The+Science+Behind+it+All

The Science Behind it ALL

HIV is a virus, like the flu or common cold... so why is it so much more dangerous, and ultimately leads to death when the common cold or flu virus can be treated ? It all has to do with the type of virus which HIV is and how it spreads and evolves. For all you science-oriented guys out there, or just the curious ones who want to know why HIV is as deadly as it is, here are some scientific explanations; take a look at the pictures as well, to understand what's going on a little better.

To briefly summarize the following information, let's simplify the life cycle of HIV, or the human immunodeficiency virus:


 * THE HUMAN IMMUNODEFICIENCY VIRUS (HIV) IS LIKE MANY VIRUSES IN THAT IT IS NOT LIVING, AND THEREFORE, CANNOT REPRODUCE ON ITS OWN. IT MUST PENETRATE A CELL OF THE BODY AND USE THE REPLICATING ENZYMES OF THE INVADED CELL TO REPRODUCE ITSELF. HIV IS A TYPE OF RETROVIRUS, MEANING THAT IT MUST USES ITS OWN ENZYMES AS WELL AS THE CELLS ENZYMES TO REPLICATE ITSELF. ALL RETROVIRUSES HAVE A MECHANISM CALLED REVERSE TRANSCRIPTION, WHICH ALLOWs THE REPLICATION OF THE VIRUS MATERIAL TO BE 'REVIEWED' BEFORE BEING FORMED. HOWEVER, THE HIV VIRUS LACKS A PROPER FORM OF THIS ENZYME, MEANING THAT THERE ARE MUTATIONS IN THE VIRUS. HIV ONLY INFECTS CELLS OF THE I MMUNE SYSTEM , MAKING IT EVEN MORE DEADLY AS IT DESTROYS THE BODY'S ABILITY TO FIGHT OFF OTHER SICKNESSES. THIS PROCESS OCCURS IN MANY STAGES:**

1. ATTACHMENT HIV has surface proteins known as gp120, as seen in the diagram to the right, that attach to cells that have CD4 receptors on their surfaces. These types of cells are cells of the human immune system; CD4 are receptors that are found on T lymphocytes, or white blood cells, and on other scavenger cells called macrophages. This simply means that the HIV virus targets white blood cells, which are responsible for help ing the body fight off unwanted diseases and bacteria. Due to this, the HIV virus weakens the immune system and leads to death as the patient becomes plagued with illnesses the body would normally be able to fight off.



2. PENETRATION The HIV virus binds to the CD4 receptors, or other cell-surface proteins, on the surface of the white blood cell; these connections are called co-receptors. When the virus forms a co-receptor with the cell it is about to penetrate, it is able to fuse with the cell. The fatty membrane of the virus, called the lipid membrane, merges into the lipid membrane of thecell, opening up to allow the viral core into the cell itself.



3. INTEGRATION When the viral core enters the cell, it sheds off its exterior coat, allowing the genetic material of the virus, called RNA, into the cell. It also releases other enzymes which aide the HIV virus in the first few steps of its replication. Before copying itself as part of the cell's DNA, the viral enzymes first convert the viral RNA into DNA compatible with the cell, known as cDNA, or complementary DNA. As mentioned previously, because the HIV virus lacks a proper reverse transcription enzyme, when the DNA is processes, it is riddled with mutations. This creates various forms of HIV, making it hard to find a cure as there are many strains and mutations.

4. BIOSYNTHESIS To create DNA from theRNA, the RNA is destroyed by an enzyme released by the virus known as ribonuclease H. The imperfect reverse transcription enzyme found in the virus can then synthesize a new DNA strand using the RNA as a 'template'. The newly formed double stranded DNA then enters the nucleus with other viral proteins such as the enzyme called integrase. Integrase enzymes help to fuse the viral DNA with that of the cell, creating a new viral DNA called a provirus. To begin creating more of the HIV virus, the proviral DNA must be changed back into RNA. This is because the RNA contains the necessary codes to produce the capsid proteins, or the outer layer of the virus, as well as any other proteins needed for the viral assemble. Then, while spliced into the helper T DNA, the RNA also contains codes for what is known as an envelope protein. These envelope proteins are produced in the Endoplasmic Reticulum and are moved through the Golgi apparatus, the packaging center of the cell, before coming to the surface of the cell.

5. ASSEMBLY AND RELEASE In the final stages of the virus life cycle, the viral RNA molecules gather at the surface of the cell with all the other viral components. There, they are assembled at the membrane and bud off from the host cell. Even though they have left the helper T cell, however, the foreign print of the virus remains on the cell. Other white blood cell detect the foreign nature of the infected helper T and destroy it before it may infect other cells or create mutation in other cells. By this time, though, the HIV virus has left the cell and moved on to infect other white blood cells, slowly deteriorating the immune system of the infected... **THAT'S A LOT OF INFORMATION ABOUT THE SCIENCE BEHIND THE HIV VIRUS, AND WHY IT IS HAZARDOUS TO OUR HEALTH. THE INFORMATION PRESENTED DEALS A LOT WITH BIOLOGY ON A MICROLEVEL, AND CAN BE DIFFICULT TO UNDERSTAND. THE BASIC THING THAT SHOULD BE REMEMBERED IS THAT HIV ITSELF IS A VIRUS LIKE ANY OTHER. HOWEVER, BECAUSE OF THE CELLS THAT HIV TARGETS, NAMELY THE CELLS OF THE I MMUNE SYSTEM, IT LEAVES AN INFECTED PERSON SUSCEPTIBLE TO MANY OTHER DISEASES WHICH THEIR BODY WILL NOT BE ABLE TO FIGHT OFF IN THE ADVANCED STAGES OF AIDS. THIS IS WHY HIV / AIDS ULTIMATELY LEADS TO DEATH. WHY CAN'T IT BE PREVENTED LIKE OTHER VIRUSES? BECAUSE OF THE MUTATIONS THAT OCCUR WITH THE IMPROPER REVERSE TRANSCRIPTION ENZYME, SCIENTIST HAVE NOT BEEN ABLE TO DEVELOP A CURE THAT CAN WORK AGAINST ALL STRAINS OF THE VIRUS.** HIV = HUMAN IMMUNODEFICIENCY VIRUS= A VIRUS CAUSING A DEFICIENCY OF THE HUMAN IMMUNE SYSTEM