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

Summary

The video explains the structure and life cycle of HIV, a retrovirus that primarily infects CD4 T cells, impairing the immune system and increasing susceptibility to infections and cancers. It details the virus's entry into host cells, the immune response, and the stages of infection, including acute HIV and the asymptomatic phase. The presentation also covers the importance of early diagnosis through various testing methods and emphasizes the role of antiretroviral therapy in managing HIV, helping individuals lead normal lives while preventing disease progression to AIDS.

Takeaways

• 😀 HIV (Human Immunodeficiency Virus) is a retrovirus that primarily infects CD4 T lymphocytes, leading to a weakened immune system.
• 😀 There are two main types of HIV: HIV-1, which is widespread globally, and HIV-2, which is mostly found in West Africa.
• 😀 The virus has a unique structure, including an icosahedral shape with a conical capsid that houses RNA and essential enzymes for replication.
• 😀 HIV's life cycle involves several key steps: attachment to CD4 receptors, fusion with the host cell membrane, reverse transcription of RNA to DNA, and integration into the host genome.
• 😀 The immune response to HIV begins with dendritic cells recognizing the virus and activating CD4 T cells, leading to the production of antibodies.
• 😀 Following initial infection, the viral load increases and can cause non-specific symptoms known as acute HIV infection, often resembling a standard viral illness.
• 😀 After the acute phase, HIV enters a latency period, during which it remains dormant and gradually reduces CD4 T cell counts over time.
• 😀 The asymptomatic phase can last around 10 years, during which the virus can still be detected but does not cause significant illness.
• 😀 AIDS (Acquired Immunodeficiency Syndrome) is diagnosed when the CD4 T cell count falls below 200 cells/mm³ or when specific opportunistic infections occur.
• 😀 Early and lifelong antiretroviral therapy is crucial for managing HIV, allowing individuals to lead normal lives and reducing the risk of opportunistic infections.

Q & A

What is HIV and how does it affect the immune system?

HIV, or Human Immunodeficiency Virus, is a retrovirus that primarily infects CD4 T lymphocytes, leading to their destruction. This impairs cell-mediated immunity, increasing the risk of cancers and opportunistic infections.

What are the differences between HIV-1 and HIV-2?

HIV-1 is the most common type of HIV worldwide, while HIV-2 is largely restricted to West Africa.

What is the structure of the HIV virus?

HIV has an icosahedral structure with a conical capsid that contains two strands of RNA and essential enzymes like integrase and reverse transcriptase, which are critical for replication.

Describe the process of HIV entry into a CD4 T cell.

HIV attaches to CD4 receptors on T cells using the gp120 spike protein, followed by the fusion of the viral and cell membranes, allowing the viral capsid to enter the cell.

What happens during reverse transcription in the HIV life cycle?

HIV reverse transcriptase converts the viral RNA into double-stranded proviral DNA, which then integrates into the host cell's DNA.

What is the significance of the asymptomatic phase in HIV infection?

During the asymptomatic phase, which can last about 10 years, the virus remains dormant, gradually reducing CD4 T cell counts while the individual may not show symptoms.

What are some common symptoms of acute HIV infection?

Symptoms of acute HIV infection can include fever, fatigue, myalgia, rash, headache, and lymphadenopathy, often resembling those of a standard viral infection.

How is HIV diagnosed?

HIV can be diagnosed using a combination assay that detects both HIV antibodies and the p24 antigen. If positive, further testing identifies the specific type of HIV.

What constitutes the definition of AIDS?

AIDS, or Acquired Immunodeficiency Syndrome, is defined by a CD4 cell count of less than 200 cells per cubic millimeter or the occurrence of AIDS-related illnesses.

What role does antiretroviral therapy play in HIV management?

Antiretroviral therapy is crucial for treating HIV, helping to manage the infection and prevent the progression to AIDS, allowing individuals to lead normal lives.