Viral vector vaccines

  • by VaccineHealthCenter

The novel Corona virus has taken a toll on the world’s healthcare systems. As with other viruses, its transmission rate is high, claiming thousands of lives daily. The illness lacks a cure but scientists have developed vaccines to control the virus.
The approved COVID-19 vaccines include Moderna, Pfizer, AstraZeneca and recently, Johnson & Johnson. The first two use the m-RNA technology while the latter were developed using viral vectors. Previous successful studies in virology have prompted researchers to explore more on the findings to develop Covid- 19 vaccines. Finally, after months of research, their hard work yielded fruit. As a medic, you are undoubtedly interested in the vaccine development process. This article will focus on how viral vectors work in the process.

Properties of viral vectors

Recombinant vectors are flexible and safe. These intrinsic features make them suitable for their role. In humans, they deliver antigens which are supposed to elicit immune responses. This in turn protects the body from infectious diseases. Medical practitioners have succeeded in using them for virotherapy, vaccine development and gene therapy.

Viral Vectors as vaccines

As earlier mentioned, viral vectors have flexibility. This feature enables them to combine with other elements so that they can function as purposed. When used in vaccines, harmless fractions of the target virus are recombined with the adenoviral vectors (Ad). When the shot is administered, the elements trigger the production of antibodies in the system. If an individual contracts the virus, the immune system reacts by producing antigen-specific antibodies to prevent illness.
Encoded antigens in the Ad are introduced to the human cells. This encoding occurs within the E1 and E3 regions of the viral vector. The Ads are engineered such that they can’t replicate and cause infection. Upon its detection, the humoral and cellular immunities respond. With the aid of T cells, plasma B cells produce antibodies to counteract the induced antigen. On the other hand, cytokines are also produced to respond to the foreign body.
This approach was considered after the successful administration of viral vector vaccines to animals. For example, neutralizing antibodies were generated after an Ad5 jab to prevent Ebola was given to some monkeys. The vector encoded a surface glycoprotein of the virus and produced the expected antibody.
However, the Ad vaccines may experience setbacks. Some individuals may develop intolerance which can result in severe side effects. Additionally, the body might clear the Ad when induced due to preexisting immunity. To deal with such a situation, researchers use adenoviruses that individuals rarely come into contact with.
For the Covid-19 virus, different manufacturers have used varying Ads. For example, the AstraZeneca vaccine uses ChAd✖1, which is a chimpanzee adenovirus. The Johnson & Johnson uses Ad26 and CanSino from China Ad5. Sputnik V from Russia is the only vector vaccine so far being administered in two doses, Ad26 and Ad5 respectively. All the rest are single doses. Patients experience common side effects like mild fever and headache as they would if they received other vaccines. However, reactogenicity varies across individuals due to different factors.

Can the vaccine alter your DNA?

Adenoviruses cannot interfere with the DNA. They don't possess the enzymatic composition necessary for the alteration of a person's DNA. This is a major reason why they are preferred in vaccine development. To further reduce the chances of replication, parts of their genome are deleted. This ensures they are safe for use. Additionally, they are nonintegrating since there is no proof showing the vector’s ability to affect the host’s DNA.

The bottom line

There has been ongoing research about adenoviruses in the medical field. Previous studies showed that when used, they boost the body’s immune system. For this reason, scientists considered it a viable option for vaccine development when Covid-19 struck. The results have been rewarding since AstraZeneca and other vaccines have been developed. As many resources are pumped into finding a cure, we can utilize these vaccines in the meantime.