of TLRs in the etiology and pathogenesis of COVID-19, including TLR7 and TLR3 rare variants, the L412F polymorphism in TLR3 that negatively regulates anti-SARS-CoV-2 immune responses, the TLR3-related cellular senescence, the interaction of TLR2 and TLR4 with SARS-CoV-2 proteins and implication of TLR2 in NET formation by SARS-CoV-2. The activation of TLRs contributes to viral clearance and disease resolution. However, TLRs may represent a double-edged sword which may elicit dysregulated immune signaling, leading to the production of proinflammatory mediators, resulting in severe disease. TLR-dependent excessive inflammation and TLR-dependent antiviral response may tip the balance towards the former or the latter, altering the equilibrium that drives the severity of disease.

CXCL12 and CXCL13 Cytokine Serum Levels Are Associated with the Magnitude and the Quality of SARS-CoV-2 Humoral Responses

A better understanding of the immunological markers associated with long-lasting immune responses to SARS-CoV-2 infection is of paramount importance. In the present study, we characterized SARS-CoV-2-specific humoral responses in hospitalized (ICU and non-ICU) and non-hospitalized individuals at six months post-onset of symptoms (POS) (N = 95). We showed that the proportion of individuals with detectable anti-SARS-CoV-2 IgG or neutralizing (NAb) responses and the titers of antibodies were significantly reduced in non-hospitalized individuals, compared to ICU- or non-ICU-hospitalized individuals at 6 months POS. Interestingly, SARS-CoV-2-specific memory B cells persist at 6 months POS in both ICU and non-ICU patients and were enriched in cells harboring an activated and/or exhausted phenotype. The frequency/phenotype of SARS-CoV-2-specific memory B cells and the magnitude of IgG or NAb responses at 6 months POS correlated with the serum immune signature detected at patient admission. In particular, the serum levels of CXCL13, IL-1RA, and G-CSF directly correlated with the frequency of Spike-specific B cells and the magnitude of Spike-specific IgG or NAb, while the serum levels of CXCL12 showed an antagonizing effect. Our results indicate that the balance between CXCL12 and CXCL13 is an early marker associated with the magnitude and the quality of the SARS-CoV-2 humoral memory.

Molecular docking and molecular dynamics study Lianhua Qingwen granules (LHQW) treats COVID-19 by inhibiting inflammatory response and regulating cell survival

Purpose

2019 Coronavirus disease (COVID-19) is endangering health of populations worldwide. Latest research has proved that Lianhua Qingwen granules (LHQW) can reduce tissue damage caused by inflammatory reactions and relieve patients' clinical symptoms. However, the mechanism of LHQW treats COVID-19 is currently lacking. Therefore, we employed computer simulations to investigate the mechanism of LHQW treats COVID-19 by modulating inflammatory response.

Methods

We employed bioinformatics to screen active ingredients in LHQW and intersection gene targets. PPI, GO and KEGG was used to analyze relationship of intersection gene targets. Molecular dynamics simulations validated the binding stability of active ingredients and target proteins. Binding free energy, radius of gyration and the solvent accessible surface area were analyzed by supercomputer platform.

Results

COVID-19 had 4628 gene targets, LHQW had 1409 gene targets, intersection gene targets were 415. Bioinformatics analysis showed that intersection targets were closely related to inflammation and immunomodulatory. Molecular docking suggested that active ingredients (including: licopyranocoumarin, Glycyrol and 3-3-Oxopropanoic acid) in LHQW played a role in treating COVID-19 by acting on CSF2, CXCL8, CCR5, NLRP3, IFNG and TNF. Molecular dynamics was used to prove the binding stability of active ingredients and protein targets.

Conclusion

The mechanism of active ingredients in LHQW treats COVID-19 was investigated by computer simulations. We found that active ingredients in LHQW not only reduce cell damage and tissue destruction by inhibiting the inflammatory response through CSF2, CXCL8, CCR5 and IFNG, but also regulate cell survival and growth through NLRP3 and TNF thereby reducing apoptosis.

Immune Determinants of Viral Clearance in Hospitalised COVID-19 Patients: Reduced Circulating Naïve CD4+ T Cell Counts Correspond with Delayed Viral Clearance

Virus-specific cellular and humoral responses are major determinants for protection from critical illness after SARS-CoV-2 infection. However, the magnitude of the contribution of each of the components to viral clearance remains unclear. Here, we studied the timing of viral clearance in relation to 122 immune parameters in 102 hospitalised patients with moderate and severe COVID-19 in a longitudinal design. Delayed viral clearance was associated with more severe disease and was associated with higher levels of SARS-CoV-2-specific (neutralising) antibodies over time, increased numbers of neutrophils, monocytes, basophils, and a range of pro-inflammatory cyto-/chemokines illustrating ongoing, partially Th2 dominating, immune activation. In contrast, early viral clearance and less critical illness correlated with the peak of neutralising antibodies, higher levels of CD4 T cells, and in particular naïve CD4+ T cells, suggesting their role in early control of SARS-CoV-2 possibly by proving appropriate B cell help. Higher counts of naïve CD4+ T cells also correlated with lower levels of MIF, IL-9, and TNF-beta, suggesting an indirect role in averting prolonged virus-induced tissue damage. Collectively, our data show that naïve CD4+ T cell play a critical role in rapid viral T cell control, obviating aberrant antibody and cytokine profiles and disease deterioration. These data may help in guiding risk stratification for severe COVID-19.

Early and Polyantigenic CD4 T Cell Responses Correlate with Mild Disease in Acute COVID-19 Donors

We assessed SARS-CoV-2-specific CD4+ and CD8+ T cell responses in samples from 89 acute COVID-19 patients, utilizing blood samples collected during the first wave of COVID-19 in Italy. The goal of the study was to examine correlations between SARS-CoV-2-specific T cell responses in the early phase comparing mild, moderate, or severe COVID-19 disease outcomes. T cell responses to the spike (S) and non-S proteins were measured in a combined activation-induced marker (AIM) and intracellular cytokine staining (ICS) assay. Early CD4+ T cell responses to SARS-CoV-2 S correlated with milder disease by both AIM and IFNγ ICS readouts. The correlation of S-specific CD4+ T cell responses with milder disease severity was most striking within the first two weeks of symptom onset compared to later time points. Furthermore, donors with milder disease were associated with polyantigenic CD4+ T cell responses that recognized more prominently non-S proteins in addition to S, while severe acute COVID-19 was characterized by lower magnitudes of CD4+ T cell responses and a narrower repertoire. In conclusion, this study highlights that both the magnitude and breadth of early SARS-CoV-2-specific CD4+ T cell responses correlated with milder disease outcomes in acute COVID-19 patients.

Long Lasting Cellular Immune Response Induced by mRNA Vaccination: Implication for Prevention Strategies

As the COVID19 pandemic continues to spread and vaccinations are administered throughout the world at different rates and with different strategies, understanding the multiple aspects of the immune response to vaccinations is required to define more efficient vaccination strategies. To date, the duration of protection induced by COVID19 vaccines is still matter of debate. To assess whether 2-doses vaccination with BNT162b2 mRNA COVID-19 vaccine was sufficient to induce a persistent specific cellular immune response, we evaluated the presence of SARS-COV2 Spike-specific B and T lymphocytes in 28 healthcare workers 1 and 7 months after completing the vaccination cycle. The results showed that at 7 months after second dose a population of Spike-specific B lymphocytes was still present in 86% of the immunized subjects, with a higher frequency when compared to not-immunized controls (0.38% ± 0.07 vs 0.13% ± 0.03, p<0.001). Similarly, specific CD4+ and CD8+ T lymphocytes, able to respond in vitro to stimulation with Spike derived peptides, were found at 7 months. These results confirm that vaccination with BNT162b2 is able to induce a specific immune response, potentially long lasting, and could be helpful in defining future vaccination strategies.