Serological reactivity of inactivated SARS-CoV-2 vaccine based on an S-RBD neutralizing antibody assay

Immunogenicity Persistence of a Third-Dose Homologous BBIBP-CorV/CoronaVac Boosting Vaccination: A Prospective Open-Label Study

The inactivated whole-virion severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine has been widely used in a two-dose schedule, but with insufficient data on the immunogenicity of homologous BBIBP-CorV/CoronaVac boosting vaccination and too little follow-up to assess the duration of the immunogenic response. We prospectively evaluated the immunogenicity of a third-dose BBIBP-CorV/CoronaVac boosting vaccination, with neutralizing titers against wild type and Omicron assessed at the baseline (immediately before the booster dose), and days 14, 28, 98, and 174 post the third-booster. Of 182 volunteers screened, 165 were assessed eligible for enrolment. No moderate/severe adverse events were observed during the term of the study. From the baseline to day 174 post the third booster, neutralizing titers against wild type and Omicron peaked by approximately sixfold increase (up to 811.83 and 33.40, respectively) at day 14 and slowly decreased over time. The geometric mean titers against Omicron were lower than against type with a 19.8-39. Sixfold reduction at all time points. The seropositivity against Omicron at the baseline, days 14, 28, 98, and 174 after the booster dose was 12.6%, 50.0%, 37.8%, 38.6%, and 22.8%, respectively. Data presented herein indicated that the BBIBP-CorV/CoronaVac booster significantly enhances the neutralizing potency against wild-type strain but elicited weaker neutralizing activity to Omicron. Our findings suggest that individuals receiving booster inactivated vaccine remain at risk for Omicron infection, which is crucial to inform ongoing and future vaccination strategies to combat coronavirus disease 2019.

Breakthrough infection evokes the nasopharyngeal innate immune responses established by SARS-CoV-2-inactivated vaccine

Nasopharyngeal immune responses are vital for defense against SARS-CoV-2 infection. Although vaccination via muscle immunization has shown a high efficacy in reducing severity and death in COVID-19 infection, breakthrough infection frequently happens because of mutant variants and incompletely established mucosal immunity, especially in the upper respiratory tract. Here, we performed a single-cell RNA and T-cell receptor repertoire sequencing and delineated a high-resolution transcriptome landscape of nasopharyngeal mucosal immune and epithelial cells in vaccinated persons with breakthrough infection and non-vaccinated persons with natural infection as control. The epithelial cells showed anti-virus gene expression diversity and potentially recruited innate immune cells into the nasopharyngeal mucous of vaccinated patients. Upon infection, they released significant pro-inflammatory cytokines and chemokines by macrophages and monocytes and expressed antigen-presenting relevant genes by dendritic cells. Such immune responses of nasopharyngeal innate immune cells would facilitate the strengthened expression of cytotoxic genes in virus-specific T-cell or B-cell differentiation into antibody-secreting cells at the early stage of breakthrough infection through cell interaction between innate and adaptive immune cells. Notably, these alterations of nasopharyngeal immune cells in breakthrough infection depended on the activated Nuclear factor-κB (NF-κB) and NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) signaling rather than type I interferon responses due to the general reduction in interferon-stimulated gene expression. Our findings suggest that vaccination potentially strengthens innate immune barriers and virus-specific memory immune cell responses, which could be quickly activated to defend against variant breakthrough infection and maintain nasopharyngeal epithelial cell integrity. Thus, this study highlights the necessity of a boost via nasal mucous after intramuscular immunization.

Dynamics of SARS-CoV-2 Antibody Responses up to 9 Months Post-Vaccination in Individuals with Previous SARS-CoV-2 Infection Receiving Inactivated Vaccines

Humoral immunity confers protection against COVID-19. The longevity of antibody responses after receiving an inactivated vaccine in individuals with previous SARS-CoV-2 infection is unclear. Plasma samples were collected from 58 individuals with previous SARS-CoV-2 infection and 25 healthy donors (HDs) who had been vaccinated with an inactivated vaccine. The neutralizing antibodies (NAbs) and S1 domain-specific antibodies against the SARS-CoV-2 wild-type and Omicron strains and nucleoside protein (NP)-specific antibodies were measured using a chemiluminescent immunoassay. Statistical analysis was performed using clinical variables and antibodies at different timepoints after SARS-CoV-2 vaccination. NAbs targeting the wild-type or Omicron strain were detected in individuals with previous SARS-CoV-2 infection at 12 months after infection (wild-type: 81%, geometric mean (GM): 20.3 AU/mL; Omicron: 44%, GM: 9.4 AU/mL), and vaccination provided further enhancement of these antibody levels (wild-type: 98%, GM: 53.3 AU/mL; Omicron: 75%, GM: 27.8 AU/mL, at 3 months after vaccination), which were significantly higher than those in HDs receiving a third dose of inactivated vaccine (wild-type: 85%, GM: 33.6 AU/mL; Omicron: 45%, GM: 11.5 AU/mL). The level of NAbs in individuals with previous infection plateaued 6 months after vaccination, but the NAb levels in HDs declined continuously. NAb levels in individuals with previous infection at 3 months post-vaccination were strongly correlated with those at 6 months post-vaccination, and weakly correlated with those before vaccination. NAb levels declined substantially in most individuals, and the rate of antibody decay was negatively correlated with the neutrophil-to-lymphocyte ratio in the blood at discharge. These results suggest that the inactivated vaccine induced robust and durable NAb responses in individuals with previous infection up to 9 months after vaccination.

Characterizing the cellular and molecular variabilities of peripheral immune cells in healthy recipients of BBIBP-CorV inactivated SARS-CoV-2 vaccine by single-cell RNA sequencing

Over 3 billion doses of inactivated vaccines for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been administered globally. However, our understanding of the immune cell functional transcription and T cell receptor (TCR)/B cell receptor (BCR) repertoire dynamics following inactivated SARS-CoV-2 vaccination remains poorly understood. Here, we performed single-cell RNA and TCR/BCR sequencing on peripheral blood mononuclear cells at four time points after immunization with the inactivated SARS-CoV-2 vaccine BBIBP-CorV. Our analysis revealed an enrichment of monocytes, central memory CD4⁺ T cells, type 2 helper T cells and memory B cells following vaccination. Single-cell TCR-seq and RNA-seq comminating analysis identified a clonal expansion of CD4⁺ T cells (but not CD8⁺ T cells) following a booster vaccination that corresponded to a decrease in the TCR diversity of central memory CD4⁺ T cells and type 2 helper T cells. Importantly, these TCR repertoire changes and CD4⁺ T cell differentiation were correlated with the biased VJ gene usage of BCR and the antibody-producing function of B cells post-vaccination. Finally, we compared the functional transcription and repertoire dynamics in immune cells elicited by vaccination and SARS-CoV-2 infection to explore the immune responses under different stimuli. Our data provide novel molecular and cellular evidence for the CD4⁺ T cell-dependent antibody response induced by inactivated vaccine BBIBP-CorV. This information is urgently needed to develop new prevention and control strategies for SARS-CoV-2 infection. (ClinicalTrials.gov Identifier: NCT04871932).Trial registration: ClinicalTrials.gov identifier: NCT04871932..

A Longitudinal Study in Turkiye of Host Ability to Produce Antibodies following a Third Homologous BNT162b2 Vaccination

Obesity is a multifaceted, complex condition that has negative impacts on one's health. There are conflicting reports regarding the COVID-19 vaccine's ability to induce antibody formation in obese people. Our study aimed to determine anti-S-RBD IgG and surrogate neutralizing antibody (snAb) levels before and after the third Pfizer-BioNTech (BNT162b2) vaccination (at 15, 60, 90, and 120 days) in normal-weight adults, overweight, and obese individuals without any comorbidity or previous SARS-CoV-2 infection history, but it did not evaluate the response to the first two doses. In this longitudinal prospective study in Istanbul, Turkey, a total of 323 consecutive adult individuals (141 normal weight, 108 overweight, and 74 patients with obesity) were included. Peripheral blood samples were collected. Anti-S-RBD IgG and surrogate neutralizing antibody levels were detected using the ELISA method. After the third dose of BNT162b2 vaccination, obese patients had significantly lower levels of snAb against SARS-CoV-2 compared with normal-weight controls, but the levels otherwise did not differ between the study groups. Across all individuals in our cohort, titers peaked about a month after this third vaccination and then gradually faded. Anti-S-RBD IgG and snAb IH% levels against SARS-CoV-2 were not correlated with IL-6 and TNF-α levels. In conclusion, anti-S-RBD IgG titers and snAb IH% levels against SARS-CoV-2 were determined longitudinally for 120 days after the third homologous BNT162b2 vaccination. Although there were no significant differences in anti-S-RBD IgG, we found significant differences in the snAb IH% levels against SARS-CoV-2 between obese and healthy control subjects.

Immune Response to CoronaVac and Its Safety in Patients with Type 2 Diabetes Compared with Healthcare Workers

Background: Vaccines for SARS-CoV-2 have been critical for preventing disease. Previous research showed patients with diabetes have impaired immunity. This study aimed to determine the immunity to coronavirus after CoronaVac by comparing patients with type 2 diabetes (T2D) and healthcare workers (HCW). Materials and methods: A prospective cohort study evaluated immune responses and safety after two doses of CoronaVac in T2D and HCW groups at Chulabhorn Hospital. The levels of total antibodies against the receptor-binding domain (anti-RBD) of the SARS-CoV-2 spike protein at baseline and 4 weeks after vaccination were collected. The level of anti-RBD concentrations was reported as geometric mean concentration (GMC) and compared between groups using the geometric mean ratio (GMR). Results: 81 participants were included; 27 had T2D and 54 were HCW. After complete vaccination, anti-RBD concentrations were not significantly different between T2D (57.68 binding antibody units (BAU)/mL, 95% confidence interval (CI) = 29.08; 114.44) and HCW (72.49 BAU/mL, 95% CI = 55.77; 94.22) groups. Subgroup analysis showed the GMC of anti-RBD was significantly lower in T2D patients with dyslipidaemia (50.04 BAU/mL) than in T2D patients without dyslipidaemia (341.64 BAU/mL). Conclusions: The immune response at 4 weeks after two doses of CoronaVac did not significantly differ between patients with T2D and HCW.

Antibody responses to COVID-19 vaccination in people with obesity: A systematic review and meta-analysis

COVID-19 vaccine is critical in preventing SARS-CoV-2 infection and transmission. However, obesity's effect on immune responses to COVID-19 vaccines is still unknown. We performed a meta-analysis of the literature and compared antibody responses with COVID-19 vaccines among persons with and without obesity. We used Pubmed, Embase, Web of Science, and Cochrane Library to identify all related studies up to April 2022. The Stata.14 software was used to analyze the selected data. Eleven studies were included in the present meta-analysis. Five of them provided absolute values of antibody titers in the obese group and non-obese group. Overall, we found that the obese population was significantly associated with lower antibody titers (standardized mean difference [SMD] = -0.228, 95% CI [-0.437, -0.019], P < 0.001) after COVID-19 vaccination. Significant heterogeneity was present in most pooled analyses but was reduced after subgroup analyses. No publication bias was observed in the present analysis. The Trim and Fill method did not change the results in the primary analysis. The present meta-analysis suggested that obesity was significantly associated with decreased antibody responses to SARS-CoV-2 vaccines. Future studies should be performed to unravel the mechanism of response to the COVID-19 vaccine in obese individuals.