How does a phage based vaccine work?

Recently amidst the COVID-19 pandemic, many scientists explored different kinds of vaccine production for the sake of saving the world. Other effective vaccines have been generated by outstanding work in the research and development of these scientists, among the most prevalent vaccine technologies. WHO has approved several vaccines to help fight against this pandemic (To read more information about COVID-19 vaccines, please visit World Health Organisation Page by clicking here). Although not yet approved, Phage-based vaccines have sparked the news on their potentiality to protect against Covid-19. According to the data obtained from the research, their efficiency was enough to be considered a potential candidate.

What are phage-based vaccines?

Phage-based vaccines, also termed phage display vaccines are the artificially modified phages with peptide or protein antigens genetically displayed on their surfaces and those with antigens chemically conjugated or biologically bound on their surfaces. As a result, they can elicit the immune response and cause the production of memory cells. Phage-based vaccines are among the less popular vaccines.

How are phage-based vaccines made?

Phage-based vaccines are made by chemically/biologically/genetically modifying the bacteriophage structure with an antigenic but harmless structure from another organism, a potential pathogen. The added structure must have antigenic features so that it can be able to elicit an immune response. An excellent example of a phage-based vaccine is modifying phages to produce spikes for a coronavirus. Those spikes can cause an immune response that will act upon secondary infection in protecting the body against the fundamental infectious particle.

Mode of action of phage-based vaccines

Phage-based vaccines are of no difference from any other vaccines' modes of action. Vaccines train our immune systems to create proteins that fight disease, known as 'antibodies,' just as would happen when exposed to an illness, but – crucially – vaccines work without making us sick. In phage-based vaccines, A phage is just an agent of transportation, while the antigenic structure is responsible for eliciting ("teaching") the immune system.

Is the phage-based vaccine safe?

Phage vaccines and other vaccines are safe as long as they follow all forms of clinical trials and get approved by World Health Organisation. It is recommended to only take vaccines authorized to be safe by professional bodies and the World Health Organisation.

Do non-modified phages stimulate immune response?

Yes, typical phages cause immune response once introduced into the body system. However, they don't cause any disease, and in fact, they can be beneficial to human health if applied professionally and purposefully (phage therapy)

Design and applications of phage-based vaccines

Design and applications of phage-based vaccines
An overview chart of the phage-based vaccine. Photo by Sanger et al., 1977

An overview of design and application of Phage based vaccines

(Refer to the diagram above)
  • (A) DNA vaccines. The whole phage particles are employed as the vehicle of the gene encoding a protective antigenic peptide. In the host's body, the genetic material will be released to express an antigen to initiate immune responses. 
  • (B) Phage-displayed vaccines are achieved via displaying peptides or proteins by genetic means. Foreign peptides or proteins can be fused with the relevant coat protein through phage display efficiently and economically. Then the phage particles can be used as ideal vaccines to trigger the host immune system. 
  • (C) Phage-displayed vaccines are achieved by allowing pre-displayed antigen-binding peptides to capture the antigens. An antigen can be directly linked to the phage surface through an artificial linker. Alternatively, an antigen-binding peptide can be identified by biopanning and displayed on the phage surface and then used to capture the antigen initially linked to a substrate through a cleavable linker. This strategy can improve the range of phage-displayed vaccines and ensure the correct exceptional conformation of the foreign antigens. Phage-based vaccines can be designed using the above techniques to indict the host immune system and produce specific antibodies against various diseases such as viral infection, cancer, bacterial infection, fungal infection, and parasites.

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