“HiV is a replicating machine.” — STEVEN DEEKS
Why some HIV
a bigger punch
By Rachel Ehrenberg
A new mathematical analysis of HIV-fighting drugs may reveal why some
combinations work better than others.
Infection with HIV was a death sentence until the introduction of multidrug
cocktails, yet the differential effectiveness of the combinations has remained
a puzzle. The research, published in the
July 13 Science Translational Medicine,
could help refine therapies for HIV and
other viruses, such as hepatitis C.
Slightly boosting the dose of some
HIV drugs has a profound effect if those
drugs are attacking multiple targets,
the new mathematical model reveals.
Finding that more bullets can kill
more targets may seem obvious, says
AIDS researcher and Howard Hughes
Medical Institute investigator Robert
Siliciano of Johns Hopkins University. But
the realization required a shift in thinking about a very old idea: the relationship
between a drug’s dose and its effect.
For the last century, drug effectiveness
has been visualized with what’s called
the dose-response curve. This relation-
ship often takes on a stretched-out “S”
shape when graphed.
Percent of targets killed
Halting HIV For two hypothetical HiV drugs, the dose that
kills half the target cells (dotted line) is defined as 1. The steep
slope of the red drug indicates that for it, a small increase in dose
has a big effect on response. Drugs that effectively attack HiV
at certain points in the virus’s life cycle have these steep slopes.
Dose-response curves for hypothetical HIV drugs
C. BiCkel/SCIENCE 2011
August 13, 2011 | SCIENCE NEWS | 9