Thousands-years-old deep-sea DNA viruses reveal the evolution of human pathogenic viruses

INTRODUCTION

In the last two decades, outbreaks of pathogenic viruses have led to significant human mortality and economic repercussions. Despite extensive investigations into tracing these viruses in terrestrial environments, their origins remain enigmatic.

OBJECTIVES

The Earth's biosphere encompasses both sunlight-dependent terrestrial and surface ocean ecosystems, as well as the sunlight-independent deep-sea ecosystem. However, the traceability of human pathogenic viruses in the deep sea has not been thoroughly explored. This study aimed to investigate the presence of human pathogenic viruses in the deep sea.

METHODS

In this study, we performed a viral metagenomic analysis using a global deep-sea sediment virome 2.0 dataset which contained 159 deep-sea sediment samples with geologic ages from 2,500 to 7,750 years.

RESULTS

A total of 554,664 viral operational taxonomic units (vOTUs) were identified and further obtained 2,254 potential pathogenic viruses of vertebrates. Among them, 23 vOTUs exhibited high homology with 12 species of human pathogenic viruses which belonged to 4 viral families. Notably, variola virus, the first human pathogenic virus eradicated from humans and now only found in laboratories, was discovered in the ancient deep-sea sediments. The evolution analysis showed that these DNA viruses might represent the ancestors or variants of human pathogenic viruses, suggesting that the deep sea could be a crucial reservoir for human pathogenic viruses.

CONCLUSION

Our findings present all the ancient pathogenic DNA viruses of humans found in the deep sea for the first time, highlighting the source of the future epidemics. It is imperative to implement the stringent virus monitoring and management measures for human activities in marine environments to address the emerging challenges of marine biosecurity and promote sustainable use of oceans.

Molecular survey on Merkel cell polyomavirus in patients with colorectal cancer

Background: Merkel cell polyomavirus (MCV) has been associated with Merkel cell carcinoma (MCC) in humans, and its role in other human cancers is under investigation. The aim of this study was to investigate MCV genome infection in patients with colorectal cancer (CRC).Methods: This retrospective, case-control study used archived formalin-fixed, paraffin-embedded (FFPE) tissue samples from colorectal cancer patients (cases) and matched healthy subjects (controls) diagnosed by an expert pathologist from hospitals affiliated with Iran University of Medical Sciences, Tehran, Iran from 2011 to 2016. After DNA extraction with a QIAamp® DNA FFPE Tissue Kit, real-time polymerase chain reaction (PCR) was used for diagnosis. A positive control was produced by cloning with the Generay Biotechnology system. SPSS v.22 was used for analysis of demographic variables.Results: There were 157 participants included in the study: 66 were cases and 91 were controls. Their mean ages (±SD) were 59.35±14.48 and 57.21±14.66, respectively. The proportion of males was 57.6% in the case group and 57.1% in the control group. None of the samples were positive for MCV expression by real-time PCR assay. Association was detected between males with CRC and tumor location in the rectum and between males with CRC and the mucinous tumor type.Conclusion: None of the tissues from the CRC or non-cancerous control groups were positive for MCV genome infection, although a low viral load, the sample type, or the method of use should not be neglected. Further studies are recommended to obtain more comprehensive results.