key: cord-0687829-7op3x309 authors: Badgujar, Kirtikumar C.; Badgujar, Vivek C.; Badgujar, Shamkant B. title: Vaccine development against coronavirus (2003 to present): An overview, recent advances, current scenario, opportunities and challenges date: 2020-07-21 journal: Diabetes Metab Syndr DOI: 10.1016/j.dsx.2020.07.022 sha: 8f6c6887ed535b4d938608c2e8d8cf73c1912d10 doc_id: 687829 cord_uid: 7op3x309 BACKGROUND AND AIM: The pandemic COVID-19 occurring due to novel emerging coronavirus-2019 (SARS-CoV-2) is severely affecting the worldwide public health, culture, economy and human social behaviour. Till date, there is no approved medicine/treatment to cure COVID-19, whereas, vaccine development efforts are going on high priority. This review aimed to provide an overview of prior art, recent advances, vaccine designing strategies, current scenario, opportunities and challenges related to development of coronavirus vaccine. METHOD: A literature survey was conducted using Scopus, PubMed and Google Scholar with the search key as: coronavirus vaccine, SARS vaccine, MERS vaccine and COVID-19 vaccine. Articles related to above search query were retrieved, sorted, analyzed and developed into an easy-to-understand review. RESULTS: The genome phylogenetic analysis suggested that genomic sequence of SARS-CoV-2 is almost 80% similar to that of SARS-CoV, further both these viruses bind to same host cell receptor ACE-2. Hence it is expected that, previously available literature data about coronavirus vaccine designing may play crucial role in development of rapid vaccine against COVID-19. In view of this, the present review discuss (i) existing information (from 2003 to present) about the type of vaccine, antigen, immunogenic response, animal model, route of administration, adjuvants and current scenario for designing of coronavirus vaccine (ii) potential factors and challenges related to rapid development of COVID-19 vaccine. CONCLUSION: In conclusion, we suggest possible target sites for designing of vaccine against SARS-CoV-2 virus. Introduction: The novel coronavirus infection has been frequently emerging periodically in various countries around the globe which are of zoonotic origin and belongs to the family Coronaviridae [1] [2] [3] . These coronaviruses are specifically enveloped positive-sense single-stranded RNA virus which are particularly segregated into four various genera namely, α-coronavirus, β-coronavirus, γcoronavirus and δ-coronavirus [4] [5] [6] . The endemic coronavirus infection was first identified around 1960, while till date various seven coronavirus infections are identified [4, 5] . Four coronavirus infections (HCoV-229E, HCoV-OC43, HCoV-NL63 and HCoV-HKU1) were endemic which causes mild illness involving immune-compromised systems, common colds and flu like symptoms [4, 6] . to treat COVID-19, however none of the drug is approved by the FDA for the COVID-19 treatment [2, 3] . Further, infectivity of SARS-CoV-2 virus is much stronger compared to SARS-CoV virus with the basic reproductive number 3.0 to 5.7 which indicate the spreading of infection of COVID- The mission for designing of vaccine against COVID-19 is on high priority and considered as an essential global problem for a molecular biologist [16] . The vaccine designing attracted serious attention of the whole world with a generous anticipation in order to overcome from this pandemic outbreak [11] . Various reasons are attributed to develop the potential rapid vaccine on high priority. The fast globalization, increased international travel, immigration and drastic environmental changes led to increase appearance and spreading of novel viruses which may causes the chronic infectivity [15] [16] [17] . Vaccination is one of the important part of public health concern to combat various kinds of infectious diseases, that saved several lives in the medical history [17] . Effective vaccination is always important to break off the chain of virus infection as well as community virus transfer/ transmission [2, 3, 16, 17] . Further, vaccination can be used as a prophylaxis for the anti-viral treatment which boosts immune response against pathogen infection and offers protection from possible epidemic [17] . Moreover, public vaccination campaign also postpones various preventive measurement events such as social distancing, quarantine, lock-down, contact history and tracing etc [11, 13, 16, 17] . Thus the fundamental objective of the vaccination is to acquire the innate immunity and to get protected against highly contagious pathogens like SARS-CoV-2 [16, 17] . Future emergence: In the last two decades coronavirus outbreak seriously affected the human culture, life-style, natural human behaviour, and economy throughout the world [2, 3] . The Universal determinant for the coronavirus vaccine development has faded up as the SARS and MERS are no longer (extremely rare) seen after 2004 and 2013 epidemic outbreaks respectively ( Figure 1 ) [13, 18] . However, at present there is an urgent need to develop the vaccine in order to curb the present pandemic [15] [16] [17] [18] . Till date various six coronaviruses are known to infect human, while no vaccine is approved against coronavirus disease [6] . SARS-CoV-2 is the newly emerging seventh coronavirus and possibility for the further remerging mutated (eighth) novel coronavirus in Thus, considering all the above reasons, an efficient vaccine against COVID-19 may play a noteworthy role in controlling the spread of SAS-CoV-2 virus and hence the whole world is looking to get the successful vaccine as early as possible. However, vaccine designing is the challenging task which involves study of various factors such as determination of viral gene/protein/amino-acid, identification of effective antigen, route of immunization, animal model study, immune-response study, clinical trials, and safety concern etc. The specific efforts to design the effective vaccine have already been attempted/ started while review of some previously reported literatures may play a crucial role in development of vaccine. Vaccines that mimic the natural infection are the most extraordinary achievement in the medical history of human beings which save several millions lives every year [21] . In public health sector, these vaccines have worldwide impact in improving the human and animal health and standard of living [22] . In vaccination, various antigen peptides in recombinant form or in derived form or inactivated pathogenic form are employed to induce cell-mediated immunity [21] [22] [23] [24] [25] . Thus, the vaccination is ideal platform to develop defence mechanism against infectious diseases considering its higher selectivity as compared to antimicrobial agents [21] [22] [23] [24] [25] . Further, effective and safe vaccination is very essential in playing a chief role to break off the chain of disease transmission from zoonotic (wild-life) reservoirs or infected person to vulnerable hosts [11, 13, 16, 17] . Considering the zoonotic viruses disease such as coronaviruses diseases 2019, the invivo efficiency of developed SARS-CoV vaccine candidate may be helpful in looking at homologous gene sequence [9] . Nevertheless, the research related to development of SARS vaccine did not get its exclusive momentum, since, no new case has been reported in last 17 years [12, 13] . In mean time, some research groups have developed some vaccine strategies against coronavirus diseases which include the live-attenuated, inactivated vaccine, protein subunits, viral vector vaccine platforms . It is always a skilful, critical and challenging task to develop the vaccine within short period of time, which may take generally an average 1.5 to 3.0 years for possible successful designing of vaccine against newly emerging pathogen [8, 15, 16, 17] . The hurry/rush/race in development of fast-track vaccine (under any influence) may be dangerous [15, 16] . Looking at this urgent need, several previous coronavirus vaccine designing attempts/ literature cannot be ignored which may offers a possible significant clue to deliver a successful vaccine against COVID-19 within a short period of time. The antiviral vaccines development strategies include first generation vaccine (live-attenuated and inactivated vaccine), second generation vaccine (protein subunit and vector base vaccine), and third generation vaccine (nucleic acid and nano-material based vaccine). Historically, live attenuated vaccines have always received great importance because of its quickly available high immunogenic response due to presence of natural antigenic material [21] . It is successfully used against various infectious diseases such as polio, rubella, chicken pox, and mumps etc [21, 26] . Further live attenuated vaccine possesses the great capacity to deliver/ present different kinds of antigens across the virus life-cycle in their parent conformations [26] [27] [28] [29] [30] . This is the first generation vaccine, various efforts have been reported to develop the live attenuated vaccine in the past against coronaviruses [26] [27] [28] [29] [30] [31] [32] [33] [34] (Table 1 , entries 1-9). Bukreyev et al., [26] developed an experimental live-attenuated SARS vaccine for direct immunization which was showed good immune response (production of neutralizing serum antibodies) in immunized eight African green monkeys [26] ( [31] proposed mechanism of the reversion to virulence in live attenuated vaccine which can be avoided by deletion of E-gene. This clue in vaccine designing was offered protection in mice against SARS- . Regla-Nava et al., [33] proposed attenuated vaccine designing against SARS-CoV virus by using mutant E-protein which offered complete protection in mice [33] ( Table 1, entry 8) . However, attenuated virus showing the lung injury, pro-inflamatory cytokine and neutrophil influx with higher CD4+ and CD8+ T Cell count [33] . DeDiego and co-workers [34] designed attenuated SARS-CoV vaccine candidate having absence of E gene, which displaying invitro as well as in-vivo inhibition of SARS infection [34] . However, they reported the inflammation to the lung of hamster [34] (Table 1, entry 9 ). In conclusion, a live-attenuated vaccine is characterized to develop protective immune response without producing actual disease related symptoms in host. Several reports were showing the production of humoral and cellular immune response against SARS-CoV live attenuated vaccine [26] [27] [28] [29] [30] [31] [32] [33] [34] . However, these vaccines possess the safety issues such as live-attenuated strain virus may return back to its original pathogenic form or development of more potent and mutant virulent strain [30] [31] [32] [33] [34] . Further, some reports showed inflammation to liver and lung, neutrophil influx, and proinflammatory cytokine after getting challenge in animal model [33, 34] . Besides this, it has drawbacks such as unsuitability of vaccination to immunologically sensitive population, requirement of multiple, frequent or high dosages of vaccination, reversing to virulence and appearance of low response in immune-compressed hosts which having comorbidities [21, 30, 32, 34] . Table 1 here Virus inactivation is carried out by using radiation technique (UV-ray, X-ray or γ-radiation) or by using chemicals (such as formaline, methanol or β-propiolactone) which preserves the antigenic character of virus particles and demolishing actual infectivity [22] . The induction of immune responses through the inactivated pathogens is measured as a standard and successful vaccination pattern from many years [22, 35] . Various inactivated vaccine formulations are successfully available against influenza, polio, hepatitis A, and rabies pathogen etc [22, [35] [36] [37] [38] . Several efforts have been attempted to design the inactivated vaccine formulations in order to get effective protection from SARS or MERS coronavirus as listed in In conclusion, the inactivated vaccine is considered as safe compared to live-attenuated form due to absence of living pathogens and their inability of possible re-infection [22] . The chances of reverting back into virulent phases are much less in case of inactivated vaccines than live attenuated vaccine [37] [38] [39] . However, mode of presentation of unexpected immune response (than that of actual pathogenecity) is the major limitation of inactivated vaccine [22, 44] . In case of inactivated coronaviruses vaccine, some reports showed inflammation and lung lesion with eosinophil infiltration [34, 39, 49] ; whereas, few articles reported that, inactivated vaccines lead to create weaker immune response or delayed immune response [42] with requirement of multiple dosages [48], since actual infection is not established. Thus, multiple/high/frequent dosage, weaker and unexpected immune response is the major limitation associated with use of inactivated vaccines. Second generation vaccine: A protein subunit vaccine involves the use of synthetic or isolated or recombinant or derived highly antigenic protein base subunits with the short antigen segment which offers safer vaccine designing approach [23] . Table 2 here Production of the vector-based vaccines is proficient in creating immunogenic responses [24] . Various viral vectors are used as a delivery tool for the vaccination such as modified vaccinia In conclusion, S gene/spike proteins are specifically reported to code in adenovirus vector which induces the immune response [60] [61] [62] . The viral vector base vaccine is more advantageous than first generation vaccine since it vaccinate the live virus by recombination of antigenic protein component of pathogenic virus into non-virulent vector [24, 61] . Thus it mimics the possible natural pathogenic infection with subsequent cellular and humoral immunogenicity [60] [61] [62] . The major challenge in designing of this kind of vaccine is to know the exact epidemiology, genotoxicity and virology of both viruses (pathogenic and vector virus) [24, 62] . Hence it is difficult to design rapid vector base vaccine for the newly emerging viruses like SARS-CoV-2. Further, major limitation is the hampering and delaying of actual expected immune response against pathogenic virus, since, primary and pre-existing immune response is mainly acquired due to vector virus which is known as the pre-existing immune response [24] . Besides this, there is a risk of mutation and unexpected virulence ability of engineered vectored virus. Nucleic acid vaccines make available stable antigenic expression (into delivery plasmid by genetic engineering) which is known to stimulate relatively lesser but constant immune responses [25] . Further, nucleic acid vaccines are cloned antigenic protein materials that mimic the natural infection and can be manufacture relatively in a short period of time [63] [64] [65] [66] [67] [68] [69] [70] . The nucleic acid vaccine is considered as safer alternative than that of inactivated and live-attenuated vaccines which are used currently to acquire immunity against dengue, malaria, typhoid and anthrax etc [25, 71] . These vaccines possess the potential advantages and can be designed against newly emerging viruses by encoding gene sequence ( pyrexia and essential need of adjuvant for long time immunity [64, 65] . Table 3 here The newly advanced methodology and technology in vaccine designing is to use of the nano-materials as a carrier of antigenic component [77] [78] [79] . The adsorption, entrapment and conjugation are the basic three interactions that are associated in between antigen and nano-particles [77] [78] [79] . Various kinds of nano-material are widely used such as nano-polymer, liposomes, inorganic nano-particles, carbon base nano-materials and quantum dots etc [77] . These nanomaterials are broadly used in designing of various vaccine candidates against pathogenic viruses such as taxoplasmosis, malaria, HIV, ebola, and influenza etc [78, 79] . Very few reports are available for the use of nano-based vaccine against coronavirus [77] [78] [79] (Table 3, entries 15-17) . SARS-coronavirus spike proteins to produce humoral and immune response (IgG, IgA, γ-interferon, interleukin-2) in mice. The nano-polymer polyethylenimine was used as a vaccine carrier [77] ( (Table 3 , entry 17). The major limitation of the nano-based vaccine is cellular toxicity of nano-material and need of the adjuvant for enhanced performance of vaccine [79] . Further various physico-chemical properties (size, shape, charge and surface area) of nano-materials are greatly affect the nano-vaccine development [78, 79] . In conclusion as of now, no licensed vaccine is available against coronavirus disease. protein can be deleted during the vaccine designing due to its virulence ability, (iii) preservation of highly antigenic receptor binding epitope and removal of immune damaging epitope from spike protein may offers better approach to fabricate an efficient vaccine against SARS-CoV-2 (iv) more conserved M protein or N protein epitope can be synergetically used with S protein epitope to get enhanced immunogenicity (v) inactivated, nucleic acid and subunit vaccine may be better and quicker option to design vaccine within short period of time. Various vaccine designing efforts are undertaken from 2003 to till date to design a successful vaccine candidate against coronavirus [5, 12, 13] . Despite of several available literature reports, NO vaccine is approved to use commercially against coronavirus disease (SARS and MERS) [5, 12, 13] . In reality, Universal spirit (will power/ determination) towards vaccine The S glycoprotein (has two subunits S1 and S2) binds to ACE-2 through the receptorbinding domain and showed induction of sufficiently high level of antibodies in host [9, 39, 50, 52, 56, 59] . The S1 subunit is responsible for the binding to host cell receptor (ACE-2), whereas S2 subunit is responsible for the fusion process [9, [81] [82] [83] . The S glycoprotein or S1 segment or S2 segment induces different kinds of immunogenic responses which can individually also work as a potential vaccine candidate [39, 50, 52, 54] . The S1 subunit is more immunogenic and hence producing more kind of antibodies than that of S2 subunit [9, 60, 68, 81] . Thus, the receptor binding domain epitopes (S protein segment) is a major component which is extensively reported in literature with the animal model response and can be useful to consider as a possible antigen for COVID-19 vaccine as they not only induces the humoral immunity but also elicit T-cell immune responses [82, 83] However, M protein is associated with the virulence ability and regeneration of viral particles [82, 85] hence very few reports are available to use M protein as an antigen in vaccine designing. Similarly the E protein is also responsible for the morphogenesis of virus, virulence capacity as well as viral assembly and hence most commonly not used as an antigen for vaccine designing [28, 31, 33, 34, 82, 85] . Netland et al., et al., [28] , Jimenez-Guardeño et al., [31] , Regla-Nava et al., [33] and DeDiego et al., [34] reported to use first generation (live attenuated) vaccine with deletion or lack of E gene in order to avoid the virulence ability. Thus, deletion of the E gene block viral production and reduces the viral number almost 200 times inside the cell [34, 86, 87] . At Developments of any kind of vaccine involves various steps/stages such as identification of effective antigen, lab-scale antigen engineering/synthesis, safety concern, animal model study, human trails, efficacy trials, large scale synthesis, regulatory clearance and huge capital investment [13, 14, 15, 17] . Thus vaccine designing is the lengthy process (take at least 18-36 months) which involves the multiple pauses in order to observe, to analyze and to conclude the clinical trials data [13] [14] [15] . However, some testing and trials can be done in parallel mode (such as animal model and human trails) with high financial risk in urgency to save the time [14, 17] . In case of the coronavirus vaccine, existing knowledge about SARS-CoV and MERS-CoV vaccine designing may be crucial to consider which may offer clues about target sites for rapid vaccine development against SARS-CoV-2 virus (COVID-19) [13, 15, 16] . Thus the next few months are very crucial for development and anticipation of successful vaccine to combat COVID-19. Table 4 The selection of animal model has some basic objectives such as (i) to characterize the disease/viral pathogenesis (ii) to characterize immunogenicity, (iii) to assess development of antiviral/anti-disease vaccines responses and (iv) to observe clinical symptoms after challenge [106] [107] [108] [109] [110] . Further, animal model is used to assess pre-clinical efficiency of vaccine which involves the vaccine-dose, vaccine-safety, vaccine-formulation and route of administration [106] [107] [108] [109] [110] . Advanced computational bio-analytical-methods are used to determine the appropriate animal model and to avoid time as well as costing of unnecessary animal model experiments [106, 107] Thus, in context of the rapid vaccine designing animal model plays a crucial role in giving details of the cellular and humoral immune response [107] . However sometimes, different kinds of immune response can also be demonstrated by the animal model which is not expected in humans [108] . Hence it is challenging task to select the appropriate animal model and to develop the safer vaccine rapidly based on animal models in order to control the pandemic [107, 109] . Furthermore, coronaviruses are the zoonotic origin virus and may have different kind of animal response than that of humans which may involves the restricted virus multiplication and less severity of the symptoms [26, 44, 55, 109] . Thus, selection of the animal model is having great importance which needs to be screened in such a way that immunogenic response of animal model should be closely associated or related with human [106] [107] [108] [109] . The success of the pre-clinical assessment of vaccine depends on the animal model and hence various non-human primates can also use as animal model to test vaccine efficacy for rapid development [106] [107] [108] 110 ]. Efficacy of the vaccine also depends on the selective route of the vaccination; various routes of administration of vaccine are available which can assist designing of effective vaccine [111] [112] [113] [114] [115] . Coronavirus disease is associated with the respiratory tract; hence it would be advantageous to induce memory response against respiratory tract infection [78] . Raghuwanshi et al., [78] investigated efficacy of plasmid DNA encoded N protein antigen loaded on chitosan nanopolymeric carrier for non-invasive intranasal immunization against SARS-CoV which induces an efficient mucosal and systemic immune response at the point of entry of virus [78] . Liu et al., [60] designed a recombinant vaccine involving adenovirus with expression of SARS-CoV S1 spike protein which can be able to induce an effective immune response against SARS-CoV in rats after subcutaneous or intranasal immunization. Hu et al., [113] was studied comparative analysis of immunogenicity induction via different routes of administration. They mentioned that, oral route of administration offered better immune response whereas; combination strategy of administration (oral + intramuscular) could be more impactful to generate the cellular and humoral immune response. However, Gai et al., [47] investigated the influence of the various immunization protocol for inactivated SARS-CoV virus which indicated significant production of IgG antibodies by an intraperitoneal immunization than intranasal immunization [47]. Recently Zhao et al., [114] observed that, intranasal route of administration offered effective cellular immune response in respiratory tract and better protection level in mice. Leyva-Grado et al., [115] proposed direct local administration into the respiratory tract which displayed better immunization efficiency. The route of vaccine administration is selected based on criteria of (i) lesser adverse impact and (ii) generation of effective and quick immunogenicity [112] [113] [114] [115] . Various routes of administration are listed in and hence it is the challenging task in this time of race to design successful rapid vaccine. Table 5 here Adjuvant is an essential component used in vaccine designing to boost the immune response with minimum amount of antigen, to regulate the immunogenicity and to offers better protection by mean of long-period impact of vaccine [116] [117] [118] . More specifically, the use of adjuvant manages (i) the vaccine dosages (ii) promotes slow release of antigen, (iii) retains antigenecity of antigen for longer time and (iv) activate selective pathways of immunity against vaccine antigen [116] [117] [118] . The actual mechanism of the adjuvant functioning is not well known, but its use offers more benefits for effective functioning of vaccine [116] [117] [118] . Various kinds of the adjuvants are reported in the literatures ( [54] reported that, antibody production was augmented by the use of adjuvant [35] [36] [37] 47, 54] . However, Spruth et al., [43] did not observe any significant impact of adjuvant on antibody induction in coronavirus vaccine designing [43] . The uses of the adjuvant make it possible to immunize to more number of people as it facilitates the requirement of small dosages [116, 117] . However in case of respiratory disease related vaccine, choice of adjuvant plays an important role, since some nano-particles, lipid and inulin based adjuvants causes toxicity to the lung tissue which are rich in immune cells and macrophages [119] [120] [121] . Honda-Okubo et al., [119] reported significant eosinophilic immunopathology associated with the use of delta inulin based adjuvant in animal model mice. Wang et al. [120] reported the lung toxicity attributed due to nano-particle based adjuvant compounds. Further Raetz et al., [121] reported cytotoxicity of the lipid based adjuvants. Other common side effects of use of adjuvants include myalegia, pyrexia, allergic action, rashes, and rarely neurotoxicity [122] . Hence, the use of adjuvant should be well optimized in vaccine designing; the ideal adjuvant is biocompatible in nature, biodegradable, should not harm cells in any way and do not induce any kind of allergic/side effects [116] [117] [118] 123 ]. Thus it is always challenging task to select the appropriate adjuvant for the respiratory disease related vaccine designing. Various FDA approved adjuvants are available commercially with high purity which can be used selectively and safely (with proper screening) in vaccine designing to improve the performance of vaccine. Table 6 antigen-dependent enhancement factor (which promote virus infectivity) is also a big concern. Live attenuated and inactivated vaccine may show reversion of the virulence. Hence, vaccine target profile must be provided with details of safety consideration to avoid adverse immunogenic effects. Thus safety is a major concern for designing of vaccine against newly emerging pathogens. Beside this, vaccine must offer long term protection and immune response against pathogenic virus with small amount of antigen dose, since large and frequent dosage are difficultly approved by the FDA. project. There should not be any kind of timeline for vaccine designing against SARS-CoV-2 virus, however this task should be treated on high priority. A safe, efficient, preventive or prophylaxis vaccine is urgently needed to control recent COVID-19 Proposed two step inactivation by formaldehyde and UV ray to design inactivated vaccine which produces high levels of neutralising antibodies and stimulates interferon-γ as well as interleukin-4 production in mice. Plasmid encoding S1 and S2 (pIRCTL-S1 Designed DNA vaccine by encoding S1 and S2 subunit which able to induce the immune response (specific antibody) in mice. like SARS-CoV open reading frame 3a gene 3a gene DNA vaccines through electroporation against SARS-CoV virus in mice. Further they proposed that, spike genes play an important role in vaccine designing, while slight modification in spike protein affects effectiveness of vaccine. To study immunogenic response and safety concern of non-replicating vector COVID-19 vaccine. 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