Hepatitis C test: serum HCV antibodies

Antibodies to HCV in the blood serum are normally absent.

Viral hepatitis C ( Hepatitis C ) is a viral disease that most often occurs as post-transfusion hepatitis with a predominance of anicteric and mild forms and tends to become chronic. The causative agent is the hepatitis C virus (HCV), which contains RNA. Based on phylogenetic analysis, 6 HCV genotypes and more than 80 subtypes have been identified. Genotype 1 is the most common genotype worldwide (40-80% of isolates). Genotype 1a is the predominant subtype for the USA, and 1b predominates in Western Europe and South Asia. Genotype 2 is common worldwide, but occurs less frequently than genotype 1 (10-40%). Genotype 3 is typical for India, Pakistan, Australia and Scotland. Genotype 4 is distributed mainly in Central Asia and Egypt, genotype 5 in South Africa, and genotype 6 in Hong Kong and Macau.

In 40-75% of patients, an asymptomatic form of the disease is registered, in 50-75% of patients with acute viral hepatitis C, chronic hepatitis is formed, in 20% of them, liver cirrhosis develops. An important role of viral hepatitis C is also assigned in the etiology of hepatocellular carcinoma.

The HCV genome is represented by a single-stranded positively charged RNA, which codes for 3 structural (nucleocapsid protein core and envelope nucleoproteins E1 _- E2 ₎ and 5 structural (NS1 _, NS2 _, NS3 _, NS4 _, NS5 ₎ proteins. ATs are synthesized for each of these proteins and are found in the blood of patients with viral hepatitis C.

A distinctive feature of viral hepatitis C is the wave-like course of the disease, in which three phases are distinguished: acute, latent and reactivation phase.

• The acute phase is characterized by an increase in the activity of liver enzymes in the blood serum, the content of IgM and IgG antibodies (to the nucleocapsid protein core) to HCV with an increase in titers, as well as HCV RNA.
• The latent phase is characterized by the absence of clinical manifestations, the presence of IgG antibodies (to the nucleocapsid protein core and non-structural proteins NS ₃ -NS ₅ ) to HCV in high titers in the blood, the absence of IgM antibodies and HCV RNA or their presence in low concentrations against the background of a slight increase in the activity of liver enzymes during periods of exacerbation.
• The reactivation phase is characterized by the appearance of clinical signs, increased activity of liver enzymes, the presence of IgG antibodies (to the nucleocapsid protein core and non-structural proteins NS) in high titers, the presence of HCV RNA and an increase in IgM antibody titers to HCV over time.

Diagnostics of viral hepatitis C is based on detection of total antibodies to HCV by ELISA, which appear in the first 2 weeks of the disease and indicate possible infection with the virus or a previous infection. Anti-HCV antibodies can persist in the blood of convalescents for 8-10 years with a gradual decrease in their concentration. Late detection of antibodies is possible a year or more after infection. In chronic viral hepatitis C, antibodies are determined constantly and in higher titers. Most of the currently used test systems for diagnostics of viral hepatitis C are based on the determination of IgG antibodies. Test systems capable of determining IgM antibodies will allow verification of active infection. IgM antibodies can be detected not only in acute viral hepatitis C, but also in chronic viral hepatitis C. A decrease in their number during treatment of patients with chronic viral hepatitis C may indicate the effectiveness of drug therapy. In the acute phase of infection, the IgM/IgG AT ratio is within 3-4 (predominance of IgM antibodies indicates high activity of the process). As recovery proceeds, this ratio decreases by 1.5-2 times, indicating minimal replicative activity.

Detection of total IgG antibodies to HCV by ELISA is not enough to diagnose viral hepatitis C; their presence must be confirmed (by immunoblotting) to exclude a false-positive test result. The patient should be examined for IgG antibodies to various HCV proteins (to the core protein and NS proteins) and IgM antibodies to HCV over time. The results of serological studies together with clinical and epidemiological data allow us to establish the diagnosis and stage of the disease (important for the correct choice of treatment method).

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