Hepatitis C Vaccine
Preventing a Silent Virus
Hepatitis C Virus (HCV) is a viral infection that leads to liver inflammation and damage and more than 200,000 cases are reported per year in the U.S. HCV is considered acute for the first six months following the initial infection, and approximately 75% of all acute cases turn into chronic HCV. Chronic HCV can lead to severe liver damage, including cirrhosis and liver cancer. The virus is spread through blood, and is most often spread through injection drug use with non-sterile equipment. Approximately 2.7-3.9 million individuals in the U.S.s have chronic HCV, and about half of these individuals do not know they are infected. The asymptomatic nature of HCV leads to increased transmission and worsened health outcomes given that it is more likely to remain untreated.
Direct acting antivirals (DAA) are generally safe and most persistent infections are cured within two to three months of therapy; improvement in DAA regimens to further reduce treatment duration is likely in the future. At least conceptually, treatment of most chronic HCV infections would substantially reduce the global disease burden caused by HCV, and perhaps interrupt virus transmission to facilitate eradication. However, a strategy to control chronic hepatitis C by antiviral therapy alone is complicated by two factors: First, although the antiviral therapies have improved significantly over the past several decades, the percentage of individuals cured of chronic hepatitis C is still remarkably low in the U.S. and globally due to the asymptomatic nature of the infection. Second, HCV transmission has accelerated in most regions of the world. In the U.S., infection rates have increased over the past decade because of an ongoing epidemic injection drug use amongst adolescents and young adults. New undiagnosed HCV infections will almost certainly develop at a rate that outpaces detection and antiviral cure. In addition, given that the most common cause of HCV is injection drug use, many individuals with HCV experience substance use disorder, continue to use injection drugs, and therefore become re-infected with HCV following treatments.
While we have preventive vaccines for Hepatitis A and B, there is no preventive measure for HCV. Arash Grakoui, PhD, an Associate Professor at the Emory Vaccine Center and Emory University’s School of Medicine and colleagues have discovered HCV mutants that are viable candidates for such a preventive vaccine. Grakoui and his colleagues found that a single amino acid (a cysteine) in the crucial structural E2 envelope protein of HCV, can be mutated to make viral particles non-infective; the immune system may recognize these non-infectious virus particles and build immunity to HCV without being compromised by the active virus. There are currently two active candidates for the vaccine. The first candidate utilizes neutralizing antibodies to prevent HCV. The second candidate uses vectors to elicit T-cell responses in order to boost the immune system, and therefore preventing infection. Justin Burns, a licensing associate in the Office of Technology Transfer, added, “The fact that a single amino acid change can effectively limit the ability of HCV to infect host cells is astounding and gives Emory researchers a leg up on developing new vaccines not only for HCV but also for other viral infections.”
According to Grakoui, "While there is improvement in treatments, there is a great deal of hope that a combination of treatment and prevention can make a significant impact on the incidence of this infection." This development is promising as researchers strive to find a means of prevention for the most common blood-borne illness in the U.S. In light of the recent opioid epidemic, the number of individuals with HCV is on the rise and heightens the need for a preventive approach to managing the infection.
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