New forms of influenza
viruses can spur production of antibodies to past pandemics in people who lived
through them
Exposure to new flu
strains can stimulate production of antibodies against older versions of the
virus, researchers have found. The work suggests how to make longer-lasting
vaccines with broader flu-fighting capabilities.
Scientists had suspected
that the immune system could draw on its prior experience to craft potent
protection against future viruses. But there was no evidence before the new
work, says Patrick Wilson, an immunologist at the University of Chicago.
Peter Palese of the Icahn School of Medicine at Mount Sinai in New York City reports August 14 in Science Translational Medicine that he and his colleagues measured antibodies in blood samples drawn from 40 participants in the Framingham Heart Study. The people were born between 1917 and 1952 and lived through the flu pandemics that struck in 1957, 1968 and 1977. The participants volunteered blood samples at five-year intervals between 1987 and 2008.
Palese’s group tracked
how antibodies against the three pandemic flu strains changed over time. The
researchers also measured levels of antibodies against altered versions of
those viruses that were in circulation in 1981 and 1991.
Over time, levels of
antibodies against the pandemic strains rose as the people encountered new
versions of the flu, the team discovered. But when directed against an
unchanging virus called cytomegalovirus, the study participants’ antibodies
didn’t climb, suggesting that new virus varieties are important for prodding
production of old antibodies.
Because the immune
system holds on to old antibodies, elderly people may run out of room in their
immunological attics, leaving less space for making new antibodies, says Ning
Jenny Jiang, a bioengineer who studies systems immunology at the University of
Texas at Austin.
The new work also
suggests which parts of the flu virus goad the immune system into making the
best antibodies. Antibodies that can fight the widest range of flu viruses are
those that latch onto the stalk portion of the hemagglutinin protein, a
molecule that sits on the flu’s outer coat.
The protein’s stalk supports the head, the business end of the molecule, which grabs onto host cells. The stalk doesn’t change much from year to year or flu virus to flu virus, making it an attractive vaccine candidate.
The protein’s stalk supports the head, the business end of the molecule, which grabs onto host cells. The stalk doesn’t change much from year to year or flu virus to flu virus, making it an attractive vaccine candidate.
But the stalk by itself
usually doesn’t inspire much of an antibody-producing reaction from the immune
system. Palese thinks that by combining the stalk with a variety of heads, he
can make a flu vaccine that will protect against a wide range of viruses and
will last longer than current seasonal vaccines do.
CITATIONS
M. S. Miller et al.
Neutralizing antibodies against previously encountered influenza virus strains
increase over time: a longitudinal analysis. Science Translational Medicine
Vol. 5, August 14, 2013, p. 198ra107. doi: 10.1126/scitranslmed.3006637 [Go to]
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