New Age Vaccines: Technologies in Developing Vaccine Candidates for RNA Virus Diseases

Vertebrate RNA viruses cause most of the infectious, contagious, transboundary diseases of mammalians in the world. Since 2000, H5N1 avian flu, H1N1/H1N2 Swine flu, SARS, MERS, CCHF, and Covid-19 have caused outbreaks. In addition, rabies, HIV, measles, viral hepatitis, respiratory viruses, dengue, in human beings, and FMD in cattle, PPR in goat, Bluetongue in sheep, infectious bronchitis and PRRS in pigs, are prevalent and endemic in different countries since many years. Whole virus inactivated and live attenuated vaccines including non-pathogenic mutants have been successful in control and eradication of many viral diseases of man and animals. The advancements in molecular virology, non-replicating designer virus vectors of adenovirus and Poxvirus origins, and replicating designer virus vectors derived from vesicular stomatitis virus are being used to deliver immunogenic genes of other viruses to confer protection. RNA vaccine in the form of nucleoside modified mRNA has been successful in control of Covid-19. Single cycle replicon (SCR) virus construct with target transgene, and codon-pair bias deoptimized (CPD) virus have been promising vaccine platforms; both mutants are live attenuated and non-transmissive between host cells. Antigenic spectrum of CPD-virus is as wide as virus attenuated by serial passage in experimental hosts, and is very quick to develop. The technique of synthetic attenuated virus engineering has been faster in developing new age viral vaccines, and also faster to update to match antigenic diversity. This review describes applications of CPD, SAM and SCR technologies in developing vaccine candidates for RNA virus diseases.