Comparative evaluation of two severe acute respiratory syndrome (SARS) vaccine candidates in mice challenged with SARS coronavirus

Immunoglobulin A response to SARS-CoV-2 infection and immunity

The novel coronavirus disease (COVID-19) and its infamous "Variants" of the etiological agent termed Severe Acute Respiratory Syndrome Corona Virus 2 (SARS-CoV-2) has proven to be a global health concern. The three antibodies, IgA, IgM, and IgG, perform their dedicated role as main workhorses of the host adaptive immune system in virus neutralization. Immunoglobulin-A (IgA), also known as "Mucosal Immunoglobulin", has been under keen interest throughout the viral infection cycle. Its importance lies because IgA is predominant mucosal antibody and SARS family viruses primarily infect the mucosal surfaces of human respiratory tract. Therefore, IgA can be considered a diagnostic and prognostic marker and an active infection biomarker for SARS CoV-2 infection. Along with molecular analyses, serological tests, including IgA detection tests, are gaining ground in application as an early detectable marker and as a minimally invasive detection strategy. In the current review, it was emphasized the role of IgA response in diagnosis, host defense strategies, treatment, and prevention of SARS-CoV-2 infection. The data analysis was performed through almost 100 published peer-reviewed research reports and comprehended the importance of IgA in antiviral immunity against SARS-CoV-2 and other related respiratory viruses. Taken together, it is concluded that secretory IgA- Abs can serve as a promising detection tool for respiratory viral diagnosis and treatment parallel to IgG-based therapeutics and diagnostics. Vaccine candidates that target and trigger mucosal immune response may also be employed in future dimensions of research against other respiratory viruses.

Intranasal Liposomal Formulation of Spike Protein Adjuvanted with CpG Protects and Boosts Heterologous Immunity of hACE2 Transgenic Mice to SARS-CoV-2 Infection

Mucosal vaccination appears to be suitable to protect against SARS-CoV-2 infection. In this study, we tested an intranasal mucosal vaccine candidate for COVID-19 that consisted of a cationic liposome containing a trimeric SARS-CoV-2 spike protein and CpG-ODNs, a Toll-like receptor 9 agonist, as an adjuvant. In vitro and in vivo experiments indicated the absence of toxicity following the intranasal administration of this vaccine formulation. First, we found that subcutaneous or intranasal vaccination protected hACE-2 transgenic mice from infection with the wild-type (Wuhan) SARS-CoV-2 strain, as shown by weight loss and mortality indicators. However, when compared with subcutaneous administration, the intranasal route was more effective in the pulmonary clearance of the virus and induced higher neutralizing antibodies and anti-S IgA titers. In addition, the intranasal vaccination afforded protection against gamma, delta, and omicron virus variants of concern. Furthermore, the intranasal vaccine formulation was superior to intramuscular vaccination with a recombinant, replication-deficient chimpanzee adenovirus vector encoding the SARS-CoV-2 spike glycoprotein (Oxford/AstraZeneca) in terms of virus lung clearance and production of neutralizing antibodies in serum and bronchial alveolar lavage (BAL). Finally, the intranasal liposomal formulation boosted heterologous immunity induced by previous intramuscular vaccination with the Oxford/AstraZeneca vaccine, which was more robust than homologous immunity.

The Coming of Age of Nucleic Acid Vaccines during COVID-19

In the 21st century, several emergent viruses have posed a global threat. Each pathogen has emphasized the value of rapid and scalable vaccine development programs. The ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has made the importance of such efforts especially clear. New biotechnological advances in vaccinology allow for recent advances that provide only the nucleic acid building blocks of an antigen, eliminating many safety concerns. During the COVID-19 pandemic, these DNA and RNA vaccines have facilitated the development and deployment of vaccines at an unprecedented pace. This success was attributable at least in part to broader shifts in scientific research relative to prior epidemics: the genome of SARS-CoV-2 was available as early as January 2020, facilitating global efforts in the development of DNA and RNA vaccines within 2 weeks of the international community becoming aware of the new viral threat. Additionally, these technologies that were previously only theoretical are not only safe but also highly efficacious. Although historically a slow process, the rapid development of vaccines during the COVID-19 crisis reveals a major shift in vaccine technologies. Here, we provide historical context for the emergence of these paradigm-shifting vaccines. We describe several DNA and RNA vaccines in terms of their efficacy, safety, and approval status. We also discuss patterns in worldwide distribution. The advances made since early 2020 provide an exceptional illustration of how rapidly vaccine development technology has advanced in the last 2 decades in particular and suggest a new era in vaccines against emerging pathogens. IMPORTANCE The SARS-CoV-2 pandemic has caused untold damage globally, presenting unusual demands on but also unique opportunities for vaccine development. The development, production, and distribution of vaccines are imperative to saving lives, preventing severe illness, and reducing the economic and social burdens caused by the COVID-19 pandemic. Although vaccine technologies that provide the DNA or RNA sequence of an antigen had never previously been approved for use in humans, they have played a major role in the management of SARS-CoV-2. In this review, we discuss the history of these vaccines and how they have been applied to SARS-CoV-2. Additionally, given that the evolution of new SARS-CoV-2 variants continues to present a significant challenge in 2022, these vaccines remain an important and evolving tool in the biomedical response to the pandemic.

Adenoviral Vector-Based Vaccine Platform for COVID-19: Current Status

The coronavirus disease (COVID-19) breakout had an unimaginable worldwide effect in the 21st century, claiming millions of lives and putting a huge burden on the global economy. The potential developments in vaccine technologies following the determination of the genetic sequence of SARS-CoV-2 and the increasing global efforts to bring potential vaccines and therapeutics into the market for emergency use have provided a small bright spot to this tragic event. Several intriguing vaccine candidates have been developed using recombinant technology, genetic engineering, and other vaccine development technologies. In the last decade, a vast amount of the vaccine development process has diversified towards the usage of viral vector-based vaccines. The immune response elicited by such vaccines is comparatively higher than other approved vaccine candidates that require a booster dose to provide sufficient immune protection. The non-replicating adenoviral vectors are promising vaccine carriers for infectious diseases due to better yield, cGMP-friendly manufacturing processes, safety, better efficacy, manageable shipping, and storage procedures. As of April 2022, the WHO has approved a total of 10 vaccines around the world for COVID-19 (33 vaccines approved by at least one country), among which three candidates are adenoviral vector-based vaccines. This review sheds light on the developmental summary of all the adenoviral vector-based vaccines that are under emergency use authorization (EUA) or in the different stages of development for COVID-19 management.

The adjuvants dmLT and mmCT enhance humoral immune responses to a pneumococcal conjugate vaccine after both parenteral or mucosal immunization of neonatal mice

Immaturity of the neonatal immune system contributes to increased susceptibility to infectious diseases and poor vaccine responses. Therefore, better strategies for early life vaccination are needed. Adjuvants can enhance the magnitude and duration of immune responses. In this study we assessed the effects of the adjuvants dmLT and mmCT and different immunization routes, subcutaneous (s.c.) and intranasal (i.n.), on neonatal immune response to a pneumococcal conjugate vaccine Pn1-CRM₁₉₇. Pn1-specific antibody (Ab) levels of neonatal mice immunized with Pn1-CRM197 alone were low. The adjuvants enhanced IgG Ab responses up to 8 weeks after immunization, more after s.c. than i.n. immunization. On the contrary, i.n. immunization with either adjuvant enhanced serum and salivary IgA levels more than s.c. immunization. In addition, both dmLT and mmCT enhanced germinal center formation and accordingly, dmLT and mmCT enhanced the induction and persistence of Pn1-specific IgG⁺ Ab-secreting cells (ASCs) in spleen and bone marrow (BM), irrespective of the immunization route. Furthermore, i.n. immunization enhanced Pn1-specific IgA⁺ ASCs in BM more than s.c. immunizatiofimmu.2022.1078904n. However, a higher i.n. dose of the Pn1-CRM₁₉₇ was needed to achieve IgG response comparable to that elicited by s.c. immunization with either adjuvant. We conclude that dmLT and mmCT enhance both induction and persistence of the neonatal immune response to the vaccine Pn1-CRM₁₉₇, following mucosal or parenteral immunization. This indicates that dmLT and mmCT are promising adjuvants for developing safe and effective early life vaccination strategies.

Longitudinal neutralization activities on authentic Omicron variant provided by three doses of BBIBP-CorV vaccination during one year

The majority of people in China have been immunized with the inactivated viral vaccine BBIBP-CorV. The emergence of the Omicron variant raised the concerns about protection efficacy of the inactivated viral vaccine in China. However, longitudinal neutralization data describing protection efficacy against Omicron variant is still lacking. Here we present one-year longitudinal neutralization data of BBIBP-CorV on authentic Omicron, Delta, and wild-type strains using 224 sera collected from 14 volunteers who have finished three doses BBIBP-CorV. The sera were also subjected for monitoring the SARS-CoV-2 specific IgG, IgA, and IgM responses on protein and peptide microarrays. The neutralization titers showed different protection efficacies against the three strains. By incorporating IgG and IgA signals of proteins and Spike protein derived peptide on microarray, panels as potential surrogate biomarkers for rapid estimation of neutralization titers were established. These data support the necessity of the 3^rd dose of BBIBP-CorV vaccination. After further validation and assay development, the panels could be used for reliable, convenient and fast evaluation of the efficacy of vaccination.

How Protective are Antibodies to SARS-CoV-2, the Main Weapon of the B-Cell Response?

Since the beginning of the Coronavirus disease (COVID)-19 pandemic in December 2019, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been responsible for more than 600 million infections and 6.5 million deaths worldwide. Given the persistence of SARS-CoV-2 and its ability to develop new variants, the implementation of an effective and long-term herd immunity appears to be crucial to overcome the pandemic. While a vast field of research has focused on the role of humoral immunity against SARS-CoV-2, a growing body of evidence suggest that antibodies alone only confer a partial protection against infection of reinfection which could be of high importance regarding the strategic development goals (SDG) of the United Nations (UN) and in particular UN SDG3 that aims towards the realization of good health and well being on a global scale in the context of the COVID-19 pandemic.In this review, we highlight the role of humoral immunity in the host defense against SARS-CoV-2, with a focus on highly neutralizing antibodies. We summarize the results of the main clinical trials leading to an overall disappointing efficacy of convalescent plasma therapy, variable results of monoclonal neutralizing antibodies in patients with COVID-19 but outstanding results for the mRNA based vaccines against SARS-CoV-2. Finally, we advocate that beyond antibody responses, the development of a robust cellular immunity against SARS-CoV-2 after infection or vaccination is of utmost importance for promoting immune memory and limiting disease severity, especially in case of (re)-infection by variant viruses.

Artificial Cell Membrane Polymersome-Based Intranasal Beta Spike Formulation as a Second Generation Covid-19 Vaccine

Current parenteral coronavirus disease 2019 (Covid-19) vaccines inadequately protect against infection of the upper respiratory tract. Additionally, antibodies generated by wild type (WT) spike-based vaccines poorly neutralize severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants. To address the need for a second-generation vaccine, we have initiated a preclinical program to produce and evaluate a potential candidate. Our vaccine consists of recombinant Beta spike protein coadministered with synthetic CpG adjuvant. Both components are encapsulated within artificial cell membrane (ACM) polymersomes, synthetic nanovesicles efficiently internalized by antigen presenting cells, including dendritic cells, enabling targeted delivery of cargo for enhanced immune responses. ACM vaccine is immunogenic in C57BL/6 mice and Golden Syrian hamsters, evoking high serum IgG and neutralizing responses. Compared to an ACM-WT spike vaccine that generates predominantly WT-neutralizing antibodies, the ACM-Beta spike vaccine induces antibodies that neutralize WT and Beta viruses equally. Intramuscular (IM)-immunized hamsters are strongly protected from weight loss and other clinical symptoms after the Beta challenge but show delayed viral clearance in the upper airway. With intranasal (IN) immunization, however, neutralizing antibodies are generated in the upper airway concomitant with rapid and potent reduction of viral load. Moreover, antibodies are cross-neutralizing and show good activity against Omicron. Safety is evaluated in New Zealand white rabbits in a repeated dose toxicological study under Good Laboratory Practice (GLP) conditions. Three doses, IM or IN, at two-week intervals do not induce an adverse effect or systemic toxicity. Cumulatively, these results support the application for a Phase 1 clinical trial of ACM-polymersome-based Covid-19 vaccine (ClinicalTrials.gov identifier: NCT05385991).

Harnessing Nasal Immunity with IgA to Prevent Respiratory Infections

The nasal cavity is a primary checkpoint for the invasion of respiratory pathogens. Numerous pathogens, including SARS-CoV-2, S. pneumoniae, S. aureus, etc., can adhere/colonize nasal lining to trigger an infection. Secretory IgA (sIgA) serves as the first line of immune defense against foreign pathogens. sIgA facilitates clearance of pathogenic microbes by intercepting their access to epithelial receptors and mucus entrapment through immune exclusion. Elevated levels of neutralizing IgA at the mucosal surfaces are associated with a high level of protection following intranasal immunizations. This review summarizes recent advances in intranasal vaccination technology and challenges in maintaining nominal IgA levels at the mucosal surface. Overall, the review emphasizes the significance of IgA-mediated nasal immunity, which holds a tremendous potential to mount protection against respiratory pathogens.

The use of adenoviral vectors in gene therapy and vaccine approaches

Adenovirus was first identified in the 1950s and since then this pathogenic group of viruses has been explored and transformed into a genetic transfer vehicle. Modification or deletion of few genes are necessary to transform it into a conditionally or non-replicative vector, creating a versatile tool capable of transducing different tissues and inducing high levels of transgene expression. In the early years of vector development, the application in monogenic diseases faced several hurdles, including short-term gene expression and even a fatality. On the other hand, an adenoviral delivery strategy for treatment of cancer was the first approved gene therapy product. There is an increasing interest in expressing transgenes with therapeutic potential targeting the cancer hallmarks, inhibiting metastasis, inducing cancer cell death or modulating the immune system to attack the tumor cells. Replicative adenovirus as vaccines may be even older and date to a few years of its discovery, application of non-replicative adenovirus for vaccination against different microorganisms has been investigated, but only recently, it demonstrated its full potential being one of the leading vaccination tools for COVID-19. This is not a new vector nor a new technology, but the result of decades of careful and intense work in this field.

Waning of SARS-CoV-2 Seropositivity among Healthy Young Adults over Seven Months

Background: We conducted a longitudinal study to estimate immunity produced in response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection among university students over seven months. Methods: All participants were attending a public university and resided in Pitt County, North Carolina. University students enrolled weekly for 10 weeks between 26 August 2020 and 28 October 2020, resulting in 136 young adults completing at least one study visit by 17 November 2020. Enrolled students completed an online survey and nasal swab collection at two-week intervals and monthly blood collection between 26 August 2020 and 31 March 2021. Results: Amongst 695 serum samples tested during follow-up, the prevalence of a positive result for anti-nucleocapsid antibodies (N-IgG) was 9.78%. In 22 students with more than one positive N-IgG serum sample, 68.1% of the group lost persistence of N-IgG below the positive threshold over 140 days. Anti-spike IgG antibodies were significantly higher among 11 vaccinated compared to 10 unvaccinated. Conclusions: In healthy young adults, N-IgG wanes below the detectable threshold within five months. S-IgG titer remained consistently elevated months after infection, and significantly increased after vaccination.

Intranasal administration of a single dose of MVA-based vaccine candidates against COVID-19 induced local and systemic immune responses and protects mice from a lethal SARS-CoV-2 infection

Current coronavirus disease-19 (COVID-19) vaccines are administered by the intramuscular route, but this vaccine administration failed to prevent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus infection in the upper respiratory tract, mainly due to the absence of virus-specific mucosal immune responses. It is hypothesized that intranasal (IN) vaccination could induce both mucosal and systemic immune responses that blocked SARS-CoV-2 transmission and COVID-19 progression. Here, we evaluated in mice IN administration of three modified vaccinia virus Ankara (MVA)-based vaccine candidates expressing the SARS-CoV-2 spike (S) protein, either the full-length native S or a prefusion-stabilized [S(3P)] protein; SARS-CoV-2-specific immune responses and efficacy were determined after a single IN vaccine application. Results showed that in C57BL/6 mice, MVA-based vaccine candidates elicited S-specific IgG and IgA antibodies in serum and bronchoalveolar lavages, respectively, and neutralizing antibodies against parental and SARS-CoV-2 variants of concern (VoC), with MVA-S(3P) being the most immunogenic vaccine candidate. IN vaccine administration also induced polyfunctional S-specific Th1-skewed CD4+ and cytotoxic CD8+ T-cell immune responses locally (in lungs and bronchoalveolar lymph nodes) or systemically (in spleen). Remarkably, a single IN vaccine dose protected susceptible K18-hACE2 transgenic mice from morbidity and mortality caused by SARS-CoV-2 infection, with MVA-S(3P) being the most effective candidate. Infectious SARS-CoV-2 viruses were undetectable in lungs and nasal washes, correlating with high titers of S-specific IgGs and neutralizing antibodies against parental SARS-CoV-2 and several VoC. Moreover, low histopathological lung lesions and low levels of pro-inflammatory cytokines in lungs and nasal washes were detected in vaccinated animals. These results demonstrated that a single IN inoculation of our MVA-based vaccine candidates induced potent immune responses, either locally or systemically, and protected animal models from COVID-19. These results also identified an effective vaccine administration route to induce mucosal immunity that should prevent SARS-CoV-2 host-to-host transmission.

The chimera of S1 and N proteins of SARS-CoV-2: can it be a potential vaccine candidate for COVID-19?

INTRODUCTION

Coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has emerged as one of the biggest global health issues. Spike protein (S) and nucleoprotein (N), the major immunogenic components of SARS-CoV-2, have been shown to be involved in the attachment and replication of the virus inside the host cell.

AREAS COVERED

Several investigations have shown that the SARS-CoV-2 nucleoprotein can elicit a cell-mediated immune response capable of regulating viral replication and lowering viral burden. However, the development of an effective vaccine that can stop the transmission of SARS-CoV-2 remains a matter of concern. Literature was retrieved using the keywords COVID-19 vaccine, role of nucleoprotein as vaccine candidate, spike protein, nucleoprotein immune responses against SARS-CoV-2, and chimera vaccine in PubMed, Google Scholar, and Google.

EXPERT OPINION

We have focussed on the use of chimera protein, consisting of N and S-1 protein components of SARS-CoV-2, as a potential vaccine candidate. This may act as a polyvalent mixed recombinant protein vaccine to elicit a strong T and B cell immune response, which will be capable of neutralizing the wild and mutated variants of SARS-CoV-2, and also restricting its attachment, replication, and budding in the host cell.

Mucosal administration of a live attenuated recombinant COVID-19 vaccine protects nonhuman primates from SARS-CoV-2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of the COVID-19 global pandemic. SARS-CoV-2 is an enveloped RNA virus that relies on its trimeric surface glycoprotein spike for entry into host cells. Here we describe the COVID-19 vaccine candidate MV-014-212, a live, attenuated, recombinant human respiratory syncytial virus expressing a chimeric SARS-CoV-2 spike as the only viral envelope protein. MV-014-212 was attenuated and immunogenic in African green monkeys (AGMs). One mucosal administration of MV-014-212 in AGMs protected against SARS-CoV-2 challenge, reducing by more than 200-fold the peak shedding of SARS-CoV-2 in the nose. MV-014-212 elicited mucosal immunoglobulin A in the nose and neutralizing antibodies in serum that exhibited cross-neutralization against virus variants of concern Alpha, Beta, and Delta. Intranasally delivered, live attenuated vaccines such as MV-014-212 entail low-cost manufacturing suitable for global deployment. MV-014-212 is currently in Phase 1 clinical trials as an intranasal COVID-19 vaccine.

Clearance of Persistent SARS-CoV-2 RNA Detection in a NFκB-Deficient Patient in Association with the Ingestion of Human Breast Milk: A Case Report

Currently, there are no evidence-based treatment options for long COVID-19, and it is known that SARS-CoV-2 can persist in part of the infected patients, especially those with immunosuppression. Since there is a robust secretion of SARS-CoV-2-specific highly-neutralizing IgA antibodies in breast milk, and because this immunoglobulin plays an essential role against respiratory virus infection in mucosa cells, being, in addition, more potent in neutralizing SARS-CoV-2 than IgG, here we report the clinical course of an NFκB-deficient patient chronically infected with the SARS-CoV-2 Gamma variant, who, after a non-full effective treatment with plasma infusion, received breast milk from a vaccinated mother by oral route as treatment for COVID-19. After such treatment, the symptoms improved, and the patient was systematically tested negative for SARS-CoV-2. Thus, we hypothesize that IgA and IgG secreted antibodies present in breast milk could be useful to treat persistent SARS-CoV-2 infection in immunodeficient patients.

A global survey in the developmental landscape of possible vaccination strategies for COVID-19

The development of COVID-19 vaccines was promptly regulated to ensure the best possible approach. By January 2022, 75 candidates reached preclinical evaluation in various animal models, 114 vaccines were in clinical trials on humans, and 48 were in the final testing stages. Vaccine platforms range from whole virus vaccines to nucleic acid vaccines, which are the most promising in prompt availability and safety. The USA and Europe have approved vaccines developed by Pfizer-BioNTech (BNT162b2) and Moderna (mRNa1273). So far, Pfizer-BioNTech, Moderna, Johnson & Johnson, AstraZeneca-University of Oxford, Sinopharm, Sinovac Biotech Gamaleya, Bharat Biotech, and Novavax have documented effective vaccines. Even with technological advances and a fast-paced development approach, many limitations and problems need to be overcome before a large-scale production of new vaccines can start. The Key is to ensure equal and fair distribution globally through regulatory measures. Recent studies link Bacillus Calmette-Guérin (BCG) vaccination programs and lower disease severity.

Respiratory Mucosal Immunity: Kinetics of Secretory Immunoglobulin A in Sputum and Throat Swabs From COVID-19 Patients and Vaccine Recipients

While IgM and IgG response to SARS-CoV-2 has been extensively studied, relatively little is known about secretory IgA (sIgA) response in respiratory mucosa. Here we report IgA response to the SARS-CoV-2 in sputum, throat swabs, and serum with nucleocapsid protein (NP) enzyme-linked immunosorbent assays (ELISA) in a cohort of 28 COVID-19 patients and 55 vaccine recipients. The assays showed sIgA in respiratory mucosa could be detected on the first day after illness onset (AIO), and the median conversion time for sIgA in sputum, throat swabs, and serum was 3, 4, and 10 days, respectively. The positive rates of sIgA first week AIO were 100% (24/28) and 85.7% (24/28) in sputum and throat swabs, respectively, and were both 100% during the mid-onset (2–3 weeks AIO). During the recovery period, sIgA positive rates in sputum and throat swabs gradually decreased from 60.7% (17/28) and 57.1% (16/28) 1 month AIO and the sIgA antibodies were all undetectable 6 months AIO. However, serum IgA positive rate was still 100% at 4 months and 53.6% (15/28) at 6 months. Throat swabs obtained from volunteers who received inactivated SARS-CoV-2 vaccines by intramuscular delivery all showed negative results in IgA ELISA. These findings will likely improve our understanding of respiratory mucosal immunity of this emerging disease and help in containing the pandemic and developing vaccines.

A chitosan-mediated inhalable nanovaccine against SARS-CoV-2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), with several antigenic variants, has grown into a global challenge, and the rapid establishment of an immune barrier is crucial to achieving long-term control of the virus. This has led to a great demand for easy preparation and scalable vaccines, especially in low-income countries. Here, we present an inhalable nanovaccine comprising chitosan and SARS-CoV-2 spike protein. The chitosan-mediated nanovaccine enabled a strong spike-specific antibody immune response and augmented local mucosal immunity in bronchoalveolar lavage and lungs, which might be capable of protecting the host from infection without systemic toxicity. In addition, the enhanced adaptive immunity stimulated by chitosan showed potential protection against SARS-CoV-2. Furthermore, inhalation of the nanovaccine induced a comparable antibody response compared to intramuscular injection. This inhalable nanovaccine against SARS-CoV-2 offers a convenient and compliant strategy to reduce the use of needles and the need for medical staff.

ELECTRONIC SUPPLEMENTARY MATERIAL

Supplementary material (the immune activation of CS-mediated nanovacccine on BMDCs, cell viability, immune responses in lungs and BALF, serum chemistry and H&E histopathological analysis.) is available in the online version of this article at 10.1007/s12274-021-4012-9.

Animal models for SARS-CoV-2 and SARS-CoV-1 pathogenesis, transmission and therapeutic evaluation

There is a critical need to develop animal models to alleviate vaccine and drug development difficulties against zoonotic viral infections. The coronavirus family, which includes severe acute respiratory syndrome coronavirus 1 and severe acute respiratory syndrome coronavirus 2, crossed the species barrier and infected humans, causing a global outbreak in the 21^st century. Because humans do not have pre-existing immunity against these viral infections and with ethics governing clinical trials, animal models are therefore being used in clinical studies to facilitate drug discovery and testing efficacy of vaccines. The ideal animal models should reflect the viral replication, clinical signs, and pathological responses observed in humans. Different animal species should be tested to establish an appropriate animal model to study the disease pathology, transmission and evaluation of novel vaccine and drug candidates to treat coronavirus disease 2019. In this context, the present review summarizes the recent progress in developing animal models for these two pathogenic viruses and highlights the utility of these models in studying SARS-associated coronavirus diseases.

Responses against infectious disease pandemics: a narrative review on COVID-19

Currently, the world is facing the coronavirus disease 2019 (COVID-19) pandemic. With this, an emerging infectious disease pandemic in the absence of effective antiviral agents and vaccines for a novel virus is no different from the 1918 influenza pandemic, which became a great disaster for humankind. We also experienced a global lockdown with a stringent implementation of social distancing, which is a first for mankind living in the present day, and has led to enormous economic damage and restrictions on individual freedom. The microorganism that will cause the next pandemic may be a highly fatal avian influenza virus, another coronavirus, or a completely different microorganism. This COVID-19 pandemic is an enormous lesson for humankind and is tantamount to a vaccine in preparation for the next pandemic. Important and urgent undertakings were given to each country in terms of complementing laws and regulations for a stronger and more resilient healthcare system, such as investment in research and development for new rapid diagnostic technologies, vaccines, new therapeutic agents, among others.

The Bacterial Mucosal Immunotherapy MV130 Protects Against SARS-CoV-2 Infection and Improves COVID-19 Vaccines Immunogenicity

COVID-19-specific vaccines are efficient prophylactic weapons against SARS-CoV-2 virus. However, boosting innate responses may represent an innovative way to immediately fight future emerging viral infections or boost vaccines. MV130 is a mucosal immunotherapy, based on a mixture of whole heat-inactivated bacteria, that has shown clinical efficacy against recurrent viral respiratory infections. Herein, we show that the prophylactic intranasal administration of this immunotherapy confers heterologous protection against SARS-CoV-2 infection in susceptible K18-hACE2 mice. Furthermore, in C57BL/6 mice, prophylactic administration of MV130 improves the immunogenicity of two different COVID-19 vaccine formulations targeting the SARS-CoV-2 spike (S) protein, inoculated either intramuscularly or intranasally. Independently of the vaccine candidate and vaccination route used, intranasal prophylaxis with MV130 boosted S-specific responses, including CD8⁺-T cell activation and the production of S-specific mucosal IgA antibodies. Therefore, the bacterial mucosal immunotherapy MV130 protects against SARS-CoV-2 infection and improves COVID-19 vaccines immunogenicity.

Protective mucosal immunity against SARS-CoV-2 after heterologous systemic prime-mucosal boost immunization

Several effective SARS-CoV-2 vaccines are currently in use, but effective boosters are needed to maintain or increase immunity due to waning responses and the emergence of novel variants. Here we report that intranasal vaccinations with adenovirus 5 and 19a vectored vaccines following a systemic plasmid DNA or mRNA priming result in systemic and mucosal immunity in mice. In contrast to two intramuscular applications of an mRNA vaccine, intranasal boosts with adenoviral vectors induce high levels of mucosal IgA and lung-resident memory T cells (TRM); mucosal neutralization of virus variants of concern is also enhanced. The mRNA prime provokes a comprehensive T cell response consisting of circulating and lung TRM after the boost, while the plasmid DNA prime induces mostly mucosal T cells. Concomitantly, the intranasal boost strategies lead to complete protection against a SARS-CoV-2 infection in mice. Our data thus suggest that mucosal booster immunizations after mRNA priming is a promising approach to establish mucosal immunity in addition to systemic responses.

Women's Lives Matter-The Critical Need for Women to Prioritize Optimal Physical Activity to Reduce COVID-19 Illness Risk and Severity

Physical activity (PA) is beneficial for the health and wellness of individuals and societies. During an infectious disease pandemic, such as the one caused by COVID-19, social distancing, quarantines, and lockdowns are used to reduce community spread of the disease. Unfortunately, such nonpharmacological interventions or physical risk mitigation measures also make it challenging to engage in PA. Reduced PA could then trigger physiological changes that affect both mental and physical health. In this regard, women are more likely to experience physical and psychological distress. PA is a safe and effective nonpharmacological modality that can help prevent and manage several mental and physical health problems when performed correctly. PA might even confer benefits that are directly related to decreasing COVID-19 morbidity and mortality in women. In this review, we summarize why optimal PA must be a priority for women during the COVID-19 pandemic. We then discuss chronic COVID-19 illness and its impact on women, which further underscores the need for worldwide preventive health strategies that include PA. Finally, we discuss the importance of vaccination against COVID-19 for women, as part of prioritizing preventive healthcare and an active lifestyle.

Discontinuation of Transmission Precautions for COVID-19 Patients: Polymerase Chain Reaction Diagnostics, Patient Delays, and Cycle Threshold Values

Background

The decision of when it is safe to discontinue transmission-based precautions for SARS-CoV-2 coronavirus disease 2019 (COVID-19) hospitalized patients has been controversial. The Centers for Disease Control and Prevention offered reverse transcriptase polymerase chain reaction (PCR) diagnostic test- or symptom-based guidelines.

Methods

A retrospective chart review of Vidant Health system, Eastern North Carolina, was conducted. Length of stay, days in isolation unit, and date appropriate for discharge or isolation discontinuation based on the symptom-based strategy were recorded.

Results

Of 196 COVID hospitalized patients, 34 had repeated COVID PCR tests 3 or more days from their first positive test result. Half of these patients experienced delays in release from transmission-based precautions because of repeated positive PCR test results and use of the test-based approach. This resulted in an additional 166 days of hospitalization, costing an estimated $415,000. Furthermore, 2 subjects had a combined 16-day delay in necessary medical procedures. Most of the COVID PCR platforms yield quantitative results in the form of cycle threshold (Ct) values, the number of cycles needed to detect the genome. These values have also been used to assess whether patients are likely to remain contagious. None of our patients who met the criteria for symptom-based strategy for transmission-based precaution discontinuation had positive PCR test results with Ct values lower than 25, but 4 had Ct values lower than 30.

Conclusions

Concerns surround immunocompromised patients and those treated with steroids who might be delayed or incapable of stopping viral replication and thus remain contagious. Our results suggest that clinicians use all available data including Ct values to evaluate the safety of discontinuation of transmission precautions.

Serological assessment of SARS-CoV-2 infection during the first wave of the pandemic in Louisville Kentucky

Serological assays intended for diagnosis, sero-epidemiologic assessment, and measurement of protective antibody titers upon infection or vaccination are essential for managing the SARS-CoV-2 pandemic. Serological assays measuring the antibody responses against SARS-CoV-2 antigens are readily available. However, some lack appropriate characteristics to accurately measure SARS-CoV-2 antibodies titers and neutralization. We developed an Enzyme-linked Immunosorbent Assay (ELISA) methods for measuring IgG, IgA, and IgM responses to SARS-CoV-2, Spike (S), receptor binding domain (RBD), and nucleocapsid (N) proteins. Performance characteristics of sensitivity and specificity have been defined. ELISA results show positive correlation with microneutralization and Plaque Reduction Neutralization assays with infectious SARS-CoV-2. Our ELISA was used to screen healthcare workers in Louisville, KY during the first wave of the local pandemic in the months of May and July 2020. We found a seropositive rate of approximately 1.4% and 2.3%, respectively. Our analyses demonstrate a broad immune response among individuals and suggest some non-RBD specific S IgG and IgA antibodies neutralize SARS-CoV-2.

Inactivation of SARS-CoV-2 by β-propiolactone causes aggregation of viral particles and loss of antigenic potential

Inactivated viral preparations are important resources in vaccine and antisera industry. Of the many vaccines that are being developed against COVID-19, inactivated whole-virus vaccines are also considered effective. β-propiolactone (BPL) is a widely used chemical inactivator of several viruses. Here, we analyze various concentrations of BPL to effectively inactivate SARS-CoV-2 and their effects on the biochemical properties of the virion particles. BPL at 1:2000 (v/v) concentrations effectively inactivated SARS-CoV-2. However, higher BPL concentrations resulted in the loss of both protein content as well as the antigenic integrity of the structural proteins. Higher concentrations also caused substantial aggregation of the virion particles possibly resulting in insufficient inactivation, and a loss in antigenic potential. We also identify that the viral RNA content in the culture supernatants can be a direct indicator of their antigenic content. Our findings may have important implications in the vaccine and antisera industry during COVID-19 pandemic.

COVID-19 diagnostic tests: Importance of the clinical context

The current SARS-CoV-2 pandemic poses numerous health challenges, including the adequate use and proper interpretation of the different available tests in different clinical settings. As any diagnostic test, those of SARS-CoV-2 have methodological limitations of sensitivity (S) and specificity (E), which eventually determine their positive (PPV) and negative (NPV) predictive value. Furthermore, their diagnostic performance depends on the clinical context in which these tests are used, that is, on the pretest probability. This article: (1) reviews the main methodological aspects that influence the S, E, PPV and NPV of the most common SARS-CoV-2 diagnostic tests; and, (2) discusses its diagnostic interpretation in different clinical settings.

Safety and immunogenicity evaluation of inactivated whole-virus-SARS-COV-2 as emerging vaccine development in Egypt

BACKGROUND

Current worldwide pandemic coronavirus disease 2019 (COVID-19) with high numbers of mortality rates and huge economic problems require an urgent demand for safe and effective vaccine development. Inactivated SARS-CoV2 vaccine with alum. Hydroxide can play an important role in reducing the impacts of the COVID-19 pandemic. In this study, vaccine efficacy was evaluated through the detection of the neutralizing antibodies that protect mice from challenge with SARS-CoV 2 3 weeks after the second dose. We conclude that the vaccine described here has safety and desirable properties, and our data support further development and plans for clinical trials.

METHODS

Characterized SARS-COV-2 strain, severe acute respiratory syndrome coronavirus 2 isolates (SARS-CoV-2/human/EGY/Egy-SERVAC/2020) with accession numbers; MT981440; MT981439; MT981441; MT974071; MT974069; and MW250352 at GenBank were isolated from Egyptian patients SARS-CoV-2-positive. Development of inactivated vaccine was carried out in a BSL-3 facilities and the immunogenicity was determined in mice at two doses (55 and 100 μg per dose).

RESULTS

The distinct cytopathic effect induced by SARS-COV-2 propagation on Vero cell monolayers and the viral particles were identified as Coronaviridae by transmission electron microscopy and RT-PCR on infected cells cultures. Immunogenicity of the developed vaccine indicated the high antigen-binding and neutralizing antibody titers, regardless of the dose concentration, with excellent safety profiles and no deaths or clinical symptoms in mice groups. The efficacy of the inactivated vaccine formulation was tested by the wild virus challenge of the vaccinated mice and viral replication detection in lung tissues.

CONCLUSIONS

Vaccinated mice recorded complete protection from challenge infection via inhibition of SARS-COV-2 replication in the lung tissues of mice following virus challenge, regardless of the level of serum neutralizing antibodies. This finding will support future trials for the evaluation of an applicable SARS-CoV-2 vaccine candidate.

Intranasal Vaccination Strategy to Control the COVID-19 Pandemic from a Veterinary Medicine Perspective

Simple Summary

Intranasal vaccination is one of the methods used to stimulate mucosal immunity. It has been widely practised to control many human and animal respiratory diseases. Coronavirus disease 2019 (COVID-19) is a highly contagious respiratory disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which resulted in a global pandemic. COVID-19 has reminded some veterinarians of various contagious veterinary diseases, including coronavirus infections in animals. This article discusses the control of highly contagious diseases of veterinary importance with emphasis on an intranasal vaccination approach, and the potential of implementing similar strategies in human medicine to control the ongoing COVID-19 pandemic.

Abstract

The world is currently facing an ongoing coronavirus disease 2019 (COVID-19) pandemic. The disease is a highly contagious respiratory disease which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Current control measures used by many countries include social distancing, wearing face masks, frequent hand washing, self-isolation, and vaccination. The current commercially available vaccines are injectable vaccines, although a few intranasal vaccines are in trial stages. The reported side effects of COVID-19 vaccines, perceptions towards the safety of the vaccines, and frequent mutation of the virus may lead to poor herd immunity. In veterinary medicine, attaining herd immunity is one of the main considerations in disease control, and herd immunity depends on the use of efficacious vaccines and the vaccination coverage in a population. Hence, many aerosol or intranasal vaccines have been developed to control veterinary respiratory diseases such as Newcastle disease, rinderpest, infectious bronchitis, and haemorrhagic septicaemia. Different vaccine technologies could be employed to improve vaccination coverage, including the usage of an intranasal live recombinant vaccine or live mutant vaccine. This paper discusses the potential use of intranasal vaccination strategies against human COVID-19, based on a veterinary intranasal vaccine strategy.

Development of SARS-CoV-2 vaccines: challenges, risks, and the way forward

The COVID-19 pandemic mandates the development of a safe and effective Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) vaccine. This review analyzes the complexities, challenges, and other vital issues associated with the development of the SARS-CoV-2 vaccine. A brief review of the immune responses (innate, antibody, and T-cell) to SARS-CoV-2, including immune targets, correlates of protection, and duration of immunity is presented. Approaches to vaccine development including different vaccine platforms, critical attributes of novel vaccine candidates, the status of the ongoing clinical trials, and the ways to speed up vaccine development are also reviewed. Despite a historical average success rate of only 6%, and a usual gestation period of 10-12 years for the development of a new vaccine, the world is on the verge of developing COVID-19 vaccines in an extraordinary short time span.

[COVID-19 diagnostic tests: importance of the clinical context]

La actual pandemia de SARS-CoV-2 plantea numerosos retos sanitarios, entre los que destaca el uso adecuado e interpretación correcta de las pruebas diagnósticas disponibles en diferentes contextos clínicos. Como cualquier prueba diagnóstica, las de SARS-CoV-2 tienen limitaciones metodológicas de sensibilidad (S) y especificidad (E) que determinan su valor predictivo positivo (VPP) y negativo (VPN). Además, su rendimiento diagnóstico depende del contexto clínico en el que se evalúen, es decir de la probabilidad pretest. Este artículo revisa los principales aspectos metodológicos que influyen sobre la S, E, VPP y VPN de las pruebas diagnósticas de SARS-CoV-2 más habituales y discute su interpretación diagnóstica en diferentes escenarios clínicos.

A Comprehensive Review of the Global Efforts on COVID-19 Vaccine Development

This report examines various vaccine platforms including inactivated vaccines, protein-based vaccines, viral vector vaccines, and nucleic acid (DNA or mRNA) vaccines, and their ways of producing immunogens in cells.

An Overview of Current Knowledge of Deadly CoVs and Their Interface with Innate Immunity

Coronaviruses are a large family of zoonotic RNA viruses, whose infection can lead to mild or lethal respiratory tract disease. Severe Acute Respiratory Syndrome-Coronavirus-1 (SARS-CoV-1) first emerged in Guangdong, China in 2002 and spread to 29 countries, infecting 8089 individuals and causing 774 deaths. In 2012, Middle East Respiratory Syndrome-Coronavirus (MERS-CoV) emerged in Saudi Arabia and has spread to 27 countries, with a mortality rate of ~34%. In 2019, SARS-CoV-2 emerged and has spread to 220 countries, infecting over 100,000,000 people and causing more than 2,000,000 deaths to date. These three human coronaviruses cause diseases of varying severity. Most people develop mild, common cold-like symptoms, while some develop acute respiratory distress syndrome (ARDS). The success of all viruses, including coronaviruses, relies on their evolved abilities to evade and modulate the host anti-viral and pro-inflammatory immune responses. However, we still do not fully understand the transmission, phylogeny, epidemiology, and pathogenesis of MERS-CoV and SARS-CoV-1 and -2. Despite the rapid application of a range of therapies for SARS-CoV-2, such as convalescent plasma, remdesivir, hydroxychloroquine and type I interferon, no fully effective treatment has been determined. Remarkably, COVID-19 vaccine research and development have produced several offerings that are now been administered worldwide. Here, we summarise an up-to-date understanding of epidemiology, immunomodulation and ongoing anti-viral and immunosuppressive treatment strategies. Indeed, understanding the interplay between coronaviruses and the anti-viral immune response is crucial to identifying novel targets for therapeutic intervention, which may even prove invaluable for the control of future emerging coronavirus.

Intranasal administration of a recombinant RBD vaccine induced protective immunity against SARS-CoV-2 in mouse

The emergence of the global Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) pandemic underscores the importance of the rapid development of a non-invasive vaccine that can be easily administered. A vaccine administered by nasal delivery is endowed with such characteristics against respiratory viruses. In this study, we generated a recombinant SARS-CoV-2 receptor-binding domain (RBD)-based subunit vaccine. Mice were immunized via intranasal inoculation, microneedle-intradermal injection, or intramuscular injection, after which the RBD-specific immune responses were compared. Results showed that when administrated intranasally, the vaccine elicited a robust systemic humoral immunity with high titers of IgG antibodies and neutralizing antibodies as well as a significant mucosal immunity. Besides, antigen-specific T cell responses were also analyzed. These results indicated that the non-invasive intranasal administration should be explored for the future SARS-CoV-2 vaccine design.

COVID-19 vaccines: The status and perspectives in delivery points of view

Due to the high prevalence and long incubation periods often without symptoms, the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has infected millions of individuals globally, causing the coronavirus disease 2019 (COVID-19) pandemic. Even with the recent approval of the anti-viral drug, remdesivir, and Emergency Use Authorization of monoclonal antibodies against S protein, bamlanivimab and casirimab/imdevimab, efficient and safe COVID-19 vaccines are still desperately demanded not only to prevent its spread but also to restore social and economic activities via generating mass immunization. Recent Emergency Use Authorization of Pfizer and BioNTech’s mRNA vaccine may provide a pathway forward, but monitoring of long-term immunity is still required, and diverse candidates are still under development. As the knowledge of SARS-CoV-2 pathogenesis and interactions with the immune system continues to evolve, a variety of drug candidates are under investigation and in clinical trials. Potential vaccines and therapeutics against COVID-19 include repurposed drugs, monoclonal antibodies, antiviral and antigenic proteins, peptides, and genetically engineered viruses. This paper reviews the virology and immunology of SARS-CoV-2, alternative therapies for COVID-19 to vaccination, principles and design considerations in COVID-19 vaccine development, and the promises and roles of vaccine carriers in addressing the unique immunopathological challenges presented by the disease.

The immune response and immune evasion characteristics in SARS-CoV, MERS-CoV, and SARS-CoV-2: Vaccine design strategies

The worldwide outbreak of SARS-CoV-2, severe acute respiratory syndrome coronavirus 2 as a novel human coronavirus, was the worrying news at the beginning of 2020. Since its emergence complicated more than 870,000 individuals and led to more than 43,000 deaths worldwide. Considering to the potential threat of a pandemic and transmission severity of it, there is an urgent need to evaluate and realize this new virus's structure and behavior and the immunopathology of this disease to find potential therapeutic protocols and to design and develop effective vaccines. This disease is able to agitate the response of the immune system in the infected patients, so ARDS, as a common consequence of immunopathological events for infections with Middle East respiratory syndrome coronavirus (MERS-CoV), SARS-CoV, and SARS-CoV-2, could be the main reason for death. Here, we summarized the immune response and immune evasion characteristics in SARS-CoV, MERS-CoV, and SARS-CoV-2 and therapeutic and prophylactic strategies with a focus on vaccine development and its challenges.

COVID-19: Current knowledge in clinical features, immunological responses, and vaccine development

The COVID-19 pandemic has unfolded to be the most challenging global health crisis in a century. In 11 months since its first emergence, according to WHO, the causative infectious agent SARS-CoV-2 has infected more than 100 million people and claimed more than 2.15 million lives worldwide. Moreover, the world has raced to understand the virus and natural immunity and to develop vaccines. Thus, within a short 11 months a number of highly promising COVID-19 vaccines were developed at an unprecedented speed and are now being deployed via emergency use authorization for immunization. Although a considerable number of review contributions are being published, all of them attempt to capture only a specific aspect of COVID-19 or its therapeutic approaches based on ever-expanding information. Here, we provide a comprehensive overview to conceptually thread together the latest information on global epidemiology and mitigation strategies, clinical features, viral pathogenesis and immune responses, and the current state of vaccine development.

Neurological involvement of COVID-19: from neuroinvasion and neuroimmune crosstalk to long-term consequences

As the coronavirus disease 2019 (COVID-19) pandemic continues to be a multidimensional threat to humanity, more evidence of neurological involvement associated with it has emerged. Neuroimmune interaction may prove to be important not only in the pathogenesis of neurological manifestations but also to prevent systemic hyperinflammation. In this review, we summarize reports of COVID-19 cases with neurological involvement, followed by discussion of possible routes of entry, immune responses against coronavirus infection in the central nervous system and mechanisms of nerve degeneration due to viral infection and immune responses. Possible mechanisms for neuroprotection and virus-associated neurological consequences are also discussed.

Distinct Features and Functions of Systemic and Mucosal Humoral Immunity Among SARS-CoV-2 Convalescent Individuals

Understanding humoral immune responses to SARS-CoV-2 infection will play a critical role in the development of vaccines and antibody-based interventions. We report systemic and mucosal antibody responses in convalescent individuals who experienced varying severity of disease. Whereas assessment of neutralization and antibody-mediated effector functions revealed polyfunctional antibody responses in serum, only robust neutralization and phagocytosis were apparent in nasal wash samples. Serum neutralization and effector functions correlated with systemic SARS-CoV-2-specific IgG response magnitude, while mucosal neutralization was associated with nasal SARS-CoV-2-specific IgA. Antibody depletion experiments support the mechanistic relevance of these correlations. Associations between nasal IgA responses, virus neutralization at the mucosa, and less severe disease suggest the importance of assessing mucosal immunity in larger natural infection cohorts. Further characterization of antibody responses at the portal of entry may define their ability to contribute to protection from infection or reduced risk of hospitalization, informing public health assessment strategies and vaccine development efforts.

IgA dominates the early neutralizing antibody response to SARS-CoV-2

Humoral immune responses are typically characterized by primary IgM antibody responses followed by secondary antibody responses associated with immune memory and composed of IgG, IgA, and IgE. Here, we measured acute humoral responses to SARS-CoV-2, including the frequency of antibody-secreting cells and the presence of SARS-CoV-2-specific neutralizing antibodies in the serum, saliva, and bronchoalveolar fluid of 159 patients with COVID-19. Early SARS-CoV-2-specific humoral responses were dominated by IgA antibodies. Peripheral expansion of IgA plasmablasts with mucosal homing potential was detected shortly after the onset of symptoms and peaked during the third week of the disease. The virus-specific antibody responses included IgG, IgM, and IgA, but IgA contributed to virus neutralization to a greater extent compared with IgG. Specific IgA serum concentrations decreased notably 1 month after the onset of symptoms, but neutralizing IgA remained detectable in saliva for a longer time (days 49 to 73 post-symptoms). These results represent a critical observation given the emerging information as to the types of antibodies associated with optimal protection against reinfection and whether vaccine regimens should consider targeting a potent but potentially short-lived IgA response.

Identification of 22 N-glycosites on spike glycoprotein of SARS-CoV-2 and accessible surface glycopeptide motifs: Implications for vaccination and antibody therapeutics

Coronaviruses hijack human enzymes to assemble the sugar coat on their spike glycoproteins. The mechanisms by which human antibodies may recognize the antigenic viral peptide epitopes hidden by the sugar coat are unknown. Glycosylation by insect cells differs from the native form produced in human cells, but insect cell-derived influenza vaccines have been approved by the US Food and Drug Administration. In this study, we analyzed recombinant severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein secreted from BTI-Tn-5B1-4 insect cells, by trypsin and chymotrypsin digestion followed by mass spectrometry analysis. We acquired tandem mass spectrometry (MS/MS) spectrums for glycopeptides of all 22 predicted N-glycosylated sites. We further analyzed the surface accessibility of spike proteins according to cryogenic electron microscopy and homolog-modeled structures and available antibodies that bind to SARS-CoV-1. All 22 N-glycosylated sites of SARS-CoV-2 are modified by high-mannose N-glycans. MS/MS fragmentation clearly established the glycopeptide identities. Electron densities of glycans cover most of the spike receptor-binding domain of SARS-CoV-2, except YQAGSTPCNGVEGFNCYFPLQSYGFQPTNGVGYQ, similar to a region FSPDGKPCTPPALNCYWPLNDYGFYTTTGIGYQ in SARS-CoV-1. Other surface-exposed domains include those located on central helix, connecting region, heptad repeats and N-terminal domain. Because the majority of antibody paratopes bind to the peptide portion with or without sugar modification, we propose a snake-catching model for predicted paratopes: a minimal length of peptide is first clamped by a paratope and sugar modifications close to the peptide either strengthen or do not hinder the binding.

Novel insights into the treatment of SARS-CoV-2 infection: An overview of current clinical trials

The emergence of the global pandemic caused by the novel SARS-CoV-2 virus has motivated scientists to find a definitive treatment or a vaccine against it in the shortest possible time. Current efforts towards this goal remain fruitless without a full understanding of the behavior of the virus and its adaptor proteins. This review provides an overview of the biological properties, functional mechanisms, and molecular components of SARS-CoV-2, along with investigational therapeutic and preventive approaches for this virus. Since the proteolytic cleavage of the S protein is critical for virus penetration into cells, a set of drugs, such as chloroquine, hydroxychloroquine, camostat mesylate have been tested in clinical trials to suppress this event. In addition to angiotensin-converting enzyme 2, the role of CD147 in the viral entrance has also been proposed. Mepolizumab has shown to be effective in blocking the virus's cellular entrance. Antiviral drugs, such as remdesivir, ritonavir, oseltamivir, darunavir, lopinavir, zanamivir, peramivir, and oseltamivir, have also been tested as treatments for COVID-19. Regarding preventive vaccines, the whole virus, vectors, nucleic acids, and structural subunits have been suggested for vaccine development. Mesenchymal stem cells and natural killer cells could also be used against SARS-CoV-2. All the above-mentioned strategies, as well as the role of nanomedicine for the diagnosis and treatment of SARS-CoV-2 infection, have been discussed in this review.

Prospects for mucosal vaccine: shutting the door on SARS-CoV-2

The sudden emergence of a highly transmissible and pathogenic coronavirus SARS-CoV-2 in December 2019 from China and its rapid global spread has posed an international health emergency. The rapid development of an effective vaccine is imperative to control the spread of SARS-CoV-2. A number of concurrent efforts to find an effective therapeutic agent or vaccine for COVID-19 (coronavirus disease 2019) are being undertaken globally. Oral and nasal mucosal surfaces serve as the primary portal of entry for pathogens like coronaviruses in the human body. As evidenced by studies on similar coronaviruses (SARS-CoV and MERS-CoV), mucosal vaccination can provide a safe and effective means for the induction of long-lasting systemic and mucosal immunity to confer protection against SARS-CoV-2. This article summarizes the approaches to an effective mucosal vaccine formulation which can be a rewarding approach to combat the unprecedented threat posed by this emerging global pandemic.

A review of COVID-19 vaccines and major considerations for diabetic patients

The necessity and impact of SARS-CoV2 on the world's health have led to developing and producing practical and useful vaccines for this deadly respiratory virus. Since April 2020, a vaccine for the virus has been developed. Given that comorbidities such as diabetes, hypertension, and cardiovascular disease are more prone to viruses and the risk of infection, vaccines should be designed to protect against high-risk respiratory illnesses. Including SARS, MERS, influenza, and the SARS-CoV-2 provide a safe immune response. Here, we review the information and studies that have been done to help develop strategies and perspectives for producing a safe and ideal vaccine to prevent COVID-19 in normal people, especially at high-risk groups such as diabetes patients.

Applying Immune Instincts and Maternal Intelligence from Comparative Microbiology to COVID-19

New data specific to COVID-19 are emerging quickly on key issues of immunity and prevention, but past research in coronavirology and for other human pathogens (e.g., Mycoplasma pneumoniae) has been available and of great relevance. Considerable study of endemic human coronaviruses has shown that neutralizing antibody correlates with protection, but effective clinical protection is variable for subsequent virus exposure. Animal coronavirus research has emphasized the importance of local mucosal protection (especially IgA) and systemic responses. Animal model and human post-infection studies for SARS-CoV and MERS-CoV are largely corroborative. Whether for passive therapeutic strategies or vaccination, these findings provide a template for COVID-19. Many approaches to vaccination have emerged, and there may be more than one vaccine that will be applied, but individualized obstacles and concerns for administration, efficacy, and safety are inevitable. Regardless of safeguards or promises that may be understood from laboratory or vertebrate experiments, observations from large-scale human trials will ultimately prove to shape the medical future. Focus on common mucosal immunity can be underrated, and equally or more, focus on lactogenic immunity may be underestimated. In understanding both passive immunity and protection, the body is already primed to educate us with decisions of what constitutes protection and harm. This review provides key insights that drive hypotheses into how the instinct of immunity and the intelligence of the maternal component of the common mucosal immune system has already guided us and may continue to do so effectively into a bright and safe future.

Adjuvants for Coronavirus Vaccines

Vaccine development utilizing various platforms is one of the strategies that has been proposed to address the coronavirus disease 2019 (COVID-19) pandemic. Adjuvants are critical components of both subunit and certain inactivated vaccines because they induce specific immune responses that are more robust and long-lasting. A review of the history of coronavirus vaccine development demonstrates that only a few adjuvants, including aluminum salts, emulsions, and TLR agonists, have been formulated for the severe acute respiratory syndrome-associated coronavirus (SARS-CoV), Middle East respiratory syndrome-related coronavirus (MERS-CoV), and currently the SARS-CoV-2 vaccines in experimental and pre-clinical studies. However, there is still a lack of evidence regarding the effects of the adjuvants tested in coronavirus vaccines. This paper presents an overview of adjuvants that have been formulated in reported coronavirus vaccine studies, which should assist with the design and selection of adjuvants with optimal efficacy and safety profiles for COVID-19 vaccines.

Overview of the current promising approaches for the development of an effective severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine

Coronavirus disease 2019 (COVID-19) is a pandemic infectious disease caused by the novel coronavirus called SARS-CoV-2. There is a gap in our understanding regarding the immunopathogenesis of COVID-19. However, many clinical trials are underway across the world for screening effective drugs against COVID-19. Nevertheless, currently, no proven effective therapies for this virus exists. The vaccines are deemed as a significant part of disease prevention for emerging viral diseases, since, in several cases, other therapeutic choices are limited or non-existent, or that diseases result in such an accelerated clinical worsening that the efficacy of treatments is restricted. Therefore, effective vaccines against COVID-19 are urgently required to overcome the tremendous burden of mortality and morbidity correlated with SARS-CoV-2. In this review, we will describe the latest evidence regarding outstanding vaccine approaches and the challenges for vaccine production.

COVID-2019 - A comprehensive pathology insight

Corona virus disease-2019 (COVID-19) caused by severe acute respiratory syndrome corona virus-2 (SARS CoV-2), a highly contagious single stranded RNA virus genetically related to SARS CoV. The lungs are the main organs affected leading to pneumonia and respiratory failure in severe cases that may need mechanical ventilation. Occasionally patient may present with gastro-intestinal, cardiac and neurologic symptoms with or without lung involvement. Pathologically, the lungs show either mild congestion and alveolar exudation or acute respiratory distress syndrome (ARDS) with hyaline membrane or histopathology of acute fibrinous organizing pneumonia (AFOP) that parallels disease severity. Other organs like liver and kidneys may be involved secondarily. Currently the treatment is principally symptomatic and prevention by proper use of personal protective equipment and other measures is crucial to limit the spread. In the midst of pandemic there is paucity of literature on pathological features including pathogenesis, hence in this review we provide the current pathology centered understanding of COVID-19. Furthermore, the pathogenetic pathway is pivotal in the development of therapeutic targets.

Perspectives on development of vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)

The recent outbreak of Coronavirus Disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has been characterized by the World Health Organization (WHO) as a controllable global pandemic. The spike (S) glycoprotein mediates binding to the angiotensin-converting enzyme 2 (ACE2) receptor for virus entry and also services as the target of virus-neutralizing antibodies, making it an attractive and leading viral antigen for vaccine development. No vaccine against any human coronavirus is available to date. In learning from the experience of developing Middle East respiratory syndrome coronavirus (MERS-CoV) and SARS-CoV vaccine candidates in preclinical and clinical trials, the most promising strategies for SARS-CoV-2 vaccines should employ viral-vector platforms, properly adjuvanted recombinant protein or DNA/mRNA encoding an engineered sequence of trimeric S protein in pre-fusion conformation.