MISC Flashcards
What is AIDS?
Acquired Immunodeficiency syndrome–> Late stage HIV
What is HIV
Human immunodeficiency virus: An RNA retrovirus
What is the most common type of HIV?
HIV-1
HIV-2 confined to West Africa
What does the HIV virus do?
Enters and destroys CD4 T helper cells.
How does HIV enter cells?
Via the GP120 envelope glycoprotein on its surface.
What happens to the infected CD4 cells?
They migrate to lymphoid tissue where the virus replicates, producing billions of new virions which are released and go on to infect new CD4 cells
What is a virion?
An entire virus particle, consisting of a capsid (outer protein shell) and inner core of DNA or RNA/
What is the structure of HIV?
Spherical RNA lentivirus. Envelope covered in glycoproteins gp120 and gp41 contains matrix with nucleus held inside the capsid.
What does HIV’s capsid contain?
Two enzymes essential for replication (reverse transcriptase and integrase) and two strands of RNA.
What cells does HIV infect?
Cells with CD4 receptors on their surface: T cells, monocytes, macrophages and dendritic cells.
How does HIV attach and enter immune cells?
The gp120 spikes lock onto the CD4 receptor and another co-receptor (CCR5 or CXCR4). The gp41 protein is then used to fuse the HIV envelope to the cell wall, allowing the capsid to enter.
What happens when HIV RNA enters the immune cell?
It must be reverse transcribed into proviral DNA before it can be integrated into the hosts DNA. This is done using reverse transcriptase
What happens after HIV RNA has been converted into DNA?
HIV’s integrase enzyme attaches itself to the end of the proviral DNA strands and it passes through the wall of the cell nucleus and binds to the host cells DNA
What is a latently infected cell?
When the proviral DNA has integrated into the host cells DNA, HIV remains dormant for a period.
When do infected CD4 cells become activated?
If they encounter an infectious agent
What happens when the infected cell becomes active?
HIV uses the hosts RNA polymerase to make new HIV RNA which are split into pieces using HIV’s protease enzyme
What happens to the newly formed HIV RNA after being produced?
They begin to assemble into new viruses at the cell wall and becomes enclosed in a capsid. It then takes lipids from the cell wall to make surface glycoproteins and buds from the cell wall.
How does HIV enter the body?
By infecting CD4 cells in the mucous membranes of the vagina or rectum, or by direct infection of CD4 T-cells in the bloodstream
What is PrEP?
Pre-exposure prophylaxis that people at risk of HIV can take consistently to prevent it.
How soon after exposure does HIV arrive at the lymph nodes?
24 to 28 hours
Where does HIV begin to replicate and how long does this stage last?
the lymph nodes for 7-21 days. Not detectable at this period
How soon after exposure is HIV detectable in the blood by viral load testing?
Several weeks after infection
What are the common symptoms of acute HIV infection and how long do they last?
Symptoms can last for up to 2 weeks: Fever Rash Swollen glands Myalgia Significant weight loss May be asymptomatic
What is the asymptomatic phase of HIV and how long does it last?
After acute infection, HIV will not cause further illness for some years and the number of infected CD4 cells falls. (usually lasts around 10 years)