Do you pride yourself on understanding exactly how vaccines work so that you can have intelligent conversations with your peers and patients?
There is a revolution underway in vaccine development. One you need to know about, one that caught me by surprise: chimeric vaccines.
Last month my veterinarian recommended a chimeric Lyme disease vaccine for my playful chocolate lab, Bodie.
We have a lot of Lyme disease where I live, so of course I wanted to protect him. It seemed like a great idea since Bodie loves to romp in the open fields on the hills surrounding our home, fields full of ticks.
Dr. Brad said it was more effective than prior Lyme vaccines and better tolerated too. Bodie didn’t even flinch when he gave it to him.
I was embarrassed, I knew chimera were a blending or graft of two different organisms. But a vaccine?
What is chimeric DNA vaccine?
Chimeric vaccines are part of a new generation of vaccines.
Over the years scientists have been working hard to improve vaccines to maximize effectiveness and minimize side effects. They are working on the third generation of vaccines. Many are in their final stages of testing before release for general use.
Note: the Lyme vaccine given to my dog, the one that got me interested in this topic, is actually a blend (or chimera) of several proteins not DNA. We’ll save that concept for another blog post. Read on for more information about DNA chimeric vaccines.
First Generation: whole organism vaccines.
They are as simple as it sounds; either a killed or weakened organism is placed in the vaccine. These were the first vaccines developed; some are not appropriate for people with weakened immunes systems. Examples are polio, Hepatitis A and MMR vaccines.
Second Generation: subunit vaccines.
Scientists create a cell line or yeast that produces the subunit, often a protein that stimulates immunity. The familiar toxoid and recombinant vaccines are widely used. They are only useful for a limited number of infections. Examples are Hepatitis B, HPV, Tdap
Third generation: DNA vaccines.
First envisioned in the 1990s these vaccines use DNA to get into cells to stimulate both humoral and cellular immunity, similar to natural disease. The research pipeline is full of these vaccines, however none are currently licensed for humans in the USA.
Most chimeric vaccines are DNA vaccines. They are highly engineered live attenuated vaccines.
Fast-forward to a recent medical conference in South Africa. I listened to discussion after discussion about chimeric vaccines in the pipeline for Zika and Dengue. Different research groups are testing so many different vaccines that I became dizzy looking at spreadsheets of promising data.
OK now I knew I had to learn more.
How do chimeric DNA vaccines work?
The chimeric vaccine is a graft or ‘chimera’ of DNA that codes for proteins hooked onto a viral DNA vector called a backbone.
The backbone ensures that the vaccine will be presented to the proper portion of our immune system and the DNA graft codes for the protein(s) we want our immune system to fight.
Chimeric vaccines were developed because the initial research into DNA vaccines showed poor response by the immune system. The DNA backbone improves deliverability of the vaccine.
Why would you want to make a chimeric vaccine?
It turns out that many infections and cancers take advantage of holes in our immune system.
Often when there are multiple disease subtypes you need to have both humoral and cellular immunity. Or, in the case of immune tolerance created by tumors, you need to ‘wake up’ the immune system to recognize the danger at hand.
Third generation vaccines produce an immune response that mimics the variability seen in natural disease. When you combine an effective backbone and DNA snippets to ‘show’ the immune system which proteins you want it to attack, you can develop effective, lasting, targeted therapies.
That is why these vaccines are ideally suited for complicated pathogens such as Dengue, Zika, HIV, West Nile, RSV, Lyme, etc. It also makes them useful for fighting cancers such as melanoma and breast cancer.
Now, I am confident we will see many chimeric vaccines approved for use in the very near future. Ones that target difficult-to-treat flaviviruses such as Dengue, Zika, and West Nile virus. The veterinarians are leading the way with several chimeric vaccines that are already on the market for large and small animals.
What piqued my interest the most was the amazing research being done to activate the immune system to fight certain cancers—with a chimeric vaccine! This really is the promise of new technology- getting our own bodies to fight invading cancer using our immune system.
I am looking forward to more research and innovative uses of this clever vaccine technology.