Those affected by the 2009 pandemic may harbour some immunity to bird flu, say scientists. The claims follow research published in Vaccine, which shows that pigs infected with a flu virus closely related to the pandemic H1N1 strain developed immunity to bird flu.
“We would expect to see the same results in humans,” Kristien Van Reeth, lead author of the study, tells Emerging Health Threats Forum News.
The researchers infected 25 pigs with the H5N1 bird flu virus in the lab, 12 of which had been infected with a swine H1N1 virus four weeks earlier. They found that H1N1 gave the pigs immunity to bird flu, as none showed symptoms of the infection. All the animals infected only with H5N1 showed symptoms of bird flu.
“There was also a very strong protection against the replication of the virus in the respiratory tract,” says Van Reeth. The virus was isolated from respiratory tract tissue in three of the 10 animals tested that were infected with both viruses. By comparison, H5N1 was isolated from all of the other pigs tested. These immune responses could last up to 2 years in the pigs, she adds.
Immune protection in humans
Andrew Pekosz, from the John Hopkins Bloomberg School of Public Health in Maryland, believes there is a “good possibility” that something similar would be seen in humans. “Data from this paper suggest that you will have some immunity to H5N1 after exposure to H1N1.”
The exact level of protection against bird flu is not known, explains Pekosz. But the parts of the immune system thought to be involved in the response documented by the authors are clearly associated with controlling infection and warding off severe disease. This could mean that people who have caught pandemic swine flu would still fall ill if they ever catch bird flu, but their immune system could prevent their illness from turning serious, he speculates.
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Source: Emerging Health Threats Forum