Question

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

Answer 1

CD4 lymphocytes or T helper cells are a subtype of T- cells and on their surfaces they can able to carry CD4+ membrane glycoprotein, so due to this reason thses are called as CD4 lymphocytes.

CD4 lymphocytes are T helper lymphocytes that present in their plasma membrane receptor proteins called CD4. These cells are crucial for defense against both extracellular and intracellular pathogens.

CD4 lymphocytes cell relationship with HIV and its replication:

CD4 lymphocytes are the cells that HIV infects and within which the virus replicates. HIV has proteins in its capsule that bind to the CD4 receptors of lymphocytes. Through that bond the virus fuses with the cell membrane and its content (RNA, reverse transcriptase, protease, etc.) penetrates into the cytoplasm and the viral replication process begins.

HIV RNA is then converted into DNA by the reverse transcriptase. The new DNA is inserted into the genetic material of the lymphocyte with the aid of enzymes called integrates. By transcription and translation this DNA commands the synthesis of proteins necessary for the assemblage of new viruses. Long polypeptides are thus produced and then fragmented into proteins and viral enzymes by the enzyme protease. So new HIV viruses are assembled and break the cell membrane to gain the circulation.

HIV replicates as:

a. The proteins in capsule of HIV help it to bind to CD4 cells. After the Virus binding and cell membrane fuse.

b. When membranes of host cell and virus fuse then viral RNA and reverse transcriptase enter host's cytoplasm.

c. Due to the presence of reverse transcriptase viral RNA is able to get copied to DNA

d. In the form of provirus, Viral DNA incorporates into chromosome of host.

e. Once this incorporation is done transcription and translation take place and viral proteins are formed. Viral RNA becomes is also transcribed.

f. Viral particles then bud out of host cell and in this process acquire an envelope.