AIDS: A Silent Killer

AIDS(Acquired Immune Deficiency Syndrome) is a syndrome resulting from the HIV virus. It is when a person’s immune system is too weak to fight off many infections, and develops when the HIV infection is very advanced.

AIDS: A Silent Killer

This is the last stage of HIV infection where the body can no longer defend itself and may develop various diseases, infections and if left untreated, causes death.

There is currently no cure for HIV or AIDS. However, with the right treatment and support, people can live long and healthy lives with HIV. To do this, it is especially important to take treatment correctly and deal with any possible side-effects.

Basic facts about AIDS

  • AIDS stands for acquired immune deficiency syndrome.
  • AIDS is also referred as advanced HIV infection or late-stage HIV.
  • Someone with AIDS may develop a wide range of other health conditions including: pneumonia, thrush, fungal infections, TB, toxoplasmosis and cytomegalovirus.
  • There is also an increased risk of developing other life-limiting conditions, including cancer and brain illnesses.
  • CD4 count refers to the number of T-helper cells in a cubic milliliter of blood. When a person’s CD4 count drops below 200 cells per milliliter of blood, it indicate AIDS to that person.

What is HIV?

HIV is a virus that gradually attacks the immune system, which is our body’s natural defense against illness. If a person becomes infected with HIV, they will find it harder to fight off infections and diseases. The virus destroys a type of white blood cell called a T-helper cell and makes copies of it-self inside them. T-helper cells are also called  CD4 cells.

Basic facts about HIV

  • HIV stands for human immunodeficiency virus.
  • If left untreated, it can take around 10 to 15 years for AIDS to develop, which is when HIV has severely damaged the immune system.
  • Body fluids of an infected person have HIV in: semen, blood, vaginal and anal fluids and breast milk.
  • HIV cannot be possibly transmitted through sweat, saliva or urine.
  • One can also risk infection by using infected needles, syringes or other drug-taking equipment (blood transfusion), or from mother-to-child during pregnancy, birth or breast feeding.

Immune Response to HIV

Innate Immune Response:

Innate defenses at first stop HIV and it cannot penetrate from unbroken skin. HIV is transmitted via direct exchange of body fluids. Sexual intercourse is the most common mode of transmission. Blood to blood contact, such as through sharing needles for intravenous injection or blood transfusion can also transmit HIV.

Initial Response:

HIV transmitted through sexual activity enters the bloodstream via mucous membranes lining the vagina, rectum and mouth. Macrophages and dendritic cells on the surface of mucous membranes bind virus and shuttle it into the lymph nodes, which contain high concentrations of helper T cells (CD4+ T cells).

A pathway showing the immune response of body against HIV infection in which primary infection gradually lead to the destruction of host immune system eventually causing AIDS

Antibodies and cytokines Production:

Once HIV has entered the body, the immune system initiates anti-HIV antibody and cytotoxic T cell production. However, it can take one to six months for an individual exposed to HIV to produce measurable quantities of antibody. The immune response is weakened as memory T cells (CD4+ CCR5+) are destroyed.

 HIV leading to AIDS

Transfer of virus to lymphoid tissues:

HIV enters the body and binds to dendritic cells (orange cells with projections) which carry the virus to CD4+ T cells in lymphoid tissue establishing the infection.

Viremia and Dissemination of virus:

Virus replication accelerates producing massive  viremia and wide dissemination of virus throughout the body’s lymphoid tissues. An immune response against virus causes some protection but a chronic persistent infection is possible to occur.

 Change in Lymphoid tissues:

The production of cytokines and cell divisions that regulate the immune response for protection also cause HIV replication. There is a rapid turnover of CD4+ T cells that ultimately leads to their destruction and to a change in lymphoid tissues that prevent immune responses.

Cellular immune responses to HIV

  • Cytotoxic lymphocyte production follows the rise of HIV in the blood.
  • Reductions in HIV specific helper T cell numbers may lead to decreased activation and survival of cytotoxic CD8 T cells.
  • Reduced CD4 T cells may also result in an incomplete activation of CD8 T cells that can remove HIV infected cells, resulting in a decreased ability to destroy virally infected cells.
  • The rapid loss of memory helper T cells, and the inability to replace these cells leads to increasing immunodeficiency.

Why there is no cure for HIV????

  • Since HIV targets T lymphocyte, so it stops all the immune activation of host.
  • The virus has a long incubation period (6-10 years)
  • HIV mutates quickly so it is difficult to design a specific antibiotic against it.

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