Hepatitis C Progress Hampered by Re-Infection and Superinfection
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Hepatitis C is the most common blood-borne infection in the United States. It is also extremely prominent in intravenous drug users. Even with all of the ongoing research into Hepatitis C prevention and therapy, the current treatment is generally only effective in approximately half of those infected. The scientific community has uncovered a variety of stumbling blocks in their quest to create a Hepatitis C vaccine or a cure. Two of the barriers complicating their search for improved Hepatitis C treatment are that the largest population of people with Hepatitis C, intravenous drug users, is often prone to re-infection or superinfection.
Hepatitis C in Intravenous (IV) Drug Users
Considered to be approximately seven times more infectious than HIV in a single drop of blood, Hepatitis C is extremely likely to be acquired if contaminated needle and syringe sharing is occurring. Investigators know the following:
- Within only six months to a year after beginning intravenous drug use, 50 to 80 percent of IV drug users test positive for the Hepatitis C antibody.
- Intravenous drug users account for about 30 to 40 percent of all identified Hepatitis C cases, and about 50 percent of all new cases.
Representing the largest single risk group for Hepatitis C, many studies have attempted to determine the percentage of IV drug users infected. While trial results vary, they all demonstrate that over half of IV drug users have the virus. And some researchers even claim that nearly 100 percent of those using needles to inject drugs have antibodies to Hepatitis C.
Hepatitis C Is Mysterious
Most experts believe that finding an effective Hepatitis C vaccine or therapy is such a challenge because of the virus’ ability to mutate. The following facts have made this infectious disease harder for scientists to eliminate:
- Hepatitis C is an RNA virus that lacks an efficient proofreading ability as it replicates.
- This inefficient proofreading allows the virus to evolve, creating a collection of quasi-species. There are currently 11 major genotypes, many subtypes and 100 different strains of Hepatitis C.
- Because it constantly mutates, many believe Hepatitis C escapes host immunologic detection and elimination.
Re-Infection
The immune system’s memory is credited for building up resistance to various diseases and is the theoretical basis behind most preventative vaccines. Many infectious diseases teach the immune system how to combat a particular pathogen so that subsequent exposure does not cause re-infection. To aid the investigation into vaccine development, researchers are trying to confirm or deny immune memory with Hepatitis C.
Superinfection
A reasonable path for the highly mutable Hepatitis C virus, superinfection is when a cell previously infected by one virus becomes co-infected with a different strain of the virus. Unfortunately, viral superinfections are common causes of treatment resistance – where a previously effective therapy loses its efficacy. In addition, superinfections have been known to reduce the overall effectiveness of the immune response.
Study
As described in an oral presentation at the 13th International Symposium on Viral Hepatitis and Liver Disease in April of 2009, investigators studied intravenous drug users to assess Hepatitis C re-infection and superinfection. Based on their results, the researchers concluded that Hepatitis C re-infection and superinfection “are common among actively injecting drug users.” They proclaimed further that these findings demonstrate Hepatitis C does not create protective immunity and further complicates the quest for developing a Hepatitis C vaccine.
Because of Hepatitis C’s high transmission rate in those sharing contaminated needles and syringes, studying IV drug users can yield very important information. By recognizing the existence of Hepatitis C re-infection and superinfection and understanding how it impedes vaccine and drug development, researchers are that much closer to unraveling the mystery of Hepatitis C.
References:
http://en.wikipedia.org/wiki/Superinfection, Superinfection, Retrieved April 14, 2009, Wikimedia Foundation, Inc., 2009.
http://www.drugabuse.gov/HepatitisAlert/HepatitisAlert.html, NIDA Community Drug Alert Bulletin – Hepatitis, Alan I. Leshner, PhD, Retrieved April 15, 2009, National Institute on Drug Abuse, 2009.
http://www.epidemic.org/theFacts/theEpidemic/USRiskGroups/, High Risk Groups – United States, Retrieved April 15, 2009, Trustees of Dartmouth College, 2009.
http://www.hivandhepatitis.com/hep_c/news/2009/032409_a.html, HCV Reinfection and Superinfection Are Common among Injection Drug Users, Retrieved April 13, 2009, hivandhepatitis.com, March 2009.
http://www.knowcrystal.org/hiv/crystalhiv_p4.htm, What is Superinfection?, Retrieved April 14, 2009, knowcrystal.org, 2009.
http://www.ncbi.nlm.nih.gov/pubmed/15378431, Frequent hepatitis C virus superinfection in injection drug users, Herring BL, et al, Retrieved April 14, 2009, The Journal of Infectious Diseases, Infectious Diseases Society of America, October 2004.
http://www.who.int/csr/disease/hepatitis/whocdscsrlyo2003/en/index2.html, The Hepatitis C Virus, Retrieved April 16, 2009, World Health Organization, 2009.
