B2 High-Intermediate US 9255 Folder Collection
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HIV/AIDS has taken the lives of over 39 million people worldwide, despite our efforts to prevent, treat and better understand it.
But with 35 million people currently infected, what exactly is it, and are we close to a cure?
To contract HIV, the virus must enter the bloodstream - and it's often transmitted
from infected bodily fluids like blood, semen, vaginal fluids or breast milk.
Once inside the bloodstream, HIV targets a variety of cells, but most specifically the T-helper cells (CD4),
which are a type of white blood cell that play an essential role in our immune system and fighting infections.
The outer envelope of HIV is covered in glycoproteins
which mutate frequently, ultimately tricking the T-cell receptors to not recognize the virus.
Once attached to specific proteins on the T-cell, it begins to fuse the membranes together,
and eventually enters the cell where it releases 2 viral RNA strands and 3 essential replication enzymes.
Because HIV is a retrovirus, the RNA is transcribed into DNA, represented here by a zipper of two RNA strands transcribing into DNA.
This DNA is then integrated into the host cell’s genome.
This makes the T-cells treat the viral genes like their own, which causes
them to make more copies of the virus. These then leave the host cell and mature, ultimately
seeking more T-cells. The virus is particularly difficult to treat because its mutation rate
is so high. Overall the replication process creates more than 10 billion new virions each day.
During these initial stages of replication, called the latency period, a person may not
show any major symptoms for up to 8 years. If not treated, the HIV eventually kills off
the specific T-cells it infects. When these T-Cells fall below 200 cells per cubic millimeter of blood,
it becomes Acquired Immune Deficiency Syndrome or AIDS.
After progressing this far, the immune system becomes suppressed is much more susceptible
to cancers and opportunistic infections such as pneumonia. A person doesn't die from AIDS
they actually die from an illness that the body could not fend off.
Nowadays there is medicine that helps fight these opportunistic infections, like Daraprim
(which was recently in the news when Martin Shkreli of Turing Pharmaceutical decided to
raise the price from $13.50 - $750 per pill.. There are also anti-retroviral drugs that
slow the virus down by blocking certain enzymes which are required for the virus to multiply.
Similarly, those without HIV but at high risk of contracting the virus may take pre-exposure
prophylaxis or PrEP. This works similar to antiretroviral drugs by blocking the enzyme reverse transcriptase.
Thankfully there is hope for a cure - a small population of people are immune to the HIV virus
because of a mutation linked to the T-cells. In one case, an HIV-positive subject
received a bone marrow transplant, meaning they were given new stem cells that generate
different T-cells, and within 20 months there was no evidence of the virus in their bloodstream.
Though this is very indivisualized medicine, it certainly opens up the possibilities of
generating HIV resistant cells. Combine this with other therapies and preventative measures
like condoms, clean needle programs and safe blood transfusions, and HIV/AIDS may one day
be a thing of the past.
Your sharing of this video is much appreciated, in the effort to help spread knowledge and awareness.
Special thanks to audible for supporting this episode to give you a free 30 day trial at
audible.com/asap. This week we wanted to recommend the book Redefining Reality, which explores
what is real and what’s illusory from both a scientific and philosophical perspective,
through a series of really awesome lectures. You can get a free 30 day trial at audible.com/asap
and choose from a massive selection! We love them as they are great when you’re on the go.
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The Science of HIV/AIDS

9255 Folder Collection
韓澐 published on July 1, 2017    Jade Weng translated    Kiara reviewed
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