HIV/AIDS

Acquired immunodeficiency syndrome (AIDS) is an immunosuppressed state, caused by infection with the human immunodeficiency virus (HIV). It is characterised by opportunistic infections, neoplasms and neurological manifestations.

According to the United Nations programme on HIV/AIDS (UNAIDS) 2, it is estimated that worldwide in 2008:

  • 33.4 million people were living with HIV, of whom 2.1 million were children under 15 years
  • 2 million people died of AIDS-related conditions, of whom 430,000 million were children under 15 years
  • 2.7 million people became newly infected with HIV

Following infection with the HIV virus, individuals experience a nonspecific, flu-like seroconversion illness, manifesting as fever, sore throat, lymphadenopathy, skin rash and malaise. This is followed by an asymptomatic incubation period, lasting several years.

The diagnosis of AIDS rests on the progression to clinical or serological evidence of immunodeficiency. According to the US CDC definition, one has AIDS if he/she is infected with HIV and presents with either:

  • CD4+ T-cell count below 200 cells/µl (or a CD4+ T-cell percentage of total lymphocytes of <14%)

or

AIDS is caused by HIV, a retrovirus, which infects the CD4+ T-cells and macrophages. Following a period of clinical latency, viral replication within these cells leads to lysis of the CD4+ cells, and macrophage driven transport of the virus into the central nervous system. This results in profound immunosuppression involving primarily the cell-mediated immunity, and in CNS disease, respectively 1.

The main modes of transmission are sexual contact, via blood (e.g. intravenous drug use or blood transfusions) and vertical transmission to the children from HIV infected mothers during childbirth.

Shortly after the sexual transmission of the HIV-1 it faces its first barrier, the mucosal epithelial cells. The HIV-1 crosses this barrier by processes such as transcytosis, dendritic cells, the complement system, damaged mucosal epithelial cells, etc. Following this transmission, the HIV-1 is free to replicate in the lymphoid tissue resulting in the spread to organs allowing a systematic persistent infection to occur. The main site for this replication is the gut associated lymphoid tissue (GALT), where there is a vast depletion of CD4+ T cells without being replaced from their differentiation sites 4. Reasons for this are:

  • spread of the HIV-1 to the thymus and/or bone marrow affects the rate of differentiation of T cells and other leukocytes resulting in pan-leukocytopaenia
  • expression of the homing markers in the GALT is decreased because there is damage to its integrity; the damage results in bacterial translocation which causes a systemic immune activation 4
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Article information

rID: 11078
Section: Pathology
Tag: cases
Synonyms or Alternate Spellings:
  • HIV
  • Acquired immunodeficiency syndrome
  • Acquired immunodeficiency syndrome (AIDS)
  • HIV AIDS
  • Human immunodeficiency virus
  • Human immunodeficiency virus (HIV)

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    Case 1: HIV lipodystrophy
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