The Science of HIV/AIDS


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 to DNA. This
DNA is then integrated into 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 and 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 individualized 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. And subscribe for more weekly science videos!