Pathophysiology of HIV/AIDS

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Pathophysiology of HIV/AIDS

The pathophysiology of HIV/AIDS is a complex process that involves the interaction between the Human Immunodeficiency Virus (HIV) and the host's immune system. This article aims to elucidate the mechanisms through which HIV infects host cells, replicates, and leads to the progressive deterioration of the immune system, culminating in the condition known as Acquired Immunodeficiency Syndrome (AIDS).

HIV Structure and Lifecycle

HIV is a retrovirus that primarily targets CD4+ T cells, which are a type of white blood cell crucial for immune response. The virus is composed of two single strands of RNA and the enzyme reverse transcriptase, encased within a protein capsule. The lifecycle of HIV can be divided into several stages:

1. Attachment and Entry: HIV binds to the CD4 receptor and either the CCR5 or CXCR4 co-receptor on the surface of the CD4+ T cell. Following binding, the virus fuses with the cell membrane and releases its RNA into the cell.
2. Reverse Transcription: The reverse transcriptase enzyme converts viral RNA into DNA.
3. Integration: The newly formed viral DNA is transported into the cell's nucleus, where it integrates into the host's DNA with the help of the integrase enzyme.
4. Transcription and Translation: The integrated viral DNA is then transcribed into mRNA, which is translated into viral proteins by the host's cellular machinery.
5. Assembly and Release: New viral particles are assembled and bud off from the host cell, acquiring a portion of its membrane as their envelope.

Immune System Evasion and Destruction

HIV evades the immune system through rapid mutation, allowing it to escape recognition by antibodies. Additionally, the virus preferentially infects and destroys CD4+ T cells, leading to a gradual decline in the host's immune function. This process is characterized by:

• Direct Cytopathic Effects: The virus induces cell death during its replication cycle.
• Immune Response: The immune system's attempt to eliminate infected cells also contributes to the depletion of CD4+ T cells.
• Chronic Inflammation: Persistent viral replication triggers chronic inflammation, further damaging the immune system and other organs.

Progression to AIDS

As the number of CD4+ T cells falls below a critical threshold (usually less than 200 cells per cubic millimeter of blood), the individual becomes increasingly susceptible to opportunistic infections and certain cancers, marking the progression to AIDS. Common opportunistic infections include Pneumocystis pneumonia, tuberculosis, and candidiasis, while Kaposi's sarcoma and non-Hodgkin lymphoma are among the cancers frequently associated with AIDS.

Treatment and Management

While there is no cure for HIV/AIDS, antiretroviral therapy (ART) can significantly slow the progression of the disease. ART involves the combination of drugs that target different stages of the HIV lifecycle, helping to reduce viral load, preserve CD4+ T cell counts, and prevent the onset of AIDS-related conditions.