The Way HIV Invades Our Cells

Ever wonder what actually happens when someone is infected with HIV?

HIV stands for Human Immunodeficiency Virus. Why is it called this? Because it makes our immune system deficient. This is a clue as to what kind of cells will be threatened by HIV. It's our immune cells! More specifically, the T cells, even more specifically, the helper-T cells. Other white blood cells, or lymphocytes can also be invaded by HIV, but the helper T cells are the most common.

Without helper-T-cells, what's happening in the cartoon below would become less common, which is a bad thing because we want those pill-shaped mofos out of our bodies!

You might be wondering why helper T cells are so important that infecting them leads to something as serious as AIDS. Well, losing them is somewhat akin to President Donald Trump losing his Secret Service protection.

There must be some wackos out there with a vendetta against the Prez. The Secret Service, upon noticing the presence of a shady and potentially dangerous character, can inform the police force of the suspect. Without the Secret Service, Trump would have a much higher likelihood of being bumped off. Likewise, helper T-cells notice when a bad foreign substance is lurking and tell the other cells to prepare for battle. For example, they signal to B cells to start secreting antibodies. Without helper T cells, our body loses the ability to respond effectively when a foreign bacteria, virus, or protozoa is around.

So then how does HIV infect our helper T cells? Here's where knowing something about the structures of cells and viruses helps.

This is a diagram of the infectious HIV virus:

And this is a diagram of a helper T cell performing it's function: i.e signaling to a B cell to start releasing that red antibody!

See that lime-green segmented part of the helper T cell labeled CD4? THAT is HIV's entry door. CD4 is a receptor that lies on the exterior of the CD4 cells and some other immune cells. You can think of the T cell as a planet, and the CD4 receptor as a marker present on top of the planet, like a mountain, ocean, or city. CD4 is normally a crucial in alarming other cells like B-Cells about host invaders.

So if the CD4 receptor on the T helper cell is the door, does HIV need a key? It does! And it's a pretty damn fancy key. If you look at the virus again, notice the little structures jutting out called gp41 and gp120 (GP stands for glycoprotein, glyco meaning sugar, and protein meaning.....protein ). These structures are what allow for entry through the CD4 receptor.

The green thing that looks like supporting rods for a tent is gp41 and the orange tangled mess is gp120. In this picture, CD4 is yellow. As you can see, gp120 binds to the CD4 receptor. Once it binds, gp120 undergoes a change of its structure that pulls it closer to the T cell, allowing gp120 to interact with another receptor called CCR5. Once bound to CCR5, the gp41 undergoes a kind of collapse, which pulls the infectious HIV virus into the helper T cell, allowing their cellular membranes to fuse. The fusion is almost like two bubbles coming together to form a slightly bigger bubble. But in this case, one bubble is releasing it's viral DNA into the bigger bubble, eventually giving the bigger bubble AIDS....

It's okay bubble buddy, just drink your bubble soap....everything's going to be A-okay....

Anyway, there is A LOT more to the HIV infection process, but I just thought it would be interesting to do a little outline about how HIV actually enters our cells. Hope you found it interesting.

STEEMMATE

Sources: 1, 2, 3, 4, 5