HIV infection, coloured transmission electron micrograph (TEM). Mature virus and budding release of HIV in human lymph tissue (RNA virus, Retroviridae Family). In retroviruses the nucleocapsid buds directly through the cytoplasmic membrane. This produces an enveloped virion during the release process. HIV (human immunodeficiency virus) is a lentivirus (a subgroup of retrovirus) that causes HIV infection. Extened HIV infection can lead to acquired immunodeficiency syndrome (AIDS). AIDS in humans lead to failure of the immune system and causes life-threatening opportunistic infections (and cancers) to thrive. Infection with HIV occurs by the transfer of blood, semen, vaginal fluid, pre-ejaculate, or breast milk. Within these body fluids, HIV exists as both free virus particles and viruses within infected immune cells. HIV infects CD4+ helper T cells), dendritic cells and macrophages. Magnification: x16, 260 when shortest axis printed at 25