HIV AND IT’S LIFE CYCLE

BY: ABHISHEKA G (MSIWM013)          

INTRODUCTION:

HIV (Human immunodeficiency virus) is a kind of virus that belongs to the retrovirus family and causes AIDS (Acquired immunodeficiency syndrome) in humans. It destroys the immune system of the individual by making the patient vulnerable to different other infections including neurological disorders. The disease of AIDS was first observed in 1981 in the united states. It is an epidemic disease present throughout the world. This disease can be preventable, but not curable.

TYPES OF HIV: There are two types of HIV viruses are present based on the origin of the virus.

1. HIV-1: It is isolated in America, Europe, and Central Africa. It is more virulent and spread among individuals very rapidly
2. HIV-2: It is isolated in West Africa, it is less virulent and does not spread rapidly as HIV-1

STRUCTURE OF HIV VIRUS:

1. It is spherical in nature and measures about 90-120nm in diameter and it is composed of two copies of positive single-stranded RNA enclosed by a conical capsid composed of viral protein P24. The capsid also contains the enzymes which are necessary for viral replication such as Reverse transcriptase (P55/66), Integrase(p32), and protease(p10).
2. The RNA genome of HIV consists of nine different genes that contain the information needed to make the structural proteins for new virus particles.
3.  The matrix is composed of the viral protein P17 which surrounds the capsid ensuring the integrity of the virion particles. And the matrix is surrounded by 2 layers of phospholipids which are embedded by 70 copies of viral glycoprotein and lipoprotein which consist of two units namely anchoring transmembrane pedicles (Gp41) and surface projecting knob like spikes (Gp120).

MODE OF TRANSMISSION OF HIV VIRUS:  HIV is transmitted in many different ways.

1.Sexual contact: Unprotected sexual relationship with an infected individual.

2. From mother to child: The virus of HIV is transmitted from mother to child through the uterus, during delivery, and also during breastmilk.

3. Through needles: Through the injections during injecting drugs and needle prick injury which are already used by the infected individuals.

4. Blood transfusion and organ transplantation: The virus is transmitted through transfusion of blood and transplantation of organs from infected individuals to normal individuals.

LIFE CYCLE OF HIV VIRUS:

There are 7 different steps in the life cycle of the HIV virus.

1. Attachment to the host/Binding to the target cell: The specific site for the HIV virus to bind are CD4 receptors and other co-receptors(CCR5/CXCR4) which are enveloped by the glycoprotein Gp120. Viral binding to host cell triggers fusion of the viral and cell membrane of the host cell, which is mediated by gp41 and allows the virus core into the cytoplasm of the host cell.
2.  Reverse transcription of its RNA: HIV consists of single-stranded RNA. The single-stranded RNA is converted into DNA. This process is carried out by the enzyme Reverse transcriptase.
3. Integration into the host genome: The viral double-stranded DNA is integrated into the genome of the infected host cell through the action of the viral integrase enzyme which causing a latent infection.
4. Transcription of viral proteins: The transcription of viral proteins is mediated by Viral reverse transcriptase. The infected DNA of the host cell makes proviral RNA and protease enzyme cuts or cleaves the polypeptides into functional HIV proteins and the virion assembles.
5. Assembly of a new viral particle: Viral strands and other proviral products combine to form a package and head for the cell membrane.
6. Release of immature virions: Immature virus finds a suitable position to push or come out of the host cell by taking a piece of the membrane with it.
7. Maturation of the virion: The new free virus matures and gets ready to infect another host cell.

SYMPTOMS OF THE DISEASE:

Diarrhea, Fatigue or weakness, fever, headache, joint pain, night sweats, rashes on the body, swollen glands, sudden weight loss, yeast infections in the body, and sexual organs that occur frequently and last for a long time.

LABORATORY DIAGNOSIS OF HIV: HIV is mainly detected by  different clinical tests:

1. ELISA (Enzyme-linked immunosorbent Assay/ Enzyme Immunoassay): This test detects and measures the antibodies in the blood sample along with the presence of antibodies related to any infections.
2. Western Blot: This test is used to detect the specific proteins called HIV antibodies present in the blood sample. If ELISA gives positive for HIV, then the western blot technique is used to confirm the positive result of ELISA and gives 99.9% accurate results.

AVAILABLE ANTIRETROVIRAL DRUGS TO HIV:

1. Nucleoside reverse transcriptase: Zidovudine and Stavudine
2. Non-nucleoside reverse transcriptase inhibitor: Efavirenz and Nevirapine.
3. Protease inhibitor: Atazanavir and Darunavir.

PREVENTION OF HIV VIRUS:

1. Avoid multiple sexual contacts.
2. Using new and sterile needles for injection.
3. Care should be taken and testing should be done during blood transfusion and pregnancy.
4. Biomedical waste should be properly disposed of from hospitals and households.
5.  Proper sex education should be provided to people.