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.