102
AIDS/HIV, Molecular and Cell Biology
the disease its name,
acquired immune
defciency syndrome
(
AIDS
). In general, the
tempo of the disease is slower with HIV-2,
possibly related to its replicating to a lower
titer. This may also explain why it is less
easily transmitted vertically from mother
to child than HIV-1.
2
The Molecular Biology of HIV
Understanding the interactions of the
virus with the immune system, its ability
to cause disease, and potential therapies
requires an understanding of the retroviral
life cycle. The genetic structure of the virus
is shown in Fig. 2. It has the conventional
gag, pol
,and
env
open reading frames of
all retroviruses together with at least seven
additional accessory and regulatory genes.
2.1
Virus Structure
HIV is a conventionally structured retro-
virus (Fig. 3) with a C-type assembly
mechanism. On the exterior, it has a lipid
envelope derived from the surface plasma
membrane of the cell from which it budded
and in this are the envelope glycoproteins
consisting of trimers of a transmembrane
(TM) protein, each of which is noncova-
lently linked to an external surface (SU)
glycoprotein. TM and SU are often re-
ferred to by their molecular weights as
gp41 and gp120 respectively (in HIV-1).
RNA species
HIV
Ψ
Gag, Pol
Env, Nef
Tat, Rev
SD
Tat
Rev
Nef
Vif
Vpu
Gag
Pol
Env
LTR
LTR
TAR stem loop
Rev response element
Vpr
Fig. 2
Genetic structure of lentivirus DNA provirus and families of RNAs transcribed.
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