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Editorial Board: Emmet B. Keeffe, MD (Chair); Anna Lok, MD; Brian McMahon, MD; Albert Min, MD;
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HBV
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Timely Information for Practicing Physicians |
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August
2004
HBsAg SEROCLEARANCE
Outcomes in Chinese
patients. HBsAg seroclearance rarely occurs in
Chinese patients who acquire chronic HBV infection early in life. Man-Fung Yuen et al reviewed medical records
of 3,843 patients with chronic hepatitis B who had been followed regularly at
the University of Hong Kong Queen Mary Hospital between August 1975 and October
2001 and identified 92 patients who had HBsAg seroclearance. Patients were compared with 92 HBsAg-positive
controls matched for age, sex, and duration of follow-up. The mean age of patients with HBsAg
seroclearance was 48.8 years, and the median duration of follow-up after
seroclearance was 51 months (range, 18.7-199.6 mo). Ninety-eight percent of patients (n=91) had
undetectable levels of serum HBV DNA (Cobas Amplicor, LLD = 200 copies/mL)
after HBsAg seroclearance. Among 66
evaluable patients, none had detectable HBV DNA in peripheral blood mononuclear
cells after HBsAg seroclearance. Of the
14 patients with assessable liver biopsie
Epidemiology
Healthcare-related
viral hepatitis transmission. IT Williams and coworkers reviewed
healthcare-related viral hepatitis transmission, with particular attention to
ambulatory care settings, and examined strategies to prevent transmission of
blood-borne pathogens. It is estimated
that therapeutic injections administered in an unsafe manner are responsible
for >21 million new HBV infections and 2 million new HCV infections annually
throughout the world. There have been 4
recent outbreaks of HBV and HCV infections in ambulatory care settings that
were due to failure to adhere to principles of aseptic technique with the
administration of parenteral medications.
The authors emphasize that healthcare workers must follow standard
precautions and fundamental infection-control principles, including safe
injection practices and appropriate aseptic techniques, in order to prevent
transmission of blood-borne pathogens.
Safe injection practices include the use of single-use, sterile,
disposable needles and syringes, use of single-dose vials whenever possible,
and prevention of contamination of injection equipment and medication. These principles should be outlined in
institutional policies, reinforced through in-service education, and
monitored. The authors conclude that, as
demonstrated by recent outbreaks, the prevention of healthcare-related
transmission of viral hepatitis warrants increased attention. (Williams IT et al. Clin Infect Dis 2004;38:1592-1598.)
Mechanisms
OF Chronic HBV Infection
Defective dendritic cell
(DC)-T cell interaction. A defect in T cell immunity has been
assumed to be central to persistent HBV infection. Recent studies in transgenic mice have
suggested that a functional defect of DCs is an underlying cause of T cell
dysfunction. More recently, BJ Zheng and
others studied monocyte-derived DCs and T cells generated from peripheral blood
mononuclear cells obtained from the following groups of patients: (1) chronic
HBV patients with low HBV load, (2) chronic HBV patients with high HBV load, (3)
anti-HBs-positive subjects who had recovered from acute HBV infection, (4)
healthy donors who had received HBV vaccination and were anti-HBs-positive, and
(5) subjects who were immunologically naive to HBV exposure or vaccination. The following DC-T cell interaction
dysfunctions were observed: (1) failure of DCs to increase expression of HLA-II
and B7 in response to HBsAg, (2) failure of DCs to increase IL-12 secretion in
response to HBsAg, (3) defective induction of T cell proliferation in response
to HBsAg, (4) failure to activate T cells to produce cytokines, and (5) defect
in induction of antigen-specific cytotoxic T lymphocytes. These defects were
especially prominent in patients with active HBV replication. The author
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