5.6 Sexually Transmitted Infections HIV

What type of genome does HIV have?

Single-stranded RNA

What shape is the HIV capsid?

Irregular cone-shaped capsid

What three viral enzymes are packaged inside the HIV capsid?

Reverse transcriptase, integrase, protease

What two proteins make up the HIV spike?

gp120 and gp41

What does gp120 bind to?

CD4 receptor on T-helper cells

What does gp41 bind to?

CCR5 co-receptor

What happens in people with the CCR5-delta32 mutation?

HIV entry is blocked because CCR5 is nonfunctional

What allows HIV to fuse with the host membrane?

gp41 activation after binding CCR5

What does reverse transcriptase do?

Converts HIV RNA into DNA provirus

What does integrase do?

Inserts the provirus into the host chromosome permanently

What are HIV polyproteins?

Large protein chains that must be cut by protease to form functional viral proteins

Why are protease enzymes required?

They mature new viruses by cutting polyproteins into final proteins

What is viral maturation?

Final processing of HIV proteins by protease so virus can replicate

What happens if protease is inhibited?

Immature HIV virions are produced that cannot replicate

What are the three stages of HIV pathogenesis?

Acute phase, chronic phase, AIDS

What happens during the acute phase?

High viral load, drop in T-helper cells, mild flu-like symptoms

How long does the acute phase last?

~3 months

Why can't HIV be eliminated from the body?

The provirus is permanently integrated into host DNA

What happens during the chronic phase?

Gradual loss of T-helper cells over 7-10 years, usually asymptomatic

At what T-helper cell level does AIDS begin?

200 cells/mL of blood

What defines AIDS?

Immune failure causing inability to fight infections or cancers

Common symptoms of AIDS

Recurrent respiratory infections, wasting, prolonged diarrhea

Reservoirs for HIV

Human hosts or carriers

Portals of exit for HIV

Blood, sexual secretions, breastmilk

Modes of transmission for HIV

Direct contact (sex), vehicle (needles/equipment), vertical (placenta, childbirth, breastfeeding)

Portals of entry for HIV

Broken skin and mucous membranes

Is HIV a primary or opportunistic pathogen?

Primary

What is ART?

Antiretroviral therapy using multiple drugs that block different replication steps

What does ART do to viral load?

Reduces it to zero (undetectable), but does not cure infection

What is PEP?

Post-exposure prophylaxis taken within 72 hours of exposure

What is PrEP?

Pre-exposure prophylaxis for people at ongoing risk

Name the four major HIV drug classes

Fusion inhibitors, reverse transcriptase inhibitors, integrase inhibitors, protease inhibitors

How do fusion inhibitors work?

Block gp41 from mediating membrane fusion

How do reverse transcriptase inhibitors work?

Prevent formation of the provirus

How do integrase inhibitors work?

Prevent insertion of proviral DNA into host chromosome

How do protease inhibitors work?

Block maturation of new HIV virions