|Staph Vaccine Shows Promise in Mouse Study
By combining four proteins of Staphylococcus aureus that
individually generated the strongest immune response in mice, scientists
have created a vaccine that significantly protects the animals
from diverse strains of the bacterium that cause disease in humans.
A report describing the University of Chicago study, funded by
the National Institute of Allergy and Infectious Diseases (NIAID)
of the National Institutes of Health, appears online this week
in the Proceedings of the National Academy of Sciences.
“This finding represents a promising step toward identifying potential
components to combine into a vaccine designed for people at high
risk of invasive S. aureus infection,” notes Anthony S.
Fauci, M.D., NIAID director.
S. aureus, the most common agent of hospital-acquired
infection, is the leading cause of bloodstream, lower respiratory
tract and skin infections. These infections can result in a variety
of illnesses, including endocarditis (inflammation of the heart),
toxic-shock syndrome and food poisoning.
Research in S. aureus has taken on new urgency: In the
past few decades, the bacterium has developed resistance to traditional
antibiotics, thus allowing infections to spread throughout the
body of the infected individual despite treatment. More recently,
healthy people with no apparent risk factors have been infected
by novel and extremely virulent strains of S. aureus acquired
from community rather than hospital sources.
Olaf Schneewind, M.D., Ph.D., led the University of Chicago research
group. Using available genome sequencing and analysis of antigenic
proteins from diverse S. aureus strains, the researchers
tested 19 surface proteins to see if they triggered an immune response
in mice. The group then identified four individual proteins — IsdA,
IsdB, SdrD and SdrE — that provided the strongest immune
response, combined them into a vaccine and tested the combination
vaccine in mice.
“When we challenged the immunized mice by exposing them to a human
strain of S. aureus, the combination vaccine provided
complete protection, whereas the control group developed bacterial
abscesses,” says Dr. Schneewind. For comparative purposes, the
researchers also tested all four proteins as individual vaccines.
These vaccines provided either no protection or modest protection,
says Dr. Schneewind.
The researchers then tested the combination vaccine in mice again,
this time challenging groups of 10 vaccinated mice for seven days
using five different S. aureus strains that infect humans.
The vaccine offered significant protection against all strains
Dr. Schneewind and his colleagues are now exploring the relationship
between antibodies that fight S. aureus infection and
surface proteins of the bacterium that facilitate the spread of
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and treat infectious diseases such as HIV/AIDS and other sexually
transmitted infections, influenza, tuberculosis, malaria and
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disorders, including autoimmune diseases, asthma and allergies. News
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on the NIAID Web site at http://www.niaid.nih.gov.
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