New Theory, HIV to AIDS
Brian Mailman
*Public release date: 31-Jul-2007
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Contact: Jennifer Fitzenberger
jfi...@uci.edu <mailto:jfi...@uci.edu>
949-824-3969
University of California - Irvine <http://www.uci.edu/>
Study helps explain how HIV becomes AIDS
Finding could help scientists seeking therapies to block virus progression
Irvine, Calif.--A new UC Irvine study sheds light on how HIV develops
into AIDS and suggests a possible way to block the deadly transformation.
UCI biologist Dominik Wodarz has shown for the first time that the
development of AIDS might require HIV to evolve within a patient into a
state where it spreads less efficiently from cell to cell. This
counters the current belief that AIDS develops when the virus evolves
over time to spread more efficiently within a patient, ultimately
leading to the collapse of the immune system.
The study also finds that multiple HIV particles must team up to infect
individual cells, called co-infection, in order for deadly strains to
emerge and to turn the infection into AIDS. If just one virus particle
infects a cell, the deadliest strains may not be able to evolve,
stopping HIV from progressing to AIDS. By keeping more than one HIV
particle from infecting a cell, scientists might be able to ward off
AIDS, the study suggests. AIDS killed more than 17,000 people in the
United States in 2005.
“If this is true, a new approach to therapy could be to block the
process of co-infection in cells,” said Wodarz, who used a mathematical
model to draw his conclusions. “This would prevent deadly HIV strains
from emerging and the patient would remain healthy, despite carrying the
virus.”
The study appears online July 31 in the Proceedings of the Royal Society B.
HIV develops in three stages. During the first few weeks, the virus
grows to very high levels and can cause symptoms similar to a general
viral infection such as the flu. The virus then drops to lower levels
and the patient enters the asymptomatic phase that lasts on average 8-10
years. During the last stage, AIDS develops and the immune system
collapses. Without an immune system, the patient cannot survive.
It is not well understood how the asymptomatic phase transitions into
AIDS. The common notion is that HIV evolves to grow better over time
following Darwin’s theory of natural selection, eventually killing the
patient.
But Wodarz’s mathematical model, which takes into account how well the
virus spreads and how quickly it kills the cells it invades, shows that
the most deadly HIV strains do not spread the fastest from cell to cell.
This surprised Wodarz because evolution tends to allow strong organisms
to thrive, while weaker organisms become extinct.
The explanation, he says, rests with the fact that multiple HIV
particles can invade a single cell. Wodarz’s calculations show that, in
this situation, viral evolution within a patient is fundamentally
altered, allowing the deadly, slower-spreading strains to emerge over
time and trigger the onset of AIDS.
These notions can be tested experimentally. If confirmed, Wodarz
believes scientists could use this knowledge to develop a drug that
blocks the cellular invasion of multiple HIV particles. This would
create an environment in which the most deadly HIV types cannot emerge.
This, he says, could keep HIV from developing into AIDS. No such drug
currently exists.
This theory could explain why certain monkeys that are naturally
infected with the monkey version of HIV never develop AIDS. According to
Wodarz’s model, multiple virus particles may infect cells at reduced
levels or not at all. Wodarz says this theory also could be tested
experimentally.
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For AIDS/HIV+ resources, visit the s.s.a.h+ website at :
http://www.webcom.com/benny/ssah/ssah+.html
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