HIV - Structure and Pathogenesis

Summary

Acquired Immunodeficiency Syndrome (AIDS) is caused by the Human Immunodeficiency Virus (HIV), which leads to severe immunosuppression and increases susceptibility to infections and neurological disorders. There are two types of HIV: HIV-1, prevalent worldwide, and HIV-2, found mainly in West Africa and India. The virus primarily targets CD4+ T cells, attaching through surface glycoproteins GP120 and GP41. Transmission occurs through sexual contact, shared needles, blood transfusions, organ transplants, and from mother to infant. The virus integrates into the host cell's DNA, eventually killing the cell and triggering immune responses.

Takeaways

• 😀 AIDS is caused by the HIV virus, which results in severe immunosuppression, making individuals vulnerable to infections, cancers, and neurological disorders.
• 😀 There are two species of HIV: HIV-1, which is more common globally, and HIV-2, which is primarily found in Western Africa and India.
• 😀 The HIV virus consists of an outer lipid bilayer envelope containing viral glycoproteins GP120 and GP41, along with a matrix protein (P17) and a viral core with proteins and RNA.
• 😀 HIV primarily spreads through sexual contact, sharing needles among drug users, blood transfusions, organ transplants, and from mother to infant (during pregnancy, birth, or breastfeeding).
• 😀 Saliva is not a significant mode of HIV transmission due to inhibitory factors that limit the virus’s infectivity.
• 😀 HIV has a predilection for attacking CD4+ T cells, macrophages, and nerve cells, with the virus entering these cells via the CD4 receptor.
• 😀 After entering a host cell, the HIV genome undergoes reverse transcription to form complementary DNA (cDNA), which integrates into the host's DNA.
• 😀 The integrated HIV genome can either remain latent or begin actively producing viral RNA and proteins, leading to the formation of new viruses.
• 😀 When new viruses are formed, they bud off from the host cell, increasing cell permeability and eventually leading to the death of the infected cell.
• 😀 The host cell may also die through apoptosis triggered by the virus’s attachment or through the immune system's response (CD8+ T cells and natural killer cells targeting infected cells).
• 😀 HIV's impact on CD4+ T cells is a key factor in immune system collapse, which is characteristic of AIDS progression.

Q & A

What is Acquired Immunodeficiency Syndrome (AIDS), and what causes it?

AIDS is an infection caused by the retrovirus Human Immunodeficiency Virus (HIV), characterized by severe immunosuppression, which makes the patient vulnerable to opportunistic infections, malignancies, and neurological disorders.

What are the two types of HIV, and where are they most commonly found?

There are two types of HIV: HIV-1 and HIV-2. HIV-1 is the most common type worldwide, predominantly found in the United States, Europe, and Central Africa. HIV-2 is mainly found in Western Africa and India.

What is the structure of the HIV virus?

The HIV virus has an outer lipid bilayer envelope containing surface glycoproteins called GP120 and GP41. Beneath the envelope is a matrix protein called P17, and the viral core includes P24 capsid, two copies of viral RNA, three enzymes (reverse transcriptase, integrase, and protease), and a nucleocapsid protein called p7 or p9.

What are the primary modes of HIV transmission?

The primary modes of HIV transmission include sexual contact (homosexual, bisexual, and heterosexual), intravenous drug use (via sharing needles), blood transfusions, organ transplantation, and mother-to-infant transmission (in utero, during birth, or breastfeeding).

Why is saliva not considered a significant mode of HIV transmission?

Saliva is not a significant mode of HIV transmission because it contains inhibitory factors that reduce the infectivity of the virus, making transmission through saliva unlikely.

Which cells does HIV primarily target in the body?

HIV primarily targets T lymphocytes, especially CD4+ T cells, as well as macrophages and nerve cells.

How does HIV attach to and enter a CD4+ T cell?

HIV attaches to the CD4+ T cell through the cell's CD4 receptor using its GP120 and GP41 surface glycoproteins. Once attachment is successful, the viral RNA enters the host cell's cytoplasm.

What happens to the HIV genome once it enters the host cell?

Once inside the host cell, the HIV genome undergoes reverse transcription by the reverse transcriptase enzyme, synthesizing complementary DNA (cDNA). This cDNA then integrates into the host cell's DNA, leading to either latency or active viral production.

What is the process of viral replication inside a host cell?

The integrated viral genome directs the host cell to produce viral RNA and proteins, which then form viral core proteins. These proteins bud off from the host cell membrane, forming new virus particles.

How does HIV cause the death of a host CD4+ T cell?

HIV-induced cell death occurs when the virus buds off from the host cell, causing increased permeability of the cell membrane. This triggers apoptosis, or programmed cell death. Additionally, cytotoxic CD8+ T cells and natural killer cells may also contribute to the death of infected CD4+ T cells.