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86.The HIV Life Cycle | gaysexguide


86.The HIV Life Cycle
HIV LIFE CYCLE- Part 2


Step 1: Binding
A virus consists of an outer envelope of protein, fat and sugar wrapped around a set of genes (in the case of HIV, genetic information is carried as RNA instead of DNA) and special enzymes.

HIV has proteins on its envelope that are strongly attracted to the CD4+ surface receptor on the outside of the T4-cell. When HIV binds to a CD4+ surface receptor, it activates other proteins on the cell's surface, allowing the HIV envelope to fuse to the outside of the cell. Entry can be blocked by entry inhibitors.

Step 2: Reverse transcription
HIV's genes are carried in two strands of RNA, while the genetic material of human cells is found in DNA. In order for the virus to infect the cell, a process called "reverse transcription" makes a DNA copy of the virus's RNA.
After the binding process, the viral capsid (the inside of the virus which contains the RNA and important enzymes) is released into the host cell. A viral enzyme called reverse transcriptase makes a DNA copy of the RNA. This new DNA is called "proviral DNA."

Reverse transcription can be blocked by Nucleoside Reverse Transcriptase Inhibitors (NRTIs), Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs) and Nucleotide Reverse Transcriptase Inhibitors.

Step 3: Integration
The HIV DNA is then carried to the cell's nucleus (center), where the cell's DNA is kept. Then, another viral enzyme called integrase hides the proviral DNA in the cell's DNA. Then, when the cell tries to make new proteins, it can accidentally make new HIV.

Integration can be blocked by integrase inhibitors, a new class of drugs that are in the earliest stage of research.

Step 4: Transcription
Once HIV's genetic material is inside the cell's nucleus, it directs the cell to produce new HIV.
The strands of viral DNA in the nucleus separate, and special enzymes create a complementary strand of genetic material called messenger RNA or mRNA (instructions for making new HIV).
Transcription can be blocked by antisense antivirals or transcription inhibitors (TIs), new classes of drugs that are in the earliest stage of research.

Step 5: Translation
The mRNA carries instructions for making new viral proteins from the nucleus to a kind of workshop in the cell. Each section of the mRNA corresponds to a protein building block for making a part of HIV.
As each mRNA strand is processed, a corresponding string of proteins is made. This process continues until the mRNA strand has been transformed or "translated" into new viral proteins needed to make a new virus.

Step 6: Viral assembly
Finally, a new virus is assembled. Long strings of proteins are cut up by a viral enzyme called protease into smaller proteins. These proteins serve a variety of functions; some become structural elements of new HIV, while others become enzymes, such as reverse transcriptase.
Once the new viral particles are assembled, they bud off the host cell and create a new virus. This virus is then able to infect new cells. Each infected cell can produce a lot of new viruses.
Viral assembly can be blocked by Protease Inhibitors (PIs).


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