This week, as expected, flu has taken over the headlines. All across Canada, hospitals are being overwhelmed by patients suffering from this well-known disease. Yet, among those looking for medical assistance, many will not have the influenza virus but another lesser known pathogen.
The pathogen is known as respiratory syncytial virus, or as its usually called, RSV. Based on the latest surveillance reports, it has infected about as many people as influenza. Although this particular infection does not receive the same amount of attention as the flu, the consequences of catching this virus represent a significant health problem.
RSV has been known since 1957 when it was isolated in cases of lungs of infants suffering from a condition called bronchiolitis. Since then, this virus has been recognized as the most common type of lower respiratory tract infection in children less than two years of age. The condition can be deadly with up to 14 deaths for every 10,000 cases, a number that is comparable to flu.
But children are not the only ones who suffer. People over 65 years are also at risk and the toll on them may be worse than influenza. Nearly twice as many cases occur each year and for those with very weak immunities, some 10 to 20 percent may end up with secondary bacterial pneumonia. Worse, up to five percent of these individuals will die.
Due to the effects of RSV, there's little doubt public health officials suggested almost as soon as the virus was discovered the best route for prevention would be a vaccine. There was even one tested back in the 1960s. Yet the work, while valiant, was unsuccessful and in some cases, made the situation worse.
Researchers since have learned our bodies fight this virus differently than the flu. Instead of using antibodies, which are made when we get the flu vaccine, the immune system utilizes a different arsenal to combat RSV called mucosal immunity. Unfortunately, this branch of immunity is harder to develop without an actual infection.
Figuring out how to stimulate mucosal immunity was no easy task. Scientists had to break down the individual components of the virus and test each of them in the hopes of finding some path forward. By 2011, the entire picture of RSV infection had been developed and yet, there was still little sign of vaccine potential. In essence, the only way to go about finding the right candidate was through the long and expensive route of trial and error.
Now there seems to be a breakthrough thanks to a large group of American researchers. Their efforts, published late last month, have identified one particular candidate - known simply as OE4 - that may finally turn the tables on RSV. The results also pave a path to an effective vaccine in the future.
The group worked with what are known as live, attenuated viruses. These are fully functioning viruses but are unable to cause infection once introduced into a host. Many flu vaccines we take today are based on this same type of virus so it was considered the best option.
Taking the decades of work into consideration, they developed several potential candidates of RSV in the hopes of finding one that would trigger the immune system to get that cellular arsenal primed and ready to respond. Eventually, they came across OE4 and were happy with the results in laboratory studies.
But success in the lab was merely the first step. To be sure they had a virus capable of making its way through the vaccine pipeline the group needed to test the vaccine in an animal model. There was no better option than a tiny rodent known as the cotton rat. It has been recognized as an excellent model to study RSV infection. The critter was the perfect choice to give the vaccine a trial run.
When the team conducted the tests on the rats, the results were promising. The virus did have the capability of making its way into the lower respiratory tract. Once it was there, it was able to stimulate mucosal immunity. Most importantly, this stimulation was beneficial and did not make the situation worse.
Yet the real test came in what is known as the challenge. This involves exposing the rats to an actual infectious form of RSV to see whether the immune system was ready to fight infection. In all cases, it was and the rats never became sick. After decades of searching, the OE4 had finally achieved the goal.
For the authors, OE4 represents the future for RSV vaccine research and development. Although this particular strain may not end up being used in humans, its presence marks a milestone for other researchers aiming to find the perfect vaccine candidate. As with all medical advancements, this study represents only the beginning of what needs to be done to get to that final stage of a vaccine on the shelf. But now that this hurdle has been crossed, we can look forward to a day when RSV will no longer be a significant threat to the very young and the elderly.
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