Vectored Vaccines.pptx

vectored vaccines

1. Vectored Vaccines Division of Veterinary Biotechnology IVRI, Izzatnagar , Bareiley U.P. Shabir Hussain Mir VMC, M-6504

2. Vectors Agents that carry selected genes encoding foreign antigens are known as vectors. Genetically engineered vectors can either be used as vaccines themselves or used to produce large amounts of antigens in-vitro that can then be incorporated into vaccines. Vectors include bacteria, DNA viruses, yeasts, plasmids, and even plants.   Some microbial vectors may also replicate within an animal and as a result stimulate protective immune responses, provided they only cause abortive infections. The first commercially available vectored vaccine used a fowlpox vector.

3. Viral vector vaccines Viral vector vaccines use a harmless virus to deliver to the hosts cells the genetic code of the antigen you want the immune system to fight. “They are basically a gene delivery system,”.  Experimental recombinant vaccines used as vaccine platforms have usually used large DNA viruses such as poxviruses, adenoviruses, and herpesviruses ; the organisms that have been most widely employed for this purpose in veterinary medicine are poxviruses such as vaccinia, fowlpox , and canarypox. Poxviruses are the most widely used vectors in vaccines because they have a very large genome that can accommodate large inserts.  No viral vector vaccine had ever been licensed for full human use before the COVID-19 pandemic.  Benefits:   Viral vector vaccines usually trigger a strong immune response. Typically, only one dose of the shot is needed to develop immunity. Boosters may be needed to maintain immunity.

4. Viral vectored vaccines have the advantage of being able to induce both antibody- and cell- mediated immune responses without the need for an adjuvant.  They do not require complex purification. They can generate antigens in the correct conformation and they can deliver more than one antigen at a time. As a result, these vaccines are safe, they cannot be transmitted by arthropods, and they are not excreted in body fluids. Their major advantage is that the antigens are synthesized within infected cells and thus act as endogenous antigens. They produce a “balanced” immune response compared to inactivated viral vaccines.  In selecting viral vectors for vaccine use, safety is of paramount importance, whereas other considerations include vector stability and the ability to scale-up production .

5. The various methods of generating live recombinant vaccines. The gene encoding the antigen of interest is isolated, inserted into a plasmid. This plasmid can then be inserted into many different potential vectors.

6. The production of an oral vaccinia rabies recombinant vaccine . Vaccinia has been selected because its genome can accommodate a very large gene insert. In addition, the recombinant vaccinia readily induces protective immunity following oral vaccination.

7. Viral vector-based vaccines differ from most conventional vaccines in that they don’t actually contain antigens, but rather use the body’s own cells to produce them. They do this by using a modified virus (the vector) to deliver genetic code for antigen, in the case of COVID-19 spike proteins found on the surface of the virus, into human cells.

8. By infecting cells and instructing them to make large amounts of antigen, which then trigger an immune response, the vaccine mimics what happens during natural infection with certain pathogens - especially viruses.

9. This has the advantage of triggering a strong cellular immune response by T cells as well the production of antibodies by B cells. An example of a viral vector vaccine is the rVSV -ZEBOV vaccine against Ebola .

10. High efficiency gene transduction Highly specific delivery of genes to target cells Induction of both humoral and cell-mediated immune responses Improved efficacy and safety Reduced administration dose Enable large-scale manufacturing Potential targets ranging from cancers to a vast number of infectious diseases Advantages Risk of integrating into the host genome and lead to other diseases The presence of pre-existing immunity against the vector caused by previous exposure to the virus and the production of neutralizing antibodies can reduce vaccine efficacy Disadvantages Advantages and disadvantages of viral vector vaccines

11. Advantages and disadvantages of different vaccine platforms

12. References   CDC.gov . Understanding Viral Vector Vaccines COVID-19 Vaccines. Available at:  https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/viralvector.html Vaccines for Veterinarians by Ian R. Tizard Daian e Silva, D.S.d.O .; da Fonseca, F.G. The Rise of Vectored Vaccines: A Legacy of the COVID-19 Global Crisis.  Vaccines   2021 ,  9 , 1101. https:// doi.org /10.3390/vaccines9101101