Based on the principles of immunology, isn't true that replication-defective virus the best way for vaccination? Because
1) It is as safe as recombinant vaccines as such RNA vaccine, AAV vaccine and
2) It is as effective as live virus.
Then why replication-defective virus has not been deployed widely for vaccine development such as in fighting the current pandemic of COVID-19?
Indeed, they are being used.
One of the most advanced candidates used this technology. The Oxford Vaccine, also known as ChAdOx1 nCov-19 or as AZD1222 used replicative defective chimpanzee adenovirus. Also, The China's CanSino candidate is based in a non replicative Adenovirus 5 (Ad5).
The bigger issues of these technologies are the development of vector immunity, which can impair the efficacy as a platform or the use of booster doses.
Also, the manufacturing process is more complex than mRNA. In any case, both technologies are suitable for the development of a pandemic vaccine.
Kind Regards
Replicative-defective virus are being used for vaccine development. Read this papar https://www.sciencedirect.com/science/article/pii/S0092867420307418 .
They have used Rd-adenovirus for the purpose.
Sergio Linares Fernández Khushbukhat Khan
Thank you both for response! In both cases you provided, the virus vector was AAV-based vector, and covid-19 spike gene was integrated into it.
But in my original post, by replication-defective virus, I mean replication-defective COVID-19 virus. It should be intact COVID-19 virus with knockout of a few essential genes so that the virus particles can still infect host cells but cannot replicate and lyse the host cell.
The advantage of this defective COVID-19 virus as a vaccine is that it presents the majority of the virus genome (40kb minus a few genes that were knocked out) to our immune system. Hence, its immunogenicity is expected to be strong and its resistance to newly evolved COVID-19 strains is high.
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