Hepatitis B
is blood-borne virus that packs a punch. Worldwide, more than 1.3 billion
people have been infected with hepatitis B, and 257 million people have
developed a life-long infection. This includes 240,000 Australians, many of
whom are Indigenous.
Globally,
transmission most commonly occurs from mother to baby or in early life. But
it's possible to be infected in adulthood, through sex or blood-to-blood
contact.
Most people
who are infected in adulthood develop a short infection which their immune response
controls. But in around 5% of adults and 90% of babies, the immune response is
ineffective and chronic infection develops.
Hepatitis B
virus causes almost 40% of all liver cancer, which is the fifth most common
cancer and the second leading cause of cancer-related death worldwide.
Australian discovery
Hepatitis B
virus was discovered in the serum of an Indigenous Australian in 1965 and was
first known as the "Australia antigen."
This quickly
led to the development of an effective vaccine in the 1980s, which is now
available worldwide. The vaccine has been given to Australian infants since May
2000.
(If you
weren't vaccinated as a baby, you might want to consider doing so through your
GP, particularly if you plan to travel to Asia and Africa where hepatitis B is
common.)
Unfortunately
the vaccine doesn't do anything for the 240,000 or so Australians who currently
live with chronic hepatitis B. Only around 60% of these people have been
diagnosed; the rest don't know they're infected and don't receive appropriate
care.
How is it currently treated?
There is no
cure for chronic hepatitis B virus.
In most
cases, treatment requires taking a pill every day for life to remain effective
and to reduce the risk of liver cancer. Even then, it doesn't eliminate the
risk.
Chronic
hepatitis B hasn't been cured so far in part because current therapies have
failed to destroy the viral reservoir, where the virus hides in the cell.
This is in
contrast to hepatitis C virus, which has no such viral reservoir and can now be
cured with as little as 12 weeks of treatment.
Despite the
huge human and economic toll of chronic hepatitis B, research to cure the
disease remains underfunded. There is a misconception that because there is a
vaccine, hepatitis B is no longer a problem.
The
availability of effective cures for the unrelated hepatitis C virus has also
led people to believe that "viral hepatitis" is no longer a problem.
Experts
estimate that liver cancer deaths will substantially increase in coming decades
without a cure for hepatitis B, despite deaths from most cancers decreasing.
How far have we got?
Some
exciting research is underway around the world, including the recent
identification of the "cell receptor" which allows the virus to
infect the body. This has enabled studies of the complete virus replication
cycle including the viral reservoir that is untouched by current therapies.
New
approaches to a possible cure include mechanisms to block the virus' entry into
the cell and to stop the virus from making the proteins it needs to replicate
and infect new cells.
Studies are
also underway to enhance patients' immune responses so their own natural
defenses can control or even eliminate the virus. This is similar to
immunotherapies already being used to treat some cancers.
It's likely
a hepatitis B cure will require a dual-pronged approach, directly targeting the
virus while also enhancing the immune response in people who are infected.
The goal is
to reduce the amount of virus in the body and restore the person's immune
responses. This is called a "functional cure" and is similar to what
happens when a person naturally gets rid of the virus. It would also mean they
didn't need to take drugs any more.
Some of these approaches are now in early stage human clinical trials. More than 30 drugs have been developed and are being tested in people with chronic hepatitis B. However, much more work needs to be done to achieve a cure.
Source:
https://medicalxpress.com/news/2019-10-vaccine-hepatitis.html
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