ABSTRACT
The coronavirus disease 2019 (COVID-19) pandemic is still ongoing. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern (VOCs) are circulating worldwide, making it resistant to existing vaccines and antiviral drugs. Therefore, the evaluation of variant-based expanded spectrum vaccines to optimize the immune response and provide broad protectiveness is very important. In this study, we expressed spike trimer protein (S-TM) based on the Beta variant in a GMP-grade workshop using CHO cells. Mice were immunized twice with S-TM protein combined with aluminum hydroxide (Al) and CpG Oligonucleotides (CpG) adjuvant to evaluate its safety and efficacy. BALB/c immunized with S-TM + Al + CpG induced high neutralizing antibody titers against the Wuhan-Hu-1 strain (wild-type, WT), the Beta and Delta variants, and even the Omicron variant. In addition, compared with the S-TM + Al group, the S-TM + Al + CpG group effectively induced a stronger Th1-biased cell immune response in mice. Furthermore, after the second immunization, H11-K18 hACE2 mice were well protected from challenge with the SARS-CoV-2 Beta strain, with a 100% survival rate. The virus load and pathological lesions in the lungs were significantly reduced, and no virus was detected in mouse brain tissue. Our vaccine candidate is practical and effective for current SARS-CoV-2 VOCs, which will support its further clinical development for potential sequential immune and primary immunization. IMPORTANCE Continuous emergence of adaptive mutations of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to challenge the use and development of existing vaccines and drugs. The value of variant-based vaccines that are capable of inducing a higher and broader protection immune response against SARS-CoV-2 variants is currently being evaluated. This article shows that a recombinant prefusion spike protein based on a Beta variant was highly immunogenic and could induced a stronger Th1-biased cell immune response in mice and was effectively protective against challenge with the SARS-CoV-2 Beta variant. Importantly, this Beta-based SARS-CoV-2 vaccine could also offer a robust humoral immune response with effectively broad neutralization ability against the wild type and different variants of concern (VOCs): the Beta, Delta, and Omicron BA.1 variants. To date, the vaccine described here has been produced in a pilot scale (200L), and the development, filling process, and toxicological safety evaluation have also been completed, which provides a timely response to the emerging SARS-CoV-2 variants and vaccine development.
ABSTRACT
Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has posed a serious threat to international public health. The SARS-COV-2 gene continues to mutate in COVID-19 outbreaks. Mutation mainly manifests in 3 forms: point mutation, gene recombination and epigenetic modification. Viral mutations are driven by multiple factors, with mutation rates modulated at 3 levels, the nature of virus, host-virus interactions and natural selection. Therefore, it is particularly important to strengthen the monitoring of the global novel coronavirus genome and the protection of immunosuppressed populations. In the early stage of virus evolution, the mutant strains exhibit greater transmissibility and less virulence than the wild-type strain, although 5 variants of concern (VOCs) showed different stability, transmission capacity, adaptability and pathogenicity. So physical interventions need to be further strengthened. As herd immunity is established, novel mutant strains tend to mutate against vaccines and antibodies. In that case, VOCs, especially the prevailing Omicron variant, bring challenges to the prevention and control of COVID-19 worldwide. The existing and potential prevention, diagnosis and treatment approaches for COVID-19 were summarized. In the vaccination part, the protective efficacy of COVID-19 vaccine against VOCs and the factors influencing the efficacy of COVID-19 vaccine were analyzed. In the detection part, the detection methods based on nucleic acid, antigen and antibody were summarized in order to satisfy the requirements for point-of-care testing and timely recognition of novel variants. And in the treatment part, the potential therapeutic drugs and targets of SARS-CoV-2 were summarized. Drug targets are generally divided into extracellular targets and intracellular targets. In general, this review proposes possible countermeasures by analyzing the impact of mutations on global epidemic prevention and control, hoping to provide theoretical basis for possible large-scale epidemic prevention and control in the future.
ABSTRACT
Multivalent vaccines combining crucial mutations from phylogenetically divergent variants could be an effective approach to defend against existing and future SARS-CoV-2 variants. In this study, we developed a tetravalent COVID-19 vaccine SCTV01E, based on the trimeric Spike protein of SARS-CoV-2 variants Alpha, Beta, Delta, and Omicron BA.1, with a squalene-based oil-in-water adjuvant SCT-VA02B. In the immunogenicity studies in naïve BALB/c and C57BL/6J mice, SCTV01E exhibited the most favorable immunogenic characteristics to induce balanced and broad-spectrum neutralizing potencies against pre-Omicron variants (D614G, Alpha, Beta, and Delta) and newly emerging Omicron subvariants (BA.1, BA.1.1, BA.2, BA.3, and BA.4/5). Booster studies in C57BL/6J mice previously immunized with D614G monovalent vaccine demonstrated superior neutralizing capacities of SCTV01E against Omicron subvariants, compared with the D614G booster regimen. Furthermore, SCTV01E vaccination elicited naïve and central memory T cell responses to SARS-CoV-2 ancestral strain and Omicron spike peptides. Together, our comprehensive immunogenicity evaluation results indicate that SCTV01E could become an important COVID-19 vaccine platform to combat surging infections caused by the highly immune evasive BA.4/5 variants. SCTV01E is currently being studied in a head-to-head immunogenicity comparison phase 3 clinical study with inactivated and mRNA vaccines (NCT05323461).
ABSTRACT
With severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) as an emergent human virus since December 2019, the world population is susceptible to coronavirus disease 2019 (COVID-19). SARS-CoV-2 has higher transmissibility than the previous coronaviruses, associated by the ribonucleic acid (RNA) virus nature with high mutation rate, caused SARS-CoV-2 variants to arise while circulating worldwide. Neutralizing antibodies are identified as immediate and direct-acting therapeutic against COVID-19. Single-domain antibodies (sdAbs), as small biomolecules with non-complex structure and intrinsic stability, can acquire antigen-binding capabilities comparable to conventional antibodies, which serve as an attractive neutralizing solution. SARS-CoV-2 spike protein attaches to human angiotensin-converting enzyme 2 (ACE2) receptor on lung epithelial cells to initiate viral infection, serves as potential therapeutic target. sdAbs have shown broad neutralization towards SARS-CoV-2 with various mutations, effectively stop and prevent infection while efficiently block mutational escape. In addition, sdAbs can be developed into multivalent antibodies or inhaled biotherapeutics against COVID-19.
ABSTRACT
The effectiveness of SARS-CoV-2 vaccines and therapeutic antibodies have been limited by the continuous emergence of viral variants and by the restricted diffusion of antibodies from circulation into the sites of respiratory virus infection. Here, we report the identification of two highly conserved regions on the Omicron variant receptor-binding domain recognized by broadly neutralizing antibodies. Furthermore, we generated a bispecific single-domain antibody that was able to simultaneously and synergistically bind these two regions on a single Omicron variant receptor-binding domain as revealed by cryo-EM structures. We demonstrated that this bispecific antibody can be effectively delivered to lung via inhalation administration and exhibits exquisite neutralization breadth and therapeutic efficacy in mouse models of SARS-CoV-2 infections. Importantly, this study also deciphered an uncommon and highly conserved cryptic epitope within the spike trimeric interface that may have implications for the design of broadly protective SARS-CoV-2 vaccines and therapeutics.
Subject(s)
COVID-19 Vaccines , Single-Domain Antibodies , Administration, Inhalation , Animals , Antibodies, Neutralizing , Antibodies, Viral , COVID-19 , COVID-19 Vaccines/administration & dosage , Disease Models, Animal , Humans , Mice , SARS-CoV-2 , Spike Glycoprotein, Coronavirus/chemistryABSTRACT
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has precipitated multiple variants resistant to therapeutic antibodies. In this study, 12 high-affinity antibodies were generated from convalescent donors in early outbreaks using immune antibody phage display libraries. Of them, two RBD-binding antibodies (F61 and H121) showed high-affinity neutralization against SARS-CoV-2, whereas three S2-target antibodies failed to neutralize SARS-CoV-2. Following structure analysis, F61 identified a linear epitope located in residues G446-S494, which overlapped with angiotensin-converting enzyme 2 (ACE2) binding sites, while H121 recognized a conformational epitope located on the side face of RBD, outside from ACE2 binding domain. Hence the cocktail of the two antibodies achieved better performance of neutralization to SARS-CoV-2. Importantly, these two antibodies also showed efficient neutralizing activities to the variants including B.1.1.7 and B.1.351, and reacted with mutations of N501Y, E484K, and L452R, indicated that it may also neutralize the recent India endemic strain B.1.617. The unchanged binding activity of F61 and H121 to RBD with multiple mutations revealed a broad neutralizing activity against variants, which mitigated the risk of viral escape. Our findings revealed the therapeutic basis of cocktail antibodies against constantly emerging SARS-CoV-2 variants and provided promising candidate antibodies to clinical treatment of COVID-19 patients infected with broad SARS-CoV-2 variants.