Hiv Virus

The HIV virus (Human Immunodeficiency Virus) is a small, spherical retrovirus with a diameter of approximately 100–120 nm, responsible for causing AIDS by attacking the body's immune system, particularly the CD4+ T cells.​

Structure

HIV consists of two copies of single-stranded positive-sense RNA tightly bound to nucleocapsid proteins and essential enzymes such as reverse transcriptase, integrase, and protease within a cone-shaped capsid (protein p24).​

The capsid is surrounded by a matrix protein (p17), and the entire complex is enveloped in a lipid bilayer taken from the host cell membrane.​

Embedded within this envelope are viral glycoproteins: gp120 (surface) and gp41 (transmembrane), which allow the virus to attach and fuse with target cells, initiating infection.​

Genome and Proteins

The HIV genome contains about 9,800 nucleotides, encoding nine major genes that produce fifteen viral proteins—these include structural proteins (Gag, Pol, Env) and regulatory/accessory proteins (Tat, Rev, Nef, Vif, Vpr, Vpu).​

Env glycoproteins (gp120/gp41) are major targets for immune response but are heavily shielded by a dense cluster of glycans, hindering neutralization by antibodies.​

Life Cycle and Function

HIV infects CD4+ T cells through a seven-stage cycle including attachment, fusion, reverse transcription, integration, replication, assembly, and budding, using host cellular machinery to reproduce.​

The virus integrates its genetic material into the host genome, leading to persistent infection and immune system decline over time.