HСV genotyping (1а, 1b, 2, 3а, 4, 5а, 6 types)

Hepatitis C virus (HCV) has the greatest variability among all pathogens of viral hepatitis and, due to its high mutational activity, is able to avoid the effects of the protective mechanisms of the immune system. The genomes of the virus differ significantly in different countries of the world and have different sensitivity to interferon preparations.

According to current recommendations, HCV genotyping should be performed in all patients before starting antiviral therapy. To date, the presence of eleven main genotypes has been established, which are further subdivided into subtypes (Simmonds classifications). For clinical practice, it is quite sufficient to distinguish the first six genotypes.

Genotype 1 is the most widespread in the world (40-80%). Type 1a is often detected in the USA, and 1b is typical for Western Europe and South Asia. Genotype 2 occurs with a frequency of 10-40%. Genotype 3 is common in Scotland, Australia, India and Pakistan. HCV type 4 is typical for Central Asia and North Africa, genotype 5 is for South Africa, and 6 is for some Asian countries. Genotype 1b prevails in Russia, then with decreasing frequency - 3, 1a, 2, in the USA – 1a/1b, 2b, and 3a.

The tactics of therapy and its effectiveness depend on the HCV genotype. Hepatitis C caused by genotypes 1 and 4 viruses is the most unfavorable in terms of the prognosis of the effectiveness of treatment, a high risk of chronic infection, and the development of severe complications. Persons infected with HCV genotypes 2 and 3 have a less severe course of the disease, a lower level of viremia (concentration of the virus in the blood), and significantly better responses to traditional antiviral therapy than patients infected with the 1a or 1b genotype virus. Genotypes 2 and 3 respond well to therapy in 80% of cases.

According to the data of the conducted clinical analysis, patients with genotype 1 and 6 have, on average, a higher baseline level of hepatitis C virus RNA, compared with individuals with genotype 2 or 3. Patients with genotype 6 do not show significant differences in relation to individual host factors, including age, history of alcohol consumption, hepatitis B infection, etc., and have similar laboratory parameters and histological picture of the liver compared with patients who have other genotypes of hepatitis C, but compared with those infected with genotype 1 virus, this category of patients it is better amenable to antiviral therapy.