|
Site Map
Home
Project Background
Credits
Site References
Glossary
Investigations
AIDS Reference
History
HIV
in the Body
Symptoms
Current Treatments
Education
AIDS-Resistance
Into
CCR5
The Role of CCR5
Our
Experiment
What
is PCR?
The Process
Photo Tour
Time-Line
Implications
Summary
| |
During the M-tropic phase of HIV infection, the virus favors macrophages, which it invades
by binding (through its gp120 protein) to the molecules CD4 and CCR5 on the macrophage
surface. Eventually, however, HIV-1 can become dual-tropic. Such strains produce
gp120 molecules capable of recognizing the CXCR4 protein on CD4-bearing T-cells. During
this phase HIV-1 may infect both macrophages and T-cells. Still later, the bulk of the
viral population may switch it's preference to the CXCR4 receptor and become T-tropic.
T-tropic viruses readily destroy infected T-cells, contributing to the collapse of
the immune system and the onset of AIDS. Alternatively, some viruses, such as
certain strains of HIV-2 could attach to CXCR4 quickly leading to AIDS.
Interactions Between HIV-1 and the Cell Surface
|
| HIV-1 interacts with a cell-surface receptor, primarily CD4, and through
conformational changes becomes more closely associated with the cell through interactions
with other cell-surface molecules, such as the chemokine receptors CXCR4 and CCR5. The
likely steps in HIV infection are as follows: |
 |
The CD4-binding site on HIV-1 gp120 interacts with the CD4 molecule on the
cell surface. |
| Conformational changes in both the viral envelope and the CD4 receptor
permit the binding of gp120 to another cell-surface receptor, such as CCR5. |
 |
 |
This second attachment brings the viral envelope closer to the cell
surface, allowing interaction between gp41 on the viral envelope and a fusion domain on
the cell surface. HIV then fuses with the cell. |
| Subsequently, the viral nucleoid enters into the cell, most likely by
means of other cellular events. Once this stage is achieved, the cycle of viral
replication begins. |
 |
Illustrations and content based on "Infection by Human Immunodeficiency Virus -
CD4 Is Not Enough" by Levy, J.A. - The New England Journal of
Medicine, Vol 335, no 20, pages 1525-1527, Nov., 1996. Illustrations (c)
Massachusetts Medical Society.
Back to Top
  
|
