Developmental Landscape of Potential Vaccine Candidates Based on Viral Vector for Prophylaxis of COVID-19

Abstract

Severe acute respiratory syndrome coronavirus 2, SARS-CoV-2, arose at the end of 2019 as a zoonotic virus, which is the causative agent of the novel coronavirus outbreak COVID-19. Without any clear indications of abatement, the disease has become a major healthcare threat across the globe, owing to prolonged incubation period, high prevalence, and absence of existing drugs or vaccines. Development of COVID-19 vaccine is being considered as the most efficient strategy to curtail the ongoing pandemic. Following publication of genetic sequence of SARS-CoV-2, globally extensive research and development work has been in progress to develop a vaccine against the disease. The use of genetic engineering, recombinant technologies, and other computational tools has led to the expansion of several promising vaccine candidates. The range of technology platforms being evaluated, including virus-like particles, peptides, nucleic acid (DNA and RNA), recombinant proteins, inactivated virus, live attenuated viruses, and viral vectors (replicating and non-replicating) approaches, are striking features of the vaccine development strategies. Viral vectors, the next-generation vaccine platforms, provide a convenient method for delivering vaccine antigens into the host cell to induce antigenic proteins which can be tailored to arouse an assortment of immune responses, as evident from the success of smallpox vaccine and Ervebo vaccine against Ebola virus. As per the World Health Organization, till January 22, 2021, 14 viral vector vaccine candidates are under clinical development including 10 nonreplicating and four replicating types. Moreover, another 39 candidates based on viral vector platform are under preclinical evaluation. This review will outline the current developmental landscape and discuss issues that remain critical to the success or failure of viral vector vaccine candidates against COVID-19.

Antigen Presentation of mRNA-Based and Virus-Vectored SARS-CoV-2 Vaccines

“…Currently, the vectors of choice for Sars-CoV-2 and suitable candidates for long-term protective immunity are both human and primate adenoviruses [ 75 , 76 ]. At the moment, there are four approved adenovector vaccines available: Ad26.CoV2.S (Janssen-Johnson & Johnson; brand name Janssen COVID-19 Vaccine), ChAdOx1 nCoV-19 or AZD1222 (Astra-Zeneca; brand names Vaxzevria and Covishield), Gam-COVID-Vac (Gamaleya National Research Centre for Epidemiology and Microbiology; brand name Sputnik-V), and Ad5-nCOV (CanSino Biologics; brand name Convidecia).…”

Exploring the COVID-19 vaccine candidates against SARS-CoV-2 and its variants: where do we stand and where do we go?

“… 82 Being a dynamic platform for large-scale manufacturing, it also allows a broad spectrum of viral vectors to be used in vaccine development; e.g., in the case of COVID-19, vectors like adenovirus, Sendai viruses, rabies viruses, influenza viruses, parainfluenza viruses, MVA, and Newcastle viruses. 83 Generally, this platform includes both replicating (attenuated) and non-replicating viral vectors. The non-replicating vectors tend to infect the host cells to produce the desired antigens without necessarily generating the new virus particles, whereas replicating vectors produces both new virus particles and the antigen of choice.…”

A Minireview of the Promising Drugs and Vaccines in Pipeline for the Treatment of COVID-19 and Current Update on Clinical Trials

“…There has been an increased focus on the pre-clinical development of COVID-19 vaccines by many research institutes and vaccine manufacturers around the world. Currently, the predominant vaccine platforms for pre-clinical studies included are DNA, RNA, inactivated virus, viral vector (Replicating and Non-Replicating), live attenuated virus, protein subunit and virus-like particle (VLP) ( Bezbaruah et al, 2021 ; Borah et al, 2021 ). Though many vaccines have been included in clinical trials, vaccine candidates such as AZD1222 (Covishield, Vaxzevria), BNT162b2 mRNA-1273 and CoronaVac are in the phase IV clinical trial ( Table 2 ).…”