Swine flu, viruses and the immune system
Tuesday November 17th, 2009
Most adults probably enjoy some immune system protection against the swine flu, researchers said yesterday.
Studies of human blood show an unexpected level of overlap between the H1N1 virus and other recent seasonal flu strains.
Researchers found that adult T-cells can recognise a "significant" percentage of molecular markers in swine flu.
This suggests that immune system has been programmed by previous flu epidemics to react against these components of swine flu.
Scientists said the findings would explain why children and pregnant women seem to be most vulnerable to the virus. Children under the age of nine need two shots of vaccine to gain immunity, it is thought.
Until now the age of 50 has been regarded as the point from which adults are likely not to succumb to the virus - because of an epidemic of a similar virus in 1958.
The findings, reported in the Proceedings of the National Academy of Sciences, show that other immune system cells, the B-cells, are much less likely to be pre-programmed against swine flu. These produce antibodies and are the cells affected by vaccination.
Researcher Dr Bjoern Peters, of the La Jolla Institute for Allergy and Immunology, San Diego, California, USA, said: "Nobody knows what level of immunity is sufficient for protection. We do know that a T cell response is not enough to prevent being infected by the virus.
"But, if infected, our data suggests that T cells in those who have previously been exposed to influenza may make the infection less severe."
Centre director Dr Alessandro Sette said: "What we have found is that the swine flu has similarities to the seasonal flu, which appear to provide some level of pre-existing immunity. This suggests that it could make the disease less severe in the general population than originally feared."
* Meanwhile British scientists last night explained why a recent effort to create an HIV vaccine using the common cold virus backfired.
The virus, an adenovirus, was disabled and made a shell to infect harmless HIV genes into patients.
Instead it increased the risk of infection. Trials of the vaccine were halted two years ago.
The new analysis shows that the virus triggered an immune system reaction in many volunteers. This put them at increased risk of HIV infection as HIV infects the immune system cells, according to the report in the Proceedings of the National Academy of Sciences.
Researcher Dr Steven Patterson, of Imperial College London, said: "When the researchers published their results and the trial was halted, we were all very surprised and disappointed. Scientists use adenoviruses in all sorts of vaccines and we did not expect this result."
J Greenbaum et al. Pre-existing immunity against swine-origin H1N1 influenza viruses in the general human populace. Proceedings of National Academy of Sciences. DOI: 10.1073/PNAS.0911580106 (2009).
Adenovirus vector vaccination induces expansion of memory CD4 T cells with a mucosal homing phenotype that are readily susceptible to HIV-1 infection" PNAS, Monday 16 November 2009
Tags: Flu & Viruses | North America | Respiratory | UK News
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