Lecture 2: HIV & Evolution
Video about HIV: http://www.ted.com/talks/seth_berkley_hiv_and_flu_the_vaccine_strategy.htm
Reading: Pg. 491-493

Epidemic: localized outbreak in particular area

HIV:
First noticed in 1981
Pandemic: occurs everywhere
Less than ½ people over 18 years become infected with HIV, 30 million are living with HIV, drug users are more likely to get HIV
However HIV is not evenly distributed:
Occurs the most in sub-Saharan Africa (15-28%)
WHY?
Don’t have access to condoms (to block disease)
Less access to public health and sexual education (awareness)
Myths exist such as having sex with a virgin will get rid of HIV
No access to anti viral treatments
MOST LIKELY BECAUSE HIV ORGINATED IN SUB-SAHARAN AFRICA
HIV is a zoonotic disease. This means it affects humans and non-humans; can cross species barrier
Zoonosis: cross species barrier to humans
HIV originated in sub-Saharan Africa from chimpanzees.
HIV (1/ M) (pronounced: subtype m) – the harmful disease everyone is afraid of getting- is genetically similar to simian immunodeficiency virus SIV – a virus that affects chimpanzees-
Theory: HIV first started by contact of bodily fluids of chimpanzees that were infected with SIV by hunting, killing and eating infected SIV chimpanzees.
Chimpanzees got SIV from monkeys
Therefore, Sub-Saharan Africa is ground zero for HIV.

Why no CURE after 32 years?
Because HIV mutates very quickly, evolves very fast there it is a moving target
HIV is the fastest moving disease known to affect people

Viruses are not on the tree of life because they are not considered alive.
Because…
1. Viruses do not have their own metabolism
2. Cannot exist independently for a long time (apart from host cell)

Antiviral drugs: have serious side effects (worse than anti bacterial drugs)
BECAUSE
there are no special “virus cells” very few specialized steps unique to virus
Therefore, you cannot knock out virus without doing collateral damage on the physiology of host cell.

Viruses = weird and parasitic

Retroviruses: type of virus HIV belongs to even “weirder” than other viruses because it disobeys central dogma
Central dogma: DNA  RNA Protein retrovirses have RNA genome therefore stores information in the form of RNA (normal living things like humans store information in nucleus in form of DNA) have an extra step called reverse transcription ;
Reverse transcription: where RNA is reversed transcribed into DNA (no proofreading)
- reverse transcription controlled by reverse transcriptase:  only found in retroviruses like HIV , has no proofreading mechanism
Therefore, reverse transcription is very error prone and has a VERY high mutation rate

Virion= Viral particle

HIV lifecycle:
1. Virion enters host cell.
Virion can survive for a bit, lives in bodily fluid of humans, has only a few genes that code for protein, can survive in saliva
Virion holds genetic information in from of RNA
Recognizes its host cell, white blood cell WBC
Fuses with cell membrane  virion injects contents into cell membrane
2. Reverse transcription occurs. - virus’ RNA (how viruses normally stores its genetic information) is reversed transcribed into DNA by enzyme reverse transcriptase - no proofreading during process therefore very error prone
3. Integrase. - Another viral enzyme - Takes strand of viral DNA that’s just been reversed transcribed, cuts & pastes it into your genome (into DNA of host)
4. Normal steps.. - host DNA (including viral DNA now) transcribed into RNA - translated into protein  more copies of integrase, reverse transcriptase and other viral proteins
5. Assembly and departure. - components of new virion now assemble and leave host cell - may kill host cell - may make millions of copies of themselves & enter back into circulation (the blood stream)
6. Eventually… kills you. - eventually