Longitudinal Postvaccine SARS-CoV-2 Immunoglobulin G Titers, Memory B-Cell Responses, and Risk of COVID-19 in Multiple Sclerosis Over 1 Year.

BACKGROUND AND OBJECTIVES: Some disease-modifying treatments impair response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines in multiple sclerosis (MS), potentially increasing the risk of breakthrough infections. We aimed to investigate longitudinal SARS-CoV-2 antibody dynamics and memory B cells after 2 and 3 messenger RNA (mRNA) vaccine doses and their association with the risk of COVID-19 in patients with MS on different treatments over 1 year. METHODS: Prospective observational cohort study in patients with MS undergoing SARS-CoV-2 mRNA vaccinations. Antispike (anti-S) immunoglobulin G (IgG) titers were measured by chemiluminescence microparticle immunoassay. Frequencies of spike-specific memory B cells were measured on polyclonal stimulation of peripheral blood mononuclear cells and screening of secreted antibodies by ELISA. RESULTS: We recruited 120 patients with MS (58 on anti-CD20 antibodies, 9 on sphingosine 1-phosphate (S1P) receptor modulators, 15 on cladribine, 24 on teriflunomide (TFL), and 14 untreated) and collected 392 samples up to 10.8 months after 2 vaccine doses. When compared with untreated patients, anti-CD20 antibodies (ß = -2.07, p < 0.001) and S1P modulators (ß = -2.02, p < 0.001) were associated with lower anti-S IgG, while TFL and cladribine were not. Anti-S IgG decreased with months since vaccine (ß = -0.14, p < 0.001), independently of treatments. Within anti-CD20 patients, anti-S IgG remained higher in those with greater baseline B-cell counts and were not influenced by postvaccine anti-CD20 infusions. Anti-S IgG increase after a 3rd vaccine was mild on anti-CD20 and S1P modulators. Spike-specific memory B-cell responses were weaker on S1P modulators and anti-CD20 than on TFL and influenced by postvaccine anti-CD20 infusions. The frequency of breakthrough infections was comparable between DMTs, but the risk of COVID-19 was predicted by the last measured anti-S IgG titer before infection (OR = 0.56, 95% CI = 0.37-0.86, p = 0.008). DISCUSSION: Postvaccine anti-S IgG titers decrease over time regardless of MS treatment and are associated with breakthrough COVID-19. Both humoral and specific memory B-cell responses are diminished on S1P modulators. Within anti-CD20-treated patients, B-cell count at first vaccine determines anti-S IgG production, whereas postvaccine anti-CD20 infusions negatively affect spike-specific memory B cells.

ACE2-binding exposes the SARS-CoV-2 fusion peptide to broadly neutralizing coronavirus antibodies.

The coronavirus spike glycoprotein attaches to host receptors and mediates viral fusion. Using a broad screening approach, we isolated seven monoclonal antibodies (mAbs) that bind to all human-infecting coronavirus spike proteins from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immune donors. These mAbs recognize the fusion peptide and acquire affinity and breadth through somatic mutations. Despite targeting a conserved motif, only some mAbs show broad neutralizing activity in vitro against alpha- and betacoronaviruses, including animal coronaviruses WIV-1 and PDF-2180. Two selected mAbs also neutralize Omicron BA.1 and BA.2 authentic viruses and reduce viral burden and pathology in vivo. Structural and functional analyses showed that the fusion peptide-specific mAbs bound with different modalities to a cryptic epitope hidden in prefusion stabilized spike, which became exposed upon binding of angiotensin-converting enzyme 2 (ACE2) or ACE2-mimicking mAbs.

Clonal analysis of immunodominance and cross-reactivity of the CD4 T cell response to SARS-CoV-2.

The identification of CD4+ T cell epitopes is instrumental for the design of subunit vaccines for broad protection against coronaviruses. Here, we demonstrate in COVID-19-recovered individuals a robust CD4+ T cell response to naturally processed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike (S) protein and nucleoprotein (N), including effector, helper, and memory T cells. By characterizing 2943 S-reactive T cell clones from 34 individuals, we found that the receptor-binding domain (RBD) is highly immunogenic and that 33% of RBD-reactive clones and 94% of individuals recognized a conserved immunodominant S346-S365 region comprising nested human leukocyte antigen DR (HLA-DR)- and HLA-DP-restricted epitopes. Using pre- and post-COVID-19 samples and S proteins from endemic coronaviruses, we identified cross-reactive T cells targeting multiple S protein sites. The immunodominant and cross-reactive epitopes identified can inform vaccination strategies to counteract emerging SARS-CoV-2 variants.

Risk assessment and seroprevalence of SARS-CoV-2 infection in healthcare workers of COVID-19 and non-COVID-19 hospitals in Southern Switzerland.

BACKGROUND: Hospital healthcare workers (HCW), in particular those involved in the clinical care of COVID-19 cases, are presumably exposed to a higher risk of acquiring the disease than the general population. METHODS: Between April 16 and 30, 2020 we conducted a prospective, SARS-CoV-2 seroprevalence study in HCWs in Southern Switzerland. Participants were hospital personnel with varying COVID-19 exposure risk depending on job function and working site. They provided personal information (including age, sex, occupation, and medical history) and self-reported COVID-19 symptoms. Odds ratio (OR) of seropositivity to IgG antibodies was estimated by univariate and multivariate logistic regressions. FINDINGS: Among 4726 participants, IgG antibodies to SARS-CoV-2 were detected in 9.6% of the HCWs. Seropositivity was higher among HCWs working on COVID-19 wards (14.1% (11.9-16.5)) compared to other hospital areas at medium (10.7% (7.6-14.6)) or low risk exposure (7.3% (6.4-8.3)). OR for high vs. medium wards risk exposure was 1.42 (0.91-2.22), P = 0.119, and 1.98 (1.55-2.53), P<0.001 for high vs. low wards risk exposure. The same was for true for doctors and nurses (10.1% (9.0-11.3)) compared to other employees at medium (7.1% (4.8-10.0)) or low risk exposure (6.6% (5.0-8.4)). OR for high vs. medium profession risk exposure was 1.37 (0.89-2.11), P = 0.149, and 1.75 (1.28-2.40), P = 0.001 for high vs. low profession risk exposure. Moreover, seropositivity was higher among HCWs who had household exposure to COVID-19 cases compared to those without (18.7% (15.3-22.5) vs. 7.7% (6.9-8.6), OR 2.80 (2.14-3.67), P<0.001). INTERPRETATION: SARS-CoV-2 antibodies are detectable in up to 10% of HCWs from acute care hospitals in a region with high incidence of COVID-19 in the weeks preceding the study. HCWs with exposure to COVID-19 patients have only a slightly higher absolute risk of seropositivity compared to those without, suggesting that the use of PPE and other measures aiming at reducing nosocomial viral transmission are effective. Household contact with known COVID-19 cases represents the highest risk of seropositivity. FUNDING: Henry Krenter Foundation, Ente Ospedaliero Cantonale and Vir Biotechnology.

Mapping Neutralizing and Immunodominant Sites on the SARS-CoV-2 Spike Receptor-Binding Domain by Structure-Guided High-Resolution Serology.

Analysis of the specificity and kinetics of neutralizing antibodies (nAbs) elicited by SARS-CoV-2 infection is crucial for understanding immune protection and identifying targets for vaccine design. In a cohort of 647 SARS-CoV-2-infected subjects, we found that both the magnitude of Ab responses to SARS-CoV-2 spike (S) and nucleoprotein and nAb titers correlate with clinical scores. The receptor-binding domain (RBD) is immunodominant and the target of 90% of the neutralizing activity present in SARS-CoV-2 immune sera. Whereas overall RBD-specific serum IgG titers waned with a half-life of 49 days, nAb titers and avidity increased over time for some individuals, consistent with affinity maturation. We structurally defined an RBD antigenic map and serologically quantified serum Abs specific for distinct RBD epitopes leading to the identification of two major receptor-binding motif antigenic sites. Our results explain the immunodominance of the receptor-binding motif and will guide the design of COVID-19 vaccines and therapeutics.