Definitions HIV and AIDS
HIV stands for human immunodeficiency virus. AIDS stands for acquired immune deficiency syndrome. These are the scientific names to describe a virus that destroys the immune system and leads to a syndrome of immune deficiency. HIV/AIDS is also known by several common names that vary not only in different languages but have developed according to regional history and cultural understanding of the disease. This is discussed further under what does HIV/AIDS stand for?
What is HIV?
HIV (Human Immunodeficiency Virus) infects a person and this is known as HIV infection although it is commonly referred to just as HIV. In HIV infection, the virus destroys the CD4+ T-lymphocytes (a type of immune cell) and by doing so it impairs the part of the immune system that protects the body by the action of immune cells (cell-mediated immunity). A person who is HIV-positive, also known as a person living with HIV, is any person who has undergone HIV testing and HIV infection has been confirmed.
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What is AIDS?
AIDS (Acquired Immune Deficiency Syndrome) is a condition of a low or weakened immune system which is not present since birth but contracted during the course of life.With AIDS, the body’s immune defenses are so severely compromised that even minor infectious ailments can be life threatening. More importantly the body is prone to contracting infections that the otherwise healthy immune system would have combated at the outset. AIDS is diagnosed in an HIV-positive person once the CD4+ T-lymphocyte level drops below 200 cells/uL and/or in the presence of certain diseases known as AIDS-defining illnesses.
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Does HIV Cause AIDS?
HIV infection can lead to AIDS although the exact time period when AIDS will develop cannot be estimated at the outset – it can happen within years or even decades. HIV infection does not mean that a person has AIDS but does mean that a person can eventually develop AIDS. There are other types and causes of immune deficiency and while some may argue that HIV and AIDS are not related and the disease process is still not completely understood, it should be accepted that HIV can lead to AIDS. Using anti-retroviral (ARV) drugs in HIV infection delays the onset of AIDS, thereby prolonging the life span and also improves the patient’s quality of life.
How does HIV Infection Occur?
Types and Spread of HIV
There are two types of HIV (viruses) – HIV-1 and HIV-2. HIV-1 is the most common cause of HIV infection globally although HIV-2 is more frequently seen in West Africa and Europe to some extent. The subtypes of HIV-1 and HIV-2 differ geographically. HIV is primarily spread by sexual transmission, IV drug use, mother-to-child and less frequently these days, through blood transfusions.
Viral Attachment and Replication
Once the virus enters the body, proteins that protrude from the surface of the virus (gp120 glycoproteins) attach to the receptors on the surface of CD4+ T-lymphocytes as well as co-receptors known as CCR5 and CXCR4. The viral and cell membrane then fuse through the involvement of another HIV glycoprotein known as gp41. A viral enzyme known as reverse transcriptase then uncoats and reverse-transcribes the viral RNA into proviral DNA within the host cell.
New HIV Virus Production
The viral integrase enzyme allows the proviral DNA that migrates to the cell nucleus to integrate into the host’s DNA. These viral genes provide a blueprint for messenger RNA to manufacture new viral proteins. The HIV protease enzyme then cleaves these new viral proteins to form HIV proteins that are used for the new virus structure and enzymes. The new viruses are then release by budding through the host cell membrane. These viruses can then attach to other Cd4+ T-lymphocyte cells and repeat the cycle.
Article reviewed by Dr. Greg. Last updated on April 16, 2011