RETROVIRIDAE AND THEIR CONCEPTS (Micro made easy pp 190)

1. Retro: Retroviridae are a group of RNA viruses. They possess an enzyme called reverse transcriptase. They enter the human cell ≫ and the reverse transcriptase convert the viral RNA into viral DNA ≫ which can integrate into human DNA

2. 2) Grow: Retroviruses can cause cancer in the cells they infect. Once retroviruses infect the human cells ≫ the proto-oncogene (“cancer time bomb”) activates and malignant transformation can occur

3. 3) Blow: Some retroviridae (i.e.: HIV) can blow up their target cells. HIV “blows” up T cells ≫ immunodeficiency.

HIV – PROPERTIES (Micro made easy 192, Fig 25-6)

The HIV virus has a core of: RNA, nucleocapsid (binds to RNA), & protease, reverse transcriptase, integrase. All of this is covered by a capsid protein (CA – used to detect HIV infection). There is an envelope that covers all this and just under the envelope there are matrix proteins (hold up glycoprotein spikes).

HIV –TRANSMISSION (Micro made easy pp 195)

Transmission: Parenteral route.

At risk individuals: Sexual intercourse (homosexuals), Blood product transfusion, Drug use (IVDU), Pregnancy (transplacental spread), Hospital acquired (students, nurses, doctors).

HIV – CELL INFECTION (Micro made easy pp 196)

In sequence:

1. HIV virion will bind to CD4 receptor possessing cell (i.e.: CD4+ T cells, macrophages, monocytes, dendritic cells)≫ fusion of envelope and cell membrane ≫ entry of capsid

2. Reverse transcription occurs: viral RNA is transcribed to DNA ≫ enters human nucleus ≫ integrates itself.

3. Viral replication: The virus now uses the human cell machinery to produce new RNA ≫ capsids form ≫ capsid virion buds through the host cell membrane using it as the envelope (smart arse viruses) to infect other cells. This process kills the CD4+ cells.

HIV – IMMUNOLOGY & PATHOGENESIS (Micro made easy pp 196, Fig 25-8)

1. Acute viral illness: This occurs 1 month after initial exposure. There is constitutional symptoms such as: fever, malaise, lymphadenopathy, pharyngitis. Then the immune system activates the symptoms disappear.

2. A clinical latent period: This period is when there is no symptoms of AIDS. The virus continues to replicate though resulting in a steady decline in CD4 T lymphocytes. This lasts for approx 8 years.

3. AIDS: After 8 years of latency ≫ you are not more susceptible to bacterial and skin infections (i.e.: Candida, pneumocystis carinii, Toxoplasmosis, CMV, TB, Cryptosporidium, HSV, cryptococcus, Isospora belli). AIDS is defined as having CD4 cell count of <>Read pp 198 for opportunistic infections and when they occur.