Sunday, July 20, 2008

How does HIV/AIDS work in the body


How does HIV/AIDS work in the body?

STDs - 6 Answers
Random Answers, Critics, Comments, Opinions :
1 :
The virus weakens the immune system. The door is then opened for all kinds of diseases to come in, and the body can't fight them. That's how people die from it.
2 :
HIV enters macrophages and CD4+ T cells by the adsorption of glycoproteins on its surface to receptors on the target cell followed by fusion of the viral envelope with the cell membrane and the release of the HIV capsid into the cell. The interactions of the trimeric envelope complex and both CD4 and a chemokine receptor (generally either CCR5 or CXCR4 but others are known to interact) on the cell surface. The gp160 spike contains binding domains for both CD4 and chemokine receptors. The first step in fusion involves the high-affinity attachment of the CD4 binding domains of gp120 to CD4. Once gp120 is bound with the CD4 protein, the envelope complex undergoes a structural change, exposing the chemokine binding domains of gp120 and allowing them to interact with the target chemokine receptor. This allows for a more stable two-pronged attachment, which allows the N-terminal fusion peptide gp41 to penetrate the cell membrane. Repeat sequences in gp41, HR1 and HR2 then interact, causing the collapse of the extracellular portion of gp41 into a hairpin. This loop structure brings the virus and cell membranes close together, allowing fusion of the membranes and subsequent entry of the viral capsid. Once HIV has bound to the target cell, the HIV RNA and various enzymes, including reverse transcriptase, integrase and protease, are injected into the cell. HIV can infect dendritic cells (DCs) by this CD4-CCR5 route, but another route using mannose-specific C-type lectin receptors such as DC-SIGN can also be used. DCs are one of the first cells encountered by the virus during sexual transmission. They are currently thought to play an important role by transmitting HIV to T cells once the virus has been captured in the mucosa by DCs. Replication and transcription Once the viral capsid enters the cell, an enzyme called reverse transcriptase liberates the single-stranded (+)RNA from the attached viral proteins and copies it into a complementary DNA of 9 kb size. This process of reverse transcription is extremely error-prone and it is during this step that mutations may occur. Such mutations may cause drug resistance. The reverse transcriptase then makes a complementary DNA strand to form a double-stranded viral DNA intermediate (vDNA). This vDNA is then transported into the cell nucleus. The integration of the viral DNA into the host cell's genome is carried out by another viral enzyme called integrase. This integrated viral DNA may then lie dormant, in the latent stage of HIV infection. To actively produce the virus, certain cellular transcription factors need to be present, the most important of which is NF-κB (NF kappa B), which is upregulated when T cells become activated. This means that those cells most likely to be killed by HIV are in fact those currently fighting infection. In this replication process, the integrated provirus is copied to mRNA which is then spliced into smaller pieces. These small pieces produce the regulatory proteins Tat (which encourages new virus production) and Rev. As Rev accumulates it gradually starts to inhibit mRNA splicing. At this stage, the structural proteins Gag and Env are produced from the full-length mRNA. The full-length RNA is actually the virus genome; it binds to the Gag protein and is packaged into new virus particles. HIV-1 and HIV-2 appear to package their RNA differently; HIV-1 will bind to any appropriate RNA whereas HIV-2 will preferentially bind to the mRNA which was used to create the Gag protein itself. This may mean that HIV-1 is better able to mutate (HIV-1 infection progresses to AIDS faster than HIV-2 infection and is responsible for the majority of global infections). Assembly and release The final step of the viral cycle, assembly of new HIV-1 virons, begins at the plasma membrane of the host cell. The Env polyprotein goes through the endoplasmic reticulum and is transported to the Golgi complex where it is cleaved by protease and processed into the two HIV envelope glycoproteins gp41 and gp120. These are transported to the plasma membrane of the host cell where gp41 anchors the gp120 to the membrane of the infected cell. The Gag and Gag-Pol polyproteins also associate with the inner surface of the plasma membrane along with the HIV genomic RNA as the forming virion begins to bud from the host cell. Maturation either occurs in the forming bud or in the immature virion after it buds from the host cell. During maturation, HIV proteases cleave the polyproteins into individual functional HIV proteins and enzymes. The various structural components then assemble to produce a mature HIV virion. This cleavage step can be inhibited by protease inhibitors. The mature virus is then able to infect another cell. EA
3 :
HIV is Human Immunodeficiency Virus and AIDS is Acquired Immuno Deficiency Syndrome. HIV is the Factor which leads to a condition known as AIDS. The HIV is of several type but mostly their mode of action is same. They come under the class of Retro Virus. They contain RNA as their genetic material. They are having one enzyme known as Reverse transcriptase. This enzyme help them to form DNA fro RNA. This DNA then get attached to the Human DNA or may be present as it is in the cell and utilizes the nutrients (proteins, nuclic acids, amino acids) in the human cell to produce large number of replicates/clone. They maily affect the Immune system. As the person gets immuno compromise, there is a high chances to have other diseases side by side. So, AIDS is not a single disease it is the Syndrome which comprises of several diseases due to the deficiency of immune factors in the Body.
4 :
hiv make my immune cell of type (t) tired and this cell cannot treated to another virus
5 :
hiv is spread when blood, semen, or vaginal fluids from an infected person enter someone else's body. Once a person becomes infected, the virus attacks and gradually weakens his or her immune system. Aids is the last phase in HIV disease, when the body is no longer able to fight infection or disease. Without treatments, AIDS develops in most people in 12 to 13 years after they first become infected with HIV. With treatment, AIDS may be delayed fo many more years.
6 :
A healthy body is equipped with CD4 helper lymphocyte cells (CD4 cells). These cells help the immune system function normally and fight off certain kinds of infections. They do this by acting as messengers to other types of immune system cells, telling them to become active and fight against an invading germ. HIV attaches to these CD4 cells, infects them, and uses them as a place to multiply. In doing so, the virus destroys the ability of the infected cells to do their job in the immune system. The body then loses the ability to fight many infections. Because their immune systems are weakened, people who have AIDS are unable to fight off many infections, particularly tuberculosis and other kinds of otherwise rare infections of the lung (such as Pneumocystis carinii pneumonia), the surface covering of the brain (meningitis), or the brain itself (encephalitis). People who have AIDS tend to keep getting sicker, especially if they are not taking antiviral medications properly. AIDS can affect every body system. The immune defect caused by having too few CD4 cells also permits some cancers that are stimulated by viral illness to occur — some people with AIDS get forms of lymphoma and a rare tumor of blood vessels in the skin called Kaposi's sarcoma. Because AIDS is fatal, it's important that doctors detect HIV infection as early as possible so a person can take medication to delay the onset of AIDS.



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Posted by HIV/AIDS at 3:57 PM