WEDNESDAY, March 13 (HealthDay News) -- Flu vaccines protect people
by activating white blood cells that, in turn, boost the development of
antibodies to the flu, a new study suggests.
The finding may lead to more effective vaccines -- especially for
people whose immune system isn't robust enough to fully protect them
from the flu, such as the elderly, the study authors said.
"It is well known that CD4 T cells are important for the generation
of antibody responses," said lead researcher Dr. Hideki Ueno, an
investigator at the Baylor Institute for Immunology Research in Dallas.
"Most importantly, we found that the appearance of these cells in
blood correlated with the development of protective antibodies against
flu. Therefore, these cells appear to be very important for the
successful flu vaccination," he said.
The failure of older people to generate a protective antibody
response after a flu vaccine might be associated with the failure to
produce these CD4 T cells, Ueno said.
This year, for example, the flu vaccine was only 9 percent effective
in older people against the dominant H3N2 strain, according to the U.S.
Centers for Disease Control and Prevention. Finding ways to boost a
vaccine's effectiveness is especially important for seniors, who are at
higher risk of complications from the flu and are more likely to die
from them.
One way to help high-risk people might be to identify those whose
immune response is likely to be insufficient to fully protect them from
the flu, the researchers said.
"You could potentially screen people for their antibody response --
particularly young children and the elderly," said Andrea Sant, a
professor with the department of microbiology and immunology at the
University of Rochester, in Rochester, N.Y.
This screening could also be important during flu pandemics, said
Sant, who was not involved with the study. "You could find out if a dose
is sufficient to protect people and those who might need a boost," she
added.
Sant said using these CD4 T cells might also be a way of making vaccines more effective.
"Theoretically, you could fine-tune vaccines so they could allow
people to have more of these cells in their body when they get a
vaccine, either by adding them to a vaccine or administering them before
a vaccination," she explained.
The new study was published online March 13 in the journal Science Translational Medicine.
Looking at small groups of children and adults, the researchers found
a special type of CD4 T cells that appear after receiving a flu shot.
Specifically, these CD4 T cells have three components -- called CXCR5,
CXCR3 and ICOS -- that are the key to boosting the immune response to a
flu vaccine, the study authors reported.
These so-called "helper cells" aid what are called "memory" B cells
to make antibodies to the flu. What these memory cells are remembering
is having seen a flu strain before and knowing how to react by making
antibodies, the researchers explained.
So, in older people who have a lot of these memory cells, boosting
CD4 T cells might help memory cells to respond and launch an immune
defense, the investigators suggested.
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