Generation and persistence of S1 IgG and neutralizing antibodies in post-COVID-19 patients

S309-CAR-NK cells bind the Omicron variants in vitro and reduce SARS-CoV-2 viral loads in humanized ACE2-NSG mice

Recent progress on chimeric antigen receptor (CAR)-NK cells has shown promising results in treating CD19-positive lymphoid tumors with minimal toxicities [including graft versus host disease (GvHD) and cytokine release syndrome (CRS) in clinical trials. Nevertheless, the use of CAR-NK cells in combating viral infections has not yet been fully explored. Previous studies have shown that CAR-NK cells expressing S309 single-chain fragment variable (scFv), hereinafter S309-CAR-NK cells, can bind to SARS-CoV-2 wildtype pseudotyped virus (PV) and effectively kill cells expressing wild-type spike protein in vitro. In this study, we further demonstrate that the S309-CAR-NK cells can bind to different SARS-CoV-2 variants, including the B.1.617.2 (Delta), B.1.621 (Mu), and B.1.1.529 (Omicron) variants in vitro. We also show that S309-CAR-NK cells reduce virus loads in the NOD/SCID gamma (NSG) mice expressing the human angiotensin-converting enzyme 2 (hACE2) receptor challenged with SARS-CoV-2 wild-type (strain USA/WA1/2020). Our study demonstrates the potential use of S309-CAR-NK cells for inhibiting infection by SARS-CoV-2 and for the potential treatment of COVID-19 patients unresponsive to otherwise currently available therapeutics.

IMPORTANCE

Chimeric antigen receptor (CAR)-NK cells can be "off-the-shelf" products that treat various diseases, including cancer, infections, and autoimmune diseases. In this study, we engineered natural killer (NK) cells to express S309 single-chain fragment variable (scFv), to target the Spike protein of SARS-CoV-2, hereinafter S309-CAR-NK cells. Our study shows that S309-CAR-NK cells are effective against different SARS-CoV-2 variants, including the B.1.617.2 (Delta), B.1.621 (Mu), and B.1.1.529 (Omicron) variants. The S309-CAR-NK cells can (i) directly bind to SARS-CoV-2 pseudotyped virus (PV), (ii) competitively bind to SARS-CoV-2 PV with 293T cells expressing the human angiotensin-converting enzyme 2 (hACE2) receptor (293T-hACE2 cells), (iii) specifically target and lyse A549 cells expressing the spike protein, and (iv) significantly reduce the viral loads of SARS-CoV-2 wild-type (strain USA/WA1/2020) in the lungs of NOD/SCID gamma (NSG) mice expressing hACE2 (hACE2-NSG mice). Altogether, the current study demonstrates the potential use of S309-CAR-NK immunotherapy as an alternative treatment for COVID-19 patients.

Nine-Month Trend of IgG Antibody Persistence and Associated Symptoms Post-SARS-CoV-2 Infection

Between 2 and 8.5% of patients who recover from COVID-19 do not develop antibodies, and the durability of IgG antibodies is under scrutiny. Therefore, the presence and persistence of IgM and IgG antibodies were evaluated in a group of patients diagnosed with SARS-CoV-2 from May to August 2020. Out of 2199 suspected COVID-19 cases, 1264 were confirmed for SARS-CoV-2 by rRT-PCR; 328 consented to participate in the study, with 220 participants followed for 9 months, including 124 men (56%) and 96 women (44%). The primary symptoms were headache, dry cough, and fever. IgG antibodies developed in 95% of patients within 4 weeks post-diagnosis, and a second evaluation at 9 months showed that 72.7% still had detectable IgG antibodies. The presence of IgM in one individual (0.45%) suggested the possibility of reinfection.

Dried blood spot eluates are suitable for testing of SARS-CoV-2 IgG antibodies targeting Spike protein 1 and Nucleocapsid protein

Dried blood spots (DBS) provide easy handling and are thus a beneficial tool for data collection, e.g. for epidemiological studies. The suitability of DBS for the assessment of antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was analyzed with regards to the use in future studies addressing seroprevalence in the population. 121 volunteers gave a venous blood sample and capillary blood samples on two DBS cards (PerkinElmer and Ahlstrom-Munksjö) via self-sampling under supervision. All samples were analyzed using the Anti-SARS-CoV-2 ELISA (IgG) and the Anti-SARS-CoV-2 NCP ELISA (IgG) from EUROIMMUN performed on the EUROIMMUN EUROLabWorkstation ELISA. Correlation coefficients between ELISA results based on the different sampling methods were calculated. Results of DBS analysis for SARS-CoV-2 IgG S1 and NCP highly correlated with the serum values (r = 0.96). In addition, the calculation of the phi coefficient showed no significant difference between the qualitative results of both sampling methods (r_φ = 0.98-1.0). Further analysis of DBS eluates after prolonged storage of 6-8 h also showed a high correlation with serum results (r = 0.97 and r = 0.93, respectively). The study results indicate suitability of DBS for the analysis of antibodies against SARS-CoV-2 S1 and NCP. For DBS eluate, a stability of 6-8 h for measurement of SARS-CoV-2 antibodies can be assumed.

Long-Term Follow-Up of Patients Needing Extracorporeal Membrane Oxygenation Following a Critical Course of COVID-19

INTRODUCTION

Severe respiratory failure is one of the most serious complications of coronavirus disease 2019 (COVID-19). In a small proportion of patients, mechanical ventilation fails to provide adequate oxygenation and extracorporeal membrane oxygenation (ECMO) is needed. The surviving individuals need long-term follow-up as it is not clear what their prognosis is.

AIM

To provide a complex clinical picture of patients during follow-up exceeding one year after the ECMO therapy due to severe COVID-19.

METHODS

All subjects involved in the study required ECMO in the acute stage of COVID-19. The survivors were followed-up for over one year at a specialized respiratory medical center.

RESULTS

Of the 41 patients indicated for ECMO, 17 patients (64.7% males) survived. The average age of survivors was 47.8 years, and the average BMI was 34.7 kg·m^-2. The duration of ECMO support was 9.4 days. A mild decrease in vital capacity (VC) and transfer factor (DLCO) was observed on the initial follow-up visit (82.1% and 60%, respectively). VC improved by 6.2% and by an additional 7.5% after 6 months and 1 year, respectively. DLCO improved by 21.1% after 6 months and remained stable after 1 year. Post-intensive care consequences included psychological problems and neurological impairment in 29% of patients; 64.7% of the survivors got vaccinated against SARS-CoV-2 within 12 months of hospitalization and 17.6% experienced reinfection with a mild course.

CONCLUSION

The COVID-19 pandemic has significantly increased the need for ECMO. Patients' quality of life after ECMO is temporarily significantly reduced but most patients do not experience permanent disability.

Kinetics of SARS-CoV-2 IgM and IgG Antibodies 3 Months after COVID-19 Onset in Moroccan Patients

Coronavirus disease (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) poses serious global public health problems. Characterization of the immune response, particularly antibodies to SARS-CoV-2, is important for establishing vaccine strategies. The purpose of this study was to evaluate longitudinally the kinetics of anti-SARS-CoV-2 antibodies against spike protein (S1) for up to 3 months in a cohort of 169 COVID-19 patients. We enrolled COVID-19 patients at two regional hospitals in Casablanca, Morocco, between March and September 2021. Blood samples were collected and N-specific IgM and S-specific IgG levels were measured by a commercial Euroimmun ELISA. IgM antibodies were assessed 2-5 (D00), 9-12 (D07), 17-20 (D15), and 32-37 (D30) days after symptom onset; IgG antibodies were assessed at these time points plus 60 (D60) and 90 (D90) days after symptom onset. We found that at 3 months after symptom onset, 79% of patients had detectable SARS-CoV-2-specific IgG antibodies, whereas their IgM seropositivity was 19% by 1 month after symptom onset. The IgM level decreased to 0.34 (interquartile range [IQR] 0.19-0.92) at 1 month after symptom onset, whereas the IgG level peaked at D30 (3.10; IQR 1.83-5.64) and remained almost stable at D90 (2.95; IQR 1.52-5.19). IgG levels were significantly higher in patients older than 50 years than in those younger than 50 at all follow-up time points (P < 0.05). Statistical analysis showed no significant difference in median anti-S1 antibody levels among infected patients based on gender or comorbidities. This study provides information on the longevity of anti-SARS-CoV-2 IgM and IgG antibodies in COVID-19 patients.

Kinetics of severe acute respiratory syndrome coronavirus 2 infection antibody responses

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread rapidly throughout the world, causing severe morbidity and mortality. Since the first reports of Coronavirus disease 2019 (COVID-19) in late 2019, research on the characteristics of specific humoral immunity against SARS-CoV-2 in patients with COVID-19 has made great progress. However, our knowledge of persistent humoral immunity to SARS-CoV-2 infection is limited. The existence of protective immunity after infection will affect future transmission and disease severity. Therefore, it is important to gather knowledge about the kinetics of antibody responses. In this review, we summarize the information obtained so far on the characteristics and kinetics of the SARS-CoV-2 infection of specific humoral immune response, especially in neutralizing antibodies and their relationship with disease severity. In addition, with the emergence of variants of concern, we summarize the neutralizing effect of specific humoral immunity on variants of concern after the initial SARS-CoV-2 infection and vaccination.