What You Should Know About Viruses….
What is a virus?
A virus is a clump of genetic material (DNA or RNA) bunched inside a protein packet. It needs a host cell to survive. Without one, it lies dormant. However, once it infiltrates a living cell within a person, plant, or animal, it taps into that cell’s reproductive equipment to duplicate itself. The virus makes many copies of itself and, in the process, damages or destroys the host cells.
Most people think of viruses as “bad.” However, most viruses play an important and helpful role in your body and the environment. For example, viruses in the digestive tract (known as virome) regulate the types and populations of bacteria that flourish in our intestines. Also, viruses keep bacteria in check in the ocean. There are many more viruses in the human digestive tract and ocean than there are bacteria!
Of course, some viruses cause human disease, as you are well aware of with the current pandemic. Some viruses are more virulent (ability to infect or damage) than others.
Viruses consist of a nucleic acid (DNA or RNA) enclosed within a protein coat (capsid), and they may or may not be enclosed by an envelope (from our cells).
VIRAL REPLICATION IN HOST CELLS
A virus depends on our cells to supply the machinery necessary to produce more viruses. In this way, it is parasitic. Also, viruses are considered by many experts not to be a living organism, since they need an organism and its cell parts for metabolism.
How do viruses enter, replicate, and damage our cells?
A virus has a unique structure located on its outer surface that allows it to attach to our cells at special sites (receptors).
Once the virus attaches to the cell, the virus then enters the cell.
Within the cell, the virus sheds its capsid. Then nucleic acid is released into the cell.
4.The virus then uses the components of the cell to replicate viral parts and to aid in the virus assembly
After the new viruses are assembled, they can exit the host cell by 1 of 3 ways: by budding off the cell membrane (enveloped virus), cellular destruction (non-enveloped virus), or crossing junctions between cells.
The new viruses are now ready to infect other cells.
VIRAL EVASION OF IMMUNE SYSTEM RESPONSE
Viruses can avoid the immune system by several means:
Growing in areas where the immune system has no access: viruses reproduce or are shed into areas that are less accessible to the immune system.
Surface antigen changes (mutations): antigens are found on the cell membranes and tell the immune system which cells are infected. Viruses can alter their antigens resulting in a delayed response by the immune system. This delay allows the virus time to replicate and assemble new viruses and increase its chances of further spreading the infection. Antigenic changes due to mutation result in a new infection due to a different strain of the original viral infection. The new virus strain is relatively unsusceptible to the antibodies of the original viral strain. Mutation can also trigger latent or non-dangerous viruses into becoming lethal through alterations in the virus’s nucleic acid. Persistence of a viral infection can be due to their ability to mutate into new strains and evading the immune system.
Suppression of the immune system: Certain viruses infect the immune system and cause direct damage and lead to the development of other infections.
IMMUNE SYSTEM RESPONSE TO VIRAL INFECTIONS
The following are some ways that your immune system responds to viruses.
Specific Anti-Viral Antibodies: develop in response to viral infections and vaccinations. Specific antibodies interact with the viruses outside of the cells (“free”) and make them inactive. They are prevented from entering the cells. Cells that are infected with a virus will display a marker on the cell surface (viral antigens). These marked cells can be recognized and destroyed by the antibodies, along with cytotoxic T-cells, natural killer cells or macrophages.
Cell-mediated Immunity (Cytotoxic T-cells and Natural Killer cells): both recognize infected cells (by viral antigens on the cell surface) and destroy the cells before the viruses are assembled. This action prevents further replication and spread.
Macrophage Proliferation: macrophages found at the site of infected cells discourage the formation of the bridges between cells. Macrophages can directly destroy the viruses by “eating” them along with infected cells.
Interferons and Cytokines: groups of proteins that either inhibit viral replication within the cells and prevent the spread to adjacent cells or activate an immune response.