Question

What are CD4 lymphocytes? What is the relationship between these cells and HIV? How does HIV replicate?

Answer 1

CD4 lymphocyte: Type of T-lymphocyte which express the distinct CD4⁺ glycoprotein on their surfaces. These are also known as T-helper cells (T_H cells).

T-cells help in eliminating Antigen presenting cells, cancer cells, virus-infected cells or grafts which have altered self cells.

What is the relationship between these cells and HIV?

CD4 count is the reflection of how good the immune system is functioning. CD 4 cells are the T-lymphocytes which fight the infection, the more we have the better is the functioning of the immune system. These are the cells that HIV virus kills and as the HIV infection progresses the CD4 cell count declines.

HIV repilcation:

HIV uses the CD4 cell machinery to multiply and spread throughout the body.

There are seven stages in the HIV replication cycle

i) Binding- HIV binds to the receptors on the CD4 cell

ii) Fusion - HIV envelope and CD4 cellmembrane fuse to allow HIV to enter into CD4 cell

iii) Reverse transcription - Inside CD4cell, HIV uses reverse transcriptase to convert HIV RNA to HIV DNA, which allows HIV entry into CD4 cell nucleus and combine with cell genetic material

iv) Integration - Inside the CD4 cell nucleus, HIV uses its integrase enzyme to integrate its viral DNA into CD4cell DNA

v) Replication - Once integrated into CD4 cell DNA, HIV makes long chains of HIV proteins which are the building blocks of more HIV

vi) Assembly - Now the HIV proteins and HIV RNA move to cell surface and assemble into immature noninfectious HIV

vii) Budding - Newly formed noninfectious immature HIV pushes itself out of the CD4 cell and release into new virus