Maturation of SARS-CoV-2 Spike-specific memory B cells drives resilience to viral escape.

Memory B cells (MBCs) generate rapid antibody responses upon secondary encounter with a pathogen. Here, we investigated the kinetics, avidity, and cross-reactivity of serum antibodies and MBCs in 155 SARS-CoV-2 infected and vaccinated individuals over a 16-month time frame. SARS-CoV-2-specific MBCs and serum antibodies reached steady-state titers with comparable kinetics in infected and vaccinated individuals. Whereas MBCs of infected individuals targeted both prefusion and postfusion Spike (S), most vaccine-elicited MBCs were specific for prefusion S, consistent with the use of prefusion-stabilized S in mRNA vaccines. Furthermore, a large fraction of MBCs recognizing postfusion S cross-reacted with human betacoronaviruses. The avidity of MBC-derived and serum antibodies increased over time resulting in enhanced resilience to viral escape by SARS-CoV-2 variants, including Omicron BA.1 and BA.2 sublineages, albeit only partially for BA.4 and BA.5 sublineages. Overall, the maturation of high-affinity and broadly reactive MBCs provides the basis for effective recall responses to future SARS-CoV-2 variants.

A phase I trial of inotuzumab ozogamicin in combination with temsirolimus in patients with relapsed or refractory CD22-positive B-cell non-Hodgkin lymphomas.

This phase I trial evaluated the safety, tolerability, and preliminary activity of inotuzumab ozogamicin in combination with temsirolimus in patients with relapsed/refractory CD22 positive B-cell non-Hodgkin lymphomas. Nineteen patients received at least one dose of both study drugs. Dose-limiting toxicities consisted of thrombocytopenia, hypertriglyceridemia, oral mucositis, clinical deterioration, and the inability to receive at least three doses of temsirolimus during cycle 1. The most common grade ≥3 treatment-related adverse events were thrombocytopenia (n = 8), neutropenia (n = 5), and two patients each hyperphosphatemia, lymphopenia, and hypertriglyceridemia. The recommended phase II dose was inotuzumab ozogamicin 0.8 mg/m2 on day 1 in combination with temsirolimus 10 mg on days 8, 15, and 22 every 28 days. Among 18 patients evaluable, seven (39%) with follicular lymphoma had a partial remission. This drug combination is not possible within a therapeutically useful range of doses due to toxicities. Antitumor activity was observed in heavily pretreated patients (ClinicalTrials.gov, Identifier NCT01535989).

Poor neutralization and rapid decay of antibodies to SARS-CoV-2 variants in vaccinated dialysis patients.

Patients on dialysis are at risk of severe course of SARS-CoV-2 infection. Understanding the neutralizing activity and coverage of SARS-CoV-2 variants of vaccine-elicited antibodies is required to guide prophylactic and therapeutic COVID-19 interventions in this frail population. By analyzing plasma samples from 130 hemodialysis and 13 peritoneal dialysis patients after two doses of BNT162b2 or mRNA-1273 vaccines, we found that 35% of the patients had low-level or undetectable IgG antibodies to SARS-CoV-2 Spike (S). Neutralizing antibodies against the vaccine-matched SARS-CoV-2 and Delta variant were low or undetectable in 49% and 77% of patients, respectively, and were further reduced against other emerging variants. The fraction of non-responding patients was higher in SARS-CoV-2-naïve hemodialysis patients immunized with BNT162b2 (66%) than those immunized with mRNA-1273 (23%). The reduced neutralizing activity correlated with low antibody avidity. Patients followed up to 7 months after vaccination showed a rapid decay of the antibody response with an average 21- and 10-fold reduction of neutralizing antibodies to vaccine-matched SARS-CoV-2 and Delta variant, which increased the fraction of non-responders to 84% and 90%, respectively. These data indicate that dialysis patients should be prioritized for additional vaccination boosts. Nevertheless, their antibody response to SARS-CoV-2 must be continuously monitored to adopt the best prophylactic and therapeutic strategy.

Maturation of SARS-CoV-2 Spike-specific memory B cells drives resilience to viral escape.

Memory B cells (MBCs) generate rapid antibody responses upon secondary encounter with a pathogen. Here, we investigated the kinetics, avidity and cross-reactivity of serum antibodies and MBCs in 155 SARS-CoV-2 infected and vaccinated individuals over a 16-month timeframe. SARS-CoV-2-specific MBCs and serum antibodies reached steady-state titers with comparable kinetics in infected and vaccinated individuals. Whereas MBCs of infected individuals targeted both pre- and postfusion Spike (S), most vaccine-elicited MBCs were specific for prefusion S, consistent with the use of prefusion-stabilized S in mRNA vaccines. Furthermore, a large fraction of MBCs recognizing postfusion S cross-reacted with human betacoronaviruses. The avidity of MBC-derived and serum antibodies increased over time resulting in enhanced resilience to viral escape by SARS-CoV-2 variants, including Omicron BA.1 and BA.2 sub-lineages, albeit only partially for BA.4 and BA.5 sublineages. Overall, the maturation of high-affinity and broadly-reactive MBCs provides the basis for effective recall responses to future SARS-CoV-2 variants.

Phase I Dose-Escalation Study of the Dual PI3K-mTORC1/2 Inhibitor Gedatolisib in Combination with Paclitaxel and Carboplatin in Patients with Advanced Solid Tumors.

PURPOSE: This phase I study evaluated safety, tolerability, pharmacokinetics, and preliminary activity of the PI3K/mTORC1/2 dual inhibitor gedatolisib combined with carboplatin and paclitaxel. PATIENTS AND METHODS: Patients with advanced solid tumors treated with ≤ 2 prior chemotherapies received intravenous gedatolisib on days 1, 8, 15, and 22 (95, 110, or 130 mg according to dose level); carboplatin (AUC5) on day 8 (day 1 following protocol amendment); and paclitaxel at 80 mg/m2 on days 8, 15, and 22 (1, 8, and 15 after amendment), every 28 days. Patients without progressive disease after cycle 6 received maintenance gedatolisib until progression. RESULTS: Seventeen patients were enrolled [11 ovarian (10 clear cell ovarian cancer, CCOC), 4 endometrial, 2 lung cancers]. Median number of prior chemotherapies was 1 (range, 0-2). Median number of administered cycles was 6 (range, 2-16). Dose-limiting toxicities occurred in 4 patients: 2 (cycle 2 delay due to G2-G3 neutropenia) at 110 mg leading to a change in the treatment schedule, 2 at 130 mg (G2 mucositis causing failure to deliver ≥ 75% of gedatolisib at cycle 1). The recommended phase II dose is gedatolisib 110 mg on days 1, 8, 15, and 22 with carboplatin AUC5 on day 1 and paclitaxel 80 mg/m2 on days 1, 8, and 15. The most frequent ≥G3 treatment-related adverse events were neutropenia (35%), anemia (18%), and mucositis (12%). The overall response rate was 65% (80% in CCOC). Pharmacokinetic parameters of gedatolisib were consistent with single-agent results. CONCLUSIONS: Gedatolisib combined with carboplatin and paclitaxel is tolerable, and preliminary efficacy was observed especially in CCOC.

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.