MICROBIOLOGY
HIV (HUMAN IMMUNODEFICIENCY VIRUS)
Cells affected
The virus, entering through which ever route, acts primarily on the following
cells:
Lymphoreticular system:
o CD4+ T-Helper cells
o CD4+ Macrophages
o CD4+ Monocytes
o B-lymphocytes
Certain endothelial cells
Central nervous system:
o Microglia of the nervous system
o Astrocytes
o Oligodendrocytes
o Neurones - indirectly by the action of cytokines and the gp-120
The effect
The virus has cytopathic effects but how it does it is still not quite clear. It
can remain inactive in these cells for long periods, though. This effect is
hypothesized to be due to the CD4-gp120 interaction.
The most prominent effect of the HIV virus is its T-helper cell
suppression and lysis. The cell is simply killed off or deranged to the
point of being function-less (they do not respond to foreign antigens).
The infected B-cells can not produce enough antibodies either. Thus
1
, the immune system collapses leading to the familiar AIDS
complications, like infections and neoplasms .
Infection of the cells of the CNS cause acute aseptic meningitis,
subacute encephalitis, vacuolar myelopathy and peripheral
neuropathy. Later it leads to even AIDS dementia complex.
The CD4-gp120 interaction is also permissive to other viruses like
Cytomegalovirus, Hepatitis virus, Herpes simplex virus, etc. These
viruses lead to further cell damage i.e. cytopathy.
Molecular basis
1- Structure and genome of HIV
Figure 1. Diagram
of HIV
HIV is different in structure from other retroviruses. It is roughly spherical
with a diameter of about 120 nm, around 60 times smaller than a red blood
cell, yet large for a virus. It is composed of two copies of positive single-
stranded RNA that codes for the virus's nine genes enclosed by a conical
capsid composed of 2,000 copies of the viral protein p24. The single-
stranded RNA is tightly bound to nucleocapsid proteins, p7 and enzymes
needed for the development of the virion such as reverse transcriptase,
proteases, ribonuclease and integrase. A matrix composed of the viral
2
HIV (HUMAN IMMUNODEFICIENCY VIRUS)
Cells affected
The virus, entering through which ever route, acts primarily on the following
cells:
Lymphoreticular system:
o CD4+ T-Helper cells
o CD4+ Macrophages
o CD4+ Monocytes
o B-lymphocytes
Certain endothelial cells
Central nervous system:
o Microglia of the nervous system
o Astrocytes
o Oligodendrocytes
o Neurones - indirectly by the action of cytokines and the gp-120
The effect
The virus has cytopathic effects but how it does it is still not quite clear. It
can remain inactive in these cells for long periods, though. This effect is
hypothesized to be due to the CD4-gp120 interaction.
The most prominent effect of the HIV virus is its T-helper cell
suppression and lysis. The cell is simply killed off or deranged to the
point of being function-less (they do not respond to foreign antigens).
The infected B-cells can not produce enough antibodies either. Thus
1
, the immune system collapses leading to the familiar AIDS
complications, like infections and neoplasms .
Infection of the cells of the CNS cause acute aseptic meningitis,
subacute encephalitis, vacuolar myelopathy and peripheral
neuropathy. Later it leads to even AIDS dementia complex.
The CD4-gp120 interaction is also permissive to other viruses like
Cytomegalovirus, Hepatitis virus, Herpes simplex virus, etc. These
viruses lead to further cell damage i.e. cytopathy.
Molecular basis
1- Structure and genome of HIV
Figure 1. Diagram
of HIV
HIV is different in structure from other retroviruses. It is roughly spherical
with a diameter of about 120 nm, around 60 times smaller than a red blood
cell, yet large for a virus. It is composed of two copies of positive single-
stranded RNA that codes for the virus's nine genes enclosed by a conical
capsid composed of 2,000 copies of the viral protein p24. The single-
stranded RNA is tightly bound to nucleocapsid proteins, p7 and enzymes
needed for the development of the virion such as reverse transcriptase,
proteases, ribonuclease and integrase. A matrix composed of the viral
2
