A spike protein S2 antibody efficiently neutralizes the Omicron variant

A Serological Analysis of the Humoral Immune Responses of Anti-RBD IgG, Anti-S1 IgG, and Anti-S2 IgG Levels Correlated to Anti-N IgG Positivity and Negativity in Sicilian Healthcare Workers (HCWs) with Third Doses of the mRNA-Based SARS-CoV-2 Vaccine: A Retrospective Cohort Study

BACKGROUND

With SARS-CoV-2 antibody tests on the market, healthcare providers must be confident that they can use the results to provide actionable information to understand the characteristics and dynamics of the humoral response and antibodies (abs) in SARS-CoV-2-vaccinated patients. In this way, the study of the antibody responses of healthcare workers (HCWs), a population that is immunocompetent, adherent to vaccination, and continuously exposed to different virus variants, can help us understand immune protection and determine vaccine design goals.

METHODS

We retrospectively evaluated antibody responses via multiplex assays in a sample of 538 asymptomatic HCWs with a documented complete vaccination cycle of 3 doses of mRNA vaccination and no previous history of infection. Our sample was composed of 49.44% males and 50.56% females, with an age ranging from 21 to 71 years, and a mean age of 46.73 years. All of the HCWs' sera were collected from April to July 2022 at the Sant'Elia Hospital of Caltanissetta to investigate the immunologic responses against anti-RBD, anti-S1, anti-S2, and anti-N IgG abs.

RESULTS

A significant difference in age between HCWs who were positive and negative for anti-N IgG was observed. For anti-S2 IgG, a significant difference between HCWs who were negative and positive compared to anti-N IgG was observed only for positive HCWs, with values including 10 (U/mL)-100 (U/mL); meanwhile, for anti-RBD IgG and anti-S1 IgG levels, there was only a significant difference observed for positive HCWs with diluted titers. For the negative values of anti-N IgG, among the titer dilution levels of anti-RBD, anti-S1, and anti-S2 IgG, the anti-S2 IgG levels were significantly lower than the anti-RBD and anti-S1 levels; in addition, the anti-S1 IgG levels were significantly lower than the anti-RBD IgG levels. For the anti-N IgG positive levels, only the anti-S2 IgG levels were significantly lower than the anti-RBD IgG and anti-S1 IgG levels. Finally, a logistic regression analysis showed that age and anti-S2 IgG were negative and positive predictors of anti-N IgG levels, respectively. The analysis between the vaccine type and mixed mRNA combination showed higher levels of antibodies in mixed vaccinated HCWs. This finding disappeared in the anti-N positive group.

CONCLUSIONS

Most anti-N positive HCWs showed antibodies against the S2 domain and were young subjects. Therefore, the authors suggest that including the anti-SARS-CoV-2-S2 in antibody profiles can serve as a complementary testing approach to qRT-PCR for the early identification of asymptomatic infections in order to reduce the impact of potential new SARS-CoV-2 variants. Our serological investigation on the type of mRNA vaccine and mixed mRNA vaccines shows that future investigations on the serological responses in vaccinated asymptomatic patients exposed to previous infection or reinfection are warranted for updated vaccine boosters.

Identification of nurse shark VNAR single-domain antibodies targeting the spike S2 subunit of SARS-CoV-2

SARS-CoV-2 is the etiological agent of the COVID-19 pandemic. Antibody-based therapeutics targeting the spike protein, specifically the S1 subunit or the receptor binding domain (RBD) of SARS-CoV-2, have gained attention due to their clinical efficacy in treating patients diagnosed with COVID-19. An alternative to conventional antibody therapeutics is the use of shark new antigen variable receptor domain (VNAR ) antibodies. VNAR s are small (<15 kDa) and can reach deep into the pockets or grooves of the target antigen. Here, we have isolated 53 VNAR s that bind to the S2 subunit by phage panning from a naïve nurse shark VNAR phage display library constructed in our laboratory. Among those binders, S2A9 showed the best neutralization activity against the original pseudotyped SARS-CoV-2 virus. Several binders, including S2A9, showed cross-reactivity against S2 subunits from other β coronaviruses. Furthermore, S2A9 showed neutralization activity against all variants of concern (VOCs) from alpha to omicron (including BA1, BA2, BA4, and BA5) in both pseudovirus and live virus neutralization assays. Our findings suggest that S2A9 could be a promising lead molecule for the development of broadly neutralizing antibodies against SARS-CoV-2 and emerging variants. The nurse shark VNAR phage library offers a novel platform that can be used to rapidly isolate single-domain antibodies against emerging viral pathogens.

Design and Immunogenicity of SARS-CoV-2 DNA Vaccine Encoding RBD-PVXCP Fusion Protein

The potential of immune-evasive mutation accumulation in the SARS-CoV-2 virus has led to its rapid spread, causing over 600 million confirmed cases and more than 6.5 million confirmed deaths. The huge demand for the rapid development and deployment of low-cost and effective vaccines against emerging variants has renewed interest in DNA vaccine technology. Here, we report the rapid generation and immunological evaluation of novel DNA vaccine candidates against the Wuhan-Hu-1 and Omicron variants based on the RBD protein fused with the Potato virus X coat protein (PVXCP). The delivery of DNA vaccines using electroporation in a two-dose regimen induced high-antibody titers and profound cellular responses in mice. The antibody titers induced against the Omicron variant of the vaccine were sufficient for effective protection against both Omicron and Wuhan-Hu-1 virus infections. The PVXCP protein in the vaccine construct shifted the immune response to the favorable Th1-like type and provided the oligomerization of RBD-PVXCP protein. Naked DNA delivery by needle-free injection allowed us to achieve antibody titers comparable with mRNA-LNP delivery in rabbits. These data identify the RBD-PVXCP DNA vaccine platform as a promising solution for robust and effective SARS-CoV-2 protection, supporting further translational study.

Structural and non-structural proteins in SARS-CoV-2: potential aspects to COVID-19 treatment or prevention of progression of related diseases

Coronavirus disease 2019 (COVID-19) is caused by a new member of the Coronaviridae family known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). There are structural and non-structural proteins (NSPs) in the genome of this virus. S, M, H, and E proteins are structural proteins, and NSPs include accessory and replicase proteins. The structural and NSP components of SARS-CoV-2 play an important role in its infectivity, and some of them may be important in the pathogenesis of chronic diseases, including cancer, coagulation disorders, neurodegenerative disorders, and cardiovascular diseases. The SARS-CoV-2 proteins interact with targets such as angiotensin-converting enzyme 2 (ACE2) receptor. In addition, SARS-CoV-2 can stimulate pathological intracellular signaling pathways by triggering transcription factor hypoxia-inducible factor-1 (HIF-1), neuropilin-1 (NRP-1), CD147, and Eph receptors, which play important roles in the progression of neurodegenerative diseases like Alzheimer's disease, epilepsy, and multiple sclerosis, and multiple cancers such as glioblastoma, lung malignancies, and leukemias. Several compounds such as polyphenols, doxazosin, baricitinib, and ruxolitinib could inhibit these interactions. It has been demonstrated that the SARS-CoV-2 spike protein has a stronger affinity for human ACE2 than the spike protein of SARS-CoV, leading the current study to hypothesize that the newly produced variant Omicron receptor-binding domain (RBD) binds to human ACE2 more strongly than the primary strain. SARS and Middle East respiratory syndrome (MERS) viruses against structural and NSPs have become resistant to previous vaccines. Therefore, the review of recent studies and the performance of current vaccines and their effects on COVID-19 and related diseases has become a vital need to deal with the current conditions. This review examines the potential role of these SARS-CoV-2 proteins in the initiation of chronic diseases, and it is anticipated that these proteins could serve as components of an effective vaccine or treatment for COVID-19 and related diseases. Video Abstract.

Oral and intranasal immunization with food-grade recombinant Lactococcus lactis expressing high conserved region of SARS-CoV-2 spike protein triggers mice's immunity responses

The COVID-19 pandemic began at the end of 2019 in Wuhan, China, and has spread throughout the world. Vaccination is still the most effective method of prevention of pathogenic infections, including viral infections. However, there is little evidence that vaccination can protect against SARS-CoV-2 virus for a long time. Thus, regular re-vaccination is necessary to control COVID-19. Vaccination by injection is invasive, and is one of the reasons people refuse to get re-vaccinated. Therefore, we developed a less invasive vaccine based on oral or nasal administration. The gene encoding the high conserved region (HCR) spike protein was inserted into pNZ8149 and expressed in L.lactis NZ3900. Mice were immunized at 3-week intervals with oral or nasal routes. Anti-SARS-CoV2 spike antibody (IgG and IgA) level were measured using ELISA method before and after treatment. Plasma cells population in lymph were analyzed using flowcytometry and the CD4 + and CD8 + cells in lymph and intestine were analyzed using immunofluorescence method. The results of nasal and oral administration in experimental animals showed that L.lactis carrying the HCR gene could induce a humoral immune response, as indicated by increased levels of IgG and IgA against SARS-CoV-2 (IgG/IgA-SARS-CoV-2). The plasma cell population after nasal and oral vaccination in mice were significantly different with control group (p < 0.05). The CD4 + and CD8 + cells in intestine were significantly higher in orally immunized group mice than control group. The CD8 + cells in lymph were significantly higher in intranasal immunized group mice than control group. Our data demonstrate L.lactis expressing spike protein can be developed into a less invasive alternative to nasal and oral vaccination.

PF-D-Trimer, a protective SARS-CoV-2 subunit vaccine: immunogenicity and application

The COVID-19 pandemic, caused by the SARS-CoV-2 virus, has had and continues to have a significant impact on global public health. One of the characteristics of SARS-CoV-2 is a surface homotrimeric spike protein, which is primarily responsible for the host immune response upon infection. Here we present the preclinical studies of a broadly protective SARS-CoV-2 subunit vaccine developed from our trimer domain platform using the Delta spike protein, from antigen design through purification, vaccine evaluation and manufacturability. The pre-fusion trimerized Delta spike protein, PF-D-Trimer, was highly expressed in Chinese hamster ovary (CHO) cells, purified by a rapid one-step anti-Trimer Domain monoclonal antibody immunoaffinity process and prepared as a vaccine formulation with an adjuvant. Immunogenicity studies have shown that this vaccine candidate induces robust immune responses in mouse, rat and Syrian hamster models. It also protects K18-hACE2 transgenic mice in a homologous viral challenge. Neutralizing antibodies induced by this vaccine show cross-reactivity against the ancestral WA1, Delta and several Omicrons, including BA.5.2. The formulated PF-D Trimer is stable for up to six months without refrigeration. The Trimer Domain platform was proven to be a key technology in the rapid production of PF-D-Trimer vaccine and may be crucial to accelerate the development and accessibility of updated versions of SARS-CoV-2 vaccines.

Immunogenicity and Safety of a Combined Intramuscular/Intranasal Recombinant Spike Protein COVID-19 Vaccine (RCP) in Healthy Adults Aged 18 to 55 Years Old: A Randomized, Double-Blind, Placebo-Controlled, Phase I Trial

Objectives: This study aimed to determine the safety and immunogenicity of a combined intramuscular/intranasal recombinant spike protein COVID-19 vaccine (RCP). Methods: We conducted a randomized, double-blind, placebo-controlled, phase I trial. Three vaccine strengths were compared with an adjuvant-only preparation. It included two intramuscular and a third intranasal dose. Eligible participants were followed for adverse reactions. Specific IgG, secretory IgA, neutralizing antibodies, and cell-mediated immunity were assessed. Results: A total of 153 participants were enrolled (13 sentinels, 120 randomized, 20 non-randomized open-labeled for IgA assessment). No related serious adverse event was observed. The geometric mean ratios (GMRs) and 95% CI for serum neutralizing antibodies compared with placebo two weeks after the second injection were 5.82 (1.46-23.13), 11.12 (2.74-45.09), and 20.70 (5.05-84.76) in 5, 10, and 20 µg vaccine groups, respectively. The GMR for anti-RBD IgA in mucosal fluid two weeks after the intranasal dose was 23.27 (21.27-25.45) in the 10 µg vaccine group. The humoral responses were sustained for up to five months. All vaccine strengths indicated a strong T-helper 1 response. Conclusion: RCP is safe and creates strong and durable humoral and cellular immunity and good mucosal immune response in its 10 µg /200 µL vaccine strengths. Trial registration: IRCT20201214049709N1.

Multivalent S2-based vaccines provide broad protection against SARS-CoV-2 variants of concern and pangolin coronaviruses

BACKGROUND

The COVID-19 pandemic continues to cause morbidity and mortality worldwide. Most approved COVID-19 vaccines generate a neutralizing antibody response that primarily targets the highly variable receptor-binding domain (RBD) of the SARS-CoV-2 spike (S) protein. SARS-CoV-2 "variants of concern" have acquired mutations in this domain allowing them to evade vaccine-induced humoral immunity. Recent approaches to improve the breadth of protection beyond SARS-CoV-2 have required the use of mixtures of RBD antigens from different sarbecoviruses. It may therefore be beneficial to develop a vaccine in which the protective immune response targets a more conserved region of the S protein.

METHODS

Here we have developed a vaccine based on the conserved S2 subunit of the S protein and optimized the adjuvant and immunization regimen in Syrian hamsters and BALB/c mice. We have characterized the efficacy of the vaccine against SARS-CoV-2 variants and other coronaviruses.

FINDINGS

Immunization with S2-based constructs elicited a broadly cross-reactive IgG antibody response that recognized the spike proteins of not only SARS-CoV-2 variants, but also SARS-CoV-1, and the four endemic human coronaviruses. Importantly, immunization reduced virus titers in respiratory tissues in vaccinated animals challenged with SARS-CoV-2 variants B.1.351 (beta), B.1.617.2 (delta), and BA.1 (omicron) as well as a pangolin coronavirus.

INTERPRETATION

These results suggest that S2-based constructs can elicit a broadly cross-reactive antibody response resulting in limited virus replication, thus providing a framework for designing vaccines that elicit broad protection against coronaviruses.

FUNDING

NIH, Japan Agency for Medical Research and Development, Garry Betty/ V Foundation Chair Fund, and NSF.

Hybrid Immunity Shifts the Fc-Effector Quality of SARS-CoV-2 mRNA Vaccine-Induced Immunity

Despite the robust immunogenicity of SARS-CoV-2 mRNA vaccines, emerging data have revealed enhanced neutralizing antibody and T cell cross-reactivity among individuals that previously experienced COVID-19, pointing to a hybrid immune advantage with infection-associated immune priming. Beyond neutralizing antibodies and T cell immunity, mounting data point to a potential role for additional antibody effector functions, including opsinophagocytic activity, in the resolution of symptomatic COVID-19. Whether hybrid immunity modifies the Fc-effector profile of the mRNA vaccine-induced immune response remains incompletely understood. Thus, here we profiled the SARS-CoV-2 specific humoral immune response in a group of individuals with and without prior COVID-19. As expected, hybrid Spike-specific antibody titers were enhanced following the primary dose of the mRNA vaccine but were similar to those achieved by naive vaccinees after the second mRNA vaccine dose. Conversely, Spike-specific vaccine-induced Fc-receptor binding antibody levels were higher after the primary immunization in individuals with prior COVID-19 and remained higher following the second dose compared to those in naive individuals, suggestive of a selective improvement in the quality, rather than the quantity, of the hybrid humoral immune response. Thus, while the magnitude of antibody titers alone may suggest that any two antigen exposures-either hybrid immunity or two doses of vaccine alone-represent a comparable prime/boost immunologic education, we find that hybrid immunity offers a qualitatively improved antibody response able to better leverage Fc-effector functions against conserved regions of the virus. IMPORTANCE Recent data indicates improved immunity to SARS-CoV-2 in individuals who experience a combination of two mRNA vaccine doses and infection, "hybrid immunity," compared to individuals who receive vaccination or experience infection alone. While previous infection accelerates the vaccine-induced immune response following the first dose of mRNA vaccination, subsequent doses demonstrate negligible increases in antibody titers or T cell immunity. Here, using systems serology, we observed a unique antibody profile induced by hybrid immunity, marked by the unique induction of robust Fc-recruiting antibodies directed at the conserved region of the viral Spike antigen, the S2-domain, induced at lower levels in individuals who only received mRNA vaccination. Thus, hybrid immunity clearly redirects vaccine-induced immunodominance, resulting in the induction of a robust functional humoral immune response to the most highly conserved region of the SARS-CoV-2 Spike antigen, which may be key to protection against existing and emerging variants of concern. Thus, next-generation vaccines able to mimic hybrid immunity and drive a balanced response to conserved regions of the Spike antigen may confer enhanced protection against disease.

Novel Regioselective Approach to Cyclize Phage-Displayed Peptides in Combination with Epitope-Directed Selection to Identify a Potent Neutralizing Macrocyclic Peptide for SARS-CoV-2

Using the regioselective cyanobenzothiazole condensation reaction with an N-terminal cysteine and the chloroacetamide reaction with an internal cysteine, a phage-displayed macrocyclic 12-mer peptide library was constructed and subsequently validated. Using this library in combination with iterative selections against two epitopes from the receptor binding domain (RBD) of the novel severe acute respiratory syndrome virus 2 (SARS-CoV-2) Spike protein, macrocyclic peptides that strongly inhibit the interaction between the Spike RBD and angiotensin-converting enzyme 2 (ACE2), the human host receptor of SARS-CoV-2, were identified. The two epitopes were used instead of the Spike RBD to avoid selection of nonproductive macrocyclic peptides that bind RBD but do not directly inhibit its interactions with ACE2. Antiviral tests against SARS-CoV-2 showed that one macrocyclic peptide is highly potent against viral reproduction in Vero E6 cells with an EC50 value of 3.1 μM. The AlphaLISA-detected IC50 value for this macrocyclic peptide was 0.3 μM. The current study demonstrates that two kinetically controlled reactions toward N-terminal and internal cysteines, respectively, are highly effective in the construction of phage-displayed macrocyclic peptides, and the selection based on the SARS-CoV-2 Spike epitopes is a promising methodology in the identification of peptidyl antivirals.

Sinopharm's BBIBP-CorV Vaccine and ChAdOx1 nCoV-19 Vaccine Are Associated with a Comparable Immune Response against SARS-CoV-2

Coronavirus disease 2019 (COVID-19) has affected millions of people worldwide. During the early stages of vaccination in Egypt, the ChAdOx1 nCoV-19 and BBIBP-CorV vaccines were the most distributed. The aim of this study was to compare the immune responses and short-term efficacies of these two vaccines. We recruited adults who received two doses of either vaccine. Samples were collected after the first dose of ChAdOx1 nCoV-1 and after the second dose of both vaccines. Antibodies against SARS-CoV-2 antigens were measured using LABScreen™ COVID Plus kits, and cell-mediated immune responses were assessed using flow cytometry. Of the 109 recruited subjects, 60 (55%) received the ChAdOx1 nCoV-19 vaccine, and the remainder received the BBIBP-CorV vaccine. The total antibody level did not significantly differ between the two groups. The level of the anti-spike subunit 2 (S2) antibody was significantly higher in the ChAdOx1 nCoV-19 group. The percentages of both total T cells and B cells were unaffected by the type of vaccination. However, the ChAdOx1 nCoV-1 vaccine was significantly associated with a higher percentage of CD8+ cells. The vaccines did not significantly differ in the number or severity of infections postvaccination. None of the participants were admitted to the hospital or died of COVID-19 infection. In conclusion, the BBIBP-CorV vaccine is associated with an immune response and protection against infection that is comparable to that of the ChAdOx1 nCoV-1 vaccine. Follow-up is needed to study the long-term protective effects of both vaccines. Inactivated vaccines are easier to manufacture in developing countries and their limited side effects may lead to better economic benefits by limiting the number of absences from work.