• Discovery of Viruses
• Introduction to Viruses
• Structure of Viruses
• Classification of Viruses
• Viral Disease
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Human Immunodeficiency Virus (HIV)
AIDS (Acquired Immunodeficiency Syndrome) is caused by HIV (Human Immunodeficiency Virus), a retrovirus, which is a single-stranded enveloped RNA virus.
Pathophysiology
- HIV infects the lymphocytic cells T4 (helper T cells) which is a very important part of the immune system.
- Due to this virus, the lymphocytic T4 cells of the body become very weak.
- The virus replicates in T4 cells or helper cells.
- These affected cells do not motivate other T-cells to fight against the virus
- When the body of the host is affected by the virus continuously, helper T cells are decreased.
- By their reduced number immune system is damaged.
Structure
- HIV belongs to a group of viruses called retroviruses, which use their genetic material for reverse transcription.
- The size of HIV is about 60 times smaller than a red blood cell. It has a spherical shape and contains two RNA molecules that are coiled and folded, carrying 9 genes enclosed in a protein coat called capsid.
- These genes are responsible for producing structural proteins that form the virus and enable it to infect host cells.
- HIV is an enveloped virus, consisting of two layers of lipids with spikes made of glycoprotein. These spikes help the virus attach to specific receptors on the surface of target cells and enter them.
- What makes this virus unique is its ability to perform reverse transcription, which means it can make DNA from its RNA using its enzymes called reverse transcriptase and integrase. Reverse transcriptase converts RNA into DNA, while integrase helps the viral genome remain integrated inside the host cell.
Life-cycle
The life cycle of HIV involves a series of steps to multiply in the body. These steps are:
- Attachment: The virus first attaches itself to a receptor on the surface of a lymphocyte cell. This allows HIV to enter the cell.
- Fusion: While attached, the virus injects its genetic material (RNA) into the host cell.
- Reverse Transcription: The viral RNA uses its enzyme called reverse transcriptase to create a new DNA copy. This process is known as reverse transcription.
- Integration: The viral DNA enters the nucleus of the host cell and integrates with the host DNA using an enzyme called integrase. This integrated DNA is called a provirus, which can remain inactive for a long time, producing few or no new copies of HIV.
- Replication: The integrated host DNA creates messenger RNA (mRNA) using the host cell's enzyme called RNA polymerase. This mRNA directs the synthesis of long chains of HIV proteins, including viral proteins.
- Assembly: Once the proteins are formed, HIV uses another enzyme called protease to cut them into smaller fragments. These fragments, along with the viral genome, come together to form new viral progeny.
- Budding: The newly formed virus progeny mature and attach to the cell membrane, forming small projections or buds on the infected cell. These buds acquire some of the cell membrane's glycoproteins as their covering. Eventually, they are released from the cell and go on to infect other cells.
Transmission:
- Sexual Contact (90%)
- Blood transfusion
- By intravenous methods
- Through cuts & wounds
- From mother to baby
Signs & Symptoms:
- Flu-like Illness
- Immune Deficiency
- Kaposis Sarcoma: Skin cancer
- Mental Deterioration: Lymphocytes are affected so the brain cells are damaged, the brain shrinks, memory loss, and mental disorders take place. The behavior of the patient is also changed.
- Septicemia: Blood Poisoning
Medical Treatment:
Antiretroviral therapy (ART) is the main treatment for AIDS, which involves using a combination of different drugs. These medications belong to a group of enzyme inhibitors that inhibit the activity of viral enzymes. Some notable drugs used in AIDS therapy include Rukobia, Descovy, and Truvada.
Methods of Prevention:
- Clean Needles
- Examination of blood
- Avoidance of Close Contact
- Education and Awareness
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