Viral STIs I Flashcards
What is the indicator for AIDS infection?
CD4 count less than 200/microliters
What are the surface proteins on the AIDS virus?
gp120 gp41 pol p17 p24
What is the family and genome type of HIV?
Retroviridae famiy
+ssRNA
Is HIV enveloped?
Yes
Where is HIV-2 found in the world?
Africa
What is the difference in HIV-2 compared to 1?
Lower CD4 decline
Lower mortality
Longer asymptomatic period
What is the function of the gp120 protein on HIV?
attachment to CD4
What is the function of gp41 protein on HIV?
Fusion protein
How many genome copies does HIV have?
2
What is the pol gene with HIV?
Reverse transcriptase
What is the p17 protein on HIV?
matrix protein
What is the p24 protein on HIV?
Capsid protein
What are the four layers of the HIV virus?
Envelope
Matrix
Nucleocapsid
Genome
What is the step that must occur outside the cell for HIV to become mature?
Protein cleavage of gag-pol polyproteins
What are the two coreceptors that allow for a conformational change in gp120 to allow binding to the cell?
CCR5
CXCR4
What is the R5 tropic HIV? When in the disease progression is this seen?
Uses CCR5 as a coreceptor
Usually early in infection
What is the X4 tropic HIV? When in the disease progression is this seen?
virus that uses CXCR4
Associated with later, and more deadly
Some individuals contain a deletion in what gene that prevents HIV from binding to gp120? Does this make them resistant to HIV?
CCR5 gene (either homo or heterozygous)
Not resistant b/c may still be affected with other
What is the protein that allows for the fusion of the HIV virus?
gp41
How error prone is the reverse transcriptase of HIV viruses? What is the significance of this?
Very (1/2000 nucleotides).
This means a high rate of mutations and evolution
What is the enzyme that integrates the HIV DNA?
Viral integrase
What is the viral DNA called when it is integrated in the host’s DNA?
Provirus
What is HIV egress?
Budding of HIV out of the cell
Where on the cell membrane does budding occur for HIV?
In lipid rafts made of viral proteins
Once outside the cell, HIV virus has to do what to mature? What mediates this?
Viral protease cleaves gag and gag-pol polyproteins
How do mature HIV particles look under EM?
have a central capsid
Which way is more effective for HIV transmission (male to female or female to male)?
Male to female
What can increase the chances of infection for HIV?
presence of other STIs that generate lesions
What is the chance that a mother will transmit HIV to her child (if not treated)? When is the chance highest?
25%
Highest during the birthing process (50-65%)
What is the risk of contracting HIV with a contaminated needle?
0.3%
What is the risk of contracting HIV from mucous membrane exposure?
0.09%
How can you lower the risk of contracting HIV when exposed/
Post-exposure prophylaxis
When is the p24 antigen seen in infection?
Peaks early in infection, and does not return until later in infection
When is the gp120 seen in infection?
Throughout infection
Which viral protein is used for diagnosing HIV? Why?
gp24 Seen in highest [C] throughout
When does acute HIV syndrome occur in infection? Symptoms? Will HIV antibodies be present?
3-6 weeks
Similar to mono
Rash
Antibodies not seen yet
What is the first viral particle detected in HIV infection? How long does this last for?
p24 antigen. Not last long
What happens immediately after the acute phase of HIV?
Curtailed viral particles
What occurs in chronic phase of HIV infection?
A low level of viremia
How can HIV cause chronic infection? (3)
Genetic drift of gp120
Inactivation of Immune response
cell-cell fusion hiding
Are patient symptomatic during a chronic infection? How long can this last?
No symptoms
up to 10 years
What is the significance of the HIV set point?
used for predicting death based on the initial level of viruses in the blood at one year
How does HIV progress to AIDS?
Reduction of CD4+ T-cells via copious budding
What causes the oral hairy leukoplakia seen in HIV pts?
epstein barr virus
What causes the pneumonia seen in HIV pts?
Pneumocystis carinii
Mycobacterium TB
What causes thrush?
Candida albicans
What causes CMV retinitis seen in HIV pts? What can this cause?
Cytomegalovirus
May cause blindness
What causes the neoplasms seen on HIV pts?
Kaposi’s sarcoma
B cell lymphoma
What are the two causes of diarrhea seen in HIV pts?
Crytosporidium
Isospora belli
What are the first two antigens seen in HIV infection?
RNA
p24
When is HIV antibody seen in an infection relative to the onset of the initial antigens?
Shortly after, but stays elevated unlike the antigens
What is the first step in screening for HIV?
HIV1/2 antigen/antibody combination immunoassay
What is the next step in diagnosing HIV infection if an HIV1/2 antigen/antibody immunoassay is positive?
HIV1/2 antibody differentiation immunoassay
How does the HIV1/2 antigen/antibody immunoassay work?
Immobilize an antibody/antigen on surface.
Add pt sample.
Add enzyme detection reaction
Besides immunoassays, what can be used for detecting HIV infections?
NAT
PCR
Which five steps can be inhibited in HIV replication pharmacologically?
- Attachment
- Fusion
- Reverse transcription
- Integration
- Protein cleavage
What is the MOA of chemokine coreceptor antagonists?
Binds co-receptor and prevents gp120 interaction
What is the MOA of fusion inhibitors?
Prevent gp41 binding/conformational change
What are the two varieties of reverse transcriptase inhibitors?
Nucleoside inhibitors
Nonnucleoside inhibitors
What is the MOA of nucleoside inhibitors?
Incorporation into growing DNA chain and causes chain termination
What is the MOA of non-nucloeside inhibitors?
Binds to reverse transcriptase and inhibit its activity
What is the MOA of integrase inhibitors?
Blocks the integration of the DNA copy of the viral genome into cell genome
What is the MOA of protease inhibitors?
Peptidomimetic (peptide mimicry) inhibitors of the viral protease
What is the goal of HIV therapy?
Reduce viral load
Why isn’t monotherapy used to treat HIV?
Rapid resistance
What is involved in highly active antiretroviral therapy?
Combination therapies
Prophylatic treatments for opportunistic infections depends on what?
CD4 count
What is the standard of care for antiretroviral therapy?
three ARV drugs from two different classes
Can HIV + mother breast feed safely?
No
Why is a caesarian section indicated for pregnant HIV pts?
Reduce chance of fetus infection
What are the three combination therapies recommended for HIV?
1 NNRTI + 2 NRTIs
1 PI + 2 NRTIs
1 II + 2 NRTIs
HIV viruses that utilize both CXCR4 and CCR5 are called what?
R5X4
Which HIV type are some people resistant to? Do they have to be homozygous or heterozygous?
CCR5
Have to be homozygous
What is the pneumonia type that is seen in AIDS patients, but very rarely in immunocompetent people?
Pneumocystis carinii
What is the fungal infection that AIDS patients often get?
Cryptococcosis
Herpes lasting over a month may indicate what?
AIDS
What is different in a chronic infection (like HIV) compared to a latent infection (like HSV)?
In chronic infections, there is still replication occurring
What is the significance of cell to cell transmission of HIV?
HIV can hide from the immune system this way
How does HIV kill cells?
Copious budding
Other viral like mechanisms
What is the end all test for HIV?
NAT for viral RNA
What is the purpose of the HIV-1/2 antigen/antibody combination immunoassay? What is detected?
p24 antigen or any antibody
Purpose = screening
What is the purpose of the HIV-1/2 antigen/antibody differentiation immunoassay? What is detected?
Only antibodies are detected
Differentiates 1 and 2
Why do you not use the rapid tests for in office tests often?
Requires follow up test
