Hepatitis is defined as inflammation of the liver. Viral infections are the most common cause of hepatitis. A type of hepatitis known as hepatitis C is caused by the hepatitis C virus (HCV). This virus is made up of a single strand of ribonucleic acid (RNA) surrounded by two layers (envelopes), one consisting of proteins and the other of lipids (fat). RNA is a nucleic acid that helps in protein synthesis, which is important for the growth and maintenance of the body.
Hepatitis C virus belongs to the Flaviviridae family, which includes viruses that mainly spread through arthropod vectors such as ticks and mosquitoes. Dengue fever, an infectious disease transmitted to humans by mosquitoes, and Japanese encephalitis, an infection that affects the nervous system which is also transmitted by mosquitoes, are some of the diseases caused by the Flaviviridae family of organisms.
In the mid 1970s, researchers found that a particular type of hepatitis that develops in a person after receiving a blood transfusion was not caused by hepatitis A or B viruses. They named the new virus non-A, non-B hepatitis (NANBH). The unknown organism was identified by scientists in 1987, and it was renamed the hepatitis C virus (HCV) in 1989.
HCV causes a liver disease known as hepatitis C. The incubation period, which is the period between infection and the onset of clinical symptoms, ranges from 15 to 150 days. Humans and chimpanzees are the only two species that are susceptible to HCV, and a similar disease process has been observed in both species.
According to the World Health Organization, an estimated 170 million people are chronically infected with HCV, with 3 to 4 million new infections occurring every year. The distribution of HCV types varies globally. For example, HCV type 1 is the most common and accounts for 70% of the HCV infections in the United States.
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types of the disease
HCV has been classified into six types based on the structure and sequence of its RNA. HCV also has multiple subtypes, which include a, b, c, based on the order in which they were discovered. The subtypes are further broken down based on their genetic diversity or variations. This classification system helps to easily identify the different organisms.
General: Researchers are conducting several studies to find better techniques for the early detection and quantification of hepatitis C virus (HCV) in infected individuals. Such techniques might also help in monitoring the treatment of these patients.
Polymerase chain reaction-based test: A polymerase chain reaction (PCR)-based enzyme-linked oligonucleotide-sorbent assay (ELOSA) has been developed to analyze the serum of patients infected with different types of HCV. A recent study was conducted to compare this method with Roche's COBAS AMPLICOR HCV Monitor assay, which is a qualitative and quantitative test to detect HCV infection. The PCR-ELOSA was demonstrated to be more sensitive, also showed a high accuracy and reproducibility, and may be considered an alternative to current HCV detection assays.
RT-PCR-based test: Researchers have recently standardized an HCV real-time reverse transcriptase polymerase chain reaction (RT-PCR) for screening, quantitation (analyzing the quantity), and detection of HCV RNA in plasma samples. Reverse transcription is the process of producing double-stranded DNA from a single-stranded RNA. This assay is more reliable and accurate than standard PCR techniques, making it easier to screen patients and monitor the disease.
Hybridization-based test: Hybridization, a process of combining various organisms or the strands of DNA and RNA, has been studied for detecting the presence of HCV RNA in infected individuals. This technique removes the need for RNA purification, an elaborate and time-consuming process of separating the viral RNA from other cellular components such as proteins. Results can therefore be obtained in a short time using the hybridization method. The assay is also highly sensitive, easy to handle, and reproducible, facilitating quick and reliable results.
Mass spectrometry-based method: Studying the diversity of protein patterns in the HCV-infected individual's peripheral blood mononuclear cells (PBMCs) may help clarify the role of these proteins and their function in chronic hepatitis C infection. PBMCs are the blood cells that help fight against foreign agents. Understanding the role of the PBMC proteins and their mechanisms in HCV infection may help in finding diagnostic tools that facilitate quicker identification of the virus. It may also assist in developing effective treatment strategies against the infection.
General: New therapies for treating infection caused by hepatitis C virus (HCV) are in various stages of development. These include studies to understand viral ribonucleic acid (RNA) and the functions or mechanisms of action of HCV-encoded proteins, which play a major role in virus replication or multiplication. Such studies help the investigators to devise techniques that facilitate early detection of HCV and may help develop effective treatment strategies against HCV infection.
Genetic tests: Researchers are examining a new method called heteroduplex mobility analysis (HMA) that detects the HCV genome, which is the sum total of genetic information in an organism, of different HCV types and subtypes. HMA is a rapid and inexpensive method for determining the genetic makeup of HCV that does not require sequencing to determine the order of the nucleotide bases in the RNA. Further research is warranted because the current analysis cannot detect a large proportion of genotypes and subtypes.
Treatment: Some studies have found that the antiviral drug amantadine (Symmetrel®), when added to the standard treatment of interferon and ribavirin, helps in achieving better results in HCV-infected individuals. However, amantadine has not received approval from the U.S. Food and Drug Administration (FDA) for treating hepatitis C.
R1479, an inhibitor of HCV replication, is being studied for its effect against HCV. It is a potent and selective inhibitor of a nonstructural protein, which can be directed against HCV replication. Initial results suggest that R1479 may be used in combination with other antiviral drugs (e.g., ribavirin and peginterferon alfa-2a) for treating chronically infected patients.
HCV infection is regulated by immune responses, which are triggered by cellular RIG-I helicase, an RNA enzyme that plays a key role in limiting the disease progression. Researchers are targeting this enzyme because it may be used to develop treatment for the HCV infection and may thereby reduce complications related to the infection.
Vaccine development: Vaccines work by stimulating the body's immune system. Vaccines contain small amounts of disease-causing organisms that allow the immune system to produce antibodies to the foreign invader. Once antibodies are developed, the immune system is able to respond more quickly to the infection if the disease-causing organism ever enters the body. Consequently, individuals become immune to the specific illness after receiving a vaccine. The extreme variability of HCV poses a major problem for developing vaccines. Some researchers have identified human monoclonal antibodies (mAbs), which neutralize diverse HCV isolates and protect against HCV types in mice. These results suggest that a preventive vaccine may be developed against the virus using these antibodies.
A therapeutic bivalent vaccine named V-5 Immunitor (V5) may help reduce liver injury caused by the hepatitis C virus. These early results must be confirmed with larger clinical trials.