HIV: The Causative Agent of AIDS

February 2024

Researcher: Noor Fatima Mushtaq

Editor: Icy Yeung

Human Immunodeficiency Virus (HIV) is a retrovirus that attacks the immune system, specifically targeting CD4 cells, which play a crucial role in the body's ability to fight infections. HIV weakens the immune system over time, making individuals more susceptible to infection and disease. If left untreated, HIV can progress to Acquired Immunodeficiency Syndrome (AIDS), the final stage of HIV infection. However, with proper medical care, HIV can be effectively managed, allowing people with HIV to live long and healthy lives.

HIV-1 virions contain two copies of a single-stranded RNA genome within a conical capsid surrounded by a plasma membrane of host cell origin containing viral envelope proteins. The RNA genome is 9750 nucleotides long, and the virions are approximately 120 nm in diameter. A detailed three-dimensional structure of HIV-1 envelope glycoprotein spikes, which are required for infection of host cells, has recently been elucidated by cryoelectron microscopy tomography.

HIV-1 RNA is tightly bound to nucleocapsid proteins p6 and p7, which protect it from digestion by nucleases. The viral core contains reverse transcriptase, integrase, and proteases. The entire complex was surrounded by an icosahedral capsid (p. 24). A myristoylated matrix protein (p17) surrounded the capsid. Also enclosed within the virion particle are the proteins Vif, Vpr, and Nef. The envelope is formed when the capsid buds from the host cell, taking part of the host cell membrane with it. Embedded within the lipid bilayer are the viral envelope glycoproteins that form HIV-1 spikes: the external surface glycoprotein (gp120) and the transmembrane glycoprotein (gp41).

The HIV genome comprises two identical copies of single-stranded RNA. This RNA contains genetic information necessary for the virus to replicate and produce new viral particles. The genome of HIV is approximately 9.7 kilobases in length and encodes several essential viral proteins, including structural proteins (such as Gag, Pol, and Env) and regulatory proteins (such as Tat and Rev). The viral genome also contains long terminal repeats (LTRs) at both ends, which play crucial roles in viral replication and transcription. The HIV genome undergoes significant genetic variation owing to its high mutation rate, leading to the emergence of diverse viral strains and the ability to evade the immune system and antiviral treatments.