Finding vaccines against swine flu

Pigs are infected by the same influenza viruses
which infect humans H1N1 and HGN2. Swine influenza is a mild disease in pigs however it is the
main cause for respiratory disease because combined with other common pathogens on the
farm it can lead to really severe respiratory disease; pneumonia and complications, so there
are serious animal welfare issues and in addition to those there are severe economical losses
for the farmers because there is loss in gain of weight, reproduction losses.
Another problem with swine influenza viruses is that they also can jump from pigs to humans
although it’s actually much more often humans to infect the pigs. When swine influenza virus
adapts to transmitting to humans it can cause pandemic. A version of that occurred in 2009,
H1N1 pandemic. Swine influenza spreads like human influenza
by contact, by droplets, sneezing in the air it can be transmitted by humans or wild animals
or birds. At present a good security measures by not allowing in infected animals on the
farm or using good disinfection and monitoring all that could help. The best prevention is
of course vaccination and there are 2 ways of cross-protection. One is to induce antibodies
which recognise the conserved part of these proteins, like proteins which are on the surface
of the virus and these antibodies they prevent the virus from entering the cells.
The second type of immune response is T-cells which recognise the conserve parts of the
internal parts of the gene and this T-cell immunity does not always prevents the entrance
of the virus into the cells but it makes the disease much less severe and also prevents
transmission. As both pigs and humans are infected by the
same sub types of viruses, the pigs are an excellent model to study not only swine influenza
and influenza infection in humans. The pigs are physiologically, anatomically, immunologically
very similar to humans. They have exactly the same structure of the lung, they have
the same receptors which binds the influenza viruses so research done in large animals
like pigs is extremely informative. You immunize the animals with the new vaccine,
you wait after that you infect the animals with influenza and you measure the virus in
their nose, in their lungs and also at post mortem. You look at the pathology in the lung.
If you want to see whether a vaccine is protective you have to test it in animals. The swine
model is a fantastic model because swine influenza, the pig is a natural health pathogen model
because swine influenza is a real disease but also because of the similarity between
swine and humans it is an excellent model to test therapeutic agents and vaccines for
humans. The universal vaccine that can protect against
any strain of viruses is highly desirable and that is the ultimate goal. We have recently
tested a candidate universal vaccine, this vaccine is called S4 and it is developed by
Anne Townsend from the University of Oxford. That is a weakened version of virus, the vaccine
does not have the surface glycoproteins hemagglutinin which is important for the entrance of virus
in the cell. Once S4 is in the cell it can replicate but it cannot spread. However, it
can produce all of the other proteins of the virus and very strong T-cell immunity response
is made against conserved parts of this internal proteins which reduces the replication of
the virus and can protect against more severe disease and also prevent transmission. We
have shown that when we gave this vaccine to pigs there was a much reduced virus in
the nose and in the lungs in the pigs. Also we have shown that this protection is very
important to induce immunity response in the lungs which is the site of entry of the pathogen
and also we have shown that the best way to induce that is by giving the vaccine by aerosol.

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