MSI HIV and AIDS Flashcards
In initial infection, HIV-specific ____ T cells rise sharply and reduce viral load (however, the virus is not fully cleared from the organism)
CD8+
CD4+ T helper lymphocyte effect on dendritic cells
increase class II co-stimulation
CD4+ T helper lymphocyte effect on B cells:
increase maturation and Ab class switching
CD4+ T helper lymphocyte effect on (infected) target cells
Induce apoptosis
CD4+ T helper lymphocyte effect on CD8 T cells:
increase cytotoxic lymphocytes and memory development
CD4+ T helper lymphocyte effect on macrophages:
increase phagocytosis
When the loss of CD4+ T helper cells weakens to the immune response to the point at which opportunistic infections occur, this is known as
AIDS
What is often the first presenting illness of AIDS (as well as the cause of death)?
Opportunistic infections such as TB, P.jiroveci pneumonia, Karposi’s sarcoma of the skin, or toxoplasmosis (CNS infection)
HIV binds to the CD4 and CCR5 receptors via which of the following proteins?
a) P4
b) P17
c) P24
d) gp120
e) gp160
d) gp120
Once gp120 binds to the CD4 and CCR5 receptor, a conformational change results in the expression of gp41 which allows the virus to enter the cell. ( It also uses a chemokine co-receptor to attach to the host cell membrane. There is a complex protein interaction and bc of this they are able to create a channel through which they can gain entry into the cell.)
What type of cells are the primary target for HIV infection?
CD4 T cells
Molecules used for HIV entry into CD4 cells?
Gp120 (also co-receptors CCr5 and CXCR4)
Receptor for Rantes, MIP-1alpha? (Molecules involved in lymphocyte chemotaxis and HIV suppression)
CCR5
Receptor for SDF-1? (Molecules involved in lymphocyte chemotaxis and HIV suppression)
CXCR-4
Lamina propria and intraepithelial CD4 T cells in the gut (ileum, colon, rectum) express high levels of the HIV entry co-receptor ____, which makes them the PRIMARY TARGETS FOR HIV INFECTION
CCR5
Which cells are eliminated rapidly from the gut mucosa during initial HIV infection (leaving the gut susceptible to infections such as CMV)?
CD4 T cells with co-receptor CCR5
What is the most commonly used co-receptor during early phase of HIV infection?
CCR5
HIV strains using CCR5 as a co-receptor are called __ viruses (these are the strains that are most commonly transmitted sexually)
R5
About 5 years into infection, most viruses are able to use the co-receptor _____ . These viruses would now be called “X4” viruses.
CXCR4
Three ways that ___ T cells are destroyed following HIV infection:
Cytophathic effects (structural changes that make the cell unable to function properly)
Apoptosis
Killing of infected cells by cytotoxic lymphocytes
CD4
In acute HIV infection, there is a rapid rise in plasma viral load and a corresponding rise in ___T cell count which tries to contain the virus.
CD8
In the early (first few weeks) stage of HIV infection, CD4 cell counts ____ while CD8 cell counts _____
decrease, increase
What are the three mucosal HIV transmission routes?
GU, rectal, and oral mucosa
Lamina propria CD4 T-cells express high levels of
CCR5
Depletion of CD4 T cell sin the gut leads to increased translocation of gram negative LPS bacteria, which causes generalised immune activation and ___ production
TNF
Inflammatory cytokines like ___ drive HIV replication, and with it, CCR5 upregulation
TNF
What is the test of choice for HIV?
Combined HIV antibody and HIV p24 ELISA (known as the “4th generation” test). These detect the p24 HIV protein Ag as well as the conventional HIV Abs
The time between HIV exposure and when a 4th gen test will identify >99% of infections is known as the _______ period. This is __days according to new guidelines.
window, 45
The ________ period is the time between the infection and when the virus RNA becomes detectable in the blood- NO TEST can identify HIV infection before the end of this period.
eclipse (the first 10 days)
A further HIV test at __ weeks post-exposure may be considered following an event as carrying a high risk of infection if previous tests were negative
8
PCR tests may be used as a confirmation test or if an exposure was very recent. Any test result should be confirmed after __ days using a 4th generation test.
45
In the event of a positive HIV test, the same material should be tested again using…
a different test.
If the result confirms the first test, an additional sample should be tested ASAP for confirmation. This should also be done if the second test is negative.
Drugs used to treat HIV infection include several different types of ___-_____ drugs such as fusion inhibitors, CCR5 receptor inhibitors, reverse transcriptase inhibitors, integrase inhibitors, and protease inhibitors
anti-retroviral
Prescribing a combination of antivirals (usually 3 different classes) is essential due to viral dynamics and …
resistance
What is the measure of viral replication?
viral load- the lower the better
Viral load marker of tx success: aim for “undetectable” level of …
<40
Normal values of CD4+ T cells?
> 500
- Significant risk of morbidity/mortality if CD4+ count is
<200
When CD4+ count drops below normal (till about 200) the patient is at increased risk of __, Kaposi’s Sarcoma, shingles, oral thrush, and seborrhoeic dermatitis
TB
When CD4+ cell count drops below 200, the patient is at increased risk of __________ pneumonia, toxoplasmosis, and lymphoma
Pneumocystis
When the CD4+ count drops below __, the patient is at risk of infections such as Mycobacterium Avium Complex, CMV, progressive multifocal leukoencephalopathy infection, and CNS lymphoma
50
When people at very high risk of HIV take daily HIV medicines to reduce the chances of getting infected, this is known as
Pre-exposure prophylaxis (or PrEP)
The ___ surface protein is used as a primary receptor for HIV entry
CD4
Most CD4 T cells in the gut mucosa are highly activated and express the chemokine receptor, ____, an HIV co-receptor
CCR5
Viruses using the ____ co-receptor are the most common strains to be sexually transmitted
CCR5
____ is an alternative co-receptor (to CCR5)
CXCR4
immune activation from___ production, drives viral replication and the progression of HIV infection towards AIDS
TNF
A negative 4th gen test at __ days after an exposure is thought to exclude HIV infection with 99% certainty
45
Viral Ag levels peak at around __ days after initial infection
28
