Heterologous booster immunization with SARS-CoV-2 spike protein after mRNA vaccine elicits durable and broad antibody responses (preprint)

Although mRNA vaccines are more immunogenic than other vaccine modalities in primary series vaccination, their immunogenicity has not been well compared to different vaccine modalities in additional boosters. Here the longitudinal analysis reveals more sustained RBD-binding IgG titers and RBD-ACE2 binding inhibitory activities with the breadth to antigenically distinct Beta and Omicron BA.1 variants by the S-268019-b spike protein booster vaccination compared to BNT162b2 mRNA homologous booster on mRNA vaccinees. The differences in the durability and breadth of plasma antibodies between BNT162b2 and S-268019-b groups are pronounced in those without systemic adverse events and were associated with different trends in the number and breadth of memory B cells. High-dimensional immune profiling identifies early CD16 + natural killer cell dynamics with CCR3 upregulation, as one of the correlates for the distinct antibody responses by the S-268019-b booster. Our results illustrate the combinational effects of heterologous booster on the immune dynamics and the durability and breadth of recalled antibody responses against emerging virus variants.

Viral load and timing of infection define neutralization diversity to SARS-CoV-2 infection (preprint)

AbstractImmunity to SARS-CoV-2 in COVID-19 cases has diversified due to complex combinations of exposure to vaccination and infection. Elucidating the drivers for upgrading neutralizing activity to SARS-CoV-2 in COVID-19 cases with pre-existing immunity will aid in understanding immunity to SARS-CoV-2 and improving COVID-19 booster vaccines with enhanced cross-protection against antigenically distinct variants. This study revealed that the magnitude and breadth of neutralization responses to SARS-CoV-2 infection in breakthrough infections are determined by upper respiratory viral load and vaccination-infection time interval, but not by the lineage of infecting viruses. Notably, the time interval, but not the viral load, may play a critical role in expanding the breadth of neutralization to SARS-CoV-2. This illustrates the importance of dosing interval optimization in addition to antigen design in the development of variant-proof booster vaccines. One-Sentence SummaryViral load and infection timing define the magnitude and breadth of SARS-CoV-2 neutralization after breakthrough infection.

Immunogenicity and Safety of Booster Dose of S-268019-b or Tozinameran in Japanese Participants: An Interim Report of Phase 2/3, Randomized, Observer-Blinded, Noninferiority Study (preprint)

In this randomized, observer-blinded, phase 2/3 study, S-268019-b (n=101), a recombinant spike protein vaccine, was analyzed for noninferiority versus tozinameran (n=103), when given as a booster ≥6 months after 2-dose tozinameran regimen in Japanese adults without prior COVID-19 infection. Interim results showed noninferiority of S-268019-b versus tozinameran in co-primary endpoints for neutralizing antibodies on day 29: geometric mean titer (GMT) (124.97 versus 109.70; adjusted-GMT ratio [95% CI], 1.14 [0.94-1.39]; noninferiority P -value, <0.0001) and seroresponse rate (both 100%; noninferiority P -value, 0.0004). Both vaccines elicited anti-spike-protein immunoglobulin G antibodies, and produced T-cell response (n=29/group) and neutralizing antibodies against Delta and Omicron pseudovirus and live virus variants (n=24/group) in subgroups. Most participants reported low-grade reactogenicity on days 1-2, the most frequent being fatigue, fever, myalgia, and injection-site pain. No serious adverse events were reported. In conclusion, S-268019-b was safe and showed robust immunogenicity as a booster, supporting its use as COVID-19 booster vaccine. JRCT ID jRCT2031210470 Highlights Third COVID-19 vaccine dose (booster) enhances immune response Interim phase 2/3 data for booster ≥6 months after the 2nd dose in Japan are shown S-268019-b was noninferior to tozinameran in inducing neutralizing antibodies Sera boosted with either vaccines neutralized Delta and Omicron virus variants S-268019-b was safe, and results support its use as a booster in vaccinated adults

Two doses of mRNA vaccine elicit cross-neutralizing memory B-cells against SARS-CoV-2 Omicron variant (preprint)

SARS-CoV-2 Beta and Omicron variants have multiple mutations in the receptor-binding domain (RBD) allowing antibody evasion. Despite the resistance to circulating antibodies in those who received two doses of mRNA vaccine, the third dose prominently recalls cross-neutralizing antibodies with expanded breadth to these variants. Herein, we longitudinally profiled the cellular composition of persistent memory B-cell subsets and their antibody reactivity against these variants following the second vaccine dose. The vaccination elicited a memory B-cell subset with resting phenotype that dominated the other subsets at 4.9 months. Notably, most of the resting memory subset retained the ability to bind the Beta variant, and the memory-derived antibodies cross-neutralized the Beta and Omicron variants at frequencies of 59% and 29%, respectively. The preservation of cross-neutralizing antibody repertoires in the durable memory B-cell subset likely contributes to the prominent recall of cross-neutralizing antibodies following the third dose of the vaccine. One Sentence Summary Fully vaccinated individuals preserve cross-neutralizing memory B-cells against the SARS-CoV-2 Omicron variant.

Factors Associated with Low IgG Response to mRNA COVID-19 Vaccine BNT162b2 (preprint)

Amid pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), vaccination is hailed as one of the most effective preventive measures. An mRNA vaccine termed BNT162b2 showed satisfactory safety and efficacy in the clinical trials but several issues including variability in the individual immune response or determination of target antibody titre that exerts sufficient immune protection needs to be assessed for planning a more efficient vaccination strategy. By monitoring IgG titres before and two months after the initial administration of BNT162b2 in 655 healthcare workers by Abbott IgG II quant that detects IgG against the receptor-binding domain in S protein of SARS-CoV-2, we confirmed that hypertension, dyslipidaemia, chronic kidney disease and use of immune suppressant in addition to male gender, advanced age, and absence of previous infection were significantly associated with low antibody response to the vaccination.

Prognostic Predictors For COVID-19 in Daily Clinical Practice in Japan: a Propensity Score-Matched Case-Control Study (preprint)

Introduction: Blood tests and computed tomography (CT) findings at diagnosis are widely used in daily clinical practice and can offer useful prognostic factors for coronavirus disease 2019. Methods: : We retrospectively evaluated 66 patients who underwent a blood test and CT between January 1 and May 31, 2020, and performed a propensity score-matched case-control study. Cases and controls were a severe respiratory failure group (non-rebreather mask, nasal high-flow, positive-pressure ventilation) and a non-severe respiratory failure group, matched at a ratio of 1:3 by propensity scores constructed by age, sex, and medical history. We compared groups for maximum body temperature up to diagnosis, laboratory findings, and CT findings in the matched cohort. Two-tailed P-values <0.05 were considered statistically significant. Results: : Nine cases and 27 controls were included in the matched cohort. Significant differences were seen in maximum body temperature up to diagnosis (p=0.0043), the number of shaded lobes (p=0.0434), amount of ground-glass opacity (GGO) in the total lung field (p=0.0071), amounts of GGO (p=0.0001), and consolidation (p=0.0036) in the upper lung field, and pleural effusion (p=0.0117). Conclusions: : Fever and CT findings (such as GGO and consolidation) may be prognostic indicators that can be easily measured at diagnosis.

Persistence of robust humoral immune response in COVID-19 convalescent individuals over 12 months after infection (preprint)

SARS-CoV-2 infection elicits varying degrees of protective immunity conferred by neutralizing antibodies (nAbs). Here we report the persistence of nAb responses over 12 months after infection despite its decreasing trend noticed from 6 months. The study included sera from 358 individuals who had been infected with SARS-CoV-2 between January and May 2020. Samples were collected at 6 and 12 months after onset. The titers of IgG to the viral nucleocapsid protein (NP) and receptor-binding domain of the spike protein (RBD) were measured by CLEIA. The nAb titer was determined using lentivirus-based pseudovirus or authentic virus. Antibody titers of NP-IgG, RBD-IgG, and nAbs were higher in severe and moderate cases than in mild cases at 12 months after onset. While the nAb levels were likely to confer adequate protection against wild-type viral infection, the neutralization activity to recently circulating variants in some of the mild cases ([~]30%) was undermined, implying the susceptibility of reinfection to the variants of concerns (VOCs). COVID-19 convalescent individuals have robust humoral immunity even at 12 months after infection albeit that the medical history and background of patients could affect the function and dynamics of antibody response to the VOCs.

Distinct immune cell dynamics mark adverse events and antibody responses of SARS-CoV-2 mRNA vaccine (preprint)

Pfizer/BioNTec BNT162b2 mRNA vaccine robustly elicits neutralizing antibodies against SARS-CoV-2 in clinical trials and real-world settings. However, booster vaccinations are frequently associated with self-limited adverse events. Here, by applying a high-dimensional immune profiling approach to peripheral blood, we linked early vaccine-induced immune dynamics with adverse events and neutralizing antibody responses. The dynamics of two dendritic cell subsets (DC3s and AS-DCs) were identified as the specific correlates for adverse events; the combination of these cell dynamics stratified the vaccinees with severe reactogenicity, while the stratification did not affect the neutralizing antibody titers. Furthermore, the NKT-like cell dynamics that correlated with adverse events and antibody titers were accounted for distinct magnitudes of both events by sex and age. The identified immune correlates for adverse events and antibody responses may pave the way for a rational vaccine strategy for reducing the reactogenicity of mRNA vaccines without compromising the immunogenicity.

Identification, crystallization and epitope determination of public TCR shared and expanded in COVID-19 patients (preprint)

T cells play pivotal roles in protective immunity against SARS-CoV-2 infection. Follicular helper T (Tfh) cells mediate the production of antigen-specific antibodies; however, T cell receptor (TCR) clonotypes used by SARS-CoV-2-specific Tfh cells have not been well characterized. Here, we first identified and crystallized public TCR of Tfh clonotypes that are shared and expanded in unhospitalized COVID-19-recovered patients. These clonotypes preferentially recognized SARS-CoV-2 spike (S) protein epitopes which are conserved among emerging SARS-CoV-2 variants. These clonotypes did not react with S proteins derived from common cold human coronaviruses, but cross-reacted with symbiotic bacteria, which might confer the publicity. Among SARS-CoV-2 S epitopes, S864-882, presented by frequent HLA-DR alleles, could activate multiple public Tfh clonotypes in COVID-19-recovered patients. Furthermore, S864-882-loaded HLA tetramer preferentially bound to CD4+ T cells expressing CXCR5. In this study, we identified and crystallized public TCR for SARS-CoV-2 that may contribute to the prevention of COVID-19 aggravation.

Corticosteroids for hospitalized patients with mild to critically-ill COVID-19: A multicenter, retrospective, propensity score–matched study (preprint)

Background: Corticosteroids use in coronavirus disease 2019 (COVID-19) is controversial, especially in mild to severe patients who do not require invasive/noninvasive ventilation. Moreover, many factors remain unclear regarding the appropriate use of corticosteroids for COVID-19. In this context, this multicenter, retrospective, propensity score–matched study was launched to evaluate the efficacy of systemic corticosteroid administration for hospitalized patients with COVID-19 ranging in the degree of severity from mild to critically-ill disease.Methods: This multicenter, retrospective study enrolled consecutive hospitalized COVID-19 patients diagnosed January–April 2020 across 30 institutions in Japan. Clinical outcomes were compared for COVID-19 patients who received or did not receive corticosteroids, after adjusting for propensity scores. The primary endpoint was the odds ratio (OR) for improvement on a 7-point ordinal score on Day 15.Results: Of 1092 COVID-19 patients analyzed, 118 patients were assigned to either the corticosteroid and non-corticosteroid group, after propensity score matching. At baseline, most patients did not require invasive/noninvasive ventilation (85.6% corticosteroid group vs. 89.8% non-corticosteroid group). The odds of improvement in a 7-point ordinal score on Day 15 was significantly lower for the corticosteroid versus non-corticosteroid group (OR, 0.611; 95% confidence interval [CI], 0.388–0.962; p = 0.034). The time to improvement in radiological findings was significantly shorter in the corticosteroid versus non-corticosteroid group (hazard ratio [HR], 1.758; 95% CI, 1.323–2.337; p < 0.001), regardless of baseline clinical status. The duration of invasive mechanical ventilation was shorter in corticosteroid versus non-corticosteroid group (HR, 1.466; 95% CI, 0.841–2.554; p = 0.177). Of the 106 patients who received methylprednisolone, the duration of invasive mechanical ventilation was significantly shorter in the pulse/semi-pulse versus standard dose group (HR, 2.831; 95% CI, 1.347–5.950; p = 0.006).Conclusions: Corticosteroids for hospitalized patients with COVID-19 did not improve clinical status on Day 15, but reduced the time to improvement in radiological findings for all patients regardless of disease severity and also reduced the duration of invasive mechanical ventilation in patients who required intubation.Trial registration: This study was registered in the University hospital Medical Information Network Clinical Trials Registry on April 21, 2020 (ID: UMIN000040211).