Detection of circulating HCV recombinant form RF1_2k/1b in blood serum of patients by real-time RT-PCR.

Globally, about 70 million people are infected with the hepatitis C virus (HCV), and about 400 thousand people die annually from chronic hepatitis C complications. The management of patients with chronic hepatitis C may require HCV genotyping, since the efficiency of some widely used antiviral drugs strongly depend on the viral genotype and/or subtype. The most prevalent HCV circulating recombinant form, RF1_2k/1b, is misclassified as genotype 2 by many commercial HCV genotyping kits, based on the RT-PCR analysis of the 5' untranslated region of the HCV genome. This leads to inappropriate patient treatment, since the accepted treatment schemes for HCV genotype 2 are ineffective for the RF1_2k/1b. Here we describe a method for detecting the RNA HCV RF1_2k/1b in blood samples by RT-PCR analysis of two regions in HCV genome (5'UTR and NS5b). The method was tested on 240 blood serum samples from HCV infected patients, in which HCV genotype was defined as 2 or mixed (2+1 or 2+3) by the two commercial genotyping kits "OT-Hepatogen-C genotype" ("DNA-Technology", Moscow) and "RealBest RNA HCV-1/2/3" ("Vector- Best ", Novosibirsk). 50 (20.8%) RF1_2k/1b cases were revealed, including three mixed infections: RF1_2k/1b + 1a, RF1_2k/1b + 3a, RF1_2k/1b + 1b. In all cases, the accuracy of HCV typing by the proposed method was confirmed by Sanger sequencing and phylogenetic analysis. The method is easy to implement into clinical practice and may be used in clinical settings equipped for RT-PCR analysis to correctly identify the recombinant variant RF1_2k/1b.