HIV and AIDs Flashcards
What is a virus?
- Totally dependent upon a living cell for replication and existence, some contain RNA/DNA polymerases
- Only possess either RNA or DNA
- Have a receptor binding protein to attach to cells and use them as virus production factories
Describe the viral structure of HIV
- Spherical
- Lipid bilayer membrane derived from host cell
- Glycoproteins
- Spherical shell of p17 proteins
- Inner conical capsule of p24 proteins
- Virus core - RNA and reverse transcriptase
What are the clinical features of AIDs
- Predisposes individual to life threatening infections with “opportunistic” organisms like CMV, Candida and HSV
- Seroconversion illness - presents with an infectious mononucleosis like illness
- AIDs-related complex or persistent generalised lymphadenopathy
- Full-blown AIDs
How long can the incubation period be for HIV
From a few months to more than 10 years
Which cancer is most common in people with HIV/AIDs and where can it present
Kaposi’s Sarcoma
Skin - Mouth - Gastrointestinal - Respiratory tract
Describe the binding phase of HIV replication
HIV attachment proteins bind to CD4+ surface receptor
This activates other proteins on cell’s surface allowing HIV envelope to fuse to outside of the cell
Describe the reverse transcription phase of HIV replication
- After the binding process the viral capsid that contains the RNA and important enzymes is released into the host cell
- Reverse transcriptase makes a DNA copy of the RNA
- This new DNA is called proviral DNA
Name some anti-HIV drugs and how they work
- Nucleoside analogues - interfere with copying of the virus genetic material preventing virus replication
- Zidovudine, Retrovir, Videx, Hivid, Zerit, Epivir
Describe the mode of action of Zidovudine
- The triphophosphate is a very potent inhibitor of viral RT enzyme and prevents nucleoside chain elongation
- The 3’ positioning of azido group blocks the essential phosphodiester linkage which would normally enable the next nucleotide to be added to the DNA chain
What are the side effects of Zidovudine
- Cellular enzymes phosphorylate the pro-drug to the active form and so the active form can accumulate in uninfected cells as well as infected cells causing toxic effects
Describe the Integration phase of HIV replication
- The HIV DNA enters the cell nucleus
- The integrase enzyme integrates the proviral DNA into the cell’s DNA
- Integration can be blocks by integrase inhibitors
Describe the transcription phase of HIV replication
- Transcription can be blocked by antisense antivirals or transcription inhibitors, these classes of drugs are still being developed
Describe the translation phase of HIV replication
- The mRNA is translated into new viral proteins
What is the final stage of HIV replication
Viral assembly
Why is antiretroviral therapy recommended for all HIV-positive people
- To prevent disease progression
- To prevent transmission of infections
