A virus is a parasite. It cannot survive on its own.
Viruses are not plants, animals, or bacteria, but they are the living kingdoms’ parasites. Viruses are not technically alive: They are like a brain without a body. To make more copies of itself, a virus must hijack our cells and use them to make new viruses. Without a host cell, viruses cannot carry out their life-sustaining functions or reproduce. Well-known diseases caused by viruses are different types of flu, Ebola, smallpox, HIV, Hepatitis, Rabies, and Herpes, to name a few.
The HIV lifecycle¹
When viruses reproduce, it is called replication. HIV uses CD4 immune cells to replicate. And each infected CD4 cell produces hundreds of new copies of new HIV particles.
CD 4 cells are white blood cells that play an important role in the immune system. Once a CD 4 cell is infected, it produces hundreds of new copies of new HIV particles. The replication cycle lasts 1-2 days, and it is called the HIV life cycle.
Explanation of the HIV Cycle:
BINDING & FUSION
1. HIV enters the body
2. The virus attaches itself to a T-helper cell (CD 4 cell) and releases HIV into the cell
The ARV medicine that blocks this process is called entry inhibitors.
CONVERSATION & INTEGRATION
3. Once inside the T-helper cell, HIV changes its genetic material to enter the cell’s nucleus and take control of it.
4. After HIV attaches to the CD4 cell, it is absorbed into the cell’s main body. As this happens, HIV first loses its outer shell. This leaves a viral capsid with HIV and three key enzymes (a protein) that HIV uses to replicate.
The ARV medicine that blocks this process is two different types of RT inhibitors (RTIs): (i) nucleoside/tide (NRTIs/NtRTIs) and (ii) non-nucleoside (NNRTIs).
5. The new double-stranded HIV crosses into the central nucleus of the CD4 cell. This is where HIV is integrated into human DNA
The ARV medicine that blocks this process is called integrase inhibitor, abbreviated to INIs or INSTIs.
REPLICATION
6. The infected T-helper cell produces more HIV proteins used to produce more HIV particles inside the cell.
The ARV medicine that blocks this process is called protease inhibitor.
ASSEMBLY, BUDDING & MATURATION
7. The newly formed virus then has to leave the cell. The new HIV particles are then released from the T-helper cell into the bloodstream, which infects other cells, and so the process begins again. The old CD4 cell then dies. This continuous process happens millions of times every day when not on ART. Without ART, HIV is one of the most active and rapidly reproducing viruses.
Although there are currently no HIV drugs that block this stage, several drugs are in development. Budding inhibitors stop new HIV from leaving the CD4 cell. Maturation inhibitors block the final assembly process.
Conclusion:¹
- An important concept about ART is that HIV drugs only work on CD 4 cells in your body that are awake and actively producing HIV.
- However, most CD 4 cells in your immune system are sleeping or resting. The resting cells, even if they contain HIV, are not affected by ART.
- Reaching HIV in resting cells is the main aim of HIV cure research.
Important to know:¹
- HIV uses CD 4 cells to replicate.
- Different HIV medications block different stages of the HIV life cycle.
- Each infected CD 4 cell produces about 300 new infectious viruses – called virions.
- ART stops the HIV life cycle. On ART, the only virus in your body is in sleeping or resting CD 4 cells.
- It would be best to continue taking ART every day because some of these sleeping cells wake up every day.
Acknowledgements:
- Dr Natasha Davies
- Dr Jackie Dunlop
- Dr Pappie Majuba
- Wits RHI Safer Conception Project
- Right to Care Training Department
¹ http://i-base.info/guides/art-in-pictures/the-hiv-lifecycle-in-detail
https://micro.magnet.fsu.edu/cells/virus.html