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August 9, 2011
A closer look at the HIV virus

Two weeks ago, we explored all the basics of HIV infection. We spoke of its prevalence and the ways you can catch it.{{more}} This week, I am going to speak of the virus itself. I will define certain terms as I go along, so when I discuss treatment it will be easier to understand.

A virus is a microscopic germ that cannot live outside a living cell, because it consists of just a piece of genetic material covered with a “shell”. The cell also contains the substances necessary for this piece of genetic material to enter and “infect” the cell. The HIV virus infects the cells of the immune system, including the macrophages, which “eat” up bugs when they enter the body, and another group of immune cells called the “T cells”. These T cells are the cells that produce substances that kill bugs when they invade the body. These “T-cells” are of two types, namely the “helper” T cells, also called the CD4+ cells and the “killer” or CD8+ cells. The cells can be looked at like the parts of a country’s defense, in which the CD4+ are like the scouts or reserves and the CD8 are the main defense. The CD4 are responsible for alerting the CD8 cells of a viral attack and recruiting the rest of the immune system to arm their defenses.

The HIV virus belongs to a family of viruses called the “lente” or slow viruses. It means that they take a long time to exhibit their potent effects. They are also RNA or “retro” viruses, in that in order for them to become parasitic inside the cell, the RNA has to be reverted to DNA genetic material. DNA is the native genetic material of all human cells, including the immune cells. Once the virus enters the cell, it is converted to DNA that is incorporated into the cell’s DNA, from where it “takes over” the cell and controls its activity. The shell of the virus also contains the substances called enzymes that help the virus to enter and take over the cell. These enzymes have long names ending in “ase” that describes what the enzyme does. The enzyme that “transcribes” the RNA to make other RNA is called “transcriptase” and the enzyme that “transcribes” RNA to make DNA is called “reverse transcriptase” while the enzyme that helps integration of the viral DNA into the host’s DNA is called “integrase”.

When the HIV virus enters the CD4 immune cell with the aid of its enzymes, it produces DNA that is incorporated into the host DNA and either becomes latent or active. The active DNA controls the cells engine to produce more viral particles and the latent DNA hides in the cell for a period of time before it becomes active. The infected CD4 cells are killed, either by themselves (cellular suicide, scientifically called apoptosis). This suicide killing is programmed into the cells’ genes, such that cells that are abnormal kill themselves. The virus may also kill the cells, usually at the end of a replication cycle or its brothers, the “killer T-cells,” may kill it. Eventually the CD4 count drops, so the body loses its surveillance system and eventually starts picking up common, everyday infections called opportunistic infections. These are infections that the normal person does not contract. Even old “healed” infections may return and cancer cells, which escape detection by a now weakened immune system, may grow. The person usually succumbs to overwhelming infection or cancer.

There are two types of HIV viruses, a type 1 and a type 2. Type 1 is more infective and more virulent than type 2. The weaker type 2 is located mainly in West Africa.

For comments or question contact:

Dr. Rohan Deshong

Tel: (784) 456-2785

email: deshong@vincysurf.com