An Introduction to Measles Virus: A Devil And An Angel
Measles is an ancient eruptive acute respiratory infection caused by the measles virus. There have been records of clinical manifestations similar to measles in ancient medical records of various countries. It was confirmed in 1675 that measles was an independent disease. Before the vaccine was used, measles was widespread all over the world, with 30 to 40 million cases occurring every year, and 800,000 people died. It is estimated that in the past 150 years, measles has caused 200 million deaths, ranking first among all vaccine-preventable diseases.
After the implementation of the measles vaccine, the mortality rate of measles has gradually decreased. However, due to vitamin A deficiency, nearly 98% of measles deaths occur in children under five years old in developing countries, which is still a serious public health problem.
Measles virus is a paramyxovirus. It is spherical under the electron microscope, with a diameter of 100-250nm. The commander of the virus is a sense RNA with a diameter of 17nm, and an underwear named nucleocapsid protects the RNA. Outside the nucleocapsid is a 10-20nm thick coat, a lipoprotein capsule, with short protrusions on the surface like small hands.
The protrusions on the surface of the lipoprotein capsule are divided into three categories:
- M protein: Between the underwear and coat, it participates in virus assembly, budding and maintaining the integrity of virus particles. Without M protein, abortive measles virus is formed, which may be the cause of subacute sclerosing panencephalitis.
- Glycosylated protein HA: Located on the surface of the capsule, just outside the coat, there are many little hands named glycosylated protein HA. It is to rely on HA to grab and destroy normal cells.
- Hemolysin HL: When HA grasps normal cells, HL, on the surface of the capsule, next to HA, quickly merges with normal cells.
The measles virus in the laboratory can be adapted to the tissue cell culture of humans, monkeys and dogs, and it is also easy to culture and passage in chicken embryo cells. But humans are the only natural host of the measles virus. The measles virus in nature cannot infect animals in the laboratory.
This virus easily loses its activity after leaving the human body. It can be inactivated by boiling, sun exposure and disinfection with general disinfectants. It can live well in cold but not in heat—it can be stored for 20 years in freeze and dried environment, 5 years at -15?, 5 months at 4?, 2 hours at 20-37?, and only 30min at 56?.
However, the measles virus is not always the enemy of mankind. In the 1970s, researchers discovered that measles infection caused cancer tumors to shrink in a child. Although this has been reported, no one had specifically studied this virus before the late 1990s. And then, Mayo's researchers began to try to use this harmful virus to treat cancer.
Mayo Clinic Cancer Center initiated a clinical study in 2006. The trial used a special measles virus vaccine to attack the recurring glioblastoma multiforme, a brain tumor that was basically incurable at the time.
"Many cancer cells, including glioma cells, overexpress a special protein, CD46, which enables tumor cells to escape the destruction of the immune system. The measles virus strain can find this protein and enter the tumor cells. Once inside the tumor, the virus begins to spread, infect and lyse the surrounding tumor cells, thereby expanding the interference effect and increasing the death of cancer cells." introduced by a scientist experting at oncolytic measles virus at Creative Biolabs.
Previously, researchers confirmed in animal models in the laboratory that the oncolytic measles virus can significantly shrink gliomas and extend the life of animals. It’s pleasing to see that this study can provide a novel and potential treatment method for patients suffering from recurrent pleomorphic malignant glioma. The researchers also published the toxicological study of this virus "missile" and proved its safety.
There are many examples of treatment with this kind of oncolytic virus, including adenovirus, vaccinia virus, vesicular stomatitis virus, etc. All have been proved to have unexpected effects in the treatment of tumors. It’s believed that with the development of biotechnology, mankind will explore more natural mysteries and overcome incurable diseases in the near future.