Are Some People Immune To Avian Flu?

Science Daily — New results from Richard Webby at St. Jude Children's Research Hospital and colleagues published in the international open-access medical journal PLoS Medicine suggest that the answer might be yes.

The H5N1 avian flu virus is quite different from the seasonal H1N1 and H3N2 flu viruses most humans have been exposed to, which is why many scientists believe that H5N1 could start a new pandemic. (The H and N refer to two virus components, the proteins hemagglutinin and neuraminidase, each of which exists in several varieties identified by a number following the letter.)

Webby and colleagues wondered whether immunity to the human type 1 neuraminidase (huN1) in H1N1 influenza virus strains (and vaccines made to protect against them) could provide protection against avian H5N1 influenza virus, which contains the closely related avian type 1 neuraminidase (avN1). In the new study, they investigated this possibility in mice and in a small group of humans.

The researchers immunized mice with DNA that caused their cells to make the neuraminidase from an H1N1 virus found in human outbreaks. They then examined the immune response of the mice to this huN1 and to avN1 from an avian H5N1 virus isolated from a human patient (A/Vietnam/1203/04). Most of the mice responded to the DNA vaccine by making antibodies that recognized huN1; a few also made antibodies against avN1. (Antibodies are proteins circulating in the body that recognize and stick to some specific part of a foreign agent such as a virus.) All the vaccinated mice survived infection with a man-made flu virus containing huN1, and half also survived infection with low doses of A/Vietnam/1203/04 or of a man-made virus containing avN1.

The researchers then tested blood samples from 38 human volunteers for their ability to inactivate neuraminidase from an H1N1 virus and two H5N1 viruses. Most of the samples were active against the protein from the H1N1 virus; and 8 or 9 also inhibited the protein from both H5N1 viruses.

The results indicate that a vaccine containing huN1 makes mice produce antibodies that partly protect them against avian H5N1 infection. In addition, the human data suggest that a proportion of people have low titer antibodies against H5N1 influenza because of prior exposure to H1N1 viruses or routine influenza vaccination.

As Laura Gillim-Ross and Kanta Subbarao (US National Institute of Allergy and Infectious Diseases) write in an accompanying Perspective article, these results provide a tantalizing suggestion but fall short of demonstrating that there is actual protection in humans against avian flu. Further work is needed to investigate this important question, and Gillim-Ross and Subbarao discuss the challenges and opportunities for such research.

Citation: Sandbulte MR, Jimenez GS, Boon ACM, Smith LR, Treanor JJ, et al. (2007) Cross-reactive neuraminidase antibodies afford partial protection against H5N1 in mice and are present in unexposed humans. PLoS Med 4(2): e59. (http://dx.doi.org/10.1371/journal.pmed.0040059)

Note: This story has been adapted from a news release issued by Public Library of Science.

Previously...

Is the Sub-continent immune to SARS menace?
|April 23, 2003 | Shakti Sharma

Posted on 04/23/2003 8:15:44 AM EDT by CathyRyan

Are people from India and Indian sub-continent immune to the fast spreading SARS virus? This question is baffling the medical community, with doctors discussing the possibility of the virus being race-specific.

Some doctors are of the view that people of the sub-continent may have a higher level of immunity to the virus. They reason that with a large number of Indians, Pakistanis, Bangladeshis and Sri Lanka frequenting SARS-affected regions like Singapore, Hong Kong and other territories, hardly anyone has contracted the virus.

WHO (Delhi HQ) Information Officer, Harsharn Pandey avers: "It has been almost five months since the first case of SARS was reported from China, and the virus has spread to 23 countries, but not a single case of SARS has been reported from Pakistan, Sri Lanka, and Bangladesh".

AIIMS virologist, Dr Shobha Broor says," Viruses are never race sensitive but it could be possible that people from this part of the sub-continent could have developed antibodies to counter the SARS virus."

Although WHO has no race-wise record of SARS victims - both dead and those affected -- available information culled from various sources points out that no person from this part of the world has died of SARS so far.

Director of the Centers for Disease Control and Prevention of the US health department, Dr Julie L Gerberding, during a recent video conference, admitted about the typical race-specific behaviour of the virus and said that in China, Hong Kong and Singapore the ongoing transmission of this virus at a very accelerated pace in "certain communities".

Doctors are also pointing out at the fact that the local transmission of the virus has so far been reported from China, Hong Kong, Canada, Singapore, Vietnam, Taiwan, UK and the USA, while in the sub-continent, people who had tested positive for the virus had brought in the disease from infected nations and the recovery rate is cent percent.

Quoting incidents of SARS, doctors say, the first ever case of SARS in India was reported from Goa where a marine engineer tested positive. The patient, however, responded well to treatment and recovered in almost no time.

In the latest SARS case reported from Pune, three members of a family -- Stanley D'silva, his mother Vimla and sister Julie -- who came to India three weeks ago, tested positive. While Stanley has completely recovered, his mother and sister are responding well to treatment.

The Indian Medical Association (Delhi Chapter) president, KK Aggarwal says the so called SARS positive cases reported cases in India may ultimately test negative, as the confirmatory test for the virus on the convalescent sample has to be done after 21 days.

http://www.freerepublic.com/focus/f-news/898592/posts

Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.