Question

. Discuss the mechanism Human Immunodeficency Virus (HIV) uses to infect cells, its life cycle, and ultimatley leads to diminishing the host’ immune system.

Answer 1

Answer is given below;

HIV stands for human immuno deficiency virus, It is a virus which is a causative agent of AIDS and was reported in 1983.

It is a member of class known as retroviruses. These viruses store their genetic information ribonucleic acid(RNA).

Mechanism:

It consists of outer envelope made up of lipid bilayer with spikes of glycoproteins (gp), viz gp41, gp 120.

Gp 120 protrudes out from the surface of virus.

Nucleocapsid (p17) is present inside this envelope which surround a central core of protein (p24).

Within this core is a single stranded RNA genome,it contains enzymes and reverse transcriptase.

HIV generally infects those type of cells which contain CD4 receptors on their surface like cells of immune system T4 lymphocytes and T helper cells.

When HIV comes in contact with CD4 receptors of these cells the spike protein gp120 bind with these receptors like lock and key ,hence virus binds with the host.

The virus loses its envelope inside and release it's contents inside the host mainly as reverse transcriptase and RNA genome .

It uses viral RNA as a template and with the help of reverse transcriptase it catalyse the production of single complementary strand of DNA inside the host cells. Once this DNA is formed it is again used to produce second strand of DNA called as proviral dna.

This is then integrated into DNA of host cell by enzyme Integrase.

In this way virus hijcaked the host cells and it's replication system.

RNA transcript is fromed from viral dna hence this viral mrna formed will be Translated into viral proteins.

This last stage requires enzyme protease which helps in making more viral particles which infects other cells in the system.

This mechanism is a life cycle of HIV, hence we can conclude that it requires 7 steps to from binding to infecting cells.

Seven steps of life cycle;

1. Binding

2. Fusion

3. Reverse transcription

4. Integration

5. Replication

6. Assembly

7. Budding