Human immunodeficiency virus. A non-taxonomic and historical term referring to any of two species, specifically HIV-1 and/or HIV-2. Prior to 1986, this was called human T-lymphotropic virus type III/lymphadenopathy-associated virus (HTLV-III/LAV). From 1986-1990, it was an official species called HIV. Since 1991, HIV was no longer considered an official species name; the two species were designated HIV-1 and HIV-2.
Source: National Library of Medicine 2013 MeSH Scope Note and Classification

Figure 1. Virions of HIV seen by tomographic electron microscopy in HIV-1 infected BLT mouse colon, with the virion components modeled and highlighted in color.

Figure 2. Detail of Figure 1, showing modeled HIV-1 virons colorized to show envelope (blue), bullet-shaped core (magenta) and presumed surface spikes (yellow).

Figure 3. Negative-stain, electron tomographic imaging of a budding HIV virion.

In Figures 1, 2 and 3, a thin slice from a montaged tomographic reconstruction of a region of a crypt of Lieberkühn in HIV-1 infected humanized Bone Marrow Liver Thymic (BLT) mouse colon is shown. In Figures 1 and 2, the virions themselves have been modeled in position (the envelopes as blue spheres, the bullet-shaped cores in magenta and presumptive surface spikes as tiny yellow spheres) and the tomographic slice superimposed beneath them. This view allows for the virions in the intercellular spaces between cells to be visualized relative to the surrounding tissue components.

The images shown were provided by Mark S. Ladinsky and Pamela J. Bjorkman, PhD, of the California Institute of Technology, Pasadena, CA and Douglas Kwon, MD PhD, of the Ragon Institute of MGH, MIT and Harvard and Harvard University, Cambridge, MA.

1. National Library of Medicine 2013 MeSH Scope Note and Classification