Viral Vector Vaccines

Viral Vector Vaccines

Definition

Viral vector vaccines are a type of vaccine that utilize a modified virus (the vector) to deliver genetic material encoding specific antigens from a pathogen, such as a virus or bacterium, into host cells. This process prompts the host’s immune system to recognize the antigen as foreign and mount an immune response, thereby providing protection against the actual disease.

Mechanism of Action

1. Viral Vector Selection: The vector used is typically a harmless virus that does not cause disease in humans. Commonly used vectors include adenoviruses, vesicular stomatitis viruses, and modified vaccinia viruses.
2. Delivery of Genetic Material: The viral vector carries genetic instructions for producing an antigen from the target pathogen. Upon administration, the vector enters human cells and delivers this genetic material.
3. Antigen Production: The host cells use their machinery to translate the delivered genetic code into proteins (antigens) that mimic those found on the surface of the actual pathogen.
4. Immune Response Activation: The immune system recognizes these antigens as foreign, leading to the activation of both humoral (antibody-mediated) and cellular (T-cell-mediated) immune responses. This prepares the immune system to respond more effectively if exposed to the actual pathogen in the future.

Advantages

• Robust Immune Response: Viral vector vaccines can induce strong and lasting immune responses due to their ability to stimulate both arms of the adaptive immune system.
• Safety: These vaccines do not cause disease because they use modified viruses that are incapable of replicating or causing illness in healthy individuals.
• Efficiency: They can be developed relatively quickly compared to traditional vaccines, making them suitable for rapid responses to emerging infectious diseases.

Examples

Several viral vector vaccines have been developed and authorized for use, particularly in response to recent health crises:

• COVID-19 Vaccines: Notable examples include the Johnson & Johnson vaccine (Ad26.COV2.S) and AstraZeneca vaccine (ChAdOx1-S), which use adenoviral vectors to deliver instructions for producing the spike protein of SARS-CoV-2.
• Ebola Vaccines: The rVSV-ZEBOV vaccine is an example that uses a vesicular stomatitis virus vector to provide immunity against Ebola virus.

Conclusion

Viral vector vaccines represent an innovative approach to immunization, leveraging the natural ability of viruses to deliver genetic material into cells. Their development has been crucial in combating infectious diseases like COVID-19 and Ebola, showcasing their potential for future vaccine strategies.

References

1. Wikipedia contributors. (2023). Viral Vector Vaccine. In Wikipedia, The Free Encyclopedia. Retrieved from Wikipedia.
2. Gavi, The Vaccine Alliance. (2020). What are viral vector-based vaccines? Retrieved from Gavi.
3. Medsafe New Zealand. (2021). Viral Vector Vaccines. Retrieved from Medsafe.
4. Nature Reviews Immunology. (2023). Viral vectored vaccines: design, development, preventive and therapeutic applications. Retrieved from Nature.
5. Public Health Ontario. (2021). What You Need to Know About Viral Vector Vaccines. Retrieved from Public Health Ontario.