HIV

Question 1

What is HIV?

Answer 1

A complex retrovirus
a positive-sense, single-stranded RNA genome that serves as a template for DNA synthesis by reverse transcription

Question 2

Which group does it belong to in the Baltimore Classification?

Answer 2

Group VI

Question 3

Describe the structure of HIV

Answer 3

• encased by matrix protein within an envelope derived from host membrane
• envelope contains viral glycoproteins, gp120 and gp41

Question 4

How does the virus enter the host cell?

Answer 4

• gp120 binds to CD4 receptors on the surface of CD4+ T cells
• this attachment triggers a conformational change in gp120 allowing it to bind to a co-receptor called CCR5 or CXCR4 on host cell
• binding of gp120 to CD4 and co-receptor facilitates fusion between viral envelope and membrane
• this leads to entry of viral genetic material

Question 5

What syndrome does HIV cause?

Answer 5

Acquired Immunodeficiency Syndrome (AIDS)

Question 6

What happens once the viral genetic material enters the host cell?

Answer 6

• reverse transcriptase converts viral RNA genome into DNA (reverse transcription)
• this process produces a complementary double-stranded DNA molecule called proviral DNA

Question 7

What happens once the DNA molecule has been synthesised?

Answer 7

• proviral DNA transported to the nucleus
• integrase integrates the viral DNA into host cell’s chromosomal DNA
• allows viral genetic material to become a permanent part of host cells genome

Question 8

What happens once the viral DNA as been integrated?

Answer 8

• integrated viral DNA transcribed by host cells machinery into viral RNA molecules
• these serve as templates for synthesis of viral proteins (gag and env) and enzyme pol

Question 9

What happens in the final step of HIV infection?

Answer 9

• progeny virus assembled at host membrane
• viral protease cleaves proteins into a functional form
• virus buds out from host cell and is released into extracellular space

Question 10

How does HIV evade immune surveillance using mutations?

Answer 10

• high mutation rate due to error-prone nature of reverse transcriptase
• leads to generation of diverse viral variants
• mutation rate = 3x10^-5 per nucleotide base per replication cycle
• continuous mutation allows HIV to remain undetected in the body and develop resistance

Question 11

How does HIV evade immune surveillance using latency and integration?

Answer 11

• HIV can integrate its viral genetic material into the host cells genome
• makes it possible to establish latent infection
• latently infected cells do not produce viral proteins, allowing them to evade detection

Question 12

How does HIV evade immune surveillance using fast replication rate?

Answer 12

• HIV has a rapid replication rate with the generation of 10^9 or 10^10 virions every day
• allows infection to persist within the body without being affected by host immune response