Dynamics of humoral immune response in SARS-CoV-2 infected individuals with different clinical stages.

Background: The COVID-19 pandemic remains a global health problem. As in other viral infections, the humoral immune response against SARS-CoV-2 is thought to be crucial for controlling the infection. However, the dynamic of B cells in the clinical spectrum of this disease is still controversial. This study aimed to characterize B cell subsets and neutralizing responses in COVID-19 patients according to disease severity through a one-month follow-up. Methods: A cohort of 71 individuals with SARS-CoV-2 infection confirmed by RT-PCR were recruited and classified into four groups: i) asymptomatic; ii) symptomatic outpatients; iii) hospitalized in ward, and iv) intensive care unit patients (ICU). Samples were taken at days 0 (inclusion to the study), 7 and 30. B cell subsets and neutralizing antibodies were assessed using multiparametric flow cytometry and plaque reduction neutralization, respectively. Results: Older age, male gender and body mass index over 25 were common factors among hospitalized and ICU patients, compared to those with milder clinical presentations. In addition, those requiring hospitalization had more comorbidities. A significant increase in the frequencies of CD19+ cells at day 0 was observed in hospitalized and ICU patients compared to asymptomatic and symptomatic groups. Likewise, the frequency of plasmablasts was significantly increased at the first sample in the ICU group compared to the asymptomatic group, but then waned over time. The frequency of naïve B cells decreased at days 7 and 30 compared to day 0 in hospitalized and ICU patients. The neutralizing antibody titers were higher as the severity of COVID-19 increased; in asymptomatic individuals, it was strongly correlated with the percentage of IgM+ switched memory B cells, and a moderate correlation was found with plasmablasts. Conclusion: The humoral immune response is variable among SARS-CoV-2 infected people depending on the severity and time of clinical evolution. In severe COVID-19 patients, a higher plasmablast frequency and neutralizing antibody response were observed, suggesting that, despite having a robust humoral immunity, this response could be late, having a low impact on disease outcome.

IL-4 receptor blockade is a global repressor of naïve B cell development and responses in a dupilumab-treated patient.

Here, we report a case of atopic dermatitis (AD) in a patient who received biweekly doses of dupilumab, an antibody against the IL-4 receptor α chain (IL-4Rα). Single cell RNA-sequencing showed that naïve B cells expressed the highest levels of IL4R compared to other B cell subpopulations. Compared to controls, the dupilumab-treated patient exhibited diminished percentages of IL4R+IGHD+ naïve B cells and down-regulation of IL4R, FCER2 (CD23), and IGHD. Dupilumab treatment resulted in upregulation of genes associated with apoptosis and inhibition of B cell receptor signaling and down-regulation of class-switch and memory B cell development genes. The dupilumab-treated patient exhibited a rapid decline in COVID-19 anti-spike and anti-receptor binding domain antibodies between 4 and 8 and 11 months post COVID-19 vaccination. Our data suggest that intact and persistent IL-4 signaling is necessary for maintaining robust survival and development of naïve B cells, and maintaining a long term vaccine response.

Persistent Autoimmune Activation and Proinflammatory State in Post-Coronavirus Disease 2019 Syndrome.

BACKGROUND: The immunopathological pathways enabling post-coronavirus disease 2019 (COVID-19) syndrome (PCS) development are not entirely known. We underwent a longitudinal analysis of patients with COVID-19 who developed PCS aiming to evaluate the autoimmune and immunological status associated with this condition. METHODS: Thirty-three patients were included for longitudinal clinical and autoantibody analyses, 12 of whom were assessed for cytokines and lymphocyte populations. Patients were followed for 7-11 months after acute COVID-19. Autoimmune profile and immunological statuses were evaluated mainly by enzyme-linked-immunosorbent assays and flow cytometry. RESULTS: Latent autoimmunity and overt autoimmunity persisted over time. A proinflammatory state was observed in patients with PCS characterized by up-regulated interferon-α, tumor necrosis factor-α, granulocyte colony-stimulating factor (G-CSF), interleukin (IL)-17A, IL-6, IL-1ß, and IL-13, whereas interferon-γ-induced protein 10 (IP-10) was decreased. In addition, PCS was characterized by increased levels of Th9, CD8+ effector T cells, naive B cells, and CD4+ effector memory T cells. Total levels of immunoglobulin G S1-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies remained elevated over time. CONCLUSIONS: The clinical manifestations of PCS are associated with the persistence of a proinflammatory and effector phenotype induced by SARS-CoV-2 infection. This long-term persistent immune activation may contribute to the development of latent and overt autoimmunity. Results suggest the need to evaluate the role of immunomodulation in the treatment of PCS.

Immunological features that associate with the strength of antibody responses to BNT162b2 mRNA vaccine against SARS-CoV-2.

Predictive clinical factors associated with favorable responses to BNT162b2 mRNA vaccine against SARS-CoV-2 have been reported in some studies; however, there is a subgroup with low antibodytiters without well-known clinical factors reducing antibody responses. To clarify the immunological backgrounds that underlie the difference in antibody responses, we analyzed peripheral blood mononuclear cells (PBMCs) of each 20 individuals with a high anti-SARS-CoV-2 antibody titer and a low antibody titer out of 1774 healthcare workers who received BNT162b2 mRNA vaccine. A higher percentage of B cells before vaccination was associated with a higher antibody titer. Among B cells, naïve and transitional B cell frequencies were positively correlated with a higher antibody titer, whereas the frequencies of late memory B cells and plasmablasts were associated with a lower antibody titer. Fold change in the frequency of activated CD8+ T cells upon vaccination was also correlated with high antibody titers.

SARS-CoV-2 sculpts the immune system to induce sustained virus-specific naïve-like and memory B-cell responses.

OBJECTIVES: SARS-CoV-2 infection induces virus-reactive memory B cells expressing unmutated antibodies, which hints at their emergence from naïve B cells. Yet, the dynamics of virus-specific naïve B cells and their impact on immunity and immunopathology remain unclear. METHODS: We longitudinally profiled SARS-CoV-2-specific B-cell responses in 25 moderate-to-severe COVID-19 patients by high-dimensional flow cytometry and isotyping and subtyping ELISA. We also explored the relationship of B-cell responses to SARS-CoV-2 with the activation of effector and regulatory cells from the innate or adaptive immune system. RESULTS: We found a virus-specific antibody response with a broad spectrum of classes and subclasses during acute infection, which evolved into an IgG1-dominated response during convalescence. Acute infection was associated with increased mature B-cell progenitors in the circulation and the unexpected expansion of virus-targeting naïve-like B cells. The latter further augmented during convalescence together with virus-specific memory B cells. In addition to a transitory increase in tissue-homing CXCR3+ plasmablasts and extrafollicular memory B cells, most COVID-19 patients showed persistent activation of CD4+ and CD8+ T cells along with transient or long-lasting changes of key innate immune cells. Remarkably, virus-specific antibodies and the frequency of naïve B cells were among the major variables defining distinct immune signatures associated with disease severity and inflammation. CONCLUSION: Aside from providing new insights into the complexity of the immune response to SARS-CoV-2, our findings indicate that the de novo recruitment of mature B-cell precursors into the periphery may be central to the induction of antiviral immunity.