Viral vector vaccine

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A viral vector vaccine is a vaccine that uses a viral vector to deliver genetic material coding for a desired antigen into the recipient's host cells. As of April 2021, six viral vector vaccines have been authorized in at least one country: four COVID-19 vaccines and two Ebola vaccines.

Technology

Viral vector vaccines use a modified version of one virus as a vector to deliver to a cell a nucleic acid coding for an antigen for another infectious agent. Viral vector vaccines do not cause infection with either the virus used as the vector, or the source of the antigen. The genetic material it delivers does not integrate into a person's genome.[1]

Viral vector vaccines enable antigen expression within cells and induce a robust cytotoxic T cell response, unlike subunit vaccines which only confer humoral immunity. Most viral vectors are designed to be incapable of replication because the necessary genes are removed.[2]

Vector viruses

Adenovirus

Adenovirus vectors have the advantage of high transduction efficiency, transgene expression, and broad viral tropism, and can infect both dividing and non-dividing cells. A disadvantage is that many people have pre-existing immunity to adenoviruses due to previous exposure. Human adenovirus serotype 5 is often used because it can be easily produced in high titers.[2]

As of April 2021, four adenovirus vector vaccines for COVID-19 have been authorized in at least one country:

Zabdeno, the first dose of the Zabdeno/Mvabea Ebola vaccine, is derived from human adenovirus serotype 26 expressing the glycoprotein of the Ebola virus Mayinga variant.[12] Both doses are non-replicating vectors and carry the genetic code of several Ebola virus proteins.[13]

Others

The rVSV-ZEBOV vaccine is an Ebola vaccine. It is a recombinant, replication-competent vaccine[14] consisting of vesicular stomatitis virus (VSV) genetically engineered[15] so that the gene for the natural VSV envelope glycoprotein is replaced with that from the Kikwit 1995 Zaire strain Ebola virus.[16][17][18]

Mvabea, the second dose of the Zabdeno/Mvabea Ebola vaccine, is a modified vaccinia Ankara vector, a type of poxvirus.[12] Both doses are non-replicating vectors and carry the genetic code of several Ebola virus proteins.[13]

Other viruses that have been investigated as vaccine vectors include adeno-associated virus, retrovirus (including lentivirus), cytomegalovirus, and Sendai virus,[2] as well as influenza virus and measles virus.[1]

History

Human clinical trials were conducted for viral vector vaccines against several infectious diseases including Zika virus, influenza viruses, respiratory syncytial virus, HIV, and malaria, before the vaccines targeting SARS-CoV-2, which causes COVID-19.[1]

Two Ebola vaccines using viral vector technology were used in Ebola outbreaks in West Africa (2013–2016) and in the Democratic Republic of the Congo (2018–2020).[1] The rVSV-ZEBOV vaccine was approved for medical use in the European Union in November 2019,[19] and in the United States in December 2019.[20][21] Zabdeno/Mvabea was approved for medical use in the European Union in July 2020.[13][22][23]

References

  1. ↑ 1.0 1.1 1.2 1.3 Lua error in package.lua at line 80: module 'strict' not found.
  2. ↑ 2.0 2.1 2.2 Lua error in package.lua at line 80: module 'strict' not found.
  3. ↑ Clinical trial number NCT04400838 for "Investigating a Vaccine Against COVID-19" at ClinicalTrials.gov
  4. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  6. ↑ Clinical trial number NCT04436471 for "An Open Study of the Safety, Tolerability and Immunogenicity of the Drug 'Gam-COVID-Vac' Vaccine Against COVID-19" at ClinicalTrials.gov
  7. ↑ Clinical trial number NCT04436276 for "A Study of Ad26.COV2.S in Adults" at ClinicalTrials.gov
  8. ↑ Clinical trial number NCT04505722 for "A Study of Ad26.COV2.S for the Prevention of SARS-CoV-2-Mediated COVID-19 in Adult Participants" at ClinicalTrials.gov
  9. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  10. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  11. ↑ Clinical trial number NCT04566770 for "Phase IIb Clinical Trial of A COVID-19 Vaccine Named Recombinant Novel Coronavirus Vaccine (Adenovirus Type 5 Vector)" at ClinicalTrials.gov
  12. ↑ 12.0 12.1 Clinical trial number NCT02313077 for "A Safety and Immunogenicity Study of Heterologous Prime-Boost Ebola Vaccine Regimens in Healthy Participants" at ClinicalTrials.gov
  13. ↑ 13.0 13.1 13.2 Lua error in package.lua at line 80: module 'strict' not found.
  14. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  15. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  16. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  17. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  18. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  19. ↑ Lua error in package.lua at line 80: module 'strict' not found. Text was copied from this source which is © European Medicines Agency. Reproduction is authorized provided the source is acknowledged.
  20. ↑ Lua error in package.lua at line 80: module 'strict' not found.  This article incorporates text from this source, which is in the public domain.
  21. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  22. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  23. ↑ Lua error in package.lua at line 80: module 'strict' not found.

Further reading

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