A simple and rapid approach for human herpesvirus type 8 subtype characterization using single base extension

In silico analysis of human herpes virus-8 genome: a comparison of the K1, VR1, and VR2 regions for genotyping and global geographical distribution

Investigations of the K1 gene revealed six main genotypes clustered according to geography. Here, the global distribution and HHV8 genotyping using the K1 gene and two hypervariable regions (VR1 and VR2) were evaluated. We searched GenBank for 6,889 HHV8-K1 genes via various keywords, selecting sequences longer than 730 bp. Afterwards, the VR1 and VR2 regions were derived from the K1 genes, and genotyping of the K1, VR1, and VR2 sequences was performed by applying phylogenetic tree and BioAfrica methods. The K1 genotyping result was most similar to that of VR1, followed by VR2. The most common genotypes and subtypes in the three regions studied were A (A2) and C (C3), which are found in Africa, America, and Asia. Although the A and C genotypes are more predominant, the other genotypes, B, D, E, and F, are more ancient and are commonly found in America, Asia, and Oceania. K1 is commonly used for HHV8 genotyping, but VR1 can be a reliable alternative when long-term PCR amplification is not possible. The genotyping and subtyping results of both methods were very similar (92%), and it can be inferred that both procedures can be applied for HHV-8 genotyping.

An innovative single-base extension method for synchronous detection of point mutations and MSI status in colorectal cancer

BACKGROUND

An accurate genotyping analysis is one of the critical prerequisites for patients with colorectal cancer receiving matched therapies. Conventional genotyping analysis is currently used to detect either gene mutations or MSI status, delaying the detection of critical tumor biomarkers and thus the optimal time for treatment. An assay that analyzes both biomarkers in a streamlined process is eagerly needed.

METHODS

We developed an assay combining Multiplex PCR Amplification, Single-base Extension and capillary electrophoresis (CE) analysis (MASE-CE) for synchronous detection of KRAS/NRAS/BRAF mutations and MSI status. In a 190 colorectal cancer cohort, we identified seven somatic mutations in KRAS, NRAS and BRAF as well as five MSI loci (D2S123/D5S346/D17S250/BAT-25/BAT-26) simultaneously. KRAS/NRAS/BRAF mutations were detected by NGS and MASE-CE, and MSI status were detected by PCR-CE and MASE-CE methods.

RESULTS

The MASE-CE method showed high consistency with NGS for mutation detection (Kappa value ≥0.8) and PCR-CE (Kappa value = 0.79). In addition, the limits of detection (LOD) of MASE-CE assay for MSI and somatic mutation were 5% and 2%, respectively.

CONCLUSIONS

In somatic mutation detection and MSI detection, the LOD of MASE-CE assay was superior to that of qPCR and NGS. MASE-CE assay is a highly sensitive, time-saving and specimen-saving method, which can greatly avoid the cumbersome testing process and provide clinical decision for doctors in time.