Human immunodeficiency virus (HIV) - life cycle, pathophysiology, investigations, diagnosis and AIDS

Introduction

This tutorial provides a comprehensive overview of the human immunodeficiency virus (HIV), including its life cycle, pathophysiology, methods of investigation, diagnosis, and its progression to AIDS. Understanding these concepts is crucial for healthcare professionals, students, and anyone interested in HIV/AIDS.

Step 1: Understand the HIV Life Cycle

The HIV life cycle is crucial for grasping how the virus infects host cells and replicates. Here are the main stages:

1. Attachment:

   • HIV binds to CD4 receptors on T-helper cells.
   • Coreceptors (CCR5 or CXCR4) assist in the entry of the virus.

2. Fusion:

   • The viral envelope fuses with the host cell membrane, allowing viral RNA and enzymes to enter the cell.

3. Reverse Transcription:

   • The viral RNA is transcribed into DNA by reverse transcriptase.

4. Integration:

   • Viral DNA integrates into the host's genome via integrase.

5. Replication:

   • The host cell's machinery is used to produce viral proteins and RNA.

6. Budding:

   • New viral particles bud off from the host cell, ready to infect other cells.

Practical Tips

• Familiarize yourself with the structure of HIV and its receptors to better understand the attachment phase.
• Review diagrams of the HIV life cycle for visual learning.

Step 2: Explore Pathophysiology of HIV

Understanding the pathophysiology of HIV helps in recognizing its effects on the immune system.

• Immune Response:

  • HIV primarily targets CD4+ T cells, leading to their depletion.
  • A decline in CD4+ cells compromises the immune response, increasing susceptibility to opportunistic infections.

• Chronic Phase:

  • HIV can remain latent for years, during which the virus replicates at a low level.

• Progression to AIDS:

  • The progression is defined by a significant drop in CD4+ count (<200 cells/mm³) and the occurrence of opportunistic infections or cancers.

Common Pitfalls

• Misunderstanding the difference between HIV and AIDS; remember that AIDS is the advanced stage of HIV infection.

Step 3: Investigate Methods for Diagnosis

Diagnosing HIV involves several tests that detect the virus or antibodies.

1. Antibody Tests:

   • Detect antibodies produced in response to HIV.
   • Examples include ELISA and rapid tests.

2. Antigen Tests:

   • Detect the HIV p24 antigen during early infection.

3. Nucleic Acid Tests (NAT):

   • Identify the actual virus in the blood.
   • Used in high-risk individuals or during acute infection.

Practical Advice

• Encourage regular testing for at-risk populations to facilitate early diagnosis and treatment.

Step 4: Understand AIDS Diagnosis

AIDS is diagnosed based on specific criteria:

• CD4+ Count:

  • A CD4+ count of less than 200 cells/mm³.

• Opportunistic Infections:

  • The presence of certain infections like Pneumocystis pneumonia or Kaposi's sarcoma.

Key Considerations

• Recognize the importance of CD4+ monitoring in managing HIV and preventing progression to AIDS.

Conclusion

Understanding the life cycle, pathophysiology, and diagnosis of HIV is essential for effective management and treatment. Key takeaways include the importance of early detection through regular testing and monitoring of CD4+ counts to prevent progression to AIDS. For further learning, consider exploring treatment options and ongoing research in HIV/AIDS management.