Rational Design of a Pan-Coronavirus Vaccine Based on Conserved CTL Epitopes

Mosaic neuraminidase-based vaccine induces antigen-specific T cell responses against homologous and heterologous influenza viruses

Seasonal influenza is an annually severe crisis for global public health, and an ideal influenza vaccine is expected to provide broad protection against constantly drifted strains. Compared to highly flexible hemagglutinin (HA), increasing data have demonstrated that neuraminidase (NA) might be a potential target against influenza variants. In the present study, a series of genetic algorithm-based mosaic NA were designed, and then cloned into recombinant DNA and replication-defective Vesicular Stomatitis Virus (VSV) vector as a novel influenza vaccine candidate. Our Results showed that DNA prime/VSV boost strategy elicited a robust NA-specific Th1-dominated immune response, but the traditional inactivated influenza vaccine elicited a Th2-dominated immune response. More importantly, the superior NA-specific immunity induced by our strategy could confer both a full protection against lethal homologous influenza challenge and a partial protection against heterologous influenza infection. These findings will provide insights on designing NA-based universal vaccine strategy against influenza variants.

Phage Display Revealed the Complex Structure of the Epitope of the Monoclonal Antibody 10H10

The annual number of reported human cases of flavivirus infections continues to increase. Measures taken by local healthcare systems and international organizations are not fully successful. In this regard, new approaches to treatment and prevention of flavivirus infections are relevant. One promising approach is to use monoclonal antibody preparations. The mouse mAb 10H10 is capable of interacting with viruses belonging to the genus Orthoflavivirus which are pathogenic to humans. ELISA and molecular modeling data can indicate that mAb 10H10 recognizes the fusion loop region of E protein. The KD of interaction between the mAb 10H10 and recombinant analogs of the E protein of the tick-borne encephalitis (TBEV), Zika (ZIKV) and dengue (DENV) viruses range from 1.5 to 4 nM. The aim of this study was to map the epitope of this antibody using phage display technology. After three rounds of biopanning, 60 individual phage clones were chosen. The amino acid sequences of the selected peptides were conveniently divided into five groups. Based on the selected peptides, bacteriophages were obtained carrying peptides on the surfaces of the pIII and pVIII proteins, which were tested for binding to the antibody in ELISA. Thus, the epitope of the mAb 10H10 is the highly conserved region 98-DRGWGNXXGLFGK-110 of the flavivirus E protein. The structures of the complexes of the identified peptides with the antibody paratope are proposed using the molecular docking and dynamics methods.

A recombinant Mycobacterium smegmatis-based surface display system for developing the T cell-based COVID-19 vaccine

The immune escape mutations of SARS-CoV-2 variants emerged frequently, posing a new challenge to weaken the protective efficacy of current vaccines. Thus, the development of novel SARS-CoV-2 vaccines is of great significance for future epidemic prevention and control. We herein reported constructing the attenuated Mycobacterium smegmatis (M. smegmatis) as a bacterial surface display system to carry the spike (S) and nucleocapsid (N) of SARS-CoV-2. To mimic the native localization on the surface of viral particles, the S or N antigen was fused with truncated PE_PGRS33 protein, which is a transportation component onto the cell wall of Mycobacterium tuberculosis (M.tb). The sub-cellular fraction analysis demonstrated that S or N protein was exactly expressed onto the surface (cell wall) of the recombinant M. smegmatis. After the immunization of the M. smegmatis-based COVID-19 vaccine candidate in mice, S or N antigen-specific T cell immune responses were effectively elicited, and the subsets of central memory CD4+ T cells and CD8+ T cells were significantly induced. Further analysis showed that there were some potential cross-reactive CTL epitopes between SARS-CoV-2 and M.smegmatis. Overall, our data provided insights that M. smegmatis-based bacterial surface display system could be a suitable vector for developing T cell-based vaccines against SARS-CoV-2 and other infectious diseases.

Effect of seasonal coronavirus immune imprinting on the immunogenicity of inactivated COVID-19 vaccination

Background

Pre-existing cross-reactive immunity among different coronaviruses, also termed immune imprinting, may have a comprehensive impact on subsequent SARS-CoV-2 infection and COVID-19 vaccination effectiveness. Here, we aim to explore the interplay between pre-existing seasonal coronaviruses (sCoVs) antibodies and the humoral immunity induced by COVID-19 vaccination.

Methods

We first collected serum samples from healthy donors prior to COVID-19 pandemic and individuals who had received COVID-19 vaccination post-pandemic in China, and the levels of IgG antibodies against sCoVs and SARS-CoV-2 were detected by ELISA. Wilcoxon rank sum test and chi-square test were used to compare the difference in magnitude and seropositivity rate between two groups. Then, we recruited a longitudinal cohort to collect serum samples before and after COVID-19 vaccination. The levels of IgG antibodies against SARS-CoV-2 S, S1, S2 and N antigen were monitored. Association between pre-existing sCoVs antibody and COVID-19 vaccination-induced antibodies were analyzed by Spearman rank correlation.

Results

96.0% samples (339/353) showed the presence of IgG antibodies against at least one subtype of sCoVs. 229E and OC43 exhibited the highest seroprevalence rates at 78.5% and 72.0%, respectively, followed by NL63 (60.9%) and HKU1 (52.4%). The levels of IgG antibodies against two β coronaviruses (OC43 and HKU1) were significantly higher in these donors who had inoculated with COVID-19 vaccines compared to pre-pandemic healthy donors. However, we found that COVID-19 vaccine-induced antibody levels were not significant different between two groups with high levelor low level of pre-existing sCoVs antibody among the longitudinal cohort.

Conclusion

We found a high prevalence of antibodies against sCoVs in Chinese population. The immune imprinting by sCoVs could be reactivated by COVID-19 vaccination, but it did not appear to be a major factor affecting the immunogenicity of COVID-19 vaccine. These findings will provide insights into understanding the impact of immune imprinting on subsequent multiple shots of COVID-19 vaccines.

Enhancement of SARS-CoV-2 N Antigen-Specific T Cell Functionality by Modulating the Autophagy-Mediated Signal Pathway in Mice

The frequent SARS-CoV-2 variants have caused a continual challenge, weakening the effectiveness of current vaccines, and thus it is of great importance to induce robust and conserved T cellular immunity for developing the next-generation vaccine against SARS-CoV-2 variants. In this study, we proposed a conception of enhancing the SARS-CoV-2 specific T cell functionality by fusing autophagosome-associated LC3b protein to the nucleocapsid (N) (N-LC3b). When compared to N protein alone, the N-LC3b protein was more effectively targeted to the autophagosome/lysosome/MHC II compartment signal pathway and thus elicited stronger CD4⁺ and CD8⁺ T cell immune responses in mice. Importantly, the frequency of N-specific polyfunctional CD4⁺ and CD8⁺ T cells, which can simultaneously secrete multiple cytokines (IFN-γ⁺/IL-2⁺/TNF-α⁺), in the N-LC3b group was significantly higher than that in the N alone group. Moreover, there was a significantly improved T cell proliferation, especially for CD8⁺ T cells in the N-LC3b group. In addition, the N-LC3b also induced a robust humoral immune response, characterized by the Th1-biased IgG2a subclass antibodies against the SARS-CoV-2 N protein. Overall, these findings demonstrated that our strategy could effectively induce a potential SARS-CoV-2 specific T cellular immunity with enhanced magnitude, polyfunctionality, and proliferation, and thus provided insights to develop a promising strategy for the design of a novel universal vaccine against SARS-CoV-2 variants and other emerging infectious diseases.

Advances in Next-Generation Coronavirus Vaccines in Response to Future Virus Evolution

Coronavirus disease (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread to more than 230 countries and territories worldwide since its outbreak in late 2019. In less than three years, infection by SARS-CoV-2 has resulted in over 600 million cases of COVID-19 and over 6.4 million deaths. Vaccines have been developed with unimaginable speed, and 11 have already been approved by the World Health Organization and given Emergency Use Listing. The administration of several first-generation SARS-CoV-2 vaccines has successfully decelerated the spread of COVID-19 but not stopped it completely. In the ongoing fight against viruses, genetic mutations frequently occur in the viral genome, resulting in a decrease in vaccine-induced antibody neutralization and widespread breakthrough infection. Facing the evolution and uncertainty of SARS-CoV-2 in the future, and the possibility of the spillover of other coronaviruses to humans, the need for vaccines with a broad spectrum of antiviral variants against multiple coronaviruses is recognized. It is imperative to develop a universal coronavirus or pan-coronavirus vaccine or drug to combat the ongoing COVID-19 pandemic as well as to prevent the next coronavirus pandemic. In this review, in addition to summarizing the protective effect of approved vaccines, we systematically summarize current work on the development of vaccines aimed at suppressing multiple SARS-CoV-2 variants of concern as well as multiple coronaviruses.

The Advantage of Using Immunoinformatic Tools on Vaccine Design and Development for Coronavirus

After the outbreak of SARS-CoV-2 by the end of 2019, the vaccine development strategies became a worldwide priority. Furthermore, the appearances of novel SARS-CoV-2 variants challenge researchers to develop new pharmacological or preventive strategies. However, vaccines still represent an efficient way to control the SARS-CoV-2 pandemic worldwide. This review describes the importance of bioinformatic and immunoinformatic tools (in silico) for guide vaccine design. In silico strategies permit the identification of epitopes (immunogenic peptides) which could be used as potential vaccines, as well as nonacarriers such as: vector viral based vaccines, RNA-based vaccines and dendrimers through immunoinformatics. Currently, nucleic acid and protein sequential as well structural analyses through bioinformatic tools allow us to get immunogenic epitopes which can induce immune response alone or in complex with nanocarriers. One of the advantages of in silico techniques is that they facilitate the identification of epitopes, while accelerating the process and helping to economize some stages of the development of safe vaccines.

Non-SARS Coronaviruses in Individuals with Psychiatric Disorders

BACKGROUND

The pandemic caused by severe acute respiratory syndrome-Coronavirus-2 (SARS-CoV-2) has highlighted the importance of coronaviruses in human health. Several seasonal, non-SARS Coronaviruses are endemic in most areas of the world. In a previous study, we found that the level of antibodies to these seasonal Coronaviruses was elevated in persons with a recent onset of psychosis. In the current study, the level of antibodies to seasonal Coronaviruses was compared between individuals with psychiatric disorders and a non-psychiatric comparison group.

METHODS

Participants (N = 195) were persons with a diagnosis of schizophrenia, bipolar disorder, major depressive disorder, or without a psychiatric disorder. Each participant had a blood sample drawn from which were measured IgG antibodies to the spike proteins in four non-SARS Coronaviruses, 229E, HKU1, NL63, and OC43, using a multiplex electrochemiluminescence assay. Linear regression models were employed to compare the levels of antibodies between each psychiatric group and the comparison group adjusting for demographic variables. Logistic regression models were employed to calculate the odds ratios associated with increased levels of antibodies to each seasonal Coronavirus based on the 50th percentile level of the comparison group.

RESULTS

The schizophrenia group had significantly increased levels of antibodies to the seasonal Coronaviruses OC43 and NL63. This group also had increased odds of having elevated antibody levels to OC43. The major depression group showed a significantly lower level of antibodies to Coronavirus 229E. There were no significant differences between any of the psychiatric groups and the comparison group in the levels of antibodies to seasonal Coronaviruses 229E or HKU1.

CONCLUSIONS

The elevated level of antibodies to OC43 and NL63 in the schizophrenia group indicates increased exposure to these agents and raises the possibility that Coronaviruses may contribute to the etiopathology of this disorder. The cause-and-effect relationship between seasonal Coronaviruses and psychiatric disorders should be the subject of additional investigations focusing on longitudinal cohort studies.

Comparison of the Immunogenicity of HIV-1 CRF07_BC Gag Antigen With or Without a Seven Amino Acid Deletion in p6 Region

HIV-1 CRF07_BC-p6Δ7, a strain with a seven amino acid deletion in the p6 region of the Gag protein, is becoming the dominant strain of HIV transmission among men who have sex with men (MSM) in China. Previous studies demonstrated that HIV-1 patients infected by CRF07_BC-p6Δ7 strain had lower viral load and slower disease progression than those patients infected with CRF07_BC wild-type strain. However, the underlying mechanism for this observation is not fully clarified yet. In this study, we constructed the recombinant DNA plasmid and adenovirus type 2 (Ad2) vector-based constructs to express the HIV-1 CRF07_BC Gag antigen with or without p6Δ7 mutation and then investigated their immunogenicity in mice. Our results showed that HIV-1 CRF07_BC Gag antigen with p6Δ7 mutation induced a comparable level of Gag-specific antibodies but stronger CD4⁺ and CD8⁺ T-cell immune responses than that of CRF07_BC Gag (07_BC-wt). Furthermore, we identified a series of T-cell epitopes, which induced strong T-cell immune response and cross-immunity with CRF01_AE Gag. These findings implied that the p6^Gag protein with a seven amino acid deletion might enhance the Gag immunogenicity in particular cellular immunity, which provides valuable information to clarify the pathogenic mechanism of HIV-1 CRF07_BC-p6Δ7 and to develop precise vaccine strategies against HIV-1 infection.

Pan-SARS neutralizing responses after third boost vaccination in non-human primate immunogenicity model

The emergence of SARS-CoV-2 variants, especially Beta and Delta, has raised concerns about the reduced protection from previous infection or vaccination based on the original Wuhan-Hu-1 (D614) virus. To identify promising regimens for inducing neutralizing titers towards new variants, we evaluated monovalent and bivalent mRNA vaccines either as primary vaccination or as a booster in nonhuman primates (NHPs). Two mRNA vaccines, D614-based MRT5500 and Beta-based MRT5500β, tested in sequential regimens or as a bivalent combination in naïve NHPs produced modest neutralizing titers to heterologous variants. However, when mRNA vaccines were administered as a booster to pre-immune NHPs, we observed a robust increase in neutralizing titers with expanded breadth towards all tested variants, and notably SARS-CoV-1. The breadth of the neutralizing response was independent of vaccine sequence or modality, as we further showed either MRT5500 or recombinant subunit Spike protein (with adjuvant) can serve as boosters to induce broadly neutralizing antibodies in the NHPs primed with MRT5500. The data support the notion that a third vaccination is key to boosting existing titers and improving the breadth of antibodies to address variants of concern, including those with an E484K mutation in the Receptor Binding Domain (RBD) (Beta, Gamma).

Shooting at a Moving Target-Effectiveness and Emerging Challenges for SARS-CoV-2 Vaccine Development

Since late 2019 the newly emerged pandemic SARS-CoV-2, the causative agent of COVID-19, has hit the world with recurring waves of infections necessitating the global implementation of non-pharmaceutical interventions, including strict social distancing rules, the wearing of masks and the isolation of infected individuals in order to restrict virus transmissions and prevent the breakdown of our healthcare systems. These measures are not only challenging on an economic level but also have a strong impact on social lifestyles. Using traditional and novel technologies, highly efficient vaccines against SARS-CoV-2 were developed and underwent rapid clinical evaluation and approval to accelerate the immunization of the world population, aiming to end the pandemic and return to normality. However, the emergence of virus variants with improved transmission, enhanced fitness and partial immune escape from the first generation of vaccines poses new challenges, which are currently being addressed by scientists and pharmaceutical companies all over the world. In this ongoing pandemic, the evaluation of SARS-CoV-2 vaccines underlies diverse unpredictable dynamics, posed by the first broad application of the mRNA vaccine technology and their compliance, the occurrence of unexpected side effects and the rapid emergence of variations in the viral antigen. However, despite these hurdles, we conclude that the available SARS-CoV-2 vaccines are very safe and efficiently protect from severe COVID-19 and are thereby the most powerful tools to prevent further harm to our healthcare systems, economics and individual lives. This review summarizes the unprecedented pathways of vaccine development and approval during the ongoing SARS-CoV-2 pandemic. We focus on the real-world effectiveness and unexpected positive and negative side effects of the available vaccines and summarize the timeline of the applied adaptations to the recommended vaccination strategies in the light of emerging virus variants. Finally, we highlight upcoming strategies to improve the next generations of SARS-CoV-2 vaccines.

Possible Targets of Pan-Coronavirus Antiviral Strategies for Emerging or Re-Emerging Coronaviruses

Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), which caused Coronaviruses Disease 2019 (COVID-19) and a worldwide pandemic, is the seventh human coronavirus that has been cross-transmitted from animals to humans. It can be predicted that with continuous contact between humans and animals, more viruses will spread from animals to humans. Therefore, it is imperative to develop universal coronavirus or pan-coronavirus vaccines or drugs against the next coronavirus pandemic. However, a suitable target is critical for developing pan-coronavirus antivirals against emerging or re-emerging coronaviruses. In this review, we discuss the latest progress of possible targets of pan-coronavirus antiviral strategies for emerging or re-emerging coronaviruses, including targets for pan-coronavirus inhibitors and vaccines, which will provide prospects for the current and future research and treatment of the disease.