Metagenomic profiling of placental tissue suggests DNA virus infection of the placenta is rare.

Adam A Witney,Sean Aller,Blair L Strang

doi:10.1099/jgv.0.001677

Abstract

It is widely recognized that pathogens can be transmitted across the placenta from mother to foetus. Recent re-evaluation of metagenomic studies indicates that the placenta has no unique microbiome of commensal bacteria. However, viral transmission across the placenta, including transmission of DNA viruses such as the human herpesviruses, is possible. A fuller understanding of which DNA virus sequence can be found in the placenta is required. We employed a metagenomic analysis to identify viral DNA sequences in placental metagenomes from full-term births (20 births), pre-term births (13 births), births from pregnancies associated with antenatal infections (12 births) or pre-term births with antenatal infections (three births). Our analysis found only a small number of DNA sequences corresponding to the genomes of human herpesviruses in four of the 48 metagenomes analysed. Therefore, our data suggest that DNA virus infection of the placenta is rare and support the concept that the placenta is largely free of pathogen infection.

Highlights

Vertical transmission of pathogens from mother to child is a mechanism of pathogen dissemination within human populations [1]
Applying a minimum cutoff of greater than or equal to two or more reads, removing any single match classifications, only four placental metagenomes had reads classified as virus derived; all classifications were attributed to herpesviruses human herpesvirus (HHVs)-6A, HHV
We sought to understand which human DNA virus genomes could be found in placental tissue and if those DNA genomes differed between patient groups

Summary

Introduction

Vertical transmission of pathogens from mother to child is a mechanism of pathogen dissemination within human populations [1]. This can occur by several well-characterized mechanisms, including post-partum infection at birth and via breast milk [1]. The fetus [13], leading to reports that the placenta harbors a unique microbiome of nonpathogenic commensal bacteria. The most prominent reports of a unique placental microbiome have been produced by Aagaard and colleagues [4,5,6], who reported the detection of a wide range of commensal bacterial DNA sequences in placental tissue using methods such as bacterial 16S sequencing and metagenomic DNA profiling

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Conclusion