Influenza pandemic (H1N1) 2009 (51): antibody deficiency
Date: Thu 17 Sep 2009
Source: Metronews.ca Toronto, Canadian Press Report [edited]
<http://www.metronews.ca/toronto/live/article/311673--low-levels-of-key-antibodies-may-lead-to-severe-disease-study-suggests>
Australian researchers may have uncovered a clue as to why some people
who catch swine flu suffer life-threatening illness. And if they are
right, there is an existing weapon in the treatment arsenal that could
help reduce the pandemic death toll. The group found that pregnant
women who became severely ill with the pandemic (H1N1) 2009 virus had
low levels of a particular antibody that is known to fight off viruses
and help the body respond to vaccine. Moderately ill women were much
less likely to have significantly suppressed levels of the antibody,
the researchers reported. "We all believe we may have stumbled onto
something very interesting," said Dr. Lindsay Grayson, director of
infectious disease at Austin Health, a network of 3 hospitals in
Melbourne. "To our knowledge, it's the 1st time that a correlation or
an association is being noted between severe influenza of any sort and
a subtle but potentially important immune deficiency."
The team made the discovery when Grayson's colleague, Dr. Claire
Gordon, ordered a test that looked at antibody levels, not just by
class, but looking at individual subtypes within those classes. The
call was made in the case of a very sick patient whose decline was
particularly rapid, and the team was debating whether immune globulin
-- a blood product containing antibodies harvested from donated blood
-- might help. The testing showed the patient had low levels of an
antibody called IgG2, which Grayson admitted came as a surprise. They
started ordering tests on all their swine flu patients in ICU
[intensive care unit]. "What we found was almost everyone, all the
patients who needed ICU were IgG2 deficient," he said in an interview
from San Francisco, where the data were presented at ICAAC, the annual
meeting of the American Society for Microbiology. Severe cases had
IgG2 levels that were about 1/3rd of those detected in people who were
moderately ill.
While the work was only done in pregnant women, Grayson and others
said it would be useful to look to see if this deficiency might
explain why a small subset of swine flu cases become gravely ill while
most people only suffer through a bout of the flu. It's known that
between 2 and 20 per cent of people have some antibody deficiency, he
said, though not all of those people would be IgG2 deficient. Three of
4 critically ill patients treated with immune globulin survived,
defying predictions of those caring for them. Dr. Donald Low, chief
microbiologist at Toronto's Mount Sinai, said the findings are
exciting, if preliminary, and might explain why aboriginals seem to be
at greater risk of developing severe disease if they contract swine
flu. He suggested the hypothesis should be studied further. "It would
be a fishing expedition, but obviously worthwhile. I think the bottom
line is that this is obviously something that has to be looked into.
And it may have therapeutic implicati!
on. ... It could be a marker for women at higher risk if they get
infected to get more severe disease."
But Dr. Anand Kumar, an intensive care specialist from Winnipeg who
treated a lot of severely ill swine flu patients in the spring and
early summer, was not as optimistic. "The results are just what I'd
expect in any group of critically ill," he said by email. Kumar, who
is also an infectious diseases specialist, said it is not uncommon for
all antibody levels to drop with critical illness, and the more severe
the sickness, the steeper the drop. But he does think the notion of
treating pandemic flu patients with antibodies harvested from other
people makes sense, though he believes the immune globulin should be
from people who've recovered from swine flu and have antibodies
specific to the virus.
Grayson admitted they can't say at this point whether there is a
cause-and-effect relationship at work here, meaning low IgG2 levels in
the patients predisposing them to suffering from more severe disease
once they caught the virus. But he doesn't believe the reverse is at
play, that the infection caused the low IgG2 levels. "We don't think
that influenza is causing this deficiency. We think that instead the
influenza is picking out those people who have the deficiency," he
said. The numbers are admittedly small and will require further study,
likely in the Northern Hemisphere. Swine flu rates are dropping in
Melbourne, Grayson said. Still, 16 of 19 severely ill patients had
very low IgG2 levels, compared to 3 of 20 with moderate illness.
The team looked at healthy pregnant women and found that about 60 per
cent of them were mildly deficient in IgG2 levels, which leads them to
believe this may be one of the immune system changes that occurs to
allow a pregnant woman to carry a foreign body -- a fetus -- without
rejecting it. But Grayson said the group needs to follow women after
they deliver to see if their IgG2 levels rise to normal levels.
Grayson said while the group's work hasn't proven their hypothesis,
northern hemisphere doctors caring for the sickest of swine flu
patients in the weeks and months to come should consider checking IgG2
levels and using immune globulin, which is often given to people
seriously ill with some bacterial infections. "In many ways, this is
applying a general principle that we apply to bacteria diseases to now
say well, 'Gee, we've made this interesting observation. This might
work for influenza,'" he said.
[Byline: Helen Branswell]
Source: Metronews.ca Toronto, Canadian Press Report [edited]
<http://www.metronews.ca/toronto/live/article/311673--low-levels-of-key-antibodies-may-lead-to-severe-disease-study-suggests>
Australian researchers may have uncovered a clue as to why some people
who catch swine flu suffer life-threatening illness. And if they are
right, there is an existing weapon in the treatment arsenal that could
help reduce the pandemic death toll. The group found that pregnant
women who became severely ill with the pandemic (H1N1) 2009 virus had
low levels of a particular antibody that is known to fight off viruses
and help the body respond to vaccine. Moderately ill women were much
less likely to have significantly suppressed levels of the antibody,
the researchers reported. "We all believe we may have stumbled onto
something very interesting," said Dr. Lindsay Grayson, director of
infectious disease at Austin Health, a network of 3 hospitals in
Melbourne. "To our knowledge, it's the 1st time that a correlation or
an association is being noted between severe influenza of any sort and
a subtle but potentially important immune deficiency."
The team made the discovery when Grayson's colleague, Dr. Claire
Gordon, ordered a test that looked at antibody levels, not just by
class, but looking at individual subtypes within those classes. The
call was made in the case of a very sick patient whose decline was
particularly rapid, and the team was debating whether immune globulin
-- a blood product containing antibodies harvested from donated blood
-- might help. The testing showed the patient had low levels of an
antibody called IgG2, which Grayson admitted came as a surprise. They
started ordering tests on all their swine flu patients in ICU
[intensive care unit]. "What we found was almost everyone, all the
patients who needed ICU were IgG2 deficient," he said in an interview
from San Francisco, where the data were presented at ICAAC, the annual
meeting of the American Society for Microbiology. Severe cases had
IgG2 levels that were about 1/3rd of those detected in people who were
moderately ill.
While the work was only done in pregnant women, Grayson and others
said it would be useful to look to see if this deficiency might
explain why a small subset of swine flu cases become gravely ill while
most people only suffer through a bout of the flu. It's known that
between 2 and 20 per cent of people have some antibody deficiency, he
said, though not all of those people would be IgG2 deficient. Three of
4 critically ill patients treated with immune globulin survived,
defying predictions of those caring for them. Dr. Donald Low, chief
microbiologist at Toronto's Mount Sinai, said the findings are
exciting, if preliminary, and might explain why aboriginals seem to be
at greater risk of developing severe disease if they contract swine
flu. He suggested the hypothesis should be studied further. "It would
be a fishing expedition, but obviously worthwhile. I think the bottom
line is that this is obviously something that has to be looked into.
And it may have therapeutic implicati!
on. ... It could be a marker for women at higher risk if they get
infected to get more severe disease."
But Dr. Anand Kumar, an intensive care specialist from Winnipeg who
treated a lot of severely ill swine flu patients in the spring and
early summer, was not as optimistic. "The results are just what I'd
expect in any group of critically ill," he said by email. Kumar, who
is also an infectious diseases specialist, said it is not uncommon for
all antibody levels to drop with critical illness, and the more severe
the sickness, the steeper the drop. But he does think the notion of
treating pandemic flu patients with antibodies harvested from other
people makes sense, though he believes the immune globulin should be
from people who've recovered from swine flu and have antibodies
specific to the virus.
Grayson admitted they can't say at this point whether there is a
cause-and-effect relationship at work here, meaning low IgG2 levels in
the patients predisposing them to suffering from more severe disease
once they caught the virus. But he doesn't believe the reverse is at
play, that the infection caused the low IgG2 levels. "We don't think
that influenza is causing this deficiency. We think that instead the
influenza is picking out those people who have the deficiency," he
said. The numbers are admittedly small and will require further study,
likely in the Northern Hemisphere. Swine flu rates are dropping in
Melbourne, Grayson said. Still, 16 of 19 severely ill patients had
very low IgG2 levels, compared to 3 of 20 with moderate illness.
The team looked at healthy pregnant women and found that about 60 per
cent of them were mildly deficient in IgG2 levels, which leads them to
believe this may be one of the immune system changes that occurs to
allow a pregnant woman to carry a foreign body -- a fetus -- without
rejecting it. But Grayson said the group needs to follow women after
they deliver to see if their IgG2 levels rise to normal levels.
Grayson said while the group's work hasn't proven their hypothesis,
northern hemisphere doctors caring for the sickest of swine flu
patients in the weeks and months to come should consider checking IgG2
levels and using immune globulin, which is often given to people
seriously ill with some bacterial infections. "In many ways, this is
applying a general principle that we apply to bacteria diseases to now
say well, 'Gee, we've made this interesting observation. This might
work for influenza,'" he said.
[Byline: Helen Branswell]
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