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Immune
System of Healthy Adults May Be Better Prepared
than Expected to Fight 2009 H1N1 Influenza Virus
A
new study shows that molecular similarities
exist between the 2009
H1N1 influenza virus and other strains of
seasonal H1N1 virus that have been circulating
in the population since 1988. These results
suggest that healthy adults may have a level
of protective immune memory that can blunt the
severity of infection caused by the 2009 H1N1
influenza virus.
The study team was led by Bjoern Peters, PhD,
and Alessandro Sette, PhD, of La Jolla Institute
for Allergy and Immunology, Calif., grantees
of the National Institute of Allergy and Infectious
Diseases (NIAID), part of the National Institutes
of Health (NIH).
The investigators looked at molecular structures
known to be recognized by the immune system
-- called epitopes -- on 2009 H1N1 influenza
and seasonal H1N1 viruses. Viral epitopes are
recognized by immune cells called B and T cells:
B cells make antibodies that can bind to viruses,
blocking infection, and T cells help to eliminate
virus-infected cells.
Using data gathered and reviewed from the scientific
literature and deposited into the NIAID-supported
Immune Epitope Database and Analysis Resource
(www.iedb.org),
the investigators found that some viral epitopes
are identical in both the 2009 and seasonal
H1N1 viral strains. Those epitopes that could
be recognized by two subsets of T cells, called
CD4 and CD8 T cells, are 41 percent and 69 percent
identical, respectively. Subsequent experiments
using blood samples taken from healthy adults
demonstrated that this level of T-cell epitope
conservation may provide some protection and
lessen flu severity in healthy adults infected
with the 2009 H1N1 influenza virus.
Analysis of the database also found that among
six viral surface epitopes that can bind antibody,
thereby preventing infection, only one is conserved
between 2009 and seasonal H1N1 viral strains.
These results suggest that healthy individuals
may have immune memory that recognizes the 2009
H1N1 strain and therefore can mount some measure
of an immune attack. The findings also may help
explain why the 2009 H1N1 influenza pandemic
affects young children more severely than it
does healthy older adults and also why two H1N1
vaccinations are needed to protect children
ages nine years and under.
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