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Hepatitis C virus
Last reviewed: 23.04.2024
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Hepatitis C virus is a small RNA-containing virus with a coat of structural proteins that form together with a group of non-structural proteins the virion nucleocapsid.
Most researchers who study the biology of the hepatitis C virus believe that it belongs to the family of Flaviviridae, and is also the only representative of the Hepacivirus gene (Dustin LB., Rice CM, 2007).
Hepatitis C virus (HCV) has a diameter of 30-60 nm, the floating density in the gradient of sucrose is 1.0-1.14 g / cm, the sedimentation coefficient is 150 S, the protein-lipid outer membrane. The HCV genome consists of a single-stranded positive RNA up to 10,000 nucleotide bases. The genome is a single-stranded unfragmented RNA of positive polarity with a length of 9500-10 000 nucleotides. The genome encodes one large polypeptide, in the process of maturation undergoing processing, involving two proteases: viral origin and cellular. The HCV genome encodes 3 structural and 5 non-structural proteins of the virus. As shown in the figure, the main structural protein (C), which is part of the nucleocapsid, has a molecular weight of 21-33 kD. The two other structural proteins, E1 and E2, serve as envelope proteins of the virus and are glycoproteins with a molecular weight of 31 and 70 kD, respectively. The remaining proteins are non-structural polyproteins [NS2 (23 kD), NS3 (70 kD), NS4A (8 kD), NS4B (27 kD), NS5A (58 kD), NS5B].
In studying the molecular biology of HCV, the heterogeneity of the genomes of the strains of this virus isolated in different countries, from different people and even from the same person, was established.
By now, there are up to 34 genotypes of the virus in 11 genetic groups. However, it is customary to identify the 5 most common genotypes numbered in Roman numerals I, Il, III, IV, V; they correspond to the designations of genotypes la, 1b, 2a, 2b and 3a. The genotype of the virus determines the course of infection, its transition to a chronic form and, subsequently, the development of cirrhosis and carcinoma of the liver. The most dangerous are the genovariants lb and 4a. The genotypes lb, 2a, 2b and 3a are circulating in Russia. The hepatitis C virus is ubiquitous. According to WHO, about 1% of the world's population is infected with HCV.
|
A country |
Genotype,% | |||
|
I (1a) 1 |
II (1b) |
III (2a) |
IV (2b) | |
|
Japan |
74.0 |
24.0 |
1.0 |
- |
|
Italy |
51.0 |
35.0 |
5.0 |
1.0 |
|
USA |
75.0 |
16.0 |
5.0 |
1.0 |
|
England |
48.0 |
14.0 |
38.0 |
- |
|
Russia (Central European part) |
9.9 |
69.6 |
4.4 |
0.6 |
As can be seen from the table, the majority of people infected with the hepatitis C virus, regardless of continents and countries, have genotype I (1a) or II (1b).
In Russia, the distribution of genotypes is not uniform. In the European part, genotype 1b is most often detected, and genotypes 2a and 3a in Western Siberia and the Far East.
Hepatitis C virus is found in the blood and liver in a very low concentration, in addition, it induces a weak immune response in the form of specific antibodies and has the ability for prolonged persistence in the human body and experimental animals (monkeys). This often causes the occurrence of a chronic process in the liver in infected HCV.
The phenomenon of HCV interference with hepatitis A and B viruses has been established; competitive infection of HCV leads to suppression of replication and expression of hepatitis A and B viruses in experimental animals (chimpanzees). This phenomenon can be of great clinical importance in the co-infection of hepatitis C with hepatitis A and B.
The source of infection is only a person. The virus in patients and carriers is found in 100% of cases in the blood (2/3 of all posttransfusion hepatitis causes HCV), in 50% in saliva, in 25% in semen, and 5% in urine. This determines the path of infection.
The clinical course of hepatitis C is easier than hepatitis B. The hepatitis C virus is called a "soft killer." Jaundice is observed in 25% of cases; up to 70% of cases occur in a latent form. Regardless of the severity of the course in 50-80% of cases, hepatitis C takes on a chronic form, and in such patients, cirrhosis and carcinoma subsequently develop in 20% of cases. In experiments on mice it was established that the hepatitis C virus in addition to hepatocytes can also damage nerve cells, causing severe consequences.
The hepatitis C virus in the cell culture reproduces poorly, so its diagnosis is difficult. This is one of the few viruses for which the determination of RNA is the only way of identification. It is possible to determine the RNA of the virus by using a DTP in the reverse transcription variant, using ELISA antibodies against the virus using recombinant proteins and synthetic peptides.
Interferon, whose production for chronic hepatitis is impaired, and the inducer of its endogenous synthesis of amixin are the main pathogenetic agents for the treatment of all viral hepatitis.
[1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16]