If you've ever wondered how
the flu virus succeeds at infecting so many people, a new study of mice may
offer some insight.
The flu actually targets
cells of the immune system that are best able to disarm the virus, according to
the study. These first responders, known as memory B cells, produce antibodies
that can bind to the virus and neutralise it. These cells also reside in the
lung where they can protect against re-exposure to the virus.
Memory B cells
Researchers found, however,
that the flu virus attacks these memory B cells first to disrupt antibody
production, allowing it to replicate more efficiently and prevent the immune
system from mounting a second defence.
"We can now add this
to the growing list of ways that the flu virus has to establish
infection," study co-author Joseph Ashour, a postdoctoral researcher at
the Whitehead Institute for Biomedical Research, said in an institute news
"This is how the virus
gains a foothold," study co-author Stephanie Dougan, also a postdoctoral
researcher in the lab of Whitehead member Hidde Ploegh, explained in the news
release. "The virus targets memory cells in the lung, which allows
infection to be established – even if the immune system has seen this flu
Memory B cells, which have
virus-specific receptors, are difficult to isolate. To address this issue, the
researchers attached a fluorescent label to the flu virus, which allowed them
to identify flu-specific B cells. They then used a cloning technique to create
a line of mice with virus-specific B cells and cell receptors.
The study authors suggested
that the infectious process of the flu is probably used by other viruses as
well. "We can now make highly effective immunological models for a variety
of pathogens," Dougan concluded. "This is actually a perfect model
for studying memory immune cells."
Scientists note, however,
that research with animals often fails to produce similar results in humans.
"This is research that
could help with rational vaccine design, leading to more effective vaccines for
seasonal flu," Ashour said. "It might even suggest novel strategies
for conferring immunity."
The study was recently
published in the journal Nature.
The US Centres for Disease
Control and Prevention has more about flu.