Smallpox
Study Reveals Tactics of a Killer
Results
of a new study in monkeys offer scientists a rare glimpse of how,
on a molecular level, the smallpox virus attacks its victims.
The findings shed light on how the virus caused mass death and
suffering, and will help point the way to new diagnostics, vaccines
and drugs that would be needed in the event of a smallpox bioterror
incident.
The study,
led by David Relman, M.D., of Stanford University, is now online
in the "Proceedings of the National Academy of Sciences"
("PNAS"). The research was funded by the National Institute
of Allergy and Infectious Diseases (NIAID), part of the National
Institutes of Health.
"In light
of today's concerns about bioterror attacks, we have an urgent
need to know as much as possible about the workings of the smallpox
virus and other bioterror agents," says Anthony S. Fauci,
M.D., director of NIAID. "This new research fills in some
of the gaps in our understanding of smallpox. Now we are better
positioned to speed the development of protective measures."
Related research,
also published online in "PNAS" this week, set the stage
for Dr. Relman's smallpox study. In this work, researchers at
the U.S. Army Medical Research Institute of Infectious Diseases,
the Centers for Disease Control and Prevention (CDC) and Stanford
University, show that cynomolgus macaque monkeys exposed to smallpox
virus can develop a disease similar to human smallpox. Previously,
scientists thought it impossible for the smallpox virus to sicken
any species other than humans.
Following
on that discovery, Dr. Relman and a separate team of researchers
did molecular-level analysis of how the smallpox infection altered
gene expression patterns in the monkeys' blood cells. Dr. Relman
used DNA microarrays, a tool unavailable in 1977 when naturally
occurring smallpox was eradicated after a global vaccination campaign.
Microarray analysis research reveals how smallpox alters gene
activity in host cells under attack by the virus. It also reveals
changes in levels of gene expression and expression of some proteins
in the blood of monkeys when they are infected with smallpox virus.
In their "PNAS" paper, Dr. Relman and colleagues suggest
possible mechanisms by which the virus subverts host defenses.
Uncovering these mechanisms gives scientists targets for developing
countermeasures to lessen or block the ability of the smallpox
virus to cause disease.
Experts believe
that this new knowledge of how smallpox acts on cells could speed
up development of smallpox countermeasures. Researchers will now
be able to compare the actions of smallpox on cells to other pox
viruses and use less lethal pox viruses in the search for smallpox
countermeasures.
CDC has the
only U.S. laboratory facility in which research using smallpox
virus is permitted. However, many more labs in the United States
have sufficient safety features for handling less-lethal pox viruses,
such as monkeypox. If monkeypox -- a pox virus less virulent in
humans -- proves to have molecular workings similar to smallpox,
researchers could test countermeasures on it in a greater number
of lab facilities, hastening the pace of research.
NIAID supports
research to develop animal models of monkeypox infection. Researchers
will evaluate the amount of virus needed to cause disease by natural
routes of infection such as inhalation, and the way in which the
disease develops. These models could potentially be used to advance
the development of diagnostics tools, vaccines and therapies for
smallpox without employing smallpox virus. NIAID is supporting
this research through its "In Vitro and Animal Models for
Emerging Infectious Diseases and Biodefense" program.
NIAID is a
component of the National Institutes of Health, an agency of the
U.S. Department of Health and Human Services. NIAID supports basic
and applied research to prevent, diagnose and treat infectious
diseases such as HIV/AIDS and other sexually transmitted infections,
influenza, tuberculosis, malaria and illness from potential agents
of bioterrorism. NIAID also supports research on transplantation
and immune-related illnesses, including autoimmune disorders,
asthma and aller