WASHINGTON, Jan 10, (Agencies): People who recovered from the 2009 H1N1 “swine flu” pandemic developed unusual antibodies that protect against a variety of different flu strains, US researchers said Monday.
Experts were surprised to find that patients’ immune response to a new flu could boost the search for a universal vaccine against a series of strains that have existed for decades, said the study in the Journal of Experimental Medicine.
Researchers in the United States examined nine patients who fell ill last year, and found antibodies that when tested in mice could protect against a lethal dose of at least three other strains of flu, including bird flu.
“The result is something like the Holy Grail for flu-vaccine research,” said study author Patrick Wilson, assistant professor of medicine at the University of Chicago.
“It demonstrates how to make a single vaccine that could potentially provide immunity to all influenza,” he said.
“The surprise was that such a very different influenza strain, as opposed to the most common strains, could lead us to something so widely applicable.”
Researchers examined nine patients, most of whom were in their 20s and 30s. Some had a mild form of the flu that cleared after a few days; others had a more severe form that required hospitalization for up to two months.
They took blood samples from the patients about 10 days after they showed symptoms, found white blood cells that produced antibodies against the flu virus, then isolated those antibodies.
“Five antibodies isolated by the team could bind all the seasonal H1N1 flu strains from the last decade, the devastating ‘Spanish flu’ strain from 1918 and also a pathogenic H5N1 avian flu strain,” said the study.
Researchers tested three of the antibodies they isolated and found they could protect mice against the 2209 H1N1 strain as well as two other prevalent forms of flu.
“Two antibodies could protect mice against an otherwise lethal dose of any of the three strains, even when the antibody was given 60 hours after infection. However, one antibody only protected against the 2009 H1N1 strain,” said the study.
That antibody came from the patient who recovered from the most severe infection of H1N1, and researchers said it was likely that the patient “had a complete lack of preexisting immunity to H1N1 viruses.”
In the other patients who experienced milder infections, their response to H1N1 appeared to form from a foundation based on immune response to prior flu shots or infections.
The virus infected an estimated 60 million people and hospitalized more than 250,000 in the United States, researchers said.
First detected in the United States and Mexico in 2009, swine flu was unusual because it was particularly dangerous for young people and pregnant women, unlike most other strains of flu which tend to be more lethal in older populations.
Many teams are working on a “universal” flu shot that could protect people from all flu strains for decades or even life.
US officials say an effective universal flu vaccine would have enormous ramifications for the control of influenza, which claims 250,000 to 500,000 lives each year, including an average of 36,000 in the United States.
Wilson’s team started making the antibodies in 2009 from nine people who had been infected in the first wave of the H1N1 swine flu pandemic before an H1N1 vaccine had been produced. The hope was to develop a way to protect healthcare personnel.
Working with researchers from Emory University School of Medicine, the team produced 86 antibodies that reacted with the H1N1 virus, and tested them on different flu strains.
Of these, five were cross-protective, meaning they could interfere with many strains of flu including the 1918 “Spanish flu” and a strain of H5N1 or avian flu.
Tests of these antibodies in mice showed they were fully protected from an otherwise lethal dose of flu.
And some of these cross-protective antibodies were similar in structure to those discovered by other teams as having potential for a universal flu vaccine.
“It demonstrates how to make a single vaccine that could potentially provide permanent immunity to all influenza,” Wilson said in a telephone interview.
Flu vaccines and drugs focus on proteins found on the surface of the flu virus called hemagglutinin and neuraminidase, which give influenza A viruses their names, as in H5N1 or H1N1.
Hemagglutinin is a lollipop-shaped structure with a big, round head. This head is so large it attracts most of the immune system antibodies, but it mutates readily.
Two years ago, researchers working for Crucell NV and a separate team found that antibodies that attach to the “stick” or stalk part of the hemagglutinin lollipop mutate much less — providing a perfect target for a vaccine that could neutralize a range of different flu viruses.
“Previously, this type of broadly protective, stalk-reactive antibody was thought to be very rare,” Jens Wrammert of Emory said in a statement. But in the H1N1 patients, he said, they were “surprisingly abundant.”
That may be because the H1N1 virus was so different from other flu strains that the immune system made antibodies for the only parts of the virus it recognized — this “stick” or stalk region that is common to many flu strains.
Died
Meanwhile, health authorities in Poland on Monday said one person died in hospital after being infected with the H1N1 virus in the country’s first swine-flu related death in 2011.
“A man in his fifties died in hospital on Sunday in Slupsk. Laboratory tests show the H1N1 virus was detected in his body,” Anna Obuchowska, a spokeswoman for the state health and sanitation inspector in Slupsk, northern Poland, told AFP Monday.
“The man succumbed to multiple complications of his respiratory and circulatory systems,” Slupsk hospital director Ryszard Stus told Polish Radio Monday.
The H1N1 virus was recently also detected in several other people in Poland, notably in two physicians in the former royal capital Krakow, who were infected by a patient.
In 2010 the H1N1 virus was responsible for around a dozen fatalities in Poland, a country of 38 million.
Unlike most European countries, Poland refused to purchase H1N1 vaccines arguing they lacked sufficient testing.