Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
30 Cards in this Set
- Front
- Back
What is AIDS characterized by?
|
Infection
Depletion of CD4+ T lymphocytes Immunosuppression that leads to secondary neoplasms, opportunistic infections, and neurologic manifestations. |
|
What are the three major routes of HIV infection?
|
Sexual contact (men who have sex with men is the largest group of infected persons)
Parenteral inoculation Passage of virus from infected mother to newborns |
|
What are two sexually transmitted diseases that are cofactors for HIV?
|
Gonorrhea and chlamydia
(they increases the seminal fluid content of inflammatory cells which presumably carry HIV) |
|
What is the major cause of pediatric AIDS?
|
Mother to infant vertical transmission
|
|
What are the three routes involved with mother-to-infant transmission of HIV?
|
1. In utero (MOST)
2. Intrapartum (during delivery) = MOST 3. Breastmilk |
|
What is the more common strain of HIV among people in the US, Europe, and Central Africa?
|
HIV-1
|
|
Which HIV strain is more common in West Africa?
|
HIV-2
|
|
What four things does the virus core of HIV contain?
|
1. Major capsid protein p24
2. Nucleocapsid protein p7/p9 3. TWO copies of genomic RNA 4. Three viral enzymes (protease, reverse transcriptase, and integrase) |
|
What is the most readily detected viral antigen and the target for antibodies used to diagnose HIV infection in blood screening?
|
p24 (part of the capsid)
|
|
What are the three standard retroviral genes?
|
Gag, pol, and env
Code for various viral proteins |
|
What is the high variability of the HIV genome due to?\
Where is most of the variation at? |
Low fidelity of viral polymerase
Envelope glycoproteins |
|
What are the two groups of HIV based on genome analysis and which one is most common?
|
M (major) and O (outlier)
M is broken down into A-J with B being the most common in the US and Western Europe |
|
What are the two major targets of HIV infection?
|
The immune system and the CNS
|
|
What does HIV require for entry into cells?
|
The CD4 molecule (a high affinity receptor for the virus)
|
|
What else must bind to facilitate cell entry?
|
gp120 to coreceptors
|
|
Describe the fusion process of HIV.
|
HIV gp120 binds to CD4 initially, conformational change that allows gp120 to bind to either CXCR4 (on T cells) or CCR5 (macrophages), gp41 then undergoes a conformational change that allows it to insert into the target membrane.
|
|
What are the two stains of HIV and what do they bind to? When are they present?
|
R5 which binds to CCR5 expressed on monocytes AND T cells (90% of HIV)
X4 which binds to CXCR4 (expressed ONLY on T cells) R5 evolves into X4 over the course of the infection |
|
Why are some patients resistant to developing AIDS?
|
Defective CCR5 receptor
|
|
HIV can infect resting T cells, but what is the initiation of proviral DNA transcription caused by?
|
Exposure to antigens or cytokines
|
|
Why is there a significant drop in T cells in HIV infection during the initial acute phase?
|
Initial infection of T cells is in the mucosal lymphoid tissue (a large reservoir of T cells), causes cell lysis and a sharp drop in T cell count
|
|
Where is the site of viral replication in the initial acute phase? Where does primary infection occur?
|
Lymph nodes
--Blood and mucosa |
|
Where is the virus replicating and destroying cells in the chronic phase of the disease?
|
Lymph nodes and the SPLEEN
|
|
What is the major mechanism of loss of CD4+ T cells in HIV infection?
|
Lytic HIV infection of the cells
Cell death during viral replication and production of virions |
|
What are three mechanisms of cell death that can result from chronic activation of CD4+ T cells?
|
Viral replication of infected cells (cytopathic death)
Activation of uninfected cells (apoptosis) Expression of HIV peptides in cells that causes death by virus specific CTLs |
|
Why is there a selective loss of memory CD4+ T cells early in the course of the disease?
|
Higher expression of CCR5 in this subset and abundance of these cells in the mucosal tissues.
|
|
What is the "vicious cycle" of the HIV viral mechanism?
|
Decreased helper T cell function leads to increased production of inflammatory cytokines, which stimulates more HIV production followed by infection and loss of additional CD4+ T cells.
|
|
What are the roles of macrophages?
|
The "gatekeepers of HIV infection" = viral reservoirs and factories
Infected early and hold on to the virus for longer periods that T cells without dying. Can transport the virus to a number of sites throughout the body (particularly the nervous system). |
|
Why do you see high levels of B cells in HIV infection?
|
--polyclonal B cell activation
--infections with CMV or EBV --gp41 can promote B cell growth --infected macrophages release IL-6 which enhances B cell proliferation --BUT, the antibodies cannot be mounted against newly encountered antigen (defective) |
|
What is brain HIV almost exclusively and why?
|
R5 stain because it was transported there by macrophages (CCR5).
|
|
What is the major cause of death among AIDS patients?
|
Opportunistic infections
|