Example of acquired immune deficiency: HIV-1 infection

The global epidemic of the acquired immune
deficiency syndrome (AIDS) due to the infection
with human immunodeficiency virus type 1
(HIV-1) poses a major public health problem of
unprecedented dimensions in modern times.
Although it was first noted in 1981 in restricted
populations, it now occurs in all populations at
all ages throughout the world (United Nations
Programme on HIV/AIDS at http://www.UNAIDS.
org/hivaidsinfo/documents-html). HIV-1
selectively infects T cells of the CD4 type. The
first step of infection is specific binding of the
extracellular domain of the viral transmembrane
glycoprotein gp120 to the CD4 receptor
(gp41 is the transmembrane protein). Two
chemokine receptors, CCR5 and CXR4, function
as major coreceptors (not shown in the figure).
Following virus genome uptake, a phase of viral
replication by reverse transcription into
double-stranded DNA occurs. Provirus DNA is
integrated into the cellular DNA by the virusencoded
integrase enzyme. As the infected cell
divides, the viral DNA (provirus) is also replicated.