Vaccines are one of the best inventions that have saved humanity by reducing morbidity and mortality. They stimulate the body’s immune system to cause an immune response. Vaccines protect people from deadly diseases like rinderpest, smallpox, and polio, among many others.
Traditional vaccines were made from inactivated or weak pathogens. Viruses and bacteria in this state were unable to reproduce, making them unable to cause disease. After introducing them to the body, the patient’s immune system kicks in, creating memory B and attacking pathogens, preventing a similar attack. With time, scientists developed vaccines using bacteria’s genetic material.
DNA and Vaccines Explained
DNA vaccines require genetic material to be able to trigger an immune response. These third-generation vaccines use circular DNA molecules known as plasmids to introduce viral or bacterial genetic material into the body. DNA travels to the nucleus, where its enzymes change genes to messenger RNA. The messenger RNA (mRNA) travels to the cell’s outer cytoplasm, where different enzymes convert the mRNA to viral protein or bacterial protein.
After the immune system has identified the protein as a foreign body, an immune response is triggered, forming memory immune cells. These cells are vital in providing immunity in the case of future attacks. Plasmid DNA degrades after a few weeks while immunity to pathogens remains.
How DNA Vaccines are Used
Sometime back, the introduction to DNA and vaccines was only used in veterinary medicine due to challenges in getting a sufficient immune response in humans. They were initially approved for use against West Nile virus in horses, melanoma in dogs, infectious hematopoietic necrosis virus in schooled salmon, and fetal loss in swine.
Today, clinical trials aim to investigate the effectiveness of DNA vaccines against severe types of cancer like Ca breast, Ca pancreas, and cancer of the lungs, as well as HIV-1. Previous and ongoing human trials showed promising results that showed boosted DNA-primed T-cell responses in the human test subjects. Clinical trials investigate DNA effectiveness against infectious diseases like Ebola, anthrax, tuberculosis, zika virus, human papillomavirus, and herpes.
Approved DNA Vaccine
Apart from the DNA vaccine examples previously given above that are still undergoing human trials, one DNA vaccine was approved recently for emergency use in humans. Zydus Cadila in India developed the ZyCoV-D vaccine. This vaccine was approved for the COVID-19 pandemic. It is given using a pressure needle to allow the vaccine to easily penetrate one’s skin. Its approval gives a lot of hope for other DNA-based vaccines.
Do Vaccines Cure Viral Diseases?
The essence of vaccines is to provide protection against diseases and prevent diseases from happening. Therapeutic vaccines are administered after one has contracted a viral or bacterial illness, which gives a way to treat disease and boost the immune system, protecting you from future infections. The immune system of a healthy individual prevents you from getting certain conditions. However, for diseases like Alzheimer’s and HIV cancer, the immune response is insufficient to fight the disease. In cases like HIV, the immune system shuts down completely.
The immune system can easily recognize a cancerous cell or virus, helping combat the disease with therapeutic vaccines. DNA vaccines are also an example of therapeutic vaccines.
The Future of Vaccines
There is continued research aimed at the immune response generated by DNA vaccines. The future of DNA vaccines is, however, bright and promising. Clinical trials that are underway have exhibited good results.
Factors to Consider when introducing DNA Vaccines in Developing Countries
Immunogenicity of the Gene(s) of Interest
Most DNA immunization studies are carried out in mice. The results obtained are promising since both cellular and humoral responses were induced. The immunogenicity of different genes varies. Other DNA vaccines for other pathogens should be developed individually. The preferred DNA vaccines can cause an effective immune response after a single injection. Introducing a booster vaccine for subsequent subclinical infection in developing countries leads to secondary relapse.
Route of delivery and Delivery System
One of the challenges in developing DNA vaccines is the huge DNA quantity required to induce immune responses in aged animals and humans. The purification and production of large plasmid DNA quantities can be a tremendous financial burden. Still, it increases the side effects of DNA immunization by causing autoimmune plasmid DNA integration or autoimmune responses in the host cells.
Though there are other delivery systems like gene guns, cationic lipids, microparticles, and bacterial delivery systems, it is more practical to introduce a delivery system that healthcare providers in developing countries can use. Some studies attest that a DNA immunization later boosts protein immunization to give an adequate immune response. This combination, however, can be challenging for health workers as they have to offer vaccination using two different vaccines.
Regarding the route of delivery, oral mucosa delivery is simple and acceptable, but monitoring and controlling DNA dosage being administered using this route can be challenging.
Preventive and Therapeutic DNA Vaccines
Preventive vaccines must be given to infants and children and should therefore be studied in newborns and young animals. Some studies show that DNA vaccines can induce immune responses in newborn animals, indicating potential effectiveness in children. Studies showing possible integration of DNA into the host genome of newborns and young animals and those showing DNA efficacy should be done.
Since DNA immunization can induce a humoral and cellular immune response in therapeutic vaccines, they are proven effective for treating persistent bacterial and viral infections.
In developing countries, HIV, AIDS, tuberculosis, and viral hepatitis B and C are still prevalent. Since antiviral drugs or antibiotics are expensive and sometimes unavailable in rural areas, DNA therapeutic vaccines will be much appreciated over antiviral medications.
Quickening the time between the first licensure of new vaccines to actual public use in public-sector immunization programs in developing countries is a huge commitment that is required but is not easy to accomplish.
This information will help you understand the whole history of the introduction of DNA to vaccines.