Acquired Immunodeficiency Syndrome (AIDS) Flashcards
What causes AIDS?
human immunodeficiency virus
What is unique about HIV?
it is a retrovirus, which refers to reverse transcription (RNA to DNA)
What is the target of the human immunodeficiency virus?
the immune system, specifically T helper cells
What is the result of infection with human immunodeficiency virus?
- immunosuppression
- opportunistic infections and cancers
Is there a cure for HIV?
no
There are two strains of HIV - what are they and which is more prevalent?
HIV-1 and HIV-2
HIV-1 is more prevalent
HIV-2 is common in West Africa
How is HIV transmitted?
- sexual transmission (semen is a major reservoir)
- contaminated blood
- maternal (in utero, labour and delivery, lactation)
- occupational (ex. health workers - needle pokes, with routine precautions risk is only 0.3%, will also depend on depth, site and viral load)
What are the three phases of pathology in AIDS?
- primary infection
- latent period
- overt AIDS
Explain the pathology during the primary infection phase of AIDS:
- lasts weeks-months
- there is a window period (time between potential exposure and point when a test will be accurate) and seroconversion (time needed to make enough antibodies to be detected in a test)
- high viral load and low CD4 count
What is CD4?
CD4 is a surface receptor on T helper cells, can be counted easier than trying to identify T helper cells
Explain the pathology during the latent period phase of AIDS.
- can be asymptomatic, sometimes for years
- lymphatic tissue damage
- recurrent respiratory infections
- fatigue
Explain the pathology during the overt AIDS phase.
- may not be until 10 years after infection (can be longer with good management)
- targets T helper cells
- B cells and macrophages also targeted
- destroys immune system, leads to suppressed immunity and defenses, this causes infections from new microbes and from latent pathogens
- various organs are affected
How is AIDS diagnosed?
- clinical progression
- ELISA
- Western blot assay
- PCR
- CD4 counts and viral loads
What is ELISA?
enzyme-linked immunosorbant assay
- uses an enzyme reaction to antibodies
- measures antibodies to antigens on the virus that aren’t necessarily specific to HIV
- need to wait 90 days before there are enough antibodies to confirm diagnosis
What is a Western blot assay? When is it done?
- done if ELISA is positive
- measures a specific antibody for an antigen that is only on the human immunodeficiency virus
What is PCR?
polymerase chain reaction - complex, expensive test, mostly used in research labs, measures viral RNA
What are two newer tests used to diagnose AIDS?
1) P24 antigen - measures a viral protein released during the first phase of infection, allows earlier detection
2) NAT (nucleic acid test) - cheaper than P24 antigen
What are the manifestations of AIDS?
- opportunistic infections
- respiratory infections (TB and pneumonia)
- GI manifestations
- nervous system is affected (dementia, encephalopathy)
- opportunistic cancers, including Kaposi’s sarcoma, non-Hodgkin’s lymphoma and cervical cancer
Explain why someone with AIDS gets opportunistic cancer.
- the immune system is compromised and it can’t detect and destroy abnormal cells, cells which can progress to cancer
- the immune system is also unable to fight off viruses, and the patient can contract viruses which cause gene mutations that lead to cancer (ex. HPV > cervical cancer)
What is Kaposi’s sarcoma?
- arises in endothelial cells (in blood vessels)
- lesions on skin, mouth, lymph nodes
How is AIDS treated?
- no cure, so try and limit progression
- use antiviral agents (anti-retrovirals) in combinations/cocktails to target different steps in the process of the virus getting into cells, replicating and lysing cells
What are the criteria for distinguishing AIDS from HIV?
according to the CDC:
- below a particular level on a CD4 count
and
- 1 or 2 opportunistic infections/cancers
according to WHO:
- 20+ opportunistic infections or cancers
