In-Situ Mutation Detection by Magnetic Beads-Probe Based on Single Base Extension and Its Application in Genotyping of Hepatitis B Virus Pre-C Region 1896nt Locus Single Nucleotide Polymorphisms.

Hepatitis B virus (HBV) is closely related to occurrence and development of viral hepatitis. A mutation of 1896nt locus in its pre-C region can promote replication of HBV DNA and improve stability of pre-genome RNA structure, and can even help HBV evade immune clearance. In this study, magnetic beads-probe (MBs@probe) method, combined with single base extension (SBE) technology, was developed for mutation detection of HBV pre-C region 1896nt locus. Before successfully completing the genotyping of 165 HBV samples, the crucial reaction conditions were first optimized, such as SBE temperature, MBs size and amount, and probe concentration on the surface of MBs. Experimental results showed that these conditions had significant effects on MBs@probe mutation detection. Comprehensive considerations, such as 58 °C of SBE temperature, high fluorescence intensity and signal-to-noise ratios (SNRs) were obtained when MBs@probe complex was made by 100 g of 300 nm-MBs and 3.0 M of probes in the system. Finally, 1896nt locus mutation in pre-C region of 165 HBV samples was successfully genotyped, among which 71 HBV samples were wild types and the remaining 94 samples were mutant types. Meanwhile, 14 randomly chosen samples were taken to further analyze fluorescence intensity and SNRs respectively, and sequencing results for the first two samples were consistent with results from the MBs@probe mutation detection method. Compared with two-color fluorescence hybridization (TCFH) genotyping technology, this method generally improves the SNRs to more than 10 (which is more than 2-fold), has higher reliability and is more suitable to detect SNPs for known sites.