Hepatitis B research: Virus-host balance and 20 years of successful vaccination
There are over 250 million people throughout the world chronically infected with hepatitis B (a hepatitis B infection is considered chronic or long-term when a person isn’t able to clear the infection from their body). According to the World Health Organization, viral hepatitis killed 1.34 million people worldwide in 2015.
Scientists at the Public Health Agency of Canada’s (PHAC) National Microbiology Laboratory (NML) are studying the disease to help protect those at risk of getting sick from hepatitis.
What is hepatitis?
Hepatitis is an inflammation of the liver, which could lead to liver cirrhosis, liver failure or liver cancer. It can be caused by a viral infection, autoimmune dysfunction, alcohol, medication, or drug toxicity.
Any liver disease can be life-threatening. For instance, long-term infection with hepatitis B or hepatitis C viruses can cause cirrhosis, a condition where the liver gradually loses function due to permanent scarring. These viruses can also cause liver cancer.
Fortunately, there are preventative measures and medications available to protect against hepatitis and to treat infection. Early diagnosis increases the effectiveness of treatment to cure hepatitis C infection. There is also a universal vaccine for the hepatitis B virus (HBV) which is safe and effective in preventing infection.
Two decades later, HBV levels decrease in the Canadian Arctic
Statistically speaking, populations in Canada’s Arctic region are disproportionately affected by HBV. NML scientists have been working to better understand why this is the situation, with the hope that their research can help inform public health measures to protect these northern populations from this virus.
Around the 1990s, universal vaccination programs for HBV were implemented for newborn infants in Canada’s Arctic. From 2013 to 2014, scientists at the NML did a mass follow-up on a proportion of individuals who are representative of the Nunavut population. They wanted to find out whether the universal vaccine had made a positive impact.
Overall, the scientists concluded that the vaccination program has been successful. They found that that the prevalence of long-term HBV infection has decreased to low (non-endemic) levels of just 1.2% in the entire population.
A virus-host ‘balance’
With their ongoing research, NML researchers strive to further prevent HBV in the North. They recently discovered that, for hundreds of years, a particularly unique strain of HBV has been evolving in some Arctic populations. This unique strain is called HBV/B5.
In 2010, it was discovered that HBV/B5 was the most prevalent strain found in Nunavut and for some reason, in the long-term, those who are infected with this strain don’t seem to suffer severe liver disease compared to persons infected with other strains of the virus.
“A balance seems to have been struck,” says PHAC scientist Carla Osiowy. “The virus continues to circulate and persists within these populations. At the same time, it doesn’t appear to result in severe disease.”
Dr. Carla Osiowy is Chief of Viral Hepatitis and Bloodborne Pathogens.
According to Osiowy, it is hard to tell if the virus could cause liver disease in other populations. To date, HBV/B5 is only found in Alaska Natives as well as Inuit populations of Canada and Greenland.
“It’s possible that this ‘balance’ is due to the patient’s immune response. Or, perhaps this is a feature of the virus,” she says. “Truthfully, we can only speculate at this point in time. Further study is needed to better understand this virus-host ‘balance.’”
As scientists continue to research hepatitis, these studies could help us understand why a particular strain may cause illness and why another does not. The results could also lead to the development of better treatments and improving disease prevention programs worldwide.
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