Evidence for deleterious hepatitis C virus quasispecies mutation loads that differentiate the response patterns in IFN-based antiviral therapy

Genome-wide capture sequencing to detect hepatitis C virus at the end of antiviral therapy

Background

Viral relapse is a major concern in hepatitis C virus (HCV) antiviral therapy. Currently, there are no satisfactory methods to predict viral relapse, especially in the era of direct acting antivirals in which the virus often quickly becomes undetectable using PCR-based approaches that focus on a small viral region. Next-generation sequencing (NGS) provides an alternative option for viral detection in a genome-wide manner. However, owing to the overwhelming dominance of human genetic content in clinical specimens, direct detection of HCV by NGS has a low sensitivity and hence viral enrichment is required.

Methods

Based on template-dependent multiple displacement amplification (tdMDA), an improved method for whole genome amplification (Wang et al., 2017. Biotechniques 63, 21–27), we evaluated two strategies to enhance the sensitivity of NGS-based HCV detection: duplex-specific nuclease (DSN)-mediated depletion of human sequences and HCV probe-based capture sequencing.

Results

In DSN-mediated depletion, human sequences were significantly reduced in the two HCV serum samples tested, 65.3% → 55.6% → 33.7% (#4727) and 68.6% → 56% → 21% (#4970), respectively for no normalization, self- and driver-applied normalization. However, this approach was associated with a loss of HCV sequences perhaps due to its micro-homology with the human genome. In capture sequencing, HCV-mapped sequencing reads occupied 96.8% (#4727) and 22.14% (#4970) in NGS data, equivalent to 1936x and 7380x enrichment, respectively. Capture sequencing was then applied to ten serum samples collected at the end of HCV antiviral therapy. Interestingly, the number of HCV-mapped reads was significantly higher in relapsed patients (n = 5) than those from patients with sustained virological response (SVR) (n = 5), 102.4 ± 72.3 vs. 2.6 ± 0.55, p = 0.014.

Conclusions

Our data provides concept evidence for a highly sensitive HCV detection by capture sequencing. The abundance difference of HCV sequencing reads at the end of HCV antiviral therapy could be applied to predict treatment outcomes.

Personalized Medicine and Infectious Disease Management

A recent study identified pathogen factors associated with an increased mortality risk in Staphylococcus aureus bacteremia, using predictive modelling and a combination of genotypic, phenotypic, and clinical data. This study conceptually validates the benefit of personalized medicine and highlights the potential use of whole genome sequencing in infectious disease management.

Interpatient mutational spectrum of human coronavirus-OC43 revealed by illumina sequencing

Human coronaviruses (HCoV) are RNA viruses that cause respiratory tract infections with viral replication of limited duration. The host and viral population heterogeneity could influence clinical phenotypes. Employing long RT‐PCR with Illumina sequencing, we quantified the gene mutation load at 0.5% mutation frequency for the 4529 bp‐domain spanning the Spike gene (4086 bp) of HCoV‐OC43 in four upper respiratory clinical specimens obtained during acute illness. There were a total of 121 mutations for all four HCoV samples with the average number of mutations at 30.3 ± 10.2, which is significantly higher than that expected from the Illumina sequencing error rate. There were two mutation peaks, one at the 5′ end and the other near position 1 550 in the S1 subunit. Two coronavirus samples were genotype B and two were genotype D, clustering with HCoV‐OC43 strain AY391777 in neighbor‐joining tree phylogenetic analysis. Nonsynonymous mutations were 76.1 ± 14% of mutation load. Although lower than other RNA viruses such as hepatitis C virus, HCoV‐OC43 did exhibit quasi‐species. The rate of nonsynonymous mutations was higher in the HCoV‐OC43 isolates than in hepatitis C (HCV) virus genotype 1a isolates analyzed for comparison in this study. These characteristics of HCoV‐OC43 may affect viral replication dynamics, receptor binding, antigenicity, evolution, transmission, and clinical illness.