HIV Life Cycle and Immune System Basics

Treatment Adherence Certification Program04/18/2013

P. Justin Goforth, RN

HIV Life Cycle

• Why is this important?– Helping our clients understand what is happening

in their body provides motivation to take control.– Doing something simply because you are told to is

hard to maintain. Doing something because you understand why you are doing it and the benefits it has for you helps you stick with the plan.

– We are visual learners; our brain needs to see something to understand it.

HIV Life Cycle: Terms

• CD4: A receptor protein on the outside of the T-cell. This normally helps activate the T-cell after coming in contact with an antigen (germs)

• Co-receptor: Another receptor protein that works together with the CD4 receptor. – Think of these like the flash drive port in a computer

• The flash drive has to fit perfectly into the computer for data to get into the computer

HIV Life Cycle: Terms

• DNA: The genetic code to everything that dictates what we are and how our body functions.

• RNA: Instructions that come from DNA in the form of genetic information and tell your cell what to do.

• Reverse Transcriptase: The super secret “decoder ring” that HIV brings with it to translate it’s genetic information into something our human cell can understand.

HIV Life Cycle: Terms

• Integrase: A protein (enzyme) that HIV brings with it to carry its decoded genetic information into the nucleus and DNA of the T-cell.

HIV Life Cycle: Terms

• Protease: Another enzyme that HIV brings with it to help assemble the new HIV viruses being produced in the T-cell.

HIV Life Cycle: Step 1 - Fusion/Entry (Docking Station)

HIV Life Cycle: Step 2 – Reverse Transcription (Decoder Ring)

HIV Life Cycle: Step 3 - Integration

HIV Life Cycle: Step 4 - Transcription

HIV Life Cycle: Step 5 - Assembly

HIV Life Cycle: Step 6 - Budding

HIV Life Cycle: Step 7 - Maturation

HIV Life Cycle: Putting it all Together

ARVs (The ones we use.)

• Multi-class fixed dose combinations:– Stribild– Complera– Atripla

• NRTIs– Truvada – Emtriva– Viread– Ziagen– Epzicom

ARVs (The ones we use.)

• NNRTIs– Edurant– Intellence– Sustiva– Viramune (rarely)

• Protease Inhibitors– Prezista– Reyataz– Kaletra (rarely)

ARVs (The ones we use.)

• Entry Inhibitors– Fuzeon (rarely)– Selzentry

• Integrase Inhibitors– Isentress– Elvitegravir (soon)

• Boosters– Norvir– Cobicistat (soon)

Immune System Basics• The immune system is a complex network of organs,

cells and chemicals. • Our immune system is so effective because of its ability

to recognize “self” vs. “non-self”.• One very important part of the immune system is

coordinated by the T-helper cell (also known as the T4 cell), which acts as a kind of orchestra conductor.

• T-helper cells tell the other immune cells what to do when a response is triggered.

• HIV targets T-helper cells specifically. Losing the coordinator of the process leaves the body open to attack by opportunistic infections.

T-helper Cell (T-cell) Immune Response

• Any infectious agent will eventually be taken up by the lymph system.

• In a lymph node, the virus bumps into a macrophage.• The macrophage ingests the viral invader.

T-helper Cell Immune Response• The macrophage takes the virus apart, and displays the

antigens on its surface for other immune cells to read.• Antigens are like ID cards that allow our immune system to

recognize invaders that need to be eliminated.• After displaying the invader’s antigens, the macrophage will

send out a message to a T-helper cell to read and recognize the antigens.

T-helper Cell Immune Response• This message activates T-helpers and triggers the immune

response.• Once the T-cell reads the antigen, it will send out messages to

activate other cells known as B-cells, which in turn come and read the antigens from the macrophage’s surface.

T-helper Cell Immune Response• The activated B-cell then produces millions of antibodies. The

antibodies bind to the antigen on the virus. Each antibody is unique to the specific invader.

• We produce antibodies because the virus’ way outnumber the macrophages, which therefore cannot fight the invader alone. Antibodies will outnumber the invaders and help get rid of them.

T-helper Cell Immune Response• The antibodies are like a

mirror image of the antigen, and when they bump into each other, the antibody grabs on without letting go.

• The antibody then broadcasts a signal that says “eat me and whatever I have captured”.

• Macrophages respond to the signal and devour the antibody-antigen complex.

T-helper Cell Immune Response• As this process continues, the

number of infectious agents will decrease, and the immune system will need to stop the battle.

• All of the immune cells are activated, and will continue to fight until they are told to rest.

• Another kind of T-cell, T-suppressor cells, send out messages to the other cells and “de-activate” them.

• If T-suppressor cells were not around, we would continue trying to fight off the disease that no longer exists. This would eventually lead to fighting our own cells.

HIV Interferes With this Normal Response

• Initially, the T-cell response is somewhat effective against HIV.

• Some of the HIV survives, and infects the T-cells that are needed to fight the virus.

• The T-cells remain activated, in response to the infection, but now instead of fighting invaders, they produce HIV, which infect more T-cells.

• T-cells become HIV factories, and eventually the number of T-cells destroyed by HIV starts to outnumber the new ones created to fight HIV.

• HIV infects other cells as well, but targets T-cells more than any other. Nervous system cells are particularly at risk, as our immune cells do not cross the blood-brain barrier.

Natural Progression of HIV Disease

Questions?