The key difference between viral vector and mRNA vaccines is that viral vector vaccines use modified virus or vectors to deliver the genetic codes for antigen into the human cells, while mRNA vaccines use a copy of mRNA to encode the gene to produce the antigens.
Vaccines prepare the body to fight against pathogens or foreign invaders to prevent an infection. They usually introduce a harmless bacteria or virus to trigger an immune response. Most vaccines contain killed or weakened bacteria or virus. Both viral vector vaccines and mRNA vaccines are newer technology. They use harmless bacteria or virus to deliver the genetic code of target antigens to the cells. This facilitates the production of antigens to stimulate an immune response.
CONTENTS
1. Overview and Key Difference
2. What are Viral Vector Vaccines
3. What are mRNA Vaccines
4. Similarities Between Viral Vector and mRNA Vaccines
5. Side by Side Comparison – Viral Vector vs mRNA Vaccines in Tabular Form
6. Summary
What are Viral Vector Vaccines?
A viral vector vaccine is a type of vaccine that uses the body’s own cells to produce antigens. Other vaccines actually contain antigens, while viral vector vaccines use the body’s own cells to produce vaccines. This uses a modified virus or vector to deliver the genetic codes for antigen into the human cells. When the cells are infected and produce large amounts of antigens, it triggers an immune response. This makes the vaccine act against natural infections with pathogens, triggering a strong immune response by T cells and producing antibodies by B cells.
Figure 01: Viral Vector Vaccine
Viruses usually replicate and survive after an invasion of a host cell. They take over the protein synthesis process, read the virus’ genetic code and produce new viruses. These viruses contain antigens that trigger immune responses. The viral vector acts as a delivery system to provide means to invade the cells and insert a code for virus’ antigens of the pathogen. There are two types of viral vector vaccines: non-replicating vector vaccines and replicating vector vaccines. The non-replicating vector vaccines do not produce new viral particles, but they produce the vaccine antigen. But, the replicating vector vaccines produce new viral particles and produce the vaccine antigen to infect the cells. Various viruses are developed as viral vectors. They are adenovirus, measles virus, and vaccinia virus. Viral vector vaccines also act against diseases like the Ebola virus and Covid 19.
What are mRNA Vaccines?
mRNA vaccine is a type of vaccine that uses a copy of mRNA to produce an immune response. mRNA or messenger RNA is a type of RNA that is essential for protein synthesis. mRNA vaccines introduce a short-lived nucleoside-modified mRNA (modRNA) of a virus into the vaccinated individual. modRNA is a synthetically created fragment of the RNA sequence. since the antigens are produced inside the host cell, it stimulates both cellular and humoral immunity. mRNA uses the information in genes for the synthesis of proteins. Once the cells finish the process of protein synthesis, they degrade the mRNA.
Figure 02: mRNA Vaccine
mRNA from vaccines does not enter the nucleus and alter DNA. mRNA vaccines introduce a copy of mRNA that corresponds to the viral protein situated in the outer membrane of the virus. Using this mRNA, cells produce the viral protein. As a result of an immune response, the immune system recognizes this as a foreign protein and produce antibodies. Once these antibodies are produced, it remains in the body even after the body has got rid of the pathogen. This allows the immune system to respond faster if it’s exposed to the pathogen again. mRNA vaccine is a vaccine targeted against infectious diseases such as influenza virus, Zika virus, rabies virus, Covid 19, etc. mRNA vaccines are also used against cancer. The aim of the mRNA vaccine is to stimulate an adaptive immune response that targets the particular pathogen.
What are the Similarities Between Viral Vector and mRNA Vaccines?
- In both viral vector vaccine and mRNA vaccine, the antigens are produced inside the host cell.
- Both vaccines are administered to muscles.
- They act against similar diseases such as Covid 19 and SARS-CoV-2.
- These vaccines contain inactivated virus.
What is the Difference Between Viral Vector and mRNA Vaccines?
Viral vectors use a modified virus or vector to deliver the genetic codes for antigen into the human cells. Replicating vector vaccines produce new viral particles and produce the vaccine antigen to infect the cells. On the other hand, mRNA vaccines use a copy of mRNA to encode the gene to produce the antigens. The mRNA vaccine deliberately introduces synthetic RNA into immunity cells. So, this is the key difference between viral vector and mRNA vaccines. Moreover, viral vector vaccines act against the Ebola virus, Covid 19, etc. mRNA vaccine targets infectious diseases such as influenza virus, Zika virus, rabies virus, Covid 19 etc. mRNA vaccines are also used against cancer. Thus, this is another difference between viral vector and mRNA vaccines.
Summary – Viral Vector vs mRNA Vaccines
Viral vector vaccines infect the body’s cells and insert their genetic materials into the nuclei of cells. Once the immune cells detect foreign antigens, they produce an immune response. These immune responses involve T cells as well as antibody-producing B cells. Various viruses are developed as viral vectors. mRNA vaccines use a copy of mRNA to encode the gene to produce the antigens. mRNA is complementary to one of the DNA strands of a gene. Here, mRNA vaccine introduces mRNA, encoding disease-specific antigens and stimulates the protein synthesis of the host cells to produce antigens. This produces an immune response. Thus, this summarizes the difference between viral vector and mRNA vaccines.
Reference:
1. Pardi, N., Hogan, M. J., Porter, F. W., & Weissman, D. (2018). Mrna vaccines — a new era in vaccinology. Nature Reviews Drug Discovery, 17(4), 261-279. doi:10.1038/nrd.2017.243
Image Courtesy:
1. “Fimmu-11-579250-g004” By Katie L. Flanagan, Emma Best, Nigel W. Crawford, Michelle Giles, Archana Koirala, Kristine Macartney, Fiona Russell, Benjamin W. Teh, and Sophie CH Wen, on behalf of the Australasian Society for Infectious Diseases (ASID) Vaccination Special Interest group (VACSIG) – (2020) Progress and Pitfalls in the Quest for Effective SARS-CoV-2 (COVID-19) Vaccines. Front. Immunol. 11:579250.https://doi.org/10.3389/fimmu.2020.579250 (CC BY 4.0) via Commons Wikimedia
2. “Coronavirus mRNA vaccines” By Biochemlife – Own work (CC BY-SA 4.0) via Commons Wikimedia