Safety and Effectiveness of SA58 Nasal Spray against COVID-19 Infection in Medical Personnel：An Open-label, Blank-controlled Study (preprint)

Approved COVID-19 vaccines to date have limited effectiveness in protecting infection and blocking transmission. A nasal spray of broad-spectrum antibody against COVID-19 (SA58 Nasal Spray) has recently been developed by Sinovac Life Sciences Co., Ltd.. From October 31 to November 30, 2022, an open-label, blank controlled study on the SA58 Nasal Spray against COVID-19 infection was conducted with the medical personnel working in the designated COVID-19 hospitals and Fangcang shelter hospitals (alternate care sites) of COVID-19 cases in Hohhot city, the Inner Mongolia Autonomous Region. A total of 6662 medical personnel were involved in this study: 3368 used SA58 Nasal Spray from the drug group, and 3294 not used from blank control group. The medication was self-administered intranasally 1~2 times per day with an interval of 6 hours for 30 days.. The safety results indicated that the SA58 Nasal Spray was well tolerant. The incidence of adverse events (AEs) was 28.6% (497/1736), and the majority of the AEs were mild and from administrative site. 135 COVID-19 cases were identified for SARS-CoV-2 by RT-PCR during the 30-day observation. The cumulative incidence of COVID-19 in the drug group and the control group were 0.026% and 0.116%, respectively. The effectiveness of the SA58 Nasal Spray for preventing COVID-19 infection among medical personnel was evaluated as 77.7% (95% CI: 52.2% - 89.6%). In conclusion, the SA58 Nasal Spray is well-tolerant and highly effective against COVID-19 infection.

Inhalable SARS-CoV-2 vaccines for single-dose dry-powder aerosol immunization and orchestrated mucosal/systemic immune responses (preprint)

The ongoing coronavirus disease pandemic has fostered major advances in vaccination technologies; however, there are urgent needs of mucosal immune responses and single-dose, non-invasive administration. Here, we develop a SARS-CoV-2 vaccine for single-dose, dry-powder aerosol inhalation that induces potent systemic and mucosal immune responses. Our vaccine encapsulates proteinaceous cholera toxin B subunit-assembled nanoparticles displaying the SARS-CoV-2 RBD antigen (R-CNP) within microcapsules of optimal aerodynamic size, and such unique nano-micro coupled structure supports efficient alveoli delivery, sustained R-CNP release, and antigen presenting cell uptake, which are favorable for invocation of immune responses. Moreover, our vaccine successfully induces robust serological IgG and secretory IgA production, collectively conferring effective protection from SARS-CoV-2 challenge (including pseudovirus and the authentic virus) in mice, hamsters, and non-human primates. Finally, we also demonstrate a “mosaic iteration” of our vaccine that co-displays ancestral and Omicron’s antigens, thus extending the breadth of antibody response against co-circulating strains and transmission of Omicron variant. These findings support our inhalable vaccine as a promising candidate to prevent SARS-CoV-2 infection, disease, and transmission.

Rational identification of potent and broad sarbecovirus-neutralizing antibody cocktails from SARS convalescents (preprint)

SARS-CoV-2 Omicron sublineages have escaped most RBD-targeting therapeutic neutralizing antibodies (NAbs), which proves the previous NAb drug screening strategies deficient against the fast-evolving SARS-CoV-2. Better broad NAb drug candidate selection methods are needed. Here, we describe a rational approach for identifying RBD-targeting broad SARS-CoV-2 NAb cocktails. Based on high-throughput epitope determination, we propose that broad NAb drugs should target non-immunodominant RBD epitopes to avoid herd immunity-directed escape mutations. Also, their interacting antigen residues should focus on sarbecovirus conserved sites and associate with critical viral functions, making the antibody-escaping mutations less likely to appear. Following the criteria, a featured non-competing antibody cocktail, SA55+SA58, is identified from a large collection of broad sarbecovirus NAbs isolated from SARS convalescents. SA55+SA58 potently neutralizes ACE2-utilizing sarbecoviruses, including circulating Omicron variants, and could serve as broad SARS-CoV-2 prophylactics to offer long-term protection. Our screening strategy can also be further applied to identify broad-spectrum NAb drugs against other fast-evolving viruses.

A subset of Memory B-derived antibody repertoire from 3-dose vaccinees is ultrapotent against diverse and highly transmissible SARS-CoV-2 variants, including Omicron (preprint)

Omicron, the most heavily mutated SARS-CoV-2 variant so far, is highly resistant to neutralizing antibodies, raising unprecedented concerns about the effectiveness of antibody therapies and vaccines. We examined whether sera from individuals who received two or three doses of inactivated vaccine, could neutralize authentic Omicron. The seroconversion rates of neutralizing antibodies were 3.3% (2/60) and 95% (57/60) for 2- and 3-dose vaccinees, respectively. For three-dose recipients, the geometric mean neutralization antibody titer (GMT) of Omicron was 15, 16.5-fold lower than that of the ancestral virus (254). We isolated 323 human monoclonal antibodies derived from memory B cells in 3-dose vaccinees, half of which recognize the receptor binding domain (RBD) and show that a subset of them (24/163) neutralize all SARS-CoV-2 variants of concern (VOCs), including Omicron, potently. Therapeutic treatments with representative broadly neutralizing mAbs individually or antibody cocktails were highly protective against SARS-CoV-2 Beta infection in mice. Atomic structures of the Omicron S in complex with three types of all five VOC-reactive antibodies defined the binding and neutralizing determinants and revealed a key antibody escape site, G446S, that confers greater resistance to one major class of antibodies bound at the right shoulder of RBD through altering local conformation at the binding interface. Our results rationalize the use of 3-dose immunization regimens and suggest that the fundamental epitopes revealed by these broadly ultrapotent antibodies are a rational target for a universal sarbecovirus vaccine. One sentence summary A sub-set of antibodies derived from memory B cells of volunteers vaccinated with 3 doses of an inactivated SARS-CoV-2 vaccine work individually as well as synergistically to keep variants, including Omicron, at bay.

A third dose of inactivated vaccine augments the potency, breadth, and duration of anamnestic responses against SARS-CoV-2 (preprint)

Emergence of variants of concern (VOC) with altered antigenic structures and waning humoral immunity to SARS-CoV-2 are harbingers of a long pandemic. Administration of a third dose of an inactivated virus vaccine can boost the immune response. Here, we have dissected the immunogenic profiles of antibodies from 3-dose vaccinees, 2-dose vaccinees and convalescents. Better neutralization breadth to VOCs, expeditious recall and long-lasting humoral response bolster 3-dose vaccinees in warding off COVID-19. Analysis of 171 complex structures of SARS-CoV-2 neutralizing antibodies identified structure-activity correlates, revealing ultrapotent, VOCs-resistant and broad-spectrum antigenic patches. Construction of immunogenic and mutational heat maps revealed a direct relationship between "hot" immunogenic sites and areas with high mutation frequencies. Ongoing antibody somatic mutation, memory B cell clonal turnover and antibody composition changes in B cell repertoire driven by prolonged and repeated antigen stimulation confer development of monoclonal antibodies with enhanced neutralizing potency and breadth. Our findings rationalize the use of 3-dose immunization regimens for inactivated vaccines. One sentence summaryA third booster dose of inactivated vaccine produces a highly sifted humoral immune response via a sustained evolution of antibodies capable of effectively neutralizing SARS-CoV-2 variants of concern.

An immunocompetent 169-day prolonged SARS-CoV-2 shedding patient with high neutralizing antibody (preprint)

Information with prolonged SARS-CoV-2 shedding among immunocompetent patients is limited. We describe a twice repositive 169-day prolonged SARS-CoV-2 shedding in an immunocompetent patient and explore potential factors from clinical, immunological and genomic perspectives. We found that continuous viral replication and infectivity could exist in an immunocompetent COVID-19 patient with high neutralizing antibody.

Single-Cell Sequencing and Immune Function Assays of Peripheral Blood Samples Demonstrate Positive Responses of an Inactivated SARS-CoV-2 Vaccine (preprint)

Background: Safe and effective vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are urgently needed to halt the spread of coronavirus disease 2019 (COVID-19) pandemic. As a promising inactivated SARS-CoV-2 vaccine, CoronaVac (developed by Sinovac Life Sciences, Beijing, China) is currently undergoing its clinical trials in several countries and showing good results. We investigated the immune mechanisms underlying CoronaVac from the perspective of single-cell gene expressions and immune function features.Methods: In this controlled study, 13 healthy participants aged 21–54 years were recruited in the vaccination group and intramuscularly injected with two doses of CoronaVac (3 μg / 0·5 mL per dose, at Day00 and Day28, right after blood sampling), with peripheral blood samples collected at Day00, Day14, Day28, Day35, and Day45 to monitor dynamic changes. As positive control, 12 participants aged 28–75 years that had recovered from COVID-19 for approximately eight months were recruited in the recovery group with peripheral blood samples collected. Considering the high cost of sequencing, 11 samples from two healthy participants (H1 and H2) with four timepoints (Day00, Day14, Day28, and Day35) and three recovered participants (R1, R2, and R3) with one timepoint (Month8) were randomly chosen for single-cell RNA sequencing of peripheral blood mononuclear cells (PBMC). The transcriptomics of PBMC and its constituent cells were analyzed as gene expression responses. For samples from all 25 participants, the serum neutralizing antibody titer to live SARS-CoV-2 and the in vitro cytokine release activity of CD4+T cells were assayed as immune function responses.Findings: Single-cell RNA sequencing showed that the PBMC transcriptomics after vaccination resembled the COVID-19 recovery control more than that before vaccination, which also applied to its constituent cells such as B cells, T cells, NK cells, and myeloid cells. Gradual transitions of PBMC transcriptomics were observed from Day14 to Day28 and Day35 in vaccination groups, which finally approached the recovery control. The B cell levels in PBMC increased after each vaccination, while the T cell levels mainly increased within four weeks after the first vaccination and peaked at Day28. The serum neutralizing antibody titer to live SARS-CoV-2 was low within four weeks after the first vaccination, but the second vaccination could induce significantly higher serum neutralizing antibody titers due to the immune memory. For both vaccinated participants and recovered participants, the upregulated JUN/FOS network and tuned expressions of immunoglobulin fragments such as IGHV3-30 and IGLV2-23 were observed in B cells. By purifying CD4+T cells from PBMC and re-stimulating them with CoronaVac in vitro, five cytokines were significantly released, including Th1 cytokines (IFN-γ and IL-2) and Th2 cytokines (IL-4, IL-6, and IL-10). Th1 cytokines were mainly activated at Day14, Day28, and Day35, supporting cellular immune responses at early stages when the serum neutralizing antibody titer was low. Th2 cytokines were mainly activated at Day28, Day35, and Day45, supporting humoral immune responses at later stages, especially after the second vaccination.Interpretation: Two vaccinations of CoronaVac (3 µg per dose, with an interval of 28 days) could make positive gene expression and immune responses in healthy participants, as revealed by single-cell PBMC transcriptomics and immune function assays.Funding Statement: China’s National Science and Technology Major Projects for Major New Drugs Innovation and Development.Declaration of Interests: QG, YH, XM, and SZ are employees of Sinovac Life Sciences, Beijing, China. The other authors declare no competing interests.Ethics Approval Statement: This study was approved by the Peking University Biomedical Ethics Committee.

Relationship between the dynamic changes of serum 2019-nCoV IgM/IgG and patient immunity after discharged six months (preprint)

Objectives To investigate the relationship between the dynamic changes of serum 2019-nCoV IgM/IgG and immunity alteration for patients after discharged six months. Methods 1 with IgM(+) and IgG(-), 32 with IgM(+) and IgG(+), 38 with IgM(-) and IgG(+), and 40 with IgM(-) and IgG(-) were included. Demographic data were collected. IgM and IgG antibodies, hypersensitive C-reactive protein (hs-CRP), interleukin-6 (IL-6) and lymphocyte subsets in serum were determined on weeks 0, 2 and 4. Results Hs-CRP and IL-6 for all patients were within the normal ranges. All testing items of the lymphocyte subsets were 12/110 (10.9%) of weeks 0, 15/110 (13.6%) of weeks 2 and 18/110 (16.4%) of weeks 4 within the normal ranges. The percentages of CD8+, NK cells and B lymphocytes in the IgM(+) and IgG(+) group were quite different from the IgM(-) and IgG(+) group and the IgM(-)and IgG(-) group, with much more the percentages of CD8+ and much less the percentages of NK cells and B lymphocytes on weeks 0, 2 and 4. 12 patients with IgM(+) had converted to IgM(-) in the IgM(+) and IgG(+) group, and the percentages of NK cells and B lymphocytes were significantly increased on weeks 4.Conclusions The changes of serum IgM and IgG are closely related to immunity for patients in recovery stage. However, immunity isn't recovery with the turning negative of antibodies.

Rapid development of an inactivated vaccine for SARS-CoV-2 (preprint)

The COVID-19 pandemic caused by SARS-CoV-2 has brought about an unprecedented crisis, taking a heavy toll on human health, lives as well as the global economy. There are no SARS-CoV-2-specific treatments or vaccines available due to the novelty of this virus. Hence, rapid development of effective vaccines against SARS-CoV-2 is urgently needed. Here we developed a pilot-scale production of a purified inactivated SARS-CoV-2 virus vaccine candidate (PiCoVacc), which induced SARS-CoV-2-specific neutralizing antibodies in mice, rats and non-human primates. These antibodies potently neutralized 10 representative SARS-CoV-2 strains, indicative of a possible broader neutralizing ability against SARS-CoV-2 strains circulating worldwide. Immunization with two different doses (3g or 6 g per dose) provided partial or complete protection in macaques against SARS-CoV-2 challenge, respectively, without any antibody-dependent enhancement of infection. Systematic evaluation of PiCoVacc via monitoring clinical signs, hematological and biochemical index, and histophathological analysis in macaques suggests that it is safe. These data support the rapid clinical development of SARS-CoV-2 vaccines for humans. One Sentence SummaryA purified inactivated SARS-CoV-2 virus vaccine candidate (PiCoVacc) confers complete protection in non-human primates against SARS-CoV-2 strains circulating worldwide by eliciting potent humoral responses devoid of immunopathology