Researchers have confirmed for the first time
the benefit of an innate defense system present in the few patients who
remain healthy after years of infection with HIV despite receiving no
treatment, according to an article published in the September edition
of the Journal of Virology.
The study found that the subset of HIV-infected
patients referred to as long-term survivors or nonprogressors have
higher amounts of a key enzyme in their white blood cells.
At the same
time,
a related biotech company is poised to begin preclinical testing on
a drug designed to confer similar protection on most HIV patients.
Approximately 5 percent of patients with HIV, or human immunodeficiency
virus, do not develop AIDS, or do so very slowly. Researchers have
been trying for years to understand what sets long-term nonprogressors
apart. Past research suggested that such patients maintain higher levels
of an enzyme in white blood cells called APOBEC-3G (A3G), and the new
study confirmed it in the first experiments on human cells.
Researchers at the University of Rochester Medical Center believe that
A3G “edits,” or introduces changes in, the HIV genetic code
every time the virus copies itself. By doing so, A3G corrupts the HIV
gene code and prevents the virus from reproducing. Unfortunately, HIV
has evolved to counter A3G with viral infectivity factor (Vif), a protein
that “grabs” A3G and tricks the body into destroying it.
With the “editing enzyme” gone, HIV is free to overwhelm
the immune system, leaving patients vulnerable to AIDS infections that
take three million lives per year.
“ Unlike nonprogressors, we believe that most people do not
make enough A3G to overcome the efforts by Vif to shut it down,” said
Harold C. Smith, Ph.D., professor of Biochemistry and Biophysics at
the University of Rochester Medical Center, co-author of the J. Virology
paper and a founder of the biotech company, OyaGen Inc.
“ Our
work supports Michael Malim’s seminal discovery while at the University
of Pennsylvania, which suggested that protecting whatever amount of A3G
that people do have from Vif represents a new way to attack HIV.”
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