Lipids saving the world
The world let out a small sigh of relief earlier this week as the first COVID-19 vaccine was approved for use in the UK. The end of the tunnel is in sight – and lipids are playing a significant role.
To date vaccines have used deactivated virus or viral proteins to elicit the immune response. The Pfizer/BioNTech vaccine is different – it is a strand of messenger RNA (mRNA). Once injected into the arm it enters cells and provides instructions to make a fragment of a protein that exists on the surface of the COVID-19 virus (shown as red protrusions on the iconic COVID-19 image above). That fragment is exported to the surface of the cell where it is recognized as ‘foreign’ by the immune system and destroyed. Having seen several of these foreign protein fragments the immune system creates antibody-producing cells primed to tag this fragment. When any COVID-19 virus enters the body, it is immediately tagged and destroyed. The person has gained immunity.
But there is an obvious problem with this approach: mRNA belongs inside cells. Any that gets out is recognized by the immune system and destroyed. Without some sort of protection or cloaking device the mRNA vaccine has little chance of delivering its instructions. This is where the lipids enter the story. The Pfizer/BioNTech vaccine is formulated with a carefully chosen mixture of lipids and surfactants. The mRNA is encapsulated in a double layer of lipids – a lipidosome – that is invisible to the body’s natural defense systems. Optimizing the lipid mixture and encapsulation is a significant part of the drug development work.
Lipidsomes are already used to package drugs such as the cholesterol-lowering medicines Repatha and Praluent and the chemotherapy Doxil so they can get to their targets with fewer unwanted side effects. But the providing sufficient high purity lipid to lift the threat of COVID-19 from the world – and identifying and producing lipid mixtures for future drugs and vaccines once this inherently faster approach to vaccine development is established - this may provide an interesting challenge for lipid researchers & suppliers as they continue to help save the world.