Development of SARS-CoV-2 neutralizing antibody detection assay by using recombinant plant-produced proteins.

Detecting immunity against SARS-CoV-2 is vital for evaluating vaccine response and natural infection, but conventional virus neutralization test (cVNT) requires BSL3 and live viruses, and pseudo-virus neutralization test (pVNT) needs specialized equipment and trained professionals. The surrogate virus neutralization test (sVNT) was developed to overcome these limitations. This study explored the use of angiotensin converting enzyme 2 (ACE2) produced from Nicotiana benthamiana for the development of an affordable neutralizing antibodies detection assay. The results showed that the plant-produced ACE2 can bind to the receptor binding domain (RBD) of the SARS-CoV-2, and was used to develop sVNT with plant-produced RBD protein. The sVNT developed using plant-produced proteins showed high sensitivity and specificity when validated with a group of 30 RBD vaccinated mice sera and the results were correlated with cVNT titer. This preliminary finding suggests that the plants could offer a cost-effective platform for producing diagnostic reagents.

Preclinical evaluation of immunogenicity, efficacy and safety of a recombinant plant-based SARS-CoV-2 RBD vaccine formulated with 3M-052-Alum adjuvant.

Cost-effective, and accessible vaccines are needed for mass immunization to control the ongoing coronavirus disease 2019 (COVID-19), especially in low- and middle-income countries (LMIC).A plant-based vaccine is an attractive technology platform since the recombinant proteins can be easily produced at large scale and low cost. For the recombinant subunit-based vaccines, effective adjuvants are crucial to enhance the magnitude and breadth of immune responses elicited by the vaccine. In this study, we report a preclinical evaluation of the immunogenicity, efficacy and safety of a recombinant plant-based SARS-CoV-2 RBD vaccine formulated with 3M-052 (TLR7/8 agonist)-Alum adjuvant. This vaccine formulation, named Baiya SARS-CoV-2 Vax 2, induced significant levels of RBD-specific IgG and neutralizing antibody responses in mice. A viral challenge study using humanized K18-hACE2 mice has shown that animals vaccinated with two doses of Baiya SARS-CoV-2 Vax 2 established immune protection against SARS-CoV-2. A study in nonhuman primates (cynomolgus monkeys) indicated that immunization with two doses of Baiya SARS-CoV-2 Vax 2 was safe, well tolerated, and induced neutralizing antibodies against the prototype virus and other viral variants (Alpha, Beta, Gamma, Delta, and Omicron subvariants). The toxicity of Baiya SARS-CoV-2 Vax 2 was further investigated in Jcl:SD rats, which demonstrated that a single dose and repeated doses of Baiya SARS-CoV-2 Vax 2 were well tolerated and no mortality or unanticipated findings were observed. Overall, these preclinical findings support further clinical development of Baiya SARS-CoV-2 Vax 2.

A recombinant subunit vaccine candidate produced in plants elicits neutralizing antibodies against SARS-CoV-2 variants in macaques.

Since the outbreak of the coronavirus disease (COVID) pandemic in 2019, the development of effective vaccines to combat the infection has been accelerated. With the recent emergence of highly transmissible severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern (VOC), there are concerns regarding the immune escape from vaccine-induced immunity. Hence an effective vaccine against VOC with a potent immune response is required. Our previous study confirmed that the two doses of the plant-produced receptor-binding domain (RBD) of SARS-CoV-2 fused with the Fc region of human IgG1, namely Baiya SARS-CoV-2 Vax 1, showed high immunogenicity in mice and monkeys. Here, we aimed to evaluate the immunogenicity of a three-dose intramuscular injection of Baiya SARS-CoV-2 Vax 1 on days 0, 21, and 133 in cynomolgus monkeys. At 14 days after immunization, blood samples were collected to determine RBD-specific antibody titer, neutralizing antibody, and pseudovirus neutralizing antibody titers. Immunized monkeys developed significantly high levels of antigen-specific antibodies against SARS-CoV-2 compared to the control group. Interestingly, the sera collected from immunized monkeys also showed a neutralizing antibody response against the SARS-CoV-2 VOCs; Alpha, Beta, Gamma, Delta, and Omicron. These findings demonstrate that a three-dose regimen of Baiya SARS-CoV-2 Vax 1 vaccine elicits neutralizing immune response against SARS-CoV-2 variants.

Plant-produced recombinant SARS-CoV-2 receptor-binding domain; an economical, scalable biomaterial source for COVID-19 diagnosis.

The outbreak of the novel coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), spread rapidly causing a severe global health burden. The standard COVID-19 diagnosis relies heavily on molecular tests to detect viral RNA in patient samples; however, this method is costly, requires highly-equipped laboratories, multiple reagents, skilled laboratory technicians, and takes 3-6 hours to complete. To overcome these limitations, we developed a plant-based production platform for the SARS-CoV-2 receptor-binding domain as an economical source of detection reagents for a lateral-flow immunoassay strip (LFIA) which is suitable for detection of IgM/IgG antibodies in human samples. Further, we validated the plant-produced SARS-CoV-2 receptor-binding domain-based LFIA as a useful diagnostic tool for COVID-19. A total of 51 confirmed COVID-19 serum samples were tested using the LFIA, and the obtained results were consistent with those from polymerase chain reaction assays, while providing sensitivity and specificity of 94.1% and 98%, respectively. The developed LFIA is rapid, scalable, user-friendly, and relatively inexpensive with a simple test procedure, making it useful for the routine monitoring of COVID-19 in clinical settings. This study was approved on March 19, 2020 by the Ethics Committee of the Faculty of Medicine, Chulalongkorn University (COA No. 354/2020 and IRB No. 236/63).

Immunogenicity and efficacy of recombinant subunit SARS-CoV-2 vaccine candidate in the Syrian hamster model.

SARS-CoV-2 causes devastating impact on the human population and has become a major public health concern. The frequent emergence of SARS-CoV-2 variants of concern urges the development of safe and efficacious vaccine against SARS-CoV-2 variants. We developed a candidate vaccine Baiya SARS-CoV-2 Vax 1, based on SARS-CoV-2 receptor-binding domain (RBD) by fusing with the Fc region of human IgG. The RBD-Fc fusion was produced in Nicotiana benthamiana. Previously, we reported that this plant-produced vaccine is effective in inducing immune response in both mice and non-human primates. Here, the efficacy of our vaccine candidate was tested in Syrian hamster challenge model. Hamsters immunized with two intramuscular doses of Baiya SARS-CoV-2 Vax 1 induced neutralizing antibodies against SARS-CoV-2 and protected from SARS-CoV-2 challenge with reduced viral load in the lungs. These preliminary results demonstrate the ability of plant-produced subunit vaccine Baiya SARS-CoV-2 Vax 1 to provide protection against SARS-CoV-2 infection in hamsters.

Plant-Produced S1 Subunit Protein of SARS-CoV-2 Elicits Immunogenic Responses in Mice.

SARS-CoV-2 is responsible for the ongoing COVID-19 pandemic. The virus spreads rapidly with a high transmission rate among humans, and hence virus management has been challenging owing to finding specific therapies or vaccinations. Hence, an effective, low-cost vaccine is urgently required. In this study, the immunogenicity of the plant-produced S1 subunit protein of SARS-CoV-2 was examined in order to assess it as a potential candidate for SARS-CoV-2. The SARS-CoV-2 S1-Fc fusion protein was transiently produced in Nicotiana benthamiana. Within four days of infiltration, the SARS-CoV-2 S1-Fc protein was expressed in high quantities, and using protein A affinity column chromatography, plant-produced S1-Fc protein was purified from the crude extracts. The characterization of plant-produced S1-Fc protein was analyzed by SDS-PAGE and Western blotting. Immunogenicity of the purified S1-Fc protein formulated with alum induced both RBD specific antibodies and T cell immune responses in mice. These preliminary results indicated that the plant-produced S1 protein is immunogenic in mice.

Preclinical evaluation of a plant-derived SARS-CoV-2 subunit vaccine: Protective efficacy, immunogenicity, safety, and toxicity.

Coronavirus disease 2019 (COVID-19) is an acute respiratory illness caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The prevention of SARS-CoV-2 transmission has become a global priority. Previously, we showed that a protein subunit vaccine that was developed based on the fusion of the SARS-CoV-2 receptor-binding domain (RBD) to the Fc portion of human IgG1 (RBD-Fc), produced in Nicotiana benthamiana, and adjuvanted with alum, namely, Baiya SARS-CoV-2 Vax 1, induced potent immunological responses in both mice and cynomolgus monkeys. Hence, this study evaluated the protective efficacy, safety, and toxicity of Baiya SARS-CoV-2 Vax 1 in K18-hACE2 mice, monkeys and Wistar rats. Two doses of vaccine were administered three weeks apart on Days 0 and 21. The administration of the vaccine to K18-hACE2 mice reduced viral loads in the lungs and brains of the vaccinated animals and protected the mice against challenge with SARS-CoV-2. In monkeys, the results of safety pharmacology tests, general clinical observations, and a core battery of studies of three vital systems, namely, the central nervous, cardiovascular, and respiratory systems, did not reveal any safety concerns. The toxicology study of the vaccine in rats showed no vaccine-related pathological changes, and all the animals remained healthy under the conditions of this study. Furthermore, the vaccine did not cause any abnormal toxicity in rats and was clinically tolerated even at the highest tested concentration. In addition, general health status, body temperature, local toxicity at the administration site, hematology, and blood chemistry parameters were also monitored. Overall, this work presents the results of the first systematic study of the safety profile of a plant-derived vaccine, Baiya SARS-CoV-2 Vax 1; this approach can be considered a viable strategy for the development of vaccines against COVID-19.

Receptor binding domain proteins of SARS-CoV-2 variants produced in Nicotiana benthamiana elicit neutralizing antibodies against variants of concern.

The constantly emerging severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) variants of concerns (VOCs) with mutations in the receptor-binding domain (RBD) spread rapidly and has become a severe public health problem worldwide. Effective vaccines and optimized booster vaccination strategies are thus highly required. Here, the gene encoding six different RBD (Alpha, Beta, Gamma, Kappa, Delta, and Epsilon variants) along with the Fc fragment of human IgG1 (RBD-Fc) was cloned into plant expression vector and produced in Nicotiana benthamiana by transient expression. Further, the immunogenicity of plant-produced variant RBD-Fc fusion proteins were tested in cynomolgus monkeys. Each group of cynomolgus monkeys was immunized three times intramuscularly with variant RBD-Fc vaccines at Day 0, 21, 42, and neutralizing antibody responses were evaluated against ancestral (Wuhan), Alpha, Beta, Gamma, and Delta variants. The results showed that three doses of the RBD-Fc vaccine significantly enhanced the immune response against all tested SARS-CoV-2 variants. In particular, the vaccines based on Delta and Epsilon mutant RBD elicit broadly neutralizing antibodies against ancestral (Wuhan), Alpha, and Delta SARS-CoV-2 variants whereas Beta and Gamma RBD-Fc vaccines elicit neutralizing antibodies against their respective SARS-CoV-2 strains. The Delta and Epsilon RBD-Fc based vaccines displayed cross-reactive immunogenicity and might be applied as a booster vaccine to induce broadly neutralizing antibodies. These proof-of-concept results will be helpful for the development of plant-derived RBD-Fc-based vaccines against SARS-CoV-2 and its variants.

Chapter 12 - SARS-CoV-2 vaccines: current trends and prospects of developing plant-derived vaccines

The recent emergence of the highly pathogenic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the pandemic of coronavirus disease 2019 (COVID-19), which has major impact on global health and economy. Due to the rampage caused by SARS-CoV-2, the World Health Organization (WHO) declared the outbreak as a public health emergency of international concern and pandemic in early 2020. Despite the substantial efforts, few licensed vaccines or drugs are available for COVID-19 treatment. Affordable and effective vaccines are the best and safest possible approach to mitigate the impact of the outbreak and prevent future infection. In this scenario, the development of cost-effective vaccines is essential to ensure equitable access especially for those living in middle-income and low-income countries. Plant expression systems offer unique advantages and are considered as low-cost alternatives for recombinant biopharmaceuticals production in the recent decades. The advancement of plant-based technologies offers many possibilities to produce recombinant vaccines in plants against SARS-CoV-2. Here, we discussed about the emergence and transmission of SARS-CoV-2 and the state of art in developing plant-based candidate vaccines in the fight against COVID-19.

Potential for Developing Plant-Derived Candidate Vaccines and Biologics against Emerging Coronavirus Infections.

The emerging human coronavirus infections in the 21st century remain a major public health crisis causing worldwide impact and challenging the global health care system. The virus is circulating in several zoonotic hosts and continuously evolving, causing occasional outbreaks due to spill-over events occurring between animals and humans. Hence, the development of effective vaccines or therapeutic interventions is the current global priority in order to reduce disease severity, frequent outbreaks, and to prevent future infections. Vaccine development for newly emerging pathogens takes a long time, which hinders rapid immunization programs. The concept of plant-based pharmaceuticals can be readily applied to meet the recombinant protein demand by means of transient expression. Plants are evolved as an expression platform, and they bring a combination of unique interests in terms of rapid scalability, flexibility, and economy for industrial-scale production of effective vaccines, diagnostic reagents, and other biopharmaceuticals. Plants offer safe biologics to fulfill emergency demands, especially during pandemic situations or outbreaks caused by emerging strains. This review highlights the features of a plant expression platform for producing recombinant biopharmaceuticals to combat coronavirus infections with emphasis on COVID-19 vaccine and biologics development.

Plant-produced SARS-CoV-2 receptor binding domain (RBD) variants showed differential binding efficiency with anti-spike specific monoclonal antibodies.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is responsible for the ongoing coronavirus disease (COVID-19) pandemic which is characterized by respiratory illness and severe pneumonia, and currently accounts for > 2.5 million deaths worldwide. Recently, diverse mutations in the spike protein of SARS-CoV-2 were reported in United Kingdom (Alpha) and South Africa (Beta) strains which raise concerns over the potential increase in binding affinity towards the host cell receptor and diminished host neutralization capabilities. In order to study the effect of mutation in the binding efficiency of SARS-CoV-2 receptor binding domain (RBD) with anti-SARS-CoV/CoV-2 monoclonal antibodies (mAbs), we have produced SARS-CoV-2 RBD and two variants SARS-CoV-2 RBD (Alpha RBD and Beta RBD) in Nicotiana benthamiana by transient expression. Plant-produced SARS-CoV-2 RBD-Fc, Alpha RBD-Fc and Beta RBD-Fc exhibited specific binding to human angiotensin converting enzyme 2 (ACE2) receptor determined by ELISA. Intriguingly, the binding of plant-produced SARS-CoV-2 RBD proteins to plant-produced mAbs CR3022, B38, and H4 was found to be different depending on the variant mutation. In contrary to the plant-produced SARS-CoV-2 RBD-Fc and Alpha RBD-Fc, Beta RBD-Fc variant showed weak binding affinity towards the mAbs. The result suggested that the Beta RBD variant might have acquired partial resistance to neutralizing antibodies compared to other variants. However, further studies with sera from convalescent or vaccinated individuals are required to confirm this finding.

Immunogenicity Studies of Plant-Produced SARS-CoV-2 Receptor Binding Domain-Based Subunit Vaccine Candidate with Different Adjuvant Formulations.

Due to the rapid transmission of the coronavirus disease 2019 (COVID-19) causing serious public health problems and economic burden, the development of effective vaccines is a high priority for controlling the virus spread. Our group has previously demonstrated that the plant-produced receptor-binding domain (RBD) of SARS-CoV-2 fused with Fc of human IgG was capable of eliciting potent neutralizing antibody and cellular immune responses in animal studies, and the immunogenicity could be improved by the addition of an alum adjuvant. Here, we performed a head-to-head comparison of different commercially available adjuvants, including aluminum hydroxide gel (alum), AddaVax (MF59), monophosphoryl lipid A from Salmonella minnesota R595 (mPLA-SM), and polyinosinic-polycytidylic acid (poly(I:C)), in mice by combining them with plant-produced RBD-Fc, and the differences in the immunogenicity of RBD-Fc with different adjuvants were evaluated. The specific antibody responses in terms of total IgG, IgG1, and IgG2a subtypes and neutralizing antibodies, as well as vaccine-specific T-lymphocyte responses, induced by the different tested adjuvants were compared. We observed that all adjuvants tested here induced a high level of total IgG and neutralizing antibodies, but mPLA-SM and poly (I:C) showed the induction of a balanced IgG1 and IgG2a (Th2/Th1) immune response. Further, poly (I:C) significantly increased the frequency of IFN-γ-expressing cells compared with control, whereas no significant difference was observed between the adjuvanted groups. This data revealed the adjuvants' role in enhancing the immune response of RBD-Fc vaccination and the immune profiles elicited by different adjuvants, which could prove helpful for the rational development of next-generation SARS-CoV-2 RBD-Fc subunit vaccines. However, additional research is essential to further investigate the efficacy and safety of this vaccine formulation before clinical trials.

Plant-Produced Receptor-Binding Domain of SARS-CoV-2 Elicits Potent Neutralizing Responses in Mice and Non-human Primates.

The emergence of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has affected global public health and economy. Despite the substantial efforts, only few vaccines are currently approved and some are in the different stages of clinical trials. As the disease rapidly spreads, an affordable and effective vaccine is urgently needed. In this study, we investigated the immunogenicity of plant-produced receptor-binding domain (RBD) of SARS-CoV-2 in order to use as a subunit vaccine. In this regard, RBD of SARS-CoV-2 was fused with Fc fragment of human IgG1 and transiently expressed in Nicotiana benthamiana by agroinfiltration. The plant-produced RBD-Fc fusion protein was purified from the crude extract by using protein A affinity column chromatography. Two intramuscular administration of plant-produced RBD-Fc protein formulated with alum as an adjuvant have elicited high neutralization titers in immunized mice and cynomolgus monkeys. Further it has induced a mixed Th1/Th2 immune responses and vaccine-specific T-lymphocyte responses which was confirmed by interferon-gamma (IFN-γ) enzyme-linked immunospot assay. Altogether, our results demonstrated that the plant-produced SARS-CoV-2 RBD has the potential to be used as an effective vaccine candidate against SARS-CoV-2. To our knowledge, this is the first report demonstrating the immunogenicity of plant-produced SARS-CoV-2 RBD protein in mice and non-human primates.

Development of Plant-Produced Recombinant ACE2-Fc Fusion Protein as a Potential Therapeutic Agent Against SARS-CoV-2.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of coronavirus disease (COVID-19) which has recently emerged as a potential threat to global public health. SARS-CoV-2 is the third known human coronavirus that has huge impact on the human population after SARS-CoV and MERS-CoV. Although some vaccines and therapeutic drugs are currently in clinical trials, none of them are approved for commercial use yet. As with SARS-CoV, SARS-CoV-2 utilizes angiotensin-converting enzyme 2 (ACE2) as the cell entry receptor to enter into the host cell. In this study, we have transiently produced human ACE2 fused with the Fc region of human IgG1 in Nicotiana benthamiana and the in vitro neutralization efficacy of the plant-produced ACE2-Fc fusion protein was assessed. The recombinant ACE2-Fc fusion protein was expressed in N. benthamiana at 100 µg/g leaf fresh weight on day 6 post-infiltration. The recombinant fusion protein showed potent binding to receptor binding domain (RBD) of SARS-CoV-2. Importantly, the plant-produced fusion protein exhibited potent anti-SARS-CoV-2 activity in vitro. Treatment with ACE2-Fc fusion protein after viral infection dramatically inhibit SARS-CoV-2 infectivity in Vero cells with an IC50 value of 0.84 µg/ml. Moreover, treatment with ACE2-Fc fusion protein at the pre-entry stage suppressed SARS-CoV-2 infection with an IC50 of 94.66 µg/ml. These findings put a spotlight on the plant-produced ACE2-Fc fusion protein as a potential therapeutic candidate against SARS-CoV-2.

Monoclonal Antibodies B38 and H4 Produced in Nicotiana benthamiana Neutralize SARS-CoV-2 in vitro.

The ongoing coronavirus disease 2019 (COVID-19) outbreak caused by novel zoonotic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was initially reported in Wuhan city, Hubei Province of China, in late December 2019. The rapid global spread of the virus calls for the urgent development of vaccines or therapeutics for human applications to combat the coronavirus infection. Monoclonal antibodies (mAbs) have been utilized as effective therapeutics for treating various infectious diseases. In the present study, we evaluated the feasibility of plant expression system for the rapid production of recently identified therapeutically suitable human anti-SARS-CoV-2 mAbs B38 and H4. Transient co-expression of heavy-chain and light-chain sequences of both the antibodies by using plant expression geminiviral vector resulted in rapid accumulation of assembled mAbs in Nicotiana benthamiana leaves within 4 days post-infiltration. Furthermore, both the mAbs were purified from the plant crude extracts with single-step protein A affinity column chromatography. The expression level of mAb B38 and H4 was estimated to be 4 and 35 µg/g leaf fresh weight, respectively. Both plant-produced mAbs demonstrated specific binding to receptor binding domain (RBD) of SARS-CoV-2 and exhibited efficient virus neutralization activity in vitro. To the best of our knowledge, this is the first report of functional anti-SARS-CoV-2 mAbs produced in plants, which demonstrates the ability of using a plant expression system as a suitable platform for the production of effective, safe, and affordable SARS-CoV-2 mAbs to fight against the spread of this highly infectious pathogen.

Rapid production of SARS-CoV-2 receptor binding domain (RBD) and spike specific monoclonal antibody CR3022 in Nicotiana benthamiana.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is responsible for the ongoing global outbreak of coronavirus disease (COVID-19) which is a significant threat to global public health. The rapid spread of COVID-19 necessitates the development of cost-effective technology platforms for the production of vaccines, drugs, and protein reagents for appropriate disease diagnosis and treatment. In this study, we explored the possibility of producing the receptor binding domain (RBD) of SARS-CoV-2 and an anti-SARS-CoV monoclonal antibody (mAb) CR3022 in Nicotiana benthamiana. Both RBD and mAb CR3022 were transiently produced with the highest expression level of 8 µg/g and 130 µg/g leaf fresh weight respectively at 3 days post-infiltration. The plant-produced RBD exhibited specific binding to the SARS-CoV-2 receptor, angiotensin-converting enzyme 2 (ACE2). Furthermore, the plant-produced mAb CR3022 binds to SARS-CoV-2, but fails to neutralize the virus in vitro. This is the first report showing the production of anti-SARS-CoV-2 RBD and mAb CR3022 in plants. Overall these findings provide a proof-of-concept for using plants as an expression system for the production of SARS-CoV-2 antigens and antibodies or similar other diagnostic reagents against SARS-CoV-2 rapidly, especially during epidemic or pandemic situation.

Emergence of Novel Coronavirus 2019-nCoV: Need for Rapid Vaccine and Biologics Development.

Novel Coronavirus (2019-nCoV) is an emerging pathogen that was first identified in Wuhan, China in late December 2019. This virus is responsible for the ongoing outbreak that causes severe respiratory illness and pneumonia-like infection in humans. Due to the increasing number of cases in China and outside China, the WHO declared coronavirus as a global health emergency. Nearly 35,000 cases were reported and at least 24 other countries or territories have reported coronavirus cases as early on as February. Inter-human transmission was reported in a few countries, including the United States. Neither an effective anti-viral nor a vaccine is currently available to treat this infection. As the virus is a newly emerging pathogen, many questions remain unanswered regarding the virus's reservoirs, pathogenesis, transmissibility, and much more is unknown. The collaborative efforts of researchers are needed to fill the knowledge gaps about this new virus, to develop the proper diagnostic tools, and effective treatment to combat this infection. Recent advancements in plant biotechnology proved that plants have the ability to produce vaccines or biopharmaceuticals rapidly in a short time. In this review, the outbreak of 2019-nCoV in China, the need for rapid vaccine development, and the potential of a plant system for biopharmaceutical development are discussed.

Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2): An Emerging Zoonotic Respiratory Pathogen in Humans

Two highly human pathogenic coronaviruses outbreak in the beginning of 21st century i.e. Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) and Middle East Respiratory Syndrome Coronavirus (MERS-CoV) in 2002 and 2012 respectively caused high pathogenicity and fatality rates in human populations. Recently, a new coronavirus named as SARS-CoV-2 or nCoV-2019 was first reported in Wuhan, China in December 2019 which is responsible for an acute human respiratory illness referred as Coronavirus Disease (COVID-19), an ongoing pandemic. SARS-CoV-2 is the third known highly pathogenic virus affecting human population. This virus spread globally within few weeks of first identification and nearly 5.52 million confirmed cases with more than 3,47,000 deaths reported as of May 25, 2020. Till date, there are no specific anti-viral drugs, therapies or vaccines to contain and prevent this infectious pathogen outbreak. The global spread of this virus to over 210 countries resulted in both human and economic losses, highlighting the need for an immediate imperative research exploration on prophylactic and therapeutic measures. Current knowledge and understanding of the pathogenesis of similar coronavirus SARS-CoV and MERS-CoV might be helpful for the rapid development of treatment strategies to prevent the further spread of this virus. In this review, we recapitulate the topical understanding on the structure, pathogenesis and epidemiology of SARS-CoV-2 that has emerged as a major health concern worldwide.