Biotechnology provides new hope against and old enemy: the Hepatitis B virus
Christina Scott
Hepatitis Day is recognised worldwide in July each year. But how many people really
understand the devastating impact of chronic hepatitis B virus infection in
Africa?
"The hepatitis B virus is endemic to sub-Saharan Africa where it is one of
the key environmental risk factors that predisposes chronic carriers to
liver cancer and cirrhosis of the liver," says Professor Patrick Arbuthnot
of the Department of Molecular Medicine and Haematology at the University of
the Witwatersrand in Johannesburg, South Africa. "The link between
Hepatitis
B and liver cancer is at least as strong as that between smoking and lung
cancer."
There are vaccines available. But there are problems with the vaccines.
Existing drugs are largely ineffective for people infected with the virus in
sub-Saharan Africa.
Arbuthnot clarifies, "This is because these drugs are designed to treat
patients in whom the virus replicates rapidly. This is not the case in
sub-Saharan Africa, where the rate of replication of the virus is slower.
This is mainly to do with the genetic properties of the virus itself. There
may be some host factors as well but this is not completely established
yet."
Even for patients who have not been infected with the virus, government
bureaucracy and costs often prevent them from receiving the existing,
life-saving vaccine. The vaccine "is only administered in 5% of babies born
in the sub-Sahara," says Arbuthnot, who heads the Hepatitis B Virus
Research
Programme.
But there are signs of hope, he says: "In South Africa, it has become
compulsory for all babies to be vaccinated against the virus since 1995.
Other countries with similar legislation in sub-Saharan Africa include
Gambia and Botswana. Zimbabwe used to vaccinate but that has stopped."
But better use of the existing vaccine does nothing to help the considerable
percentage of the population of sub-Saharan Africa already infected with the
virus.
It is estimated that 387 million people worldwide are persistently infected
with this virus, which amounts to 6% of the world's population. In
sub-Saharan Africa, it is thought that the figure is even higher, and that
about 10 percent of the population has chronic hepatitis B. From this total
of chronic carriers, approximately 25% will develop liver cancer.
It is accepted that the hepatitis B virus alters the gene properties in
human liver cells to cause cancer. In South Africa, liver cancer usually
develops during early adulthood and has a particularly grave prognosis. "It
is rare for tumours to be surgically resectable and most patients die within
three months of diagnosis of the malignancy," says Arbuthnot. "There
is
definitely a need for the development of a new treatment to prevent the
serious complications of chronic infection with the virus."
The impact of hepatitis B goes beyond the personal tragedies to generate
significant negative impact on economies as people fall ill and are unable
to work or farm, or spend their time taking care of sick members of the
family instead of more financially rewarding activities.
Using biotechnology, Arbuthnot and his team have already generated
therapeutic RNA sequences, or genetically designed treatments, and tested
them in liver cell cultures. The three types of RNA sequences that are being
used are ribozymes, small interfering RNA and micro RNA. "These are
molecular scissors which cut the material of the hepatitis B virus,"
explains Arbuthnot.
The team has developed the technology that allows these RNA sequences to
inactivate hepatitis B virus gene expression specifically. Following these
laboratory tests and toxicology assessments, it is planned to test the new
treatment in human clinical trials.
"The ultimate goal is to find an effective treatment for hepatitis B for
people living in sub-Saharan Africa," clarifies Arbuthnot. In the
long-term,
he hopes for an effective drug which could be injected.
This is the only study in South Africa focusing on the development of a new
treatment for Hepatitis B and certain aspects of the study have already been
submitted for patenting. The study was initiated almost four years ago in
the Wits University Faculty of Health Sciences. The team will know within
about two years whether the therapy will work or not.
"We have had promising and encouraging results," says Professor
Arbuthnot.
Funding comes from the Innovation Fund of the South African department of
science and technology, with a view to job creation in the medical and
pharmaceutical fields and reducing dependence on international
pharmaceutical companies. But there may also be other spin-offs beneficial
to other researchers targeting other viral enemies, such as HIV.
More information:
Prof. Patrick Arbuthnot on (011)
717-2365 or email arbuthnotpb@pathology.wits.ac.za
or visit The Hepatitis B
Virus Research Programme online. Thanks to Shirona Hassim of Wits University
for access to original material.
University of the Witwatersrand www.wits.ac.za
Related articles:
Aflatoxin in peanut butter
Sterols/ sterolins: Marketing hype or science?
|
