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Acquired Immunodeficiency Syndrome (AIDS)


AIDS is a serious infection of the immune system. Its name suggests that it consists of a syndrome of various clinical manifestations brought about not by the virus itself, but by secondary infections and inability of the immune system to combat these. Initial symptoms of HIV infection are mono-like and difficult to diagnose. True symptoms of AIDS take years to develop.

Many secondary infections occur much more frequently in the AIDS population than in healthy individuals. These infections can help to identify undiagnosed cases of AIDS, but are also the predominant cause of mortality in this population. These infections include:

Secondary infection Cause
Mycobacterium avium (MAC) Bacterial
Tuberculosis Bacterial
Pneumocystis jirovecii pneumonia Fungal
Candidiasis Fungal
Aspergillus  Fungal
Cryptococcus  Fungal
Histoplasmosis Fungal
Zygomycosis Fungal
Toxoplasma  Protozoan
Amoebiasis Protozoan
Cryptosporidiosis Protozoan
Microsporidiosis Protozoan
Cyclosporiasis Protozoan
cytomegalovirus infection Viral
lymphoma  Viral
Kaposi's sarcoma Viral
Herpes simplex Viral


Pathogenesis of HIV - detail

  1. Attachment of HIV to CD4+ cell via gp120 protein spike. Spike also binds to a second receptor on macrophages (CCR5) or T-cells (CXCR4). People with genetic deficiency in these receptors are resistant to HIV infection
  2. HIV enters cell by envelope fusion with cell membrane (gp41)
  3. Reverse transcriptase converts viral ssRNA to dsDNA; makes ~ 5 errors per genome
  4. dsDNA enters nucleus, is spliced into host chromosome with help of integrase
  5. Integrated DNA can be transcribed to form virion proteins (gag, gag-pol, env)
  6. Gag and gag-pol must be cleaved by protease into viral proteins
  7. Viral genome, tRNA and proteins associate at membrane. After protease cleavage, virions bud off from host membrane