Micro 24 - HIV Flashcards
What 2 proteins does the HIV lipid membrane contain and what do they do?
gp120 and gp41 which are important in the binding of the host cell.
gp120: It is the grabber of the HIV: it hooks on to the CD4+ binding site. It then changes its formation to bind on to something else called Coreceptors (either CCR5 or CXCR4). This is called tropism. Grabbing both receptors is called dual tropism.
gp41: Responsible of fusion and entry into the host virus.
What is usually the first cell that the HIV virus infects?
A macrophage or dendritic cell that resides in the exposed mucosa.
Which cells have more CCR5 coreceptors than CXCR4?
Macrophages and dendritic cells.
What kind of genome does HIV have?
A diploid genome: composed of 2 molecules of RNA. This RNA is enclosed by a conical capsid, which is composed of viral protein P24.
Which cells have more CXCR4 coreceptors than CCR5?
CD4+ T cells.
What are the three main structural genes of the HIV virus?
- gag gene: p24 capsid protein.
- env gene: gp120, gp41
- pol gene: Reverse transcriptase, Integrase
What does the reverse transcriptase of HIV do?
The reverse transcriptase is injected with the RNA when it invades a host cell. Inside the host cell, the transcriptase synthesizes double stranded DNA using the RNA.
What does the Integrase of HIV do?
An enzyme that helps integrate the viral DNA into the host DNA.
How do we make the diagnosis of HIV?
ELISA - High sensitivity
Western Blot - High specificity
What is a viral load test for HIV and why is it used for?
PCR test that quantifies HIV RNA in blood. Used to monitor effectiveness of drug therapies or confirm diagnosis (but only acute infection or if newborn since newborns might have the antibodies but may not necessarily have the virus.)
What is the window period for HIV infection?
ELISA and Western blot are used to find the antibodies for gp120 and p24. Therefore, these test give false negatives in the first one to two months: the window period.
How is the diagnosis of AIDS made?
- CD4 T cell count less than 200 (normal is 500-1500).
2. Percentage of CD4 T cells
What are three infections that AIDS patients most commonly present?
- Pneumocystis jirovecii pneumonia (PCP): Interstitial infiltrates on CXR and CD4 count.
What symptoms would histoplasma capsulatum cause in someone who is immunocompetent versus someone who has HIV/AIDS?
Immunocompetent: Mild pulmonary disease, associated with bird and bat droppings in Ohio and Mississippi river valleys.
AIDS patients: Systemic disease with hepatosplenomegaly, fever, cough, especially in CD4 count
What does a ring-enhancing lesions on the brain on an HIV patients suggest?
Toxoplasmosis > HIV associated Primary CNS lymphoma.
