Live-Attenuated Viruses (LAVs)

LAVs are vaccines which still contain a weakened ‘live’ virus and can cause a strong response from the immune system – nearly as good as if the person has been infected with the real virus.

Since LAVs are still live, there is a degree of unpredictability which can cause some safety and stability concerns e.g. the potential to cause disease in immune-compromised individuals (HIV) or the potential to become virulent (wake up), infect the person and able to pass on.

Nucleic acid-based vaccines

Nucleic acid-based vaccines are a new development. Cells are injected with a genetically engineered ‘plasmid’ – a bit of DNA that is separate to the cells’ own chromosomes which can replicate independently – which contains an antigen to cause an immune response.

That means the cell produces the antibody for an effective immune response. DNA vaccines have potential advantages over conventional vaccines, including the ability to induce a wider range of immune response types.

Currently no DNA vaccines have been approved for human use. Research is investigating the approach for viral, bacterial and parasitic diseases in humans, as well as for several cancers.

mRNA vaccines

RNA vaccines work by introducing an mRNA sequence (the molecule which tells cells what proteins to build) which is coded for a disease specific antigen; once produced within the body, the antigen is recognised by the immune system, preparing it to fight the real thing.

RNA vaccines are faster and cheaper to produce than traditional vaccines, and an RNA-based vaccine is also safer for the patient, as they are not produced using infectious elements. Two forms of mRNA vaccines have been developed:

conventional mRNA vaccines – The simplest type of RNA vaccine, an mRNA strand is packaged and delivered to the body, where it is taken up by the body’s cells to make the antigen.

self-amplifying mRNA vaccines – The pathogen-mRNA strand is packaged with additional RNA strands that ensure it will be copied once the vaccine is inside a cell. This means that greater quantities of the antigen are made from a smaller amount of vaccine, helping to ensure a more robust immune response.

Recombinant DNA platforms

Recombinant DNA platforms produce an exact genetic match to proteins of a virus. The protein’s DNA will be combined with DNA from a virus harmless to humans, and once injected, will rapidly produce large quantities of antigen which stimulate the immune system to protect against the virus

Virus-Like Particle (VLP) based vaccines

Virus-like particles (VLPs) are molecules that closely resemble viruses but are non-infectious because they contain no viral genetic material. VLPs contain repetitive, high density displays of viral surface proteins that present ‘conformational viral epitopes’ – the part that causes an immune response.

Non-replicating Viral Vectors

Viral vectors are tools commonly used to deliver genetic material into cells. A viral vector vaccine induces expression of pathogen proteins within host cells similarly to other attenuated vaccines. However, since viral vector vaccines contain only a small fraction of pathogen genes, they are much safer and infection by the pathogen is impossible.

Recombinant Nanoparticles

Recombinant DNA is artificially created DNA. These types of vaccines use genetically engineered three-dimensional nanostructures that incorporate recombinant proteins critical to disease pathogenesis (the biological process that allows it to happen). In short, they support production of the antigens that cause an immune response.

Peptide vaccines

Synthetic proteins that mimic naturally occurring proteins from viruses, causing an immune response.

• Adjuvant technology – this boosts the immune system’s response to a vaccine, improving its efficacy and giving the potential for vaccines to be developed that are longer lasting and more effective in older populations
• Bioconjugation technology – developments in the process of joining a protein to an antigen could increase vaccines effectiveness