Download - HIV and AIDS
Human Immunodeficiency Virus
Acquired Immune Deficiency Syndrome
2005-2006
Measles
Polio
Hepatitis
Chicken pox
2005-2006
30-40 million deaths world-wide
RNA virus
Eradicated in 1976 vaccinations ceased in 1980 at risk population?
2005-2006
Viruses that “jump” host switch species Ebola, SARS, bird flu, hantavirus
SARS
Ebola hantavirus
2005-2006
DNA or RNA enclosed in a protein coat Viruses are not cells So…they are not alive Extremely tiny
electron microscope size smaller than ribosomes ~20–50 nm
2005-2006
1st discovered in plants (1800s) tobacco mosaic virus
A package of genes in transit from one host cell to another
Most viruses carry their own DNA
DNA (genes) RNA Proteins
These proteins form antigens and new viruses that then further invade the body
bacteriophage influenza
“A piece of bad news wrapped in protein”
– Peter Medawar
Lipid bilayer membranes surrounding a viral capsid envelopes are derived from host cell
membrane (so it is slightly disguised) glycoproteins on surface
HIV
Retroviruses have to copy viral RNA into host DNA
enzyme = reverse transcriptase RNA → DNA → mRNA
host’s RNA polymerase now transcribes viral DNA into viral mRNA mRNA codes for viral components host’s ribosomes produce new viral proteins
Why is this significant?
protein RNA DNA
transcription translation
replication
HIV stands for Human Immunodeficiency Virus
While most viruses carry DNA, HIV is a RETROVIRUS which means it carries 2 strands of RNA instead of DNA
Contains an envelope with glycoproteins for binding to specific receptor
As well as 2 copies of reverse transcriptase!
When RNA is copied to DNA, it can get kind of messy…
This allows for many mutations in HIV *BUT IS THIS A GOOD THING?
The first ever photo of HIV
Envelope binds to host cell membrane and capsid released
HIV enters host cell: macrophage & CD4 T Cells reverse transcriptase synthesizes
double stranded DNA from viral RNA high mutation rate
Transcription produces more copies of viral RNA translated into viral proteins proteins & viral RNA self-assemble
into virus particles released from cell by “budding”
Imagine the immune system is like FREMONT HIGH SCHOOL
Our Helper T-Cells are like the Security Guards (“Charlies”)
Now, these Security Guards never see each other, but they communicate using walkie talkies
They communicate with each other to make sure the campus is safe
But now imagine these security guards have been infected by a virus, and are no longer on campus…
Kaposi Sarcoma – a rare form of cancer and one of the leading causes of HIV/AIDS related deaths…
AIDS stands for Acquired Immune Deficiency Syndrome
People develop AIDS because HIV has damaged too many of their CD4+ cells (they have less than 200 per cubic millimeter)
Before getting AIDS, a person usually goes through 3 phases in the PROGRESSION OF HIV:
1. Primary Infection (several weeks of the flu)
2. Asymptomatic phase (up to 10 years with no real health problems)
3. Symptomatic phase (opportunistic infections begin to occur)
4. AIDS (T-Cell count low, severe health problems)
At present in the US and UK, an AIDS DIAGNOSIS is confirmed if a person with HIV develops one or more of a specific number of severe opportunistic infections or cancers
Can you see on the graph where a person has been diagnosed with AIDS?
It is possible for someone to be very ill with HIV but not have an AIDS diagnosis.
HIV is a descendent of African SIV (simian chimpanzee immunodeficiency virus), but how did it get transferred to humans?
1. The “Hunter” Theory: SIV was transferred as a result of chimps being killed and eaten or their
blood getting into cuts or wounds on the hunter Normally the hunter's body would have fought off SIV, but on a few
occasions it adapted itself to its new human host 2. The Oral Polio Vaccine (OPV) theory:
Many believe that HIV can be traced to the testing of an oral polio vaccine called Chat, given to about a million people in the Belgian Congo and Ruanda in the late 1950s.
To be reproduced, live polio vaccine needs to grow in living tissue, and Chat was grown in kidney cells taken from local chimps infected with SIV
This would cause contamination of the vaccine with chimp SIV, and a large number of people subsequently becoming infected with an adapted form of SIV HIV
However, the OPV theory has been shot down due to insufficient evidence to cause infection in most people, SIV/HIV needs to get directly into the bloodstream to cause infection (BUT this was an oral vaccine)