Handout #3 - HIV Part 2 - Lecture Flashcards
What is the virus that causes AIDS?
HIV
What family does HIV belong to?
Retroviridae
What genus does HIV belong to?
Lentivirus
Lente is from the Latin word for what? And why is that root used in the word Lentivirus?
“Slow.” Lentiviruses have long incubation periods.
What cells does HIV attack?
T-helper cells.
Why are T-helper cells important?
They activate and regulate our immune system.
When is a diagnosis of AIDS made?
When an affected individual has been infected by one or more opportunistic infections and has their CD4+ T count below 200 per ml^3 of blood.
What are normal CD4+ T cell levels?
500-1200 cells per ml^3
What is the probability of heterosexual transmission of HIV?
~0.005 to 0.0001 per contact.
What five conditions are required for transmission of HIV?
Source of infection, means of transmission, host susceptibility, route to susceptible cells in the body, enough virus introduced to cause infection.
In absence of drug therapy, what is the risk in infant will be infected with HIV across the placenta?
Approximately 5-10% risk
In absence of drug therapy, what is the risk in infant will be infected with HIV during delivery?
Approximately 20%
In absence of drug therapy, what is the risk in infant will be infected with HIV via breast feeding?
Approximately 15%
What two body fluids are the highest risk in transmission of HIV?
Cerebrospinal fluid (although unlikely to ever contact it) and plasma (much more likely to come into contact with).
How does HIV usually enter host cells?
Via mucosal surfaces.
What are three ways HIV can enter cells?
Via mucosal surfaces, exposure to the circulatory system, or needle transmission.
Compared to non-circumcised males, what risk of HIV do circumcised males have of infection?
Approximately half the risk.
Why do circumcised males have a lower risk of infection of HIV?
Reduced mucosal surfaces associated with loss of the foreskin, so the penis is drier.
How many membrane layers does the envelope of HIV have?
Two
What are some examples of enzymes that HIV requires that are associated with RNA?
Reverse transcriptase, protease, ribonuclease, and integrase.
7 steps of HIV reproduction
Attachment, entry, formation of viral DNA, integration, translation, formation of immature virus particles, maturation.
Are new strains of HIV likely or unlikely to develop during the initial infection stage?
Unlikely.
What sorts of responses do HIV viral proteins stimulate in host cells?
Blockage of host cell protein activity and host protein destruction, cytotoxicity (helps kill host cells), attraction of WBCs (triggers immune system), stimulation of expression of co-receptor proteins, and stimulation of immune system proteins.
What stage of HIV Reproduction can a cell not recover from?
Stage 4 - Integration
What stimulates transcription of viral HIV genes into viral mRNA?
A combination of host and viral factors.
What do most widely used anti-HIV drugs target?
Either protease or reverse transcriptase.
What do HIV vaccine development efforts target?
Surface proteins.
Where to do the first cells to be infected travel to first?
Lymph nodes, where the virus can access T-cells.
Where is the second place that infected cells move to?
Into the bloodstream, where they can access major regions of the immune system such as the GI tract.
What stage of infection is the GI tract especially important in?
The acute stage of infection.
What do lymphatic tissues in the GI tract contain?
~40% of total WBCs and high numbers of CD4+ T cells.
Rapid reproduction of the virus in the GALT facilitates spread of the virus to what other parts of the body?
Other parts of the lymphatic system including the spleen and the bone marrow.
What is correlated with the peak of the acute stage of HIV infection?
Massive CD4+ T cell death (30-40% of total population in the GALT).
When does viral spread and onset of the acute phase of HIV infection typically occur?
2-3 weeks after initial viral acquisition.
What are symptoms of the acute phase of HIV infection?
Similar symptoms as a bad flu: lymph node swelling.
What happens after the acute symptoms of HIV infection?
Killer T cells and antibodies produced by B-cells significantly reduce the viral load, and CD4+T cells rise in numbers.
In untreated individuals, how long does it take from the acute phase to progress to AIDS?
2-3 years to more than a decade.
During the clinical latency phase of HIV infection, the immune system as as a….
Selective mechanism for mutant strains that are more able to escape the immune system. It’s why the viral mutates so much.
What happens after lymphoid tissues is destroyed?
Patient starts showing symptoms associated with AIDs.
Why does the immune system get destroyed?
A combination of: continuing viral replication which creates persistent antigenic stimulation; ongoing depletion of T cells; inflammation; build up of scar tissue in the lymph nodes.
