— Christine M. Kukka, Project Manager, HBV Advocate
Researchers studying the health effects of "occult" hepatitis B are
finding that this infection that can "hide" from conventional lab tests
carries a higher risk of liver cancer and poses a risk to the general
population when undiagnosed.
This type of hepatitis B occurs when a mutation in
the virus' outer coat, made up of the hepatitis B surface antigen
(HBsAg), makes it impossible for common lab tests that look for that
protein to identify an active HBV infection. The HBsAg lab test is
commonly used to identify hepatitis B in patients and even blood
supplies.
When lab tests fail to identity HBV infection,
people can unknowingly spread the infection to their partners, family
members and newborns. And when occult HBV infection goes untreated, a
patient's risk of liver cancer is 3.7-fold higher than in patients with
"regular" or non-occult hepatitis B, according to a recent report in
the August issue of the Journal of Hepatology.
HBsAg has three proteins and in the case of occult
HBV, the immune system attacks one of the three surface proteins–the
same protein that lab tests look for when screening blood for HBsAg.
Most vaccines contain this exact same HBsAg
protein in order to spur production of surface antibodies to fight off
an actual infection. In most cases, the vaccine is very effective, but
when occult hepatitis B occurs, the vaccine-induced antibodies are
powerless against the remaining two surface proteins and viral
reproduction and infection can continue.
This concern has grown recently as scientists find
a number of children born to HBV-infected mothers, who were immunized
at birth, have developed "occult" hepatitis B. Additionally, people
with occult hepatitis B can transmit the mutated, "occult" version of
HBV to partners and close contacts (even if they're vaccinated), adding
to the spread of this hard-to-identify viral hepatitis infection.
Because of the unique genetic make-up of this
mutated HBsAg and how it interacts with liver cells, this mutation
appears to cause more rapid liver damage and cancer.
Scientists suggest that drug resistance,
especially to the antiviral lamivudine (Epivir-HBV), may contribute to
development of this mutation.
"Recent studies have reported that (surface
mutations) tend to (emerge) with the drug resistance-associated
mutations in lamivudine-treated patients, and that the (mutations) ....
play a supportive role in the replication of lamivudine-resistant
viruses," Italian researchers wrote in the report.
"Therefore it appears of the utmost importance
that patients with chronic hepatitis B are screened for the presence of
(surface antigen) mutant infection," they recommended. "The detection
of these specific HBV variants may indeed be useful for the
identification of those patients requiring a preventive and appropriate
treatment and a more intensive follow-up strategy for early detection
of liver cancer."
Source: www.journal-of-hepatology.eu/article/S0168-8278(14)00304-3/fulltext
Source: HBV Journal Review: August 1, 2014, Vol 11, no 8
Labels: Occult HBV
