HIV: the virus

Basics

HIV is a RNA retrovirus of the lentivirus genus (lentiviruses are characterized by a long incubation period)
two variants - HIV-1 and HIV-2
HIV-2 is more common in west Africa, has a lower transmission rate and is thought to be less pathogenic with a slower progression to AIDS

Basics structure

spherical in shape with two copies of single-stranded RNA enclosed by a capsid of the viral protein p24
a matrix composed of viral protein p17 surrounds the capsid
envelope proteins: gp120 and gp41
pol gene encodes for viral enzymes reverse transcriptase, integrase and HIV protease

Cell entry

HIV can infect CD4 T cells, macrophages and dendritic cells
gp120 binds to CD4 and CXCR4 on T cells and CD4 and CCR5 on macrophages
mutations in CCR5 can give immunity to HIV

Replication

after entering a cell the enzyme reverse transcriptase creates dsDNA from the RNA for integration into the host cell's genome

An illustration model of the HIV Replication Cycle. Each step of the cycle is numbered and concisely described. Credit: NIAID