Question

How does HIV infect T-lymphocytes?

Answer 1

HIV or human immunodeficiency virus causes AIDS ( Acquired Deficiency Syndrome ) which weakens the immune system of the body.HIV is a retrovirus and the genetic material is RNA.HIV affect macrophages in the blood.

Complete answer:
AIDS-causing virus also known as human immunodeficiency virus affects CD4 cells, T cells and monocytes which decreases the amount of these cells below the critical level thereby affecting the cell-mediated immunity. This increases the risk of infections.

T cells are infected due to high-affinity interaction between the CD4 molecule and glycoprotein present on the envelope of the virion.HIV infects T cells as follows :
i) gp120 glycoprotein on the virion envelope attaches to CD4 on the T cell.
ii) Enzymes and nucleocapsids enclosing the viral genome enter the T cell.
iii) RNA is converted to RNA-DNA hybrids by reverse transcriptase
iv) Now RNA template is degraded by ribonuclease H and the second DNA strand is synthesised to form ds DNA.
v) Viral dsDNA is now translocated in nuclease and integrase enzymes integrate the DNA with the genome of the host.
vi) Proviral DNA is now transcribed into ssRNA which is then transferred to the cytoplasm.
vii) In the cytoplasm, viral precursor proteins are synthesised which are catalysed by ribosomes.
viii) Viral proteases then cleave viral proteins followed by assembly of ssRNA and proteins inside of the plasma membrane and then form buds
ix) HIV polyproteins are cleaved into infectious HIV proteins and the mature virions then cause infection in the other cells.

Note: HIV is a retrovirus that affects a specific type of white blood cell known as CD4 cells or T helper cells.HIV infection in T cells is assisted by CXR4 co-receptor and in monocytes interact with CCR5 co-receptor.