Comparison of the immunogenicity & protective efficacy of various SARS-CoV-2 vaccine candidates in non-human primates

Development of animal models for emerging infectious diseases by breaking the barrier of species susceptibility to human pathogens

Outbreaks of emerging infectious diseases pose a serious threat to public health security, human health and economic development. After an outbreak, an animal model for an emerging infectious disease is urgently needed for studying the etiology, host immune mechanisms and pathology of the disease, evaluating the efficiency of vaccines or drugs against infection, and minimizing the time available for animal model development, which is usually hindered by the nonsusceptibility of common laboratory animals to human pathogens. Thus, we summarize the technologies and methods that induce animal susceptibility to human pathogens, which include viral receptor humanization, pathogen-targeted tissue humanization, immunodeficiency induction and screening for naturally susceptible animal species. Furthermore, the advantages and deficiencies of animal models developed using each method were analyzed, and these will guide the selection of susceptible animals and potentially reduce the time needed to develop animal models during epidemics.

Inactivated COVID-19 vaccines in peri-pregnancy period: Evaluation of safety for both pregnant women and neonates

BACKGROUND

Pregnant women have been excluded from vaccination of COVID-19 due to the lack of strong clinical evidence, which may place pregnant women at greater risk of contracting COVID-19. We conducted this study in China to investigate the maternal and neonatal safety of inactivated COVID-19 vaccination administered during the peri-pregnancy period.

METHODS

This prospective observational cohort study enrolled pregnant women who received pregnancy care between January 1, 2021, and December 31, 2021. Pregnant women were categorized into vaccine group (n = 60) and control group (n = 60) based on whether they had received an inactivated COVID-19 vaccine within peri-pregnancy period. The primary outcomes were the incidence of maternal premature rupture of membranes (PROM) and neonatal adverse events, including induced labor/death, premature birth, low birth weight, and neonatal intensive care unit (NICU) admission and several secondary outcomes related to pregnant women and neonates. Inverse probability treatment weighting (IPTW) was employed to adjust for baseline covariates. Linear and logistic regression models were established after IPTW for continuous and binary outcomes, respectively. In sensitivity analysis, E-values were calculated and propensity score matching analysis and multivariate regression analysis used to demonstrate the robustness of IPTW results. Moreover, vaccination time subgroup analysis and medication subgroup analysis were conducted.

RESULTS

Out of 120 neonates delivered, there was no significant difference in PROM (25.42 % vs. 19.67 %, p = 0.438) or neonatal adverse events (11.86 % vs. 4.92 %, p = 0.148) between the vaccine and control groups. Moreover, among the secondary outcomes only serum alanine transaminase (ALT) at first trimester had a statistically significant difference between the groups, ALT levels were significantly higher in the vaccine group during the first trimester (20.67 ± 20.34 vs. 13.05 ± 9.43; RR: 5.38; p = 0.04). In sensitivity analysis, the E-values calculated for the primary outcomes PROM and neonatal adverse events are 2.04 and 5.00 respectively. PSM analysis and multivariate regression analysis reached the same conclusion. The results of primary outcomes are both consistent across the vaccination time subgroup and medication subgroup.

CONCLUSION

The sensitivity analysis illustrates the robustness of our results, so we can conclude that the vaccination of inactivated COVID-19 vaccine during the peri-pregnancy period is safe for both the pregnant woman and neonates no matter what time of vaccination and the use of medication. In addition, it is recommended to monitor ALT levels throughout the first trimester of pregnancy.

Cytokine and Chemokine Production in Mice Inoculated with NVX-CoV2373 (Nuvaxovid®) in Comparison with Omicron BA.4/5 Bivalent BNT162b2 (Comirnaty®)

A recombinant SARS-CoV-2 spike protein vaccine (NVX-CoV2373) has been licensed and has a lesser incidence of adverse events. To know the immunological mechanisms of adverse events, the production of cytokines and chemokines was investigated in mice inoculated with NVX-CoV2373. Serum IL-6 was detected on Day 1 of the first and second doses and the IFN-γ, IL-4, IL-10, TNF-α, and IL-6 levels increased on Day 1 of the second dose at the inoculation site. The enhanced production of the inflammatory chemokines (CCL2), homeostatic chemokine (CXCL13), and Th2 chemokine (CCL17) was observed at the inoculation site on Day 1 of the second dose. These findings were compared with data obtained following inoculation with BNT162b2 bivalent vaccine containing omicron BA.4/5. Significantly lower levels of inflammatory chemokines were detected on Day 1 after the first dose of NVX-CoV2373 in sera and inoculation site than those following inoculation with bivalent BNT162b2 (p < 0.01), reflecting a lower incidence of adverse events after immunization with NVX-CoV2373 in humans. NVX-CoV2373 induced significantly higher concentrations of IFN-γ, TNF-α, and IL-10 at the inoculation site obtained on Day 1 of the second dose (p < 0.05). Significant higher levels of Th2 chemokines, CCL11 and CCL17, were induced at the inoculation site on Day 1 of the second dose (p < 0.01) and they explain the booster IgG EIA antibody response after the second dose of NVX-CoV2373.

SARS-CoV-2 in lions, gorillas and zookeepers in the Rotterdam Zoo, the Netherlands, a One Health investigation, November 2021

In November 2021, seven western lowland gorillas and four Asiatic lions were diagnosed with COVID-19 at Rotterdam Zoo. An outbreak investigation was undertaken to determine the source and extent of the outbreak and to identify possible transmission routes. Interviews were conducted with staff to identify human and animal contacts and cases, compliance with personal protective equipment (PPE) and potential transmission routes. Human and animal contacts and other animal species suspected to be susceptible to SARS-CoV-2 were tested for SARS-CoV-2 RNA. Positive samples were subjected to sequencing. All the gorillas and lions that could be tested (3/7 and 2/4, respectively) were RT-PCR positive between 12 November and 10 December 2021. No other animal species were SARS-CoV-2 RNA positive. Forty direct and indirect human contacts were identified. Two direct contacts tested RT-PCR positive 10 days after the first COVID-19 symptoms in animals. The zookeepers' viral genome sequences clustered with those of gorillas and lions. Personal protective equipment compliance was suboptimal at instances. Findings confirm transmission of SARS-CoV-2 among animals and between humans and animals but source and directionality could not be established. Zookeepers were the most likely source and should have periodic PPE training. Sick animals should promptly be tested and isolated/quarantined.

No association of vaccination with inactivated COVID-19 vaccines before conception with pregnancy complications and adverse birth outcomes: A cohort study of 5457 Chinese pregnant women

Data on the safety of inactivated COVID-19 vaccines in pregnant women is limited and monitoring pregnancy outcomes is required. We aimed to examine whether vaccination with inactivated COVID-19 vaccines before conception was associated with pregnancy complications or adverse birth outcomes. We conducted a birth cohort study in Shanghai, China. A total of 7000 healthy pregnant women were enrolled, of whom 5848 were followed up through delivery. Vaccine administration information was obtained from electronic vaccination records. Relative risks (RRs) of gestational diabetes mellitus (GDM), hypertensive disorders in pregnancy (HDP), intrahepatic cholestasis of pregnancy (ICP), preterm birth (PTB), low birth weight (LBW), and macrosomia associated with COVID-19 vaccination were estimated by multivariable-adjusted log-binomial analysis. After exclusion, 5457 participants were included in the final analysis, of whom 2668 (48.9%) received at least two doses of an inactivated vaccine before conception. Compared with unvaccinated women, there was no significant increase in the risks of GDM (RR = 0.80, 95% confidence interval [CI], 0.69, 0.93), HDP (RR = 0.88, 95% CI, 0.70, 1.11), or ICP (RR = 1.61, 95% CI, 0.95, 2.72) in vaccinated women. Similarly, vaccination was not significantly associated with any increased risks of PTB (RR = 0.84, 95% CI, 0.67, 1.04), LBW (RR = 0.85, 95% CI, 0.66, 1.11), or macrosomia (RR = 1.10, 95% CI, 0.86, 1.42). The observed associations remained in all sensitivity analyses. Our findings suggested that vaccination with inactivated COVID-19 vaccines was not significantly associated with an increased risk of pregnancy complications or adverse birth outcomes.

Association of COVID-19 vaccination before conception with maternal thyroid function during early pregnancy: A single-center study in China

Despite the high vaccination coverage, potential COVID-19 vaccine-induced adverse effects, especially in pregnant women, have not been fully characterized. We examined the association between COVID-19 vaccination before conception and maternal thyroid function during early pregnancy. We conducted a retrospective cohort study in Shanghai, China. A total of 6979 pregnant women were included. Vaccine administration was obtained from electronic vaccination records. Serum levels of thyroid hormone were measured by fluorescence and chemiluminescence immunoassays. Among the 6979 included pregnant women, 3470 (49.7%) received at least two doses of an inactivated vaccine. COVID-19 vaccination had a statistically significant association with both maternal serum levels of free thyroxine (FT4) and thyroid stimulating hormone (TSH). Compared with unvaccinated pregnant women, the mean FT4 levels were lower in pregnant women who had been vaccinated within 3 months before the date of conception by 0.27 pmol/L (β = -0.27, 95% confidence interval [CI], -0.42, -0.12), and the mean TSH levels were higher by 0.08 mIU/L (β = 0.08, 95% CI, 0.00, 0.15). However, when the interval from vaccination to conception was prolonged to more than 3 months, COVID-19 vaccination was not associated with serum FT4 or TSH levels. Moreover, we found that COVID-19 vaccination did not significantly associate with maternal hypothyroidism. Our study suggested that vaccination with inactivated COVID-19 vaccines before conception might result in a small change in maternal thyroid function, but this did not reach clinically significant levels.

Autoimmune and inflammatory thyroid diseases following vaccination with SARS-CoV-2 vaccines: from etiopathogenesis to clinical management

Since the Covid-19 pandemic emerged in 2019, several adenoviral-vectored, mRNA-based and inactivated whole-virus vaccines have been developed. A massive vaccination campaign has been undertaken around the world, and an increasing number of SARS-CoV-2 vaccine-induced thyroid diseases have been described in the literature. Subacute thyroiditis has been reported in 52 patients, mean age 45.5 ± 1.8 years, mainly in women (n = 39). Graves' disease is more frequent in women (n = 22) than in men (n = 10), mean age 46.2 ± 2.6 years, reported as new onset, recurrent or exacerbation of well-controlled hyperthyroidism. The mean time to symptoms onset is 9.0 ± 0.8 days in subacute thyroiditis, and 15.1 ± 2.6 days in Graves' patients. Rare patients (n = 6) present silent or painless autoimmune thyroiditis. Thyroid function and autoimmune tests, inflammatory markers, thyroid echography with colour flow Doppler, radio-activity uptake on thyroid scan, medical treatment and follow-up are described and compared in patients with SARS-CoV-2 vaccine-induced thyroid diseases. The underlying pathogenic mechanisms of vaccine-induced thyroid diseases, molecular mimicry (various SARS-CoV-2 proteins sharing a genetic homology with a large heptapeptide human protein) or autoimmune/inflammatory syndrome induced by adjuvants (ASIA) are discussed in the context of predisposition or genetic susceptibility. The benefits of SARS-CoV-2 vaccination far outweigh the potential vaccine-induced adverse effects, but clinicians should be aware of possible autoimmune and inflammatory thyroid diseases, and can advise patients to seek medical assistance when experiencing anterior neck pain, fever or palpitations following SARS-CoV-2 vaccines. Further studies are warranted to investigate the etiopathogenesis and to clarify the factors which predispose patients to SARS-CoV-2 vaccine-induced thyroid diseases.

Infectious Disease Spreading Fought by Multiple Vaccines Having a Prescribed Time Effect

We propose a framework for the description of the effects of vaccinations on the spreading of an epidemic disease. Different vaccines can be dosed, each providing different immunization times and immunization levels. Differences due to individuals' ages are accounted for through the introduction of either a continuous age structure or a discrete set of age classes. Extensions to gender differences or to distinguish fragile individuals can also be considered. Within this setting, vaccination strategies can be simulated, tested and compared, as is explicitly described through numerical integrations.

Vaccines against SARS-CoV-2 variants and future pandemics

INTRODUCTION

Vaccination continues to be the most effective method for controlling COVID-19 infectious diseases. Nonetheless, SARS-CoV-2 variants continue to evolve and emerge, resulting in significant public concerns worldwide, even after more than 2 years since the COVID-19 pandemic. It is important to better understand how different COVID-19 vaccine platforms work, why SARS-CoV-2 variants continue to emerge, and what options for improving COVID-19 vaccines can be considered to fight against SARS-CoV-2 variants and future pandemics.

AREA COVERED

Here, we reviewed the innate immune sensors in the recognition of SARS-CoV-2 virus, innate and adaptive immunity including neutralizing antibodies by different COVID-19 vaccines. Efficacy comparison of the several COVID-19 vaccine platforms approved for use in humans, concerns about SARS-CoV-2 variants and breakthrough infections, and the options for developing future COIVD-19 vaccines were also covered.

EXPERT OPINION

Owing to the continuous emergence of novel pathogens and the reemergence of variants, safer and more effective new vaccines are needed. This review also aims to provide the knowledge basis for the development of next-generation COVID-19 and pan-coronavirus vaccines to provide cross-protection against new SARS-CoV-2 variants and future coronavirus pandemics.

SARS-CoV-2 does not infect pigs, but this has to be verified regularly

For successful xenotransplantation, freedom of the xenocraft donor from certain viral infections that may harm the organ recipient is important. A novel human coronavirus (CoV) with a respiratory tropism, designated as SARS-CoV-2, was first identified in January 2020 in China, but likely has been circulating unnoticed for some time before. Since then, this virus has reached most inhabited areas, resulting in a major global pandemic which is still ongoing. Due to a high number of subclinical infections, re-infections, geographic differences in diagnostic tests used, and differences in result reporting programs, the percentage of the population infected with SARS-CoV-2 at least once has been challenging to estimate. With continuous ongoing infections in people and an overall high viral load, it makes sense to look into possible viral spillover events in pets and farm animals, who are often in close contact with humans. The pig is currently the main species considered for xenotransplantation and hence there is interest to know if pigs can become infected with SARS-CoV-2 and if so what the infection dynamics may look like. This review article summarizes the latest research findings on this topic. It would appear that pigs can currently be considered a low risk species, and hence do not pose an immediate risk to the human population or xenotransplantation recipients per se. Monitoring the ever-changing SARS-CoV-2 variants appears important to recognize immediately should this change in the future.

Association of COVID-19 vaccination before conception with maternal liver function during early pregnancy: a cohort study of 7745 Chinese pregnant women

Multicenter case series has reported patients with hepatic injury following COVID-19 vaccination, which raised concern for the possibility of vaccine-induced liver dysfunction. We aimed to assess the impact of COVID-19 vaccination on liver function of pregnant women, who may be uniquely susceptible to vaccine-induced liver dysfunction. We conducted a retrospective cohort study at a tertiary hospital in Shanghai, China. Vaccine administration was obtained from the electronic vaccination record. Serum levels of alanine transaminase (ALT), aspartate transaminase (AST), total bile acid (TBA) and total bilirubin (TBIL) in early pregnancy were determined by enzymatic methods. Among the 7745 included pregnant women, 3832 (49.5%) received at least two doses of an inactivated vaccine. COVID-19 vaccination was significantly associated with higher levels of maternal serum TBA. Compared with unvaccinated pregnant women, the mean TBA levels increased by 0.17 μmol/L (β = 0.17, 95% CI, 0.04, 0.31) for women who had been vaccinated within 3 months before the date of conception. Moreover, COVID-19 vaccination was significantly associated with an increased risk of maternal hyperbileacidemia. The risk of hyperbileacidemia increased by 113% (RR = 2.13; 95% CI, 1.17-3.87) for pregnant women who had been vaccinated within 3 months before conception compared with unvaccinated pregnant women. However, when the interval from complete vaccination to conception was prolonged to more than 3 months, COVID-19 vaccination was not associated with serum TBA levels or maternal hyperbileacidemia. Our findings suggest that vaccination with inactivated COVID-19 vaccines more than 3 months before conception have no detrimental effects on maternal liver function in early pregnancy.

SARS-CoV-2 variants and COVID-19 vaccines: Current challenges and future strategies

The ongoing COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become a global threat. Despite strict control measures implemented worldwide and immunization using novel vaccines, the pandemic continues to rage due to emergence of several variants of SARS-CoV-2 with increased transmission and immune escape. The rapid spread of variants of concern (VOC) in the recent past has created a massive challenge for the control of COVID-19 pandemic via the currently used vaccines. Vaccines that are safe and effective against the current and future variants of SARS-CoV-2 are essential in controlling the COVID-19 pandemic. Rapid production and massive rollout of next-generation vaccines against the variants are key steps to control the COVID-19 pandemic and to help us return to normality. Coordinated surveillance of SARS-CoV-2, rapid redesign of new vaccines and extensive vaccination are needed to counter the current SARS-CoV-2 variants and prevent the emergence of new variants. In this article, we review the latest information on the VOCs and variants of interest (VOIs) and present the information on the clinical trials that are underway on evaluating the effectiveness of COVID-19 vaccines on VOCs. We also discuss the current challenges posed by the VOCs in controlling the COVID-19 pandemic and future strategies to overcome the threat posed by the highly virulent and rapidly transmissible variants of SARS-CoV2.

Successive Site Translocating Inoculation Improved T Cell Responses Elicited by a DNA Vaccine Encoding SARS-CoV-2 S Protein

A variety of methods have been explored to increase delivery efficiencies for DNA vaccine. However, the immunogenicity of DNA vaccines has not been satisfactorily improved. Unlike most of the previous attempts, we provided evidence suggesting that changing the injection site successively (successively site-translocated inoculation, SSTI) could significantly enhance the immunogenicity of DNA vaccines in a previous study. To simplify the strategy and to evaluate its impact on candidate SARS-CoV-2 vaccines, we immunized mice with either a SARS-CoV-2 spike-based DNA vaccine or a spike protein subunit vaccine via three different inoculation strategies. Our data demonstrated that S protein specific antibody responses elicited by the DNA vaccine or the protein subunit vaccine showed no significant difference among different inoculation strategies. Of interest, compared with the conventional site fixed inoculation (SFI), both successive site-translocating inoculation (SSTI) and the simplified translocating inoculation (STI) strategy improved specific T cell responses elicited by the DNA vaccine. More specifically, the SSTI strategy significantly improved both the monofunctional (IFN-γ+IL-2-TNF-α-CD8+) and the multifunctional (IFN-γ+IL-2-TNF-α+CD8+, IFN-γ+IL-2-TNF-α+CD4+, IFN-γ+IL-2+TNF-α+CD4+) T cell responses, while the simplified translocating inoculation (STI) strategy significantly improved the multifunctional CD8+ (IFN-γ+IL-2-TNF-α+CD8+, IFN-γ+IL-2+TNF-α+CD8+) and CD4+ (IFN-γ+IL-2-TNF-α+CD4+, IFN-γ+IL-2+TNF-α+CD4+) T cell responses. The current study confirmed that changing the site of intra muscular injection can significantly improve the immunogenicity of DNA vaccines.

Covid-19: virology, variants, and vaccines

As of 25 January 2022, over 349 million individuals have received a confirmed diagnosis of covid-19, with over 5.59 million confirmed deaths associated with the SARS-CoV-2 virus. The covid-19 pandemic has prompted an extensive global effort to study the molecular evolution of the virus and develop vaccines to prevent its spread. Although rigorous determination of SARS-CoV-2 infectivity remains elusive, owing to the continuous evolution of the virus, steps have been made to understand its genome, structure, and emerging genetic mutations. The SARS-CoV-2 genome is composed of several open reading frames and structural proteins, including the spike protein, which is essential for entry into host cells. As of 25 January 2022, the World Health Organization has reported five variants of concern, two variants of interest, and three variants under monitoring. Additional sublineages have since been identified, and are being monitored. The mutations harboured in these variants confer an increased transmissibility, severity of disease, and escape from neutralising antibodies compared with the primary strain. The current vaccine strategy, including booster doses, provides protection from severe disease. As of 24 January 2022, 33 vaccines have been approved for use in 197 countries. In this review, we discuss the genetics, structure, and transmission methods of SARS-CoV-2 and its variants, highlighting how mutations provide enhanced abilities to spread and inflict disease. This review also outlines the vaccines currently in use around the world, providing evidence for every vaccine's immunogenicity and effectiveness.

A Single Dose of an MVA Vaccine Expressing a Prefusion-Stabilized SARS-CoV-2 Spike Protein Neutralizes Variants of Concern and Protects Mice From a Lethal SARS-CoV-2 Infection

We generated an optimized COVID-19 vaccine candidate based on the modified vaccinia virus Ankara (MVA) vector expressing a full-length prefusion-stabilized SARS-CoV-2 spike (S) protein, termed MVA-CoV2-S(3P). The S(3P) protein was expressed at higher levels (2-fold) than the non-stabilized S in cells infected with the corresponding recombinant MVA viruses. One single dose of MVA-CoV2-S(3P) induced higher IgG and neutralizing antibody titers against parental SARS-CoV-2 and variants of concern than MVA-CoV2-S in wild-type C57BL/6 and in transgenic K18-hACE2 mice. In immunized C57BL/6 mice, two doses of MVA-CoV2-S or MVA-CoV2-S(3P) induced similar levels of SARS-CoV-2-specific B- and T-cell immune responses. Remarkably, a single administration of MVA-CoV2-S(3P) protected all K18-hACE2 mice from morbidity and mortality caused by SARS-CoV-2 infection, reducing SARS-CoV-2 viral loads, histopathological lesions, and levels of pro-inflammatory cytokines in the lungs. These results demonstrated that expression of a novel full-length prefusion-stabilized SARS-CoV-2 S protein by the MVA poxvirus vector enhanced immunogenicity and efficacy against SARS-CoV-2 in animal models, further supporting MVA-CoV2-S(3P) as an optimized vaccine candidate for clinical trials.

Advances in the design and development of SARS-CoV-2 vaccines

Since the end of 2019, coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread worldwide. The RNA genome of SARS-CoV-2, which is highly infectious and prone to rapid mutation, encodes both structural and nonstructural proteins. Vaccination is currently the only effective method to prevent COVID-19, and structural proteins are critical targets for vaccine development. Currently, many vaccines are in clinical trials or are already on the market. This review highlights ongoing advances in the design of prophylactic or therapeutic vaccines against COVID-19, including viral vector vaccines, DNA vaccines, RNA vaccines, live-attenuated vaccines, inactivated virus vaccines, recombinant protein vaccines and bionic nanoparticle vaccines. In addition to traditional inactivated virus vaccines, some novel vaccines based on viral vectors, nanoscience and synthetic biology also play important roles in combating COVID-19. However, many challenges persist in ongoing clinical trials.

[Vaccine against COVID-19]

The COVID-19 pandemic has produced a huge health, economic and psychological collapse in our society. Health workers have had to face one of the greatest challenges in history, trying to show the population how to deal with this disease. We have learned that vaccines are the great instrument for the fight against infectious diseases and a large number of them began to appear, not as a product of chance but as a product of the enormous progress experienced in recent years with vaccines against new infectious diseases, against other diseases such as Alzheimer's and especially against cancer. All this knowledge has been applied to this disease. Practitioners lamented the little information available to them when asked questions from patients. This document wanted to be a response to these concerns, with a scientific desire, with evidence that put aside unverified data and hoaxes. Faced with an avalanche of information, most of it without the appropriate "peer review" as indicated in the introduction, any publication becomes obsolete at the time of publication, and we opted for an "online" publication, with the incorporation of versions. This online publication has been published in the documents of Spanish Society of Chemotherapy, at https://seq.es/vacunacion-covid-19.

Counting on COVID-19 Vaccine: Insights into the Current Strategies, Progress and Future Challenges

The emergence of a novel coronavirus viz., severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in late 2019 and its subsequent substantial spread produced the coronavirus disease 2019 (COVID-19) pandemic worldwide. Given its unprecedented infectivity and pathogenicity, the COVID-19 pandemic had a devastating impact on human health, and its clinical management has been a great challenge, which has led to the development and speedy trials of several vaccine candidates against SARS-CoV-2 at an exceptional pace. As a result, several COVID-19 vaccines were made commercially available in the first half of 2021. Although several COVID-19 vaccines showed promising results, crucial insights into their epidemiology, protective mechanisms, and the propensities of reinfection are not largely reviewed. In the present report, we provided insights into the prospects of vaccination against COVID-19 and assessed diverse vaccination strategies including DNA, mRNA, protein subunits, vector-based, live attenuated, and inactivated whole/viral particle-based vaccines. Next, we reviewed major aspects of various available vaccines approved by the World Health Organization and by the local administrations to use against COVID-19. Moreover, we comprehensively assessed the success of these approved vaccines and also their untoward effects, including the possibility of reinfection. We also provided an update on the vaccines that are under development and could be promising candidates in the future. Conclusively, we provided insights into the COVID-19 vaccine epidemiology, their potency, and propensity for SARS-CoV-2 reinfection, while a careful review of their current status, strategies, success, and future challenges was also presented.

Development of an Inactivated Vaccine against SARS CoV-2

The rapid spread of SARS-CoV-2 with its mutating strains has posed a global threat to safety during this COVID-19 pandemic. Thus far, there are 123 candidate vaccines in human clinical trials and more than 190 candidates in preclinical development worldwide as per the WHO on 1 October 2021. The various types of vaccines that are currently approved for emergency use include viral vectors (e.g., adenovirus, University of Oxford/AstraZeneca, Gamaleya Sputnik V, and Johnson & Johnson), mRNA (Moderna and Pfizer-BioNTech), and whole inactivated (Sinovac Biotech and Sinopharm) vaccines. Amidst the emerging cases and shortages of vaccines for global distribution, it is vital to develop a vaccine candidate that recapitulates the severe and fatal progression of COVID-19 and further helps to cope with the current outbreak. Hence, we present the preclinical immunogenicity, protective efficacy, and safety evaluation of a whole-virion inactivated SARS-CoV-2 vaccine candidate (ERUCoV-VAC) formulated in aluminium hydroxide, in three animal models, BALB/c mice, transgenic mice (K18-hACE2), and ferrets. The hCoV-19/Turkey/ERAGEM-001/2020 strain was used for the safety evaluation of ERUCoV-VAC. It was found that ERUCoV-VAC was highly immunogenic and elicited a strong immune response in BALB/c mice. The protective efficacy of the vaccine in K18-hACE2 showed that ERUCoV-VAC induced complete protection of the mice from a lethal SARS-CoV-2 challenge. Similar viral clearance rates with the safety evaluation of the vaccine in upper respiratory tracts were also positively appreciable in the ferret models. ERUCoV-VAC has been authorized by the Turkish Medicines and Medical Devices Agency and has now entered phase 3 clinical development (NCT04942405). The name of ERUCoV-VAC has been changed to TURKOVAC in the phase 3 clinical trial.

The Fc-mediated effector functions of a potent SARS-CoV-2 neutralizing antibody, SC31, isolated from an early convalescent COVID-19 patient, are essential for the optimal therapeutic efficacy of the antibody

Although SARS-CoV-2-neutralizing antibodies are promising therapeutics against COVID-19, little is known about their mechanism(s) of action or effective dosing windows. We report the generation and development of SC31, a potent SARS-CoV-2 neutralizing antibody, isolated from a convalescent patient. Antibody-mediated neutralization occurs via an epitope within the receptor-binding domain of the SARS-CoV-2 Spike protein. SC31 exhibited potent anti-SARS-CoV-2 activities in multiple animal models. In SARS-CoV-2 infected K18-human ACE2 transgenic mice, treatment with SC31 greatly reduced viral loads and attenuated pro-inflammatory responses linked to the severity of COVID-19. Importantly, a comparison of the efficacies of SC31 and its Fc-null LALA variant revealed that the optimal therapeutic efficacy of SC31 requires Fc-mediated effector functions that promote IFNγ-driven anti-viral immune responses, in addition to its neutralization ability. A dose-dependent efficacy of SC31 was observed down to 5mg/kg when administered before viral-induced lung inflammatory responses. In addition, antibody-dependent enhancement was not observed even when infected mice were treated with SC31 at sub-therapeutic doses. In SARS-CoV-2-infected hamsters, SC31 treatment significantly prevented weight loss, reduced viral loads, and attenuated the histopathology of the lungs. In rhesus macaques, the therapeutic potential of SC31 was evidenced through the reduction of viral loads in both upper and lower respiratory tracts to undetectable levels. Together, the results of our preclinical studies demonstrated the therapeutic efficacy of SC31 in three different models and its potential as a COVID-19 therapeutic candidate.

A Synthetic Peptide CTL Vaccine Targeting Nucleocapsid Confers Protection from SARS-CoV-2 Challenge in Rhesus Macaques

BACKGROUND

Persistent transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has given rise to a COVID-19 pandemic. Several vaccines, conceived in 2020, that evoke protective spike antibody responses are being deployed in mass public health vaccination programs. Recent data suggests, however, that as sequence variation in the spike genome accumulates, some vaccines may lose efficacy.

METHODS

Using a macaque model of SARS-CoV-2 infection, we tested the efficacy of a peptide-based vaccine targeting MHC class I epitopes on the SARS-CoV-2 nucleocapsid protein. We administered biodegradable microspheres with synthetic peptides and adjuvants to rhesus macaques. Unvaccinated control and vaccinated macaques were challenged with 1 × 108 TCID50 units of SARS-CoV-2, followed by assessment of clinical symptoms and viral load, chest radiographs, and sampling of peripheral blood and bronchoalveolar lavage (BAL) fluid for downstream analysis.

RESULTS

Vaccinated animals were free of pneumonia-like infiltrates characteristic of SARS-CoV-2 infection and presented with lower viral loads relative to controls. Gene expression in cells collected from BAL samples of vaccinated macaques revealed a unique signature associated with enhanced development of adaptive immune responses relative to control macaques.

CONCLUSIONS

We demonstrate that a room temperature stable peptide vaccine based on known immunogenic HLA class I bound CTL epitopes from the nucleocapsid protein can provide protection against SARS-CoV-2 infection in nonhuman primates.

SARS-CoV-2: Pathogenesis, Molecular Targets and Experimental Models

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a recent pandemic outbreak threatening human beings worldwide. This novel coronavirus disease-19 (COVID-19) infection causes severe morbidity and mortality and rapidly spreading across the countries. Therefore, there is an urgent need for basic fundamental research to understand the pathogenesis and druggable molecular targets of SARS-CoV-2. Recent sequencing data of the viral genome and X-ray crystallographic data of the viral proteins illustrate potential molecular targets that need to be investigated for structure-based drug design. Further, the SARS-CoV-2 viral pathogen isolated from clinical samples needs to be cultivated and titrated. All of these scenarios demand suitable laboratory experimental models. The experimental models should mimic the viral life cycle as it happens in the human lung epithelial cells. Recently, researchers employing primary human lung epithelial cells, intestinal epithelial cells, experimental cell lines like Vero cells, CaCo-2 cells, HEK-293, H1299, Calu-3 for understanding viral titer values. The human iPSC-derived lung organoids, small intestinal organoids, and blood vessel organoids increase interest among researchers to understand SARS-CoV-2 biology and treatment outcome. The SARS-CoV-2 enters the human lung epithelial cells using viral Spike (S1) protein and human angiotensin-converting enzyme 2 (ACE-2) receptor. The laboratory mouse show poor ACE-2 expression and thereby inefficient SARS-CoV-2 infection. Therefore, there was an urgent need to develop transgenic hACE-2 mouse models to understand antiviral agents' therapeutic outcomes. This review highlighted the viral pathogenesis, potential druggable molecular targets, and suitable experimental models for basic fundamental research.

Essential considerations during vaccine design against COVID-19 and review of pioneering vaccine candidate platforms

The calamity of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV2), COVID-19, is still a global human tragedy. To date, no specific antiviral drug or therapy has been able to break the widespread of SARS-CoV2. It has been generally believed that stimulating protective immunity via universal vaccination is the individual strategy to manage this pandemic. Achieving an effective COVID-19 vaccine requires attention to the immunological and non-immunological standpoints mentioned in this article. Here, we try to introduce the considerable immunological aspects, potential antigen targets, appropriate adjuvants as well as key points in the various stages of COVID-19 vaccine development. Also, the principal features of the preclinical and clinical studies of pioneering COVID-19 vaccine candidates were pointed out by reviewing the available information. Finally, we discuss the key challenges in the successful design of the COVID-19 vaccine and address the most fundamental strengths and weaknesses of common vaccine platforms.