Disclaimer: I am not a physician or a virologist. I have a PhD in cell and molecular biology. I did research in medical schools and was part of a clinical trial in a biopharma company. I have grown several viruses, but none in the coronavirus family. I am not associated with any group making vaccines to SARS-CoV-2. I have performed most of the laboratory tests described in this blog to detect virus and antibodies. I have made monoclonal antibodies, but not for COVID.
Summary: Currently over one hundred candidates for a vaccine against SARS-CoV-2 are in development. The best ones will provide lasting immunity, which is lifetime resistance to disease. Because Pfizer and Moderna have announced results, I will lead with their novel vaccine developments.
What is a messenger RNA (mRNA) vaccine and why is it different? In the previous post, this virus was followed as its mRNA entered a lung cell and made copies of itself. That is exactly how the mRNA vaccines work. However, be assured several modifications are used in the mRNA injected as vaccines. First, the complete virus RNA is NOT injected as a vaccine. The complete RNA for this virus is known, but both vaccines only use a section of the RNA that codes for the Spike surface protein. To further protect you and to create a greater immune response, a synthetic copy of the mRNA is made in the lab. The Pfizer mRNA is called BNT162b2; Moderna is mRNA-1273.
What else is in the vaccine? RNA is a very fragile molecule. In the lab, gloves have to be worn and glassware is baked at 350 ͦ F for 2 hours. RNA can fall apart in seconds. The vaccines use lipids to stabilize the mRNA, but cold is still required. The Pfizer vaccine mRNA is formulated with lipids as the mRNA–lipid nanoparticle drug product. It requires -100 ͦ F or dry ice for storage. Moderna coats its mRNA with an ionizable (cationic) lipid; cholesterol; DSPC (phospholipid) and PEG2000-DMG (conjugated anti-aggregation lipid). This combination permits regular freezer and even refrigerator storage of the vaccine for a short time.
How does the mRNA vaccine create immunity? When the vaccine is injected into the muscle, it is noticed as a foreign substance by muscle cells and several immune cells. Blood cells notice and react. There are immune cells in the skin and muscles called dendritic cells. These cells take up the mRNA and like lung cells, they use the mRNA and start making spike proteins. Spike proteins are REALLY noticed as foreign and a whole cascade of immune events begin. It appears that one dose of the vaccine is not enough to cause a full response. However, within days of a second injection, a full blown immune reaction begins. The response is such that 95% of those given a second injection are protected from COVID or at least get a mild case. Spike is a good antigen to invoke immune response.
How have vaccines been made through time and what are the new strategies being used for COVID protection? Vaccines mimic natural infection of a virus or bacteria. The vaccine must be at a low enough dose to not create a full blown illness or use a modified virus or bacteria to create a response that protects from the dangerous pathogen.
How does immunity to a virus naturally happen? Let’s use measles as an example. When measles enters your body, it is recognized as foreign mainly because of two envelope knobs known as H and F. Immune cells in your body take in viruses and start a response that ends with B white blood cells making antibodies to neutralize the measles viruses. This is one of the tests used for vaccine efficacy—production of neutralizing or virus-killing antibodies. To have lasting immunity, some of the B cells convert to Memory B cells that last the rest of your life. This sequence takes about three weeks. If you confront measles viruses in the future, Memory B cells will come out of hiding and within days make lots of antibodies that will bind viruses and help destroy them before the infection can make you ill again.
How can a vaccine replicate those events?
- Use a similar virus. Some of the first vaccinations were like Jenner’s use of cowpox virus to give protection to the similar smallpox virus.
- Use small amounts of virus. This will give a response without disease, like cowpox, but is no longer used.
- Use a virus inactivated or fixed with formalin. The virus will be intact and recognized as foreign, but will not be able to cause disease because it is dead. Pertussis is an example as are Salk polio vaccines.
- Use an attenuated (A Ten you A ted) virus. Viruses are grown in chicken embryos or cell cultures. Once viruses adapt to grow in non-human cells, they will no longer grow in human cells. The measles, mumps and rubella MMR trio are attenuated as are chicken pox, influenza, yellow fever and oral polio vaccines.
- Use a surface protein, like Spike. Antigens, like Spike, can be purified for a vaccine. Spike could even be changed slightly. Spike particles would not be infectious, but enough of them, would cause a response. The Spike protein could also be made synthetically to not have any virus involved. The drawback would be viral mutations changing Spike so new viruses would not be recognized. The Hepatitis B surface antigen and HIB b (Haemophilus influenza b) that causes infant meningitis are antigen vaccines.
- Build an artificial nanoparticle to mimic a virus. Bill Gates is funding such a project. An artificial nano particle with lots of sides is built by machines. It would take a billion nano particles to go end to end on your meter or yardstick. So really, really, small. The final step is to decorate the nanoparticle with Spike pieces so it looks like a porcupine. Ordered arrays are most antigenic. This can be given as a vaccine without any live genetic material. One fantastic advantage in development thus far is its stability in heat.
- Use an adeno virus to transport viral RNA turned into DNA. Adeno viruses cause common colds in humans and our genetic relatives, chimpanzees and gorillas. At least 26 human adeno variants are known. There have been problems with some adeno viruses previously used as vectors, but lots of research has helped that. This virus RNA for spike converted to DNA is placed into the virus. Vaccine is injected or used as a nasal spray. Again Spike is made in response and you develop an immune response. These vectors are used by Astrazeneca with Oxford and a similar vector used by Johnson&Johnson.
SUMMARY. Vaccines usually take years to develop. This is not just the design phase, but the testing phase. The ultimate tests of a vaccine are how long does immunity last and are you completely protected from the disease.