The success of SARS-CoV-2 vaccines and challenges ahead

Engineered ACE2 decoy in dry powder form for inhalation: A novel therapy for SARS-CoV-2 variants

The persistent threat of SARS-CoV-2 and the emergence of new variants has prompted the development of a novel, easily administered modality that can overcome viral mutations. The engineered ACE2 decoy shows neutralizing activity comparable to monoclonal antibodies and is broadly effective against SARS-CoV-2 variants and ACE2-utilizing sarbecoviruses. In addition to intravenous administration, this decoy has shown antiviral efficacy through nebulized aerosol inhalation in murine and primate models, offering a dose-sparing advantage. Clinically, dry powder formulation is ideal for convenience and storage but poses challenges for protein biologics. This study developed a freeze-dried spray formulation of the ACE2 decoy for inhalation. The trehalose and leucine-based excipient maintained neutralizing activity and prevented aggregate formation. The dry powder showed aerodynamic distribution from bronchi to alveoli, aiding protection against SARS-CoV-2 infections. Neutralizing activity, structural stability, and powder dispersibility were preserved after 6 months of storage. In a mouse model of SARS-CoV-2 infection, significant reductions in viral replication and lung pathology were observed with intratracheal administration 24 h post-infection. The ACE2 decoy retained activity against recent JN.1 and current KP.3 strains, confirming its robust efficacy against viral mutations. This ACE2 decoy powder inhalant is a self-administered, next-generation treatment addressing the ongoing immune-evading evolution of SARS-CoV-2.

Intranasal influenza virus-vectored vaccine offers protection against clade 2.3.4.4b H5N1 infection in small animal models

The highly pathogenic avian influenza (HPAI) H5N1 virus has been endemic in aquatic birds since 1997, causing outbreaks in domestic poultry and occasional human infections worldwide. Recently, the cross-species transmission of a new reassortant variant from clade 2.3.4.4b of H5N1 to cattle in the US has heightened concerns regarding the expansion of host range and potential human infection. As eradicating the H5N1 virus from its reservoir is impossible, it is essential to prepare for a potential pandemic caused by an H5N1 derivative. Utilizing a deleted-NS1 live attenuated influenza viral vector vaccine system (DelNS1 LAIV), a system we have previously used in the development of a COVID-19 vaccine, we have rapidly developed an intranasal vaccine for cattle H5N1 and related clade 2.3.4.4b strains, based on publicly available sequences. Our research demonstrates that a single intranasal immunization can provide effective protection against lethal challenges from HPAI cattle or mink H5N1 variants, offering strong, sustained immunity after two months in female mouse and male hamster models. Immunogenicity analysis reveals that intranasal vaccination with DelNS1 LAIV induces robust neutralizing antibody, mucosal IgA and T cell responses in mice. It is crucial to further evaluate the DelNS1-H5N1 LAIV system to prepare for potential future H5N1 outbreaks in humans.

Disparities in anti-SARS-CoV-2 reactivity according to vaccines administered in the era of omicron in Cameroon: Lessons for future outbreak response

With the advent of COVID-19, anti-SARS-CoV-2 vaccines were a global health priority, but evidence on their significance within tropical settings remained limited. We sought to assess the distribution of anti-SARS-CoV-2 antibodies according to vaccine status and types of vaccines administered in Cameroon during Omicron waves. A community based cross-sectional sero-survey was conducted from February-15 through July-31 2022 among individuals tested for COVID-19 in Yaoundé-Cameroon. Sociodemographic data were collected from participants. Anti-SARS-CoV-2 antibodies (both IgG and IgM) were tested on plasma and statistical analyses were performed wherever appropriate. Logistic regression was done with p<0.05 considered statistically significant. Overall, 2449 participants were enrolled: median-age was 40 [31-49], 56.4% (1382/2449) men, 2.2% (54/2449) with flu-like symptoms and 19.6% (481/2449) reporting previous SARS-CoV-2 positivity. Regarding COVID-19 vaccination, 67.5% (1652/2449) had received at least one dose, 55.0% (909/1652) two-dose series and 37.1% (613/1652) received additional booster doses. Median duration from vaccination to phlebotomy was 5 [4-9] months. Seroprevalence of anti-SARS-CoV-2 antibodies was 81.1% (1987/2449). Following logistic regression, vaccine status (aOR=1.95), booster doses (aOR=1.36), post-vaccination time (≤5 months; aOR=1.64), Pfizer (aOR=2.07) and Moderna (aOR=1.52) vaccines, were all associated with a high prevalence of anti-SARS-CoV-2 antibodies (all p<0.05). This high seroprevalence of anti-SARS-CoV-2 antibodies suggests a certain degree of immunity/protection at community-level in Cameroon during Omicron waves, with Pfizer and Moderna inducing greater immunogenicity. However, rapid antibody waning (~5 months) calls for vaccine updates with novel variants (arising from a rapidly evolving virus) that could compromise already acquired immunity.

Effects of protein boosters on antibody responses

SARS-CoV-2 has infected a large fraction of the human population. Currently, most individuals have developed immunity either through vaccination or natural infection. Despite this, SARS-CoV-2 booster immunizations are still recommended to reduce the risk of reinfections, but there is still limited understanding on how different booster vaccine platforms influence antibody responses. We conducted immunological studies in mice to evaluate the boosting effects of different vaccine platforms on antibody responses. C57BL/6 mice were first primed with an adenovirus serotype 5 (Ad5) vaccine expressing the SARS-CoV-2 spike protein. The mice were then boosted with the same Ad5-based vaccine (homologous boosting) or with a protein-based vaccine (heterologous boosting). Interestingly, the heterologous regimen (Ad5 prime + protein boost) elicited superior antibody responses, relative to the homologous regimen (Ad5 prime + Ad5 boost). Similar potentiation of antibody responses was reported when mice were primed with poxvirus or rhabdovirus vectors and then boosted with protein. These findings highlight a potential advantage of protein booster immunizations to potentiate humoral immunity.

Rapid clonal expansion and somatic hypermutation contribute to the fate of SARS-CoV-2 broadly neutralizing antibodies

Several vaccines and immunization strategies, including inactivated vaccines, have proven effective in eliciting antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), providing an opportunity to characterize the antibody response. In this study, we investigated the monoclonal antibody responses elicited by wild-type SARS-CoV-2 inactivated vaccination compared to those elicited by natural infection and mRNA vaccination. The analysis showed that antibodies encoded by biased germline genes were shared between SARS-CoV-2 vaccinated and naturally infected individuals. Among the 35 shared clonotypes identified, besides the well-known IGHV3-53 and IGHV1-58, we identified a class of IGHV4-59 antibodies characterized by rapid response and neutralizing activity, elicited by 3 doses of inactivated vaccine. Members of this lineage exhibited similar sensitivity against wild-type SARS-CoV-2, whereas different neutralizing activities against SARS-CoV-2 variants, especially against various Omicron subvariants, BA.1, BA.2, BA.2.12.1, BA.4/5, and BA.2.75. Structural analysis of BA.1 spike complexed with VacBB-639 revealed that the IGHV4-59-lineage antibodies belonged to the Class 2/3 group. Using sequence alignment, site-mutation assays, and functional verification, we identified two substitutions, N60K in HFR3 and S56G in HCDR2, contributing to opposite neutralization changes of IGHV4-59-lineage antibodies against these Omicron subvariants. These results demonstrate the importance of somatic hypermutation in the evolution of prototypical antigen-elicited antibodies in terms of their neutralization breadth and potency against SARS-CoV-2 Omicron variants.

Phenomenological Modeling of Antibody Response from Vaccine Strain Composition

The elicitation of broadly neutralizing antibodies (bnAbs) is a major goal of vaccine design for highly mutable pathogens, such as influenza, HIV, and coronavirus. Although many rational vaccine design strategies for eliciting bnAbs have been devised, their efficacies need to be evaluated in preclinical animal models and in clinical trials. To improve outcomes for such vaccines, it would be useful to develop methods that can predict vaccine efficacies against arbitrary pathogen variants. As a step in this direction, here, we describe a simple biologically motivated model of antibody reactivity elicited by nanoparticle-based vaccines using only antigen amino acid sequences, parametrized with a small sample of experimental antibody binding data from influenza or SARS-CoV-2 nanoparticle vaccinations. Results: The model is able to recapitulate the experimental data to within experimental uncertainty, is relatively insensitive to the choice of the parametrization/training set, and provides qualitative predictions about the antigenic epitopes exploited by the vaccine, which are testable by experiment. For the mosaic nanoparticle vaccines considered here, model results suggest indirectly that the sera obtained from vaccinated mice contain bnAbs, rather than simply different strain-specific Abs. Although the present model was motivated by nanoparticle vaccines, we also apply it to a mutlivalent mRNA flu vaccination study, and demonstrate good recapitulation of experimental results. This suggests that the model formalism is, in principle, sufficiently flexible to accommodate different vaccination strategies. Finally, we show how the model could be used to rank the efficacies of vaccines with different antigen compositions. Conclusions: Overall, this study suggests that simple models of vaccine efficacy parametrized with modest amounts of experimental data could be used to compare the effectiveness of designed vaccines.

A Purely Biomanufactured System for Delivering Nanoparticles and STING Agonists

Nanovaccines have significantly contributed in the prevention and treatment of diseases. However, most of these technologies rely on chemical or hybrid semibiological synthesis methods, which limit the manufacturing performance advantages and improved inoculation outcomes compared with traditional vaccines. Herein, a universal and purely biological nanovaccine system is reported. This system integrates three modules: (1) self-assembling nanoparticles, (2) self-catalyzed synthesis of small-molecule stimulator of interferon gene (STING) agonists, and (3) delivery vectors that target the cytosolic surveillance system. Various nanoparticles are efficiently self-assembled using this system. After confirming the excellent immunostimulatory and lymph node targeting of this system, its broad-spectrum antiviral efficacy is further demonstrated. By leveraging the comprehensive biosynthetic capabilities of bacterial cells, this system can efficiently combine various adjuvant-active modular components and antigenic cargo, thereby providing a highly diversified and potent vaccine platform.

Receptor Binding Domain-Specific B Cell Memory Responses Among Individuals Vaccinated Against SARS-CoV-2

Background: The COVID-19 pandemic prompted unprecedented vaccine development efforts against SARS-CoV-2. India, which was one of the countries most impacted by COVID-19, developed its indigenous vaccine in addition to utilizing the ones developed by other countries. While antibody levels and neutralizing antibody titres are considered initial correlates of immune protection, long-term protection from the pathogen relies on memory B and T cells and their recall responses. In this regard, global research has primarily focused on mRNA-based vaccines. The studies on immune memory response, particularly B cell memory response induced by the vaccines given to Indians, remain relatively obscure. Methods: We assessed Receptor Binding Domain-specific memory B cells in the peripheral circulation and their ability to secrete antigen-specific antibodies among Indians vaccinated with Covaxin (BBV152), Covishield (AZD1222), Corbevax (BECOV2D), and Sputnik Light, as well as unvaccinated individuals. Results: Corbevax and Sputnik Light conferred better antibody-secreting cell (ASC) responses over time compared to other groups. Conclusions: These findings contribute to our understanding of vaccine-induced immune memory in the Indian population; providing insights that could inform future vaccine strategies.

Boosting DNA vaccine power by lipid nanoparticles surface engineered with amphiphilic bioresorbable copolymer

Successful DNA vaccination generally requires the aid of either a viral vector within vaccine components or an electroporation device into the muscle or skin of the host. However, these systems come with certain obstacles, including limited transgene capacity, broad preexisting immunity in humans, and substantial cell death caused by high voltage pulses, respectively. In this study, we repurposed the use of an amphiphilic bioresorbable copolymer (ABC), called PLA-PEG, as a surface engineering agent that conciliates lipid nanoparticles (LNPs) between stability during preparation and biocompatibility post-vaccination. The LNP carrier can be loaded with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike-specific DNA; in this form, the DNA-LNP is immunogenic in hamsters and elicits protective immunity following DNA-LNP vaccination against heterologous virus challenge or as a hybrid-type vaccine booster against SARS-CoV-2 variants. The data provide comprehensive information on the relationships between LNP composition, manufacturing process, and vaccine efficacy. The outcomes of this study offer new insights into designing next-generation LNP formulations and pave the way for boosting vaccine power to combat existing and possible emerging infectious diseases/pathogens.

The timing of local SARS-Cov-2 outbreaks and vaccination coverage during the Delta wave in Melbourne

OBJECTIVE

This article presents a longitudinal analysis of COVID-19 infection and vaccination coverage in Melbourne metropolitan local government areas (LGAs) during the 2021 Delta wave.

METHODS

COVID-19 vaccination and infection data from 12 July to 27 November 2021 were sourced from government websites. Summary statistics and associated 95% confidence intervals (95% CI) were compared by LGA ranked according to socioeconomic status: total "burden" (total infections per thousand), "peak" (highest weekly infection rate), "lag" (interval between peak and 70% double vaccination).

RESULTS

LGAs in the bottom five deciles for social advantage experienced higher infection rates (39.0 per thousand [95% CI: 38.5, 39.5] vs. 14.8 [14.7, 14.9]), and had lower two-dose vaccination coverage (23.8% [23.6, 23.9] vs. 32.7% [32.6, 32.7]) compared with LGAs in the top five deciles. LGAs that achieved 70% coverage two weeks or more after the infection peak experienced nearly twice the total infection burden (27.7 per 1000 [27.3, 28.0] compared with 14.9 [14.7, 15.0]) than LGAs with a shorter lag.

CONCLUSIONS

Exposure and transmission risk factors cluster within disadvantaged LGAs. The potential for large local outbreaks is heightened if vaccination uptake trails in these communities.

IMPLICATIONS FOR PUBLIC HEALTH

In a pandemic, decision-makers must prioritise disease control and harm reduction interventions for at-risk LGAs.

Post-COVID-19: Time to Change Our Way of Life for a Better Future

Background and Objectives: From the year 1 anno Domini until 1855, with the third plague, major pandemics occurred on average every 348 years. Since then, they have occurred on average every 33 years, with coronavirus disease 2019 (COVID-19) now underway. Even though current technologies have greatly improved the way of life of human beings, COVID-19, with more than 700,000,000 cases and 6,950,000 deaths worldwide by the end of 2023, reminds us that much remains to be done. This report looks back at 18 months of COVID-19, from March 2020 to August 2021, with the aim of highlighting potential solutions that could help mitigate the impact of future pandemics. Materials and Methods: COVID-19 data, including case and death reports, were extracted daily from the Worldometer platform to build a database for the macroscopic analysis of the spread of the virus around the world. Demographic data were integrated into the COVID-19 database for a better understanding of the spatial spread of the SARS-CoV-2 virus in cities/municipalities. Without loss of generality, only data from the top 30 (out of 200 and above) countries ranked by total number of COVID-19 cases were analyzed. Statistics (regression, t-test (p < 0.05), correlation, mean ± std, etc.) were carried out with Excel software (Microsoft® Excel® 2013 (15.0.5579.1001)). Spectral analysis, using Matlab software (license number: 227725), was also used to try to better understand the temporal spread of COVID-19. Results: This study showed that COVID-19 mainly affects G20 countries and that cities/municipalities with high population density are a powerful activator of the spread of the virus. In addition, spectral analysis highlighted that the very first months of the spread of COVID-19 were the most notable, with a strong expansion of the SARS-CoV-2 virus. On the other hand, the following six months showed a certain level of stability, mainly due to multiple preventive measures such as confinement, the closure of non-essential services, the wearing of masks, distancing of 2 m, etc. Conclusion: Given that densely populated cities and municipal areas have largely favored the spread of the SARS-CoV-2 virus, it is believed that such a demographic context is becoming a societal problem that developed countries must address in a manner that is adequate and urgent. COVID-19 has made us understand that it is time to act both preventatively and curatively. With phenomenological evidence suggesting that the next pandemic could occur in less than 50 years, it may be time to launch new societal projects aimed at relieving congestion in densely populated regions.

Injectable Hydrogel Mucosal Vaccine Elicits Protective Immunity against Respiratory Viruses

Intranasal vaccines, eliciting mucosal immune responses, can prevent early invasion, replication, and transmission of pathogens in the respiratory tract. However, the effective delivery of antigens through the nasal barrier and boosting of a robust systematic and mucosal immune remain challenges in intranasal vaccine development. Here, we describe an intranasally administered self-healing hydrogel vaccine with a reversible strain-dependent sol-gel transition by precisely modulating the self-assembly processes between the natural drug rhein and aluminum ions. The highly bioadhesive hydrogel vaccine enhances antigen stability and prolongs residence time in the nasal cavity and lungs by confining the antigen to the surface of the nasal mucosa, acting as a "mucosal mask". The hydrogel also stimulates superior immunoenhancing properties, including antigen internalization, cross-presentation, and dendritic cell maturation. Furthermore, the formulation recruits immunocytes to the nasal mucosa and nasal-associated lymphoid tissue (NALT) while enhancing antigen-specific humoral, cellular, and mucosal immune responses. Our findings present a promising strategy for preparing intranasal vaccines for infectious diseases or cancer.

Nanobody engineering for SARS-CoV-2 neutralization and detection

In response to the ongoing COVID-19 pandemic, the quest for coronavirus inhibitors has inspired research on a variety of small proteins beyond conventional antibodies, including robust single-domain antibody fragments, i.e., "nanobodies." Here, we explore the potential of nanobody engineering in the development of antivirals and diagnostic tools. Through fusion of nanobody domains that target distinct binding sites, we engineered multimodular nanobody constructs that neutralize wild-type SARS-CoV-2 and the Alpha and Delta variants at high potency, with IC50 values as low as 50 pM. Despite simultaneous binding to distinct epitopes, Beta and Omicron variants were more resistant to neutralization by the multimodular nanobodies, which highlights the importance of accounting for antigenic drift in the design of biologics. To further explore the applications of nanobody engineering in outbreak management, we present an assay based on fusions of nanobodies with fragments of NanoLuc luciferase that can detect sub-nanomolar quantities of the SARS-CoV-2 spike protein in a single step. Our work showcases the potential of nanobody engineering to combat emerging infectious diseases.

IMPORTANCE

Nanobodies, small protein binders derived from the camelid antibody, are highly potent inhibitors of respiratory viruses that offer several advantages over conventional antibodies as candidates for specific therapies, including high stability and low production costs. In this work, we leverage the unique properties of nanobodies and apply them as building blocks for new therapeutic and diagnostic tools. We report ultra-potent SARS-CoV-2 inhibition by engineered nanobodies comprising multiple modules in structure-guided combinations and develop nanobodies that carry signal molecules, allowing rapid detection of the SARS-CoV-2 spike protein. Our results highlight the potential of engineered nanobodies in the development of effective countermeasures, both therapeutic and diagnostic, to manage outbreaks of emerging viruses.

mRNA delivery systems for cancer immunotherapy: Lipid nanoparticles and beyond

mRNA-based vaccines are emerging as a promising alternative to standard cancer treatments and the conventional vaccines. Moreover, the FDA-approval of three nucleic acid based therapeutics (Onpattro, BNT162b2 and mRNA-1273) has further increased the interest and trust on this type of therapeutics. In order to achieve a significant therapeutic efficacy, the mRNA needs from a drug delivery system. In the last years, several delivery platforms have been explored, being the lipid nanoparticles (LNPs) the most well characterized and studied. A better understanding on how mRNA-based therapeutics operate (both the mRNA itself and the drug delivery system) will help to further improve their efficacy and safety. In this review, we will provide an overview of what mRNA cancer vaccines are and their mode of action and we will highlight the advantages and challenges of the different delivery platforms that are under investigation.

A receptor-binding domain-based nanoparticle vaccine elicits durable neutralizing antibody responses against SARS-CoV-2 and variants of concern

Numerous vaccines have been developed to address the current COVID-19 pandemic, but safety, cross-neutralizing efficacy, and long-term protectivity of currently approved vaccines are still important issues. In this study, we developed a subunit vaccine, ASD254, by using a nanoparticle vaccine platform to encapsulate the SARS-CoV-2 spike receptor-binding domain (RBD) protein. As compared with the aluminum-adjuvant RBD vaccine, ASD254 induced higher titers of RBD-specific antibodies and generated 10- to 30-fold more neutralizing antibodies. Mice vaccinated with ASD254 showed protective immune responses against SARS-CoV-2 challenge, with undetectable infectious viral loads and reduced typical lesions in lung. Besides, neutralizing antibodies in vaccinated mice lasted for at least one year and were effective against various SARS-CoV-2 variants of concern, including B.1.1.7 (Alpha), B.1.351 (Beta), P.1 (Gamma), B.1.617.2 (Delta), and B.1.1.529 (Omicron). Furthermore, particle size, polydispersity index, and zeta-potential of ASD254 remained stable after 8-month storage at 4°C. Thus, ASD254 is a promising nanoparticle vaccine with good immunogenicity and stability to be developed as an effective vaccine option in controlling upcoming waves of COVID-19.

Free Energy Simulations of Receptor-Binding Domain Opening of the SARS-CoV-2 Spike Indicate a Barrierless Transition with Slow Conformational Motions

Infection by sarbecoviruses begins with the attachment of the homotrimeric viral "spike" protein to the angiotensin-converting enzyme 2 receptor on the surface of mammalian cells. This requires one or more receptor-binding domains (RBDs) to be in the open (up) position. Here, we present the results of long molecular dynamics simulations with umbrella sampling (US) to compute a one-dimensional free energy profile of RBD opening/closing and the associated transition times. After ≃3.58μs of simulation time per US window (∼229 μs in total), which was required to approach trajectory decorrelation, the computed free energy profile was found to be without large barriers. This suggests that the RBD diffuses between the open and closed positions without significant energetic hindrance. This interpretation appears consistent with experiments but is at odds with some previous simulations. Modeling the RBD motion as diffusive dynamics along the computed free energy profile, we find that the overall time required for the transition is only about 2 μs, which is 5 orders of magnitude shorter than experimentally measured transition times. We speculate that the most likely reason for the transition time mismatch is our use of very short glycans, which was required to make the simulations performed here feasible. Despite the long simulation times, the final free energy profile is not fully converged with statistical errors of ≃1.16 kcal/mol, which were found to be consistent with the slow time decay in the autocorrelation of the conformational motions of the protein. The simulation lengths that would be required to obtain fully converged results remain unknown, but the present calculations would benefit from at least an order-of-magnitude extension.

Design of Potent Inhibitors Targeting the Main Protease of SARS-CoV-2 Using QSAR Modeling, Molecular Docking, and Molecular Dynamics Simulations

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is a serious global public health threat. The evolving strains of SARS-CoV-2 have reduced the effectiveness of vaccines. Therefore, antiviral drugs against SARS-CoV-2 are urgently needed. The main protease (Mpro) of SARS-CoV-2 is an extremely potent target due to its pivotal role in virus replication and low susceptibility to mutation. In the present study, a quantitative structure-activity relationship (QSAR) study was performed to design new molecules that might have higher inhibitory activity against SARS-CoV-2 Mpro. In this context, a set of 55 dihydrophenanthrene derivatives was used to build two 2D-QSAR models using the Monte Carlo optimization method and the Genetic Algorithm Multi-Linear Regression (GA-MLR) method. From the CORAL QSAR model outputs, the promoters responsible for the increase/decrease in inhibitory activity were extracted and interpreted. The promoters responsible for an increase in activity were added to the lead compound to design new molecules. The GA-MLR QSAR model was used to ensure the inhibitory activity of the designed molecules. For further validation, the designed molecules were subjected to molecular docking analysis and molecular dynamics simulations along with an absorption, distribution, metabolism, excretion, and toxicity (ADMET) analysis. The results of this study suggest that the newly designed molecules have the potential to be developed as effective drugs against SARS-CoV-2.

An intranasal influenza virus-vectored vaccine prevents SARS-CoV-2 replication in respiratory tissues of mice and hamsters

Current available vaccines for COVID-19 are effective in reducing severe diseases and deaths caused by SARS-CoV-2 infection but less optimal in preventing infection. Next-generation vaccines which are able to induce mucosal immunity in the upper respiratory to prevent or reduce infections caused by highly transmissible variants of SARS-CoV-2 are urgently needed. We have developed an intranasal vaccine candidate based on a live attenuated influenza virus (LAIV) with a deleted NS1 gene that encodes cell surface expression of the receptor-binding-domain (RBD) of the SARS-CoV-2 spike protein, designated DelNS1-RBD4N-DAF. Immune responses and protection against virus challenge following intranasal administration of DelNS1-RBD4N-DAF vaccines were analyzed in mice and compared with intramuscular injection of the BioNTech BNT162b2 mRNA vaccine in hamsters. DelNS1-RBD4N-DAF LAIVs induced high levels of neutralizing antibodies against various SARS-CoV-2 variants in mice and hamsters and stimulated robust T cell responses in mice. Notably, vaccination with DelNS1-RBD4N-DAF LAIVs, but not BNT162b2 mRNA, prevented replication of SARS-CoV-2 variants, including Delta and Omicron BA.2, in the respiratory tissues of animals. The DelNS1-RBD4N-DAF LAIV system warrants further evaluation in humans for the control of SARS-CoV-2 transmission and, more significantly, for creating dual function vaccines against both influenza and COVID-19 for use in annual vaccination strategies.

A research and development (R&D) roadmap for broadly protective coronavirus vaccines: A pandemic preparedness strategy

Broadly protective coronavirus vaccines are an important tool for protecting against future SARS-CoV-2 variants and could play a critical role in mitigating the impact of future outbreaks or pandemics caused by novel coronaviruses. The Coronavirus Vaccines Research and Development (R&D) Roadmap (CVR) is aimed at promoting the development of such vaccines. The CVR, funded by the Bill & Melinda Gates Foundation and The Rockefeller Foundation, was generated through a collaborative and iterative process, which was led by the Center for Infectious Disease Research and Policy (CIDRAP) at the University of Minnesota and involved 50 international subject matter experts and recognized leaders in the field. This report summarizes the major issues and areas of research outlined in the CVR and identifies high-priority milestones. The CVR covers a 6-year timeframe and is organized into five topic areas: virology, immunology, vaccinology, animal and human infection models, and policy and finance. Included in each topic area are key barriers, gaps, strategic goals, milestones, and additional R&D priorities. The roadmap includes 20 goals and 86 R&D milestones, 26 of which are ranked as high priority. By identifying key issues, and milestones for addressing them, the CVR provides a framework to guide funding and research campaigns that promote the development of broadly protective coronavirus vaccines.

Indirect Dispersion of SARS-CoV-2 Live-Attenuated Vaccine and Its Contribution to Herd Immunity

It has been 34 months since the beginning of the SARS-CoV-2 coronavirus pandemic, which causes the COVID-19 disease. In several countries, immunization has reached a proportion near what is required to reach herd immunity. Nevertheless, infections and re-infections have been observed even in vaccinated persons. That is because protection conferred by vaccines is not entirely effective against new virus variants. It is unknown how often booster vaccines will be necessary to maintain a good level of protective immunity. Furthermore, many individuals refuse vaccination, and in developing countries, a large proportion of the population has not yet been vaccinated. Some live-attenuated vaccines against SARS-CoV-2 are being developed. Here, we analyze the indirect dispersion of a live-attenuated virus from vaccinated individuals to their contacts and the contribution that this phenomenon could have to reaching Herd Immunity.

The efficacy of Paxlovid against COVID-19 is the result of the tight molecular docking between Mpro and antiviral drugs (nirmatrelvir and ritonavir)

Purpose

Currently, a number of medications for coronavirus disease 2019 (COVID-19) treatment are tested in clinical trials; however, credible clinical studies are becoming increasingly difficult to come by. Paxlovid is a ritonavir-boosted nirmatrelvir drug that the U.S. Food and Drug Administration (FDA) authorized for the treatment of COVID-19.

This study aimed to demonstrate the interaction of nirmatrelvir and ritonavir on the active site of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) main protease (M^pro).

Materials and methods

To locate the optimal docking between M^pro and antiviral drugs, and to conduct dynamic simulations between atoms in the fusion areas, various bioinformatics and mathematical equations were applied.

Results

According to the docking data, nirmatrelvir has a stronger interaction with M^pro than ritonavir, which has more multiple bonds. Molecular docking of antiviral drugs such as Paxlovid has a significant impact on the treatment of COVID-19 virus.

Conclusions

According to this study, Paxlovid may work on new strains, including Omicron, because the M^pro mutation P132H in the Omicron variant has no direct effect on the protein.

The importance of combining serological testing with RT-PCR assays for efficient detection of COVID-19 and higher diagnostic accuracy

Misdiagnosing suspected COVID-19 individuals could largely contribute to the viruses transmission, therefore, making an accurate diagnosis of infected subjects vital in minimizing and containing the disease. Although RT-PCR is the standard method in detecting COVID-19, it is associated with some limitations, including possible false negative results. Therefore, serological testing has been suggested as a complement assay to RT-PCR to support the diagnosis of acute infections. In this study, 15 out of 639 unvaccinated healthcare workers (HCWs) were tested negative for COVID-19 by RT-PCR and were found seropositive for SARS-CoV-2 nucleocapsid protein-specific IgM and IgG antibodies. These participants underwent additional confirmatory RT-PCR and SARS-CoV-2 spike-specific ELISA tests. Of the 15 individuals, nine participants were found negative by second RT-PCR but seropositive for anti-spike IgM and IgG antibodies and neutralizing antibodies confirming their acute infection. At the time of collection, these nine individuals were in close contact with COVID-19-confirmed patients, with 77.7% reporting COVID-19-related symptoms. These results indicate that including serological tests in the current testing profile can provide better outcomes and help contain the spread of the virus by increasing diagnostic accuracy to prevent future outbreaks rapidly.

Immunogenicity of BNT162b2, BBIBP-CorV, Gam-COVID-Vac and ChAdOx1 nCoV-19 Vaccines Six Months after the Second Dose: A Longitudinal Prospective Study

Many available SARS-CoV-2 vaccines demonstrated good humoral response, but studies directly comparing their immunogenicity in the general population are lacking. We evaluated the medium−term kinetics of anti-S SARS-CoV-2 antibodies (Abs) at one and six months after the second dose of BNT162b2, BBIBP-CorV, and Gam-COVID-Vac. Immunogenicity at six months was directly compared between BNT162b2, BBIBP-CorV, Gam-COVID-Vac, and ChAdOx1 nCoV-19. Participants ≥ 20 years old from Novi Sad, Serbia, without prior SARS-CoV-2 infection, were included. Anti S1/S2 IgG antibodies were measured using quantitative LIAISON SARS-CoV-2 assay. A total of 368 participants were included: 231 (62.77%) had sera collected at two time points. Two doses of BNT162b2 were received by 37.50% of participants, followed by BBIBP-CorV (22.01%), Gam-COVID-Vac (21.47%), and ChAdOx1 nCoV-19 (19.02%). Mean Ab levels at the 28th day and 6 months were 216.55 (SD = 105.73) AU/mL and 75.68 (SD = 57.30) for BNT162b2, 194.38 (SD = 140.24) and 90.53 (SD = 111.30) for Gam-COVID-Vac, and 72.74 (SD = 80.04) and 24.43 (SD = 38.43) for BBIBP-CorV group (p < 0.01, between two time points across all three groups), with a significant difference between women and men (p < 0.01, for both sexes). At the sixth month post-vaccination, the highest mean Ab level was detected in Gam-COVID-Vac group (91.28 AU/mL, SD = 95.96), followed by BNT162b2 (85.25 AU/mL, SD = 60.02), ChAdOx1 nCoV-19 (64.22 AU/mL, SD = 65.30), and BBIBP-CorV (25.26 AU/mL, SD = 36.92) (p < 0.01). Anti-spike IgG persistence was demonstrated six months post-vaccination with a significant decline in Ab levels. These results suggest a lower protection against SARS-CoV-2 over time. Our findings support the introduction of additional (booster) doses.

Optimization of potential non-covalent inhibitors for the SARS-CoV-2 main protease inspected by a descriptor of the subpocket occupancy

The main protease is regarded as an essential drug target for treating Coronavirus Disease 2019. In the present study, 13 marketed drugs were investigated to explore the possible binding mechanism, utilizing molecular docking, molecular dynamics simulation, and MM-PB(GB)SA binding energy calculations. Our results suggest that fusidic acid, polydatin, SEN-1269, AZD6482, and UNC-2327 have high binding affinities of more than 23 kcal mol^-1. A descriptor was defined for the energetic occupancy of the subpocket, and it was found that S4 had a low occupancy of less than 10% on average. The molecular optimization of ADZ6482 via reinforcement learning algorithms was carried out to screen out three lead compounds, in which slight structural changes give more considerable binding energies and an occupancy of the S4 subpocket of up to 43%. The energetic occupancy could be a useful descriptor for evaluating the local binding affinity for drug design.

Influence of COVID-19 vaccines on endocrine system

The COVID-19 pandemic has posed a significant health threat globally. Timely and appropriate vaccination is a key step to reduce the morbidity and mortality from COVID-19. The clinical course of COVID-19 infection and the effects of COVID-19 vaccination are influenced by patients' health situations and involve a systemic physiological reaction. Just like an "endocrine phenotype" of COVID-19 infection, endocrine dysfunction after COVID-19 vaccination also acquired clinical concerns. In the present review, we briefly introduce the commonly available vaccines against SARS-CoV-2, summarize the influence of COVID-19 vaccines on the endocrine system, and explore the underlying pathogenic mechanisms.

SARS-CoV-2 and COVID-19: A Narrative Review

The World Health Organisation has reported that the viral disease known as COVID-19, caused by SARS-CoV-2, is the leading cause of death by a single infectious agent. This narrative review examines certain components of the pandemic: its origins, early clinical data, global and UK-focussed epidemiology, vaccination, variants, and long COVID.

Molecular detection of SARS-CoV-2 strains and differentiation of Delta variant strains

The Delta variant of SARS-CoV-2 has now become the predominant strain in the global COVID-19 pandemic. Strain coverage of some detection assays developed during the early pandemic stages has declined due to periodic mutations in the viral genome. We have developed a real-time RT-PCR (RT-qPCR) for SARS-CoV-2 detection that provides nearly 100% strain coverage, and differentiation of highly transmissible Delta variant strains. All full or nearly full (≥28 kb) SARS-CoV-2 genomes (n = 403,812), including 6422 Delta and 280 Omicron variant strains, were collected from public databases at the time of analysis and used for assay design. The two amino acid deletions in the spike gene (S-gene, Δ156-157) that is characteristic of the Delta variant were targeted during the assay design. Although strain coverage for the Delta variant was very high (99.7%), detection coverage for non-Delta wild-type strains was 93.9%, mainly due to the confined region of design. To increase strain coverage of the assay, the design for CDC N1 target was added to the assay. In silico analysis of 403,812 genomes indicated a 95.4% strain coverage for the CDC N1 target, however, in combination with our new non-Delta S-gene target, total coverage for non-Delta wild-type strains increased to 99.8%. A human 18S rRNA gene was also analyzed and used as an internal control. The final four-plex RT-qPCR assay generated PCR amplification efficiencies between 95.4% and 102.0% with correlation coefficients (R2 ) of >0.99 for cloned positive controls; Delta and non-Delta human clinical samples generated PCR efficiencies of 93.4%-97.0% and R2  > 0.99. The assay also detects 98.6% of 280 Omicron sequences. Assay primers and probes have no match to other closely related human coronaviruses, and did not produce a signal from samples positive to selected animal coronaviruses. Genotypes of selected clinical samples identified by the RT-qPCR were confirmed by Sanger sequencing.

Replicating RNA platform enables rapid response to the SARS-CoV-2 Omicron variant and elicits enhanced protection in naïve hamsters compared to ancestral vaccine

BACKGROUND

In late 2021, the SARS-CoV-2 Omicron (B.1.1.529) variant of concern (VoC) was reported with many mutations in the viral spike protein that were predicted to enhance transmissibility and allow viral escape of neutralizing antibodies. Within weeks of the first report of B.1.1.529, this VoC has rapidly spread throughout the world, replacing previously circulating strains of SARS-CoV-2 and leading to a resurgence in COVID-19 cases even in populations with high levels of vaccine- and infection-induced immunity. Studies have shown that B.1.1.529 is less sensitive to protective antibody conferred by previous infections and vaccines developed against earlier lineages of SARS-CoV-2. The ability of B.1.1.529 to spread even among vaccinated populations has led to a global public health demand for updated vaccines that can confer protection against B.1.1.529.

METHODS

We rapidly developed a replicating RNA vaccine expressing the B.1.1.529 spike and evaluated immunogenicity in mice and hamsters. We also challenged hamsters with B.1.1.529 and evaluated whether vaccination could protect against viral shedding and replication within respiratory tissue.

FINDINGS

We found that mice previously immunized with A.1-specific vaccines failed to elevate neutralizing antibody titers against B.1.1.529 following B.1.1.529-targeted boosting, suggesting pre-existing immunity may impact the efficacy of B.1.1.529-targeted boosters. Furthermore, we found that our B.1.1.529-targeted vaccine provides superior protection compared to the ancestral A.1-targeted vaccine in hamsters challenged with the B.1.1.529 VoC after a single dose of each vaccine.

INTERPRETATION

Our data suggest that B.1.1.529-targeted vaccines may provide superior protection against B.1.1.529 but pre-existing immunity and timing of boosting may need to be considered for optimum protection.

FUNDING

This research was supported in part by the Intramural Research Program, NIAID/NIH, Washington Research Foundation and by grants 27220140006C (JHE), AI100625, AI151698, and AI145296 (MG).

Alum/CpG Adjuvanted Inactivated COVID-19 Vaccine with Protective Efficacy against SARS-CoV-2 and Variants

Since the beginning of the COVID-19 pandemic, numerous variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have emerged, including five variants of concern (VOC) strains listed by the WHO: Alpha, Beta, Gamma, Delta and Omicron. Extensive studies have shown that most of these VOC strains, especially the currently dominant variant Omicron, can escape the host immune response induced by existing COVID-19 vaccines to different extents, which poses considerable risk to the health of human beings around the world. In the present study, we developed a vaccine based on inactivated SARS-CoV-2 and an adjuvant consisting of aluminum hydroxide (alum) and CpG. The immunogenicity and safety of the vaccine were investigated in rats. The candidate vaccine elicited high titers of SARS-CoV-2-spike-specific IgG antibody and neutralizing antibody in immunized rats, which not only neutralize the original SARS-CoV-2, but also showed great cross-neutralization activity against the Beta, Delta and Omicron variants.

Characterization and Utilization of Disulfide-Bonded SARS-CoV-2 Receptor Binding Domain of Spike Protein Synthesized by Wheat Germ Cell-Free Production System

The spike protein (SP) of SARS-CoV-2 is an important target for COVID-19 therapeutics and vaccines as it binds to the ACE2 receptor and enables viral infection. Rapid production and functional characterization of properly folded SP is of the utmost importance for studying the immunogenicity and receptor-binding activity of this protein considering the emergence of highly infectious viral variants. In this study, we attempted to express the receptor-binding region (RBD) of SARS-CoV-2 SP containing disulfide bonds using the wheat germ cell-free protein synthesis system. By adding protein disulfide isomerase (PDI) and endoplasmic reticulum oxidase (ERO1α) to the translational reaction mixture, we succeeded in synthesizing a functionally intact RBD protein that can interact with ACE2. Using this RBD protein, we have developed a high-throughput AlphaScreen assay to evaluate the RBD–ACE2 interaction, which can be applied for drug screening and mutation analysis. Thus, our method sheds new light on the structural and functional properties of SARS-CoV-2 SP and has the potential to contribute to the development of new COVID-19 therapeutics.

Immune Response to SARS-CoV-2 Vaccines

COVID-19 vaccines have been developed to confer immunity against the SARS-CoV-2 infection. Prior to the pandemic of COVID-19 which started in March 2020, there was a well-established understanding about the structure and pathogenesis of previously known Coronaviruses from the SARS and MERS outbreaks. In addition to this, vaccines for various Coronaviruses were available for veterinary use. This knowledge supported the creation of various vaccine platforms for SARS-CoV-2. Before COVID-19 there are no reports of a vaccine being developed in under a year and no vaccine for preventing coronavirus infection in humans had ever been developed. Approximately nine different technologies are being researched and developed at various levels in order to design an effective COVID-19 vaccine. As the spike protein of SARS-CoV-2 is responsible for generating substantial adaptive immune response, mostly all the vaccine candidates have been targeting the whole spike protein or epitopes of spike protein as a vaccine candidate. In this review, we have compiled the immune response to SARS-CoV-2 infection and followed by the mechanism of action of various vaccine platforms such as mRNA vaccines, Adenoviral vectored vaccine, inactivated virus vaccines and subunit vaccines in the market. In the end we have also summarized the various adjuvants used in the COVID-19 vaccine formulation.

The Protective Role of pVHL in Imiquimod-Induced Psoriasis-like Skin Inflammation

Psoriasis is a chronic inflammatory disease distinguished by an excessive proliferation and abnormal differentiation of keratinocytes. Immune cells, such as T lymphocytes and neutrophils, and inflammatory cytokines, such as Tumor Necrosis Factor-α (TNF-α) and interleukin 17 (IL-17), are essential for maintaining psoriatic lesions. Additionally, a hypoxic milieu present in the skin promotes the expression of transcriptional factor hypoxia-inducible factor-1 alpha (HIF-1α). This protein regulates the expression of angiogenic and glycolytic factors, such as vascular endothelial grown factor and lactate dehydrogenase (LDH), both relevant in chronic inflammation. The von Hippel–Lindau protein (pVHL) is a negative regulator of HIF-1α. Previously, we found that pVHL was almost absent in the lesions of psoriasis patients; therefore, we investigated the impact of rescue pVHL expression in lesional skin. We used the imiquimod-induced psoriasis-like mouse model as an adenoviral vector that allowed us to express pVHL in the skin. Our data show that, in lesional skin, pVHL expression was reduced, whereas HIF-1α was increased. Remarkably, the retrieval of pVHL prevented psoriatic lesions, diminishing erythema, scale, and epidermal and vascular thickness. Furthermore, pVHL expression was capable of reducing HIF-1α, LDH, TNF-α and immune cell infiltration (mainly IL-17⁺ neutrophils). In conclusion, our results demonstrate that pVHL has a protective role to play in the pathophysiology of psoriasis.

Study of humoral and cellular immunity in vaccinated with mRNA-1273

The new vaccines against SARS‐CoV‐2 have raised a lot of expectations about their ability to induce immunity and the duration of this. This is the case of mRNA vaccines such as Moderna's mRNA‐1273. Therefore, it is necessary to study the humoral and cellular immunity generated by these vaccines. Our objectives are determining what is the normal response of antibody production, and what is the level of protective antibodies and monitoring patients in case of subsequent infection with COVID‐19. We present the first results of a longitudinal study of the humoral response in 601 health workers vaccinated with Moderna. The results show a humoral immunity at 90 days after the second dose of 100%, with a strong decrease between the levels of circulating anti‐S IgG antibodies between days 30 and 90 post‐vaccination. Observing a steeper decline in those who had higher titles at the beginning. In addition, we present a cellular response of 86% at three months after the second dose, which is related to low humoral response.

A single intranasal dose of human parainfluenza virus type 3-vectored vaccine induces effective antibody and memory T cell response in the lungs and protects hamsters against SARS-CoV-2

Respiratory tract vaccination has an advantage of needle-free delivery and induction of mucosal immune response in the portal of SARS-CoV-2 entry. We utilized human parainfluenza virus type 3 vector to generate constructs expressing the full spike (S) protein of SARS-CoV-2, its S1 subunit, or the receptor-binding domain, and tested them in hamsters as single-dose intranasal vaccines. The construct bearing full-length S induced high titers of neutralizing antibodies specific to S protein domains critical to the protein functions. Robust memory T cell responses in the lungs were also induced, which represent an additional barrier to infection and should be less sensitive than the antibody responses to mutations present in SARS-CoV-2 variants. Following SARS-CoV-2 challenge, animals were protected from the disease and detectable viral replication. Vaccination prevented induction of gene pathways associated with inflammation. These results indicate advantages of respiratory vaccination against COVID-19 and inform the design of mucosal SARS-CoV-2 vaccines.

Factors Influencing the Acceptance of COVID-19 Vaccines in a Country with a High Vaccination Rate

Control of the COVID-19 pandemic largely depends on the effectiveness of the vaccination process. An understanding of the factors that underlie the willingness to accept vaccination contributes pivotal information to controlling the pandemic. We analyzed the association between the willingness to accept the available COVID-19 vaccines and vaccine determinants amidst the Chilean vaccination process. Individual-level survey data was collected from 744 nationally representative respondents and multivariate regression models were used to estimate the association between outcome and explanatory variables. We found that trust in COVID-19 vaccines, scientists, and medical professionals significantly increased the willingness to: accept the vaccines and booster doses, as well as annual vaccinations and the vaccination of children. Our results are critical to understanding the acceptance of COVID-19 vaccines in the context of a country with one of the world’s highest vaccination rates. We provide useful information for decision-making and policy design, in addition to establishing guidelines regarding how to effectively explain vaccination programs to citizens.

Using COVID-19 Pandemic as a Prism: A Systematic Review of Methodological Approaches and the Quality of Empirical Studies on Physical Activity Behavior Change

Background

The COVID-19 pandemic has highlighted the importance of scientific endeavors. The goal of this systematic review is to evaluate the quality of the research on physical activity (PA) behavior change and its potential to contribute to policy-making processes in the early days of COVID-19 related restrictions.

Methods

We conducted a systematic review of methodological quality of current research according to PRISMA guidelines using Pubmed and Web of Science, of articles on PA behavior change that were published within 365 days after COVID-19 was declared a pandemic by the World Health Organization (WHO). Items from the JBI checklist and the AXIS tool were used for additional risk of bias assessment. Evidence mapping is used for better visualization of the main results. Conclusions about the significance of published articles are based on hypotheses on PA behavior change in the light of the COVID-19 pandemic.

Results

Among the 1,903 identified articles, there were 36% opinion pieces, 53% empirical studies, and 9% reviews. Of the 332 studies included in the systematic review, 213 used self-report measures to recollect prepandemic behavior in often small convenience samples. Most focused changes in PA volume, whereas changes in PA types were rarely measured. The majority had methodological reporting flaws. Few had very large samples with objective measures using repeated measure design (pre and during the pandemic). In addition to the expected decline in PA duration, these studies show that many of those who were active prepandemic, continued to be active during the pandemic.

Conclusions

Research responded quickly at the onset of the pandemic. However, most of the studies lacked robust methodology, and PA behavior change data lacked the accuracy needed to guide policy makers. To improve the field, we propose the implementation of longitudinal cohort studies by larger organizations such as WHO to ease access to data on PA behavior, and suggest those institutions set clear standards for this research. Researchers need to ensure a better fit between the measurement method and the construct being measured, and use both objective and subjective measures where appropriate to complement each other and provide a comprehensive picture of PA behavior.

Interferon Treatments for SARS-CoV-2: Challenges and Opportunities

Interferon (IFN) therapies are used to treat a variety of infections and diseases and could be used to treat SARS-CoV-2. However, optimal use and timing of IFN therapy to treat SARS-CoV-2 is not well documented. We aimed to synthesize available evidence to understand whether interferon therapy should be recommended for treatment compared to a placebo or standard of care in adult patients. We reviewed literature comparing outcomes of randomized control trials that used IFN therapy for adults diagnosed with SARS-CoV-2 between 2019 and 2021. Data were extracted from 11 of 669 screened studies. Evidence of IFN effectiveness was mixed. Five studies reported that IFN was a better therapy than the control, four found no or minimal difference between IFN and the control, and two concluded that IFN led to worse patient outcomes than the control. Evidence was difficult to compare because of high variability in outcome measures, intervention types and administration, subtypes of IFNs used and timing of interventions. We recommend standardized indicators and reporting for IFN therapy for SARS-CoV-2 to improve evidence synthesis and generation. While IFN therapy has the potential to be a viable treatment for SARS-CoV-2, especially when combined with antivirals and early administration, the lack of comparable of study outcomes prevents evidence synthesis and uptake.

The E484K Substitution in a SARS-CoV-2 Spike Protein Subunit Vaccine Resulted in Limited Cross-Reactive Neutralizing Antibody Responses in Mice

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), especially emerging variants, poses an increased threat to global public health. The significant reduction in neutralization activity against the variants such as B.1.351 in the serum of convalescent patients and vaccinated people calls for the design of new potent vaccines targeting the emerging variant. However, since most vaccines approved and in clinical trials are based on the sequence of the original SARS-CoV-2 strain, the immunogenicity and protective efficacy of vaccines based on the B.1.351 variant remain largely unknown. In this study, we evaluated the immunogenicity, induced neutralization activity, and protective efficacy of wild-type spike protein nanoparticle (S-2P) and mutant spike protein nanoparticle (S-4M-2P) carrying characteristic mutations of B.1.351 variant in mice. Although there was no significant difference in the induction of spike-specific IgG responses in S-2P- and S-4M-2P-immunized mice, neutralizing antibodies elicited by S-4M-2P exhibited noteworthy, narrower breadth of reactivity with SARS-CoV-2 variants compared with neutralizing antibodies elicited by S-2P. Furthermore, the decrease of induced neutralizing antibody breadth at least partly resulted from the amino acid substitution at position 484. Moreover, S-4M-2P vaccination conferred insufficient protection against live SARS-CoV-2 virus infection, while S-2P vaccination gave definite protection against SARS-CoV-2 challenge in mice. Together, our study provides direct evidence that the E484K substitution in a SARS-CoV-2 subunit protein vaccine limited the cross-reactive neutralizing antibody breadth in mice and, more importantly, draws attention to the unfavorable impact of this mutation in spike protein of SARS-CoV-2 variants on the induction of potent neutralizing antibody responses.

Strategies for fighting pandemic virus infections: Integration of virology and drug delivery

Respiratory viruses have sometimes resulted in worldwide pandemics, with the influenza virus and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) being major participants. Long-term efforts have made it possible to control the influenza virus, but seasonal influenza continues to take many lives each year, and a pandemic influenza virus sometimes emerges. Although vaccines for coronavirus disease 2019 (COVID-19) have been developed, we are not yet able to coexist with the SARS-CoV-2. To overcome such viruses, it is necessary to obtain knowledge about international surveillance systems, virology, ecology and to determine that immune responses are effective. The information must then be transferred to drugs. Delivery systems would be expected to contribute to the rational development of drugs. In this review, virologist and drug delivery system (DDS) researchers discuss drug delivery strategies, especially the use of lipid-based nanocarriers, for fighting to respiratory virus infections.

SARS-CoV2 variant-specific replicating RNA vaccines protect from disease following challenge with heterologous variants of concern

Despite mass public health efforts, the SARS-CoV2 pandemic continues as of late 2021 with resurgent case numbers in many parts of the world. The emergence of SARS-CoV2 variants of concern (VoCs) and evidence that existing vaccines that were designed to protect from the original strains of SARS-CoV-2 may have reduced potency for protection from infection against these VoC is driving continued development of second-generation vaccines that can protect against multiple VoC. In this report, we evaluated an alphavirus-based replicating RNA vaccine expressing Spike proteins from the original SARS-CoV-2 Alpha strain and recent VoCs delivered in vivo via a lipid inorganic nanoparticle. Vaccination of both mice and Syrian Golden hamsters showed that vaccination induced potent neutralizing titers against each homologous VoC but reduced neutralization against heterologous challenges. Vaccinated hamsters challenged with homologous SARS-CoV2 variants exhibited complete protection from infection. In addition, vaccinated hamsters challenged with heterologous SARS-CoV-2 variants exhibited significantly reduced shedding of infectious virus. Our data demonstrate that this vaccine platform can be updated to target emergent VoCs, elicits significant protective immunity against SARS-CoV2 variants and supports continued development of this platform.

Main protease mutants of SARS-CoV-2 variants remain susceptible to nirmatrelvir

The COVID-19 pandemic continues to be a public health threat. Multiple mutations in the spike protein of emerging variants of SARS-CoV-2 appear to impact on the effectiveness of available vaccines. Specific antiviral agents are keenly anticipated but their efficacy may also be compromised in emerging variants. One of the most attractive coronaviral drug targets is the main protease (M^pro). A promising M^pro inhibitor of clinical relevance is the peptidomimetic nirmatrelvir (PF-07321332). We expressed M^pro of six SARS-CoV-2 lineages (C.37 Lambda, B.1.1.318, B.1.2, B.1.351 Beta, B.1.1.529 Omicron, P.2 Zeta), each of which carries a strongly prevalent missense mutation (G15S, T21I, L89F, K90R, P132H, L205V). Enzyme kinetics reveal that these M^pro variants are catalytically competent to a similar degree as the wildtype. We show that nirmatrelvir has similar potency against the variants as the wildtype. Our in vitro data suggest that the efficacy of the specific M^pro inhibitor nirmatrelvir is not compromised in current COVID-19 variants.

The antigenicity of SARS-CoV-2 Delta variants aggregated 10 high-frequency mutations in RBD has not changed sufficiently to replace the current vaccine strain

Emerging SARS-CoV-2 variants are the most serious problem for COVID-19 prophylaxis and treatment. To determine whether the SARS-CoV-2 vaccine strain should be updated following variant emergence like seasonal flu vaccine, the changed degree on antigenicity of SARS-CoV-2 variants and H3N2 flu vaccine strains was compared. The neutralization activities of Alpha, Beta and Gamma variants' spike protein-immunized sera were analysed against the eight current epidemic variants and 20 possible variants combining the top 10 prevalent RBD mutations based on the Delta variant, which were constructed using pseudotyped viruses. Meanwhile, the neutralization activities of convalescent sera and current inactivated and recombinant protein vaccine-elicited sera were also examined against all possible Delta variants. Eight HA protein-expressing DNAs elicited-animal sera were also tested against eight pseudotyped viruses of H3N2 flu vaccine strains from 2011-2019. Our results indicate that the antigenicity changes of possible Delta variants were mostly within four folds, whereas the antigenicity changes among different H3N2 vaccine strains were approximately 10-100-fold. Structural analysis of the antigenic characterization of the SARS-CoV-2 and H3N2 mutations supports the neutralization results. This study indicates that the antigenicity changes of the current SARS-CoV-2 may not be sufficient to require replacement of the current vaccine strain.

Immune Enhancement by the Tetra-Peptide Hydrogel as a Promising Adjuvant for an H7N9 Vaccine against Highly Pathogenic H7N9 Virus

BACKGROUND

Short peptide hydrogel was reported as a possible adjuvant for vaccines. In order to evaluate whether the Tetra-Peptide Hydrogel can be a promising adjuvant for an H7N9 vaccine against the highly pathogenic H7N9 virus, we conducted this study.

METHODS

Tetra-Peptide Hydrogels (D and L conformations) were prepared by a self-assembly system using a Naproxen acid modified tetra peptide of GFFY (Npx-GFFY). Mice received two immunizations with the D-Tetra-Peptide Hydrogel adjuvant vaccine, the L-Tetra-Peptide Hydrogel adjuvant vaccine, or the split vaccine. Fourteen days following the second dose, the mice were challenged with the highly pathogenic A/Guangdong/GZ8H002/2017(H7N9) virus. The mice were observed for signs of illness, weight loss, pathological alterations of the lung tissues and immune responses in the following 2 weeks.

RESULTS

The D/L-Tetra-Peptide Hydrogels resembled long bars with hinges on each other, with a diameter of ~10 nm. The H7N9 vaccine was observed to adhere to the hydrogel. All the unvaccinated mice were dead by 8 days post infection with H7N9. The mice immunized by the split H7N9 vaccine were protected against infection with H7N9. Mice immunized by D/L-Tetra-Peptide Hydrogel adjuvant vaccines experienced shorter symptomatic periods and their micro-neutralization titers were higher than in the split H7N9 vaccine at 2 weeks post infection. The hemagglutinating inhibition (HI) titer in the L-Tetra-Peptide Hydrogel adjuvant vaccine group was higher than that in the split H7N9 vaccine 1 week and 2 weeks post infection. The HI titer in the D-Tetra-Peptide Hydrogel adjuvant vaccine group was higher than that in the split H7N9 vaccine at 2 weeks post infection.

CONCLUSION

The D/L Tetra-Peptide Hydrogels increased the protection of the H7N9 vaccine and could be promising adjuvants for H7N9 vaccines against highly pathogenic H7N9 virus.

Aggregation of high-frequency RBD mutations of SARS-CoV-2 with three VOCs did not cause significant antigenic drift

Variants of SARS‐CoV‐2 continue to emerge, posing great challenges in outbreak prevention and control. It is important to understand in advance the impact of possible variants of concern (VOCs) on infectivity and antigenicity. Here, we constructed one or more of the 15 high‐frequency naturally occurring amino acid changes in the receptor‐binding domain (RBD) of Alpha, Beta, and Gamma variants. A single mutant of A520S, V367F, and S494P in the above three VOCs enhanced infectivity in ACE2‐overexpressing 293T cells of different species, LLC‐MK2 and Vero cells. Aggregation of multiple RBD mutations significantly reduces the infectivity of the possible three VOCs. Regarding neutralization, it is noteworthy that E484K, N501Y, K417N, and N439K predispose to monoclonal antibodies (mAbs) protection failure in the 15 high‐frequency mutations. Most importantly, almost all possible VOCs (single RBD mutation or aggregation of multiple mutations) showed no more than a fourfold decrease in neutralizing activity with convalescent sera, vaccine sera, and immune sera of guinea pigs with different immunogens, and no significant antigenic drift was formed. In conclusion, our pseudovirus results could reduce the concern that the aggregation of multiple high‐frequency mutations in the RBD of the spike protein of the three VOCs would lead to severe antigenic drift, and this would provide value for vaccine development strategies.

Infectivity increased by adding three VOCs of V367F, S494P, or A520S.

The infectivity of the three VOCs with multiple high‐frequency mutations decreased.

Almost all of the possible variants of the three VOCs did not show severe antigenic drift.

COVID-19, Influenza and RSV: Surveillance-informed prevention and treatment - Meeting report from an isirv-WHO virtual conference

The International Society for Influenza and other Respiratory Virus Diseases (isirv) and the WHO held a joint virtual conference from 19th-21st October 2021. While there was a major focus on the global response to the SARS-CoV-2 pandemic, including antivirals, vaccines and surveillance strategies, papers were also presented on treatment and prevention of influenza and respiratory syncytial virus (RSV). Potential therapeutics for SARS-CoV-2 included host-targeted therapies baricitinib, a JAK inhibitor, tocilizumab, an IL-6R inhibitor, verdinexor and direct acting antivirals ensovibep, S-217622, AT-527, and monoclonal antibodies casirivimab and imdevimab, directed against the spike protein. Data from trials of nirsevimab, a monoclonal antibody with a prolonged half-life which binds to the RSV F-protein, and an Ad26.RSV pre-F vaccine were also presented. The expanded role of the WHO Global Influenza Surveillance and Response System to address the SARS-CoV-2 pandemic was also discussed. This report summarizes the oral presentations given at this meeting for the benefit of the broader medical and scientific community involved in surveillance, treatment and prevention of respiratory virus diseases.

SARS-CoV2 variant-specific replicating RNA vaccines protect from disease and pathology and reduce viral shedding following challenge with heterologous SARS-CoV2 variants of concern

Despite mass public health efforts, the SARS-CoV2 pandemic continues as of late-2021 with resurgent case numbers in many parts of the world. The emergence of SARS-CoV2 variants of concern (VoC) and evidence that existing vaccines that were designed to protect from the original strains of SARS-CoV-2 may have reduced potency for protection from infection against these VoC is driving continued development of second generation vaccines that can protect against multiple VoC. In this report, we evaluated an alphavirus-based replicating RNA vaccine expressing Spike proteins from the original SARS-CoV-2 Alpha strain and recent VoCs delivered in vivo via a lipid inorganic nanoparticle. Vaccination of both mice and Syrian Golden hamsters showed that vaccination induced potent neutralizing titers against each homologous VoC but reduced neutralization against heterologous challenges. Vaccinated hamsters challenged with homologous SARS-CoV2 variants exhibited complete protection from infection. In addition, vaccinated hamsters challenged with heterologous SARS-CoV-2 variants exhibited significantly reduced shedding of infectious virus. Our data demonstrate that this vaccine platform elicits significant protective immunity against SARS-CoV2 variants and supports continued development of this platform.

Fractionating a COVID-19 Ad5-vectored vaccine improves virus-specific immunity

[Figure: see text].