HIV Flashcards
When did HIV begin?
1981 - initially called GRID - gay related immune deficiency
Over 50% of new infections are transmitted by…?
People unaware of their HIV status
That is why it is a critical public health initiative to know your HIV status
What populations are most affected by HIV infections in Canada?
Men who have sex with men
Injection drug users
Indigenous people
**Indigenous people overrepresented in Canada’s HIV epidemic = rate of new infections 2.7x higher than other groups
What is the largest population of people living with HIV?
Globally 38.4 million people living with HIV
Largest population is sub-Saharan Africa = 69% of all global HIV infections
Compare and contrast HIV-1 and HIV-2.
Similarities: both have similar structure and function
Differentiated by: envelope glycoproteins, point of origin, latency period
Where is HIV-1 found? Where was it believed to have originated?
Central Africa **origin
North America,
Europe,
Australia
What are the major classes of HIV-1?
M = main
N = new
O = outlier
+/- P = newest class
Where is HIV-2 found and what are the diseases general characteristics?
Found primarily in West Africa
1. milder disease
2. less virulent
3. longer latency period,
4. no clades
What are clades?
Distinctive branches or subtypes that HIV can be further divided into
- HIV has lots of clades due to the rapid rate of mutation
* individuals can be infected with more than one clade of HIV
How many clades are within HIV-1?
9 clades within the 3 main classes
What are the 3 methods of HIV transmission?
- Blood contact
- Sexual contact
- Mother to child transmission
What is HIV transmission a result of?
Exposure of bodily fluid of infected person, nature of exposure relates to risk of infection
Describe how HIV is transmitted through sexual contact
- Anal sex - homo or heterosexual, highest risk of tearing/injury, receptive or insertive anal sex
- Vaginal sex
- Oral sex - oral lesions & contact with infections semen/secretions
Which age group is most at risk for contacting HIV through vaginal sex?
Young women, 13-25 yr are more vulnerable due to:
1. immature genital tract mucosa = less reliable mucous production = higher risk of injury + columnar cells are more column like so more place for bacteria to hide
2. More likely to practice unsafe sex
3. Less likely to seek out or access healthcare
What are 3 categories of transmission under blood contact? Give examples of each.
- Injections/needles
eg: sharing needles, needle stick injuries, infected tattoo/skin piercing instruments - Contact with broken skin
eg: exposure through sports, occupation hazard, developing countries - Transfusions or transplants of infected organs/tissues (higher risk in developing countries)
When can MTCT or vertical transmission occur?
Pregnancy
Delivery
Breastfeeding
What 6 factors influence MTCT vertical transmission of HIV?
- Stage of infection
- Breastfeeding pattern
- Oral or breast lesions
- Gastrointestinal illness
- Antiretroviral therapy
- Invasive procedures
How does stage of infections influence risk of vertical transmission?
Higher viral load in early infection = increased risk of transmission = if an infection occurs during or just before pregnancy
How does breastfeeding pattern influence vertical transmission of HIV?
Breastfeeding patterns: exclusive vs mixed
- Exclusive has decreased risk than mixed in developing countries because of unreliable water sources/formula
How do oral or breast lesions influence vertical transmission of HIV?
Oral lesions in baby or breast lesions in mother = increase risk due to:
- increased portals of entry
- increased exposure to blood
How do GI illnesses in babies influence vertical transmission of HIV?
In a baby who has a weakened gut there may
be increased portals of entry for the virus
found in breast milk
+ risk of ulcerations
How does antiretroviral therapy (ART) influence vertical transmission of HIV?
ART significantly decreases risk during of transmission during pregnancy & labour/delivery
How do invasive procedures influence vertical transmission of HIV?
Ex. of invasive procedure = use of forceps during delivery
– can cause increased portals of entry and increase blood exposure
What is HIV not transmitted through?
Tears, sweat, saliva, vomit, faces or urine
They may contain HIV but not in enough amounts to cause an infection
What virus family does HIV belong to?
Retrovirus family: viruses that carry their genetic material in the form of RNA and use the reverse transcriptase enzyme to convert RNA into viral DNA
What genus does HIV belong to?
Lentivirus genus: viruses (within the retrovirus family) that
- affect the nervous and immune systems
- have long latency periods
- have persistent viremia
- have more complex genome structure than other retroviruses
Describe the main elements of HIV’s structure.
- Envelope - gp120 spikes with gp41 stems
- Core - bullet shaped, surrounded by the capsid
- Within the core
- 2 identical strands of RNA
- 3 critical enzymes: reverse transcriptase, integrase, protease
Where can HIV be found at any given time? (6)
- Mucous membranes - macrophages & dendritic cells
- Actively infected CD4 lymphocytes
- Latently infected CD4 lymphocytes (can be latent for 2 years)
- Memory CD4 cells
- Floating or “free” virus
- Sanctuary state in brain or CNS where ART cannot find
What are the sanctuary sites of the HIV?
- Brain / CNS
- Immune system
What cells are a vulnerable target for HIV?
Uninfected but activated CD4 cells as they become infected when they arrive at the site of injury
Describe the summary of events for IV infection
- Portal of entry
- Virus is taken up by macrophages or CD4 cells
- Virus replicates and either
a) becomes latin or
b) buds out of the cell - IF it buds out, it increased the overall viral load in blood AND cytolysis the infected less
- This leads to immunodeficiency, loss of B cell function and opportunistic infection
Explain the receptors and co-receptors that are required for HIV to bind to host cells.
gp120 protein spike binds to CD4 receptors
co-receptors are required for different cell types:
- CCR5: co-receptors for binding to macrophages, early stages of infection (are m-trophic)
- CXCR4: co-receptors for binding to T-helper cells, later stages of infection (are t-trophic)
When do certain cell types become infected?
Macrophages become infected during early stages of infection
T-helper cells become infected during later stages of infection
Why is CD4 testing useful?
It’s used to determine the degree of immunocompromised, the more it decreases the more further progressed the disease is
What is HIV staging based on?
- CD4 and T lymphocyte count
- Count takes precedence over percentage, percentage only used if count is missing
- If no CD4 results available, stage is unknown
How long is the progression of infection in an untreated person?
8-12 years