Assessment of bacterial and viral gut communities in healthy and tumoral colorectal tissue using RNA and DNA deep sequencing.

BACKGROUND: Colorectal cancer (CRC) is known to present a distinct microbiome profile compared to healthy mucosa. Non-targeted deep-sequencing strategies enable nowadays full microbiome characterization up to species level. AIM: We aimed to analyze both bacterial and viral communities in CRC using these strategies. MATERIALS & METHODS: We analyzed bacterial and viral communities using both DNA and RNA deep-sequencing (Novaseq) in colorectal tissue specimens from 10 CRC patients and 10 matched control patients. Following taxonomy classification using Kraken 2, different metrics for alpha and beta diversities as well as relative and differential abundance were calculated to compare tumoral and healthy samples. RESULTS: No viral differences were identified between tissue types, but bacterial species Polynucleobacter necessarius had a highly increased presence for DNA in tumors (p = 0.001). RNA analyses showed that bacterial species Arabia massiliensis had a highly decreased transcription in tumors (p = 0.002) while Fusobacterium nucleatum transcription was highly increased in tumors (p = 0.002). DISCUSSION: Sequencing of both DNA and RNA enables a wider perspective of micriobiome profiles. Lack of RNA transcription (Polynucleobacter necessarius) casts doubt on possible role of a microorganism in CRC. The association of F. nucleatum mainly with transcription, may provide further insights on its role in CRC. CONCLUSION: Joint assessment of the metagenome (DNA) and the metatranscriptome (RNA) at the species level provided a huge coverage for both bacteria and virus and identifies differential specific bacterial species as tumor associated.

Metatranscriptome analysis in human papillomavirus negative cervical cancers.

Human papillomavirus (HPV) negative cancers are associated with symptomatic detection, late-stage diagnosis, and worse prognosis. It is thus essential to investigate all possible infectious agents and biomarkers that could early identify these HPV negative cancers. We aimed to analyze and compare the metatranscriptome present in HPV positive and HPV negative cervical cancers. We analyzed the whole RNA sequencing files from 223 HPV negative cervical cancers (negativity established after confirming cervical cancer diagnosis, sample adequacy and subjecting specimens to PCR and unbiased RNA sequencing), 223 HPV positive tumors and 11 blank paraffin block pools (used as controls) using Kraken2 software. Overall, 84 bacterial genera were detected, with 6/84 genera showing a positive median number of reads/sample and being present in both cervical tumor groups (HPV positive and negative). Viral reads belonged to 63 different viral genera, with 6/63 genera showing a positive median annotated read/sample value. No significant difference among genera was detected except for the presence of alpha-papillomaviruses. Metatranscriptome of bacteria and viruses present in HPV positive and HPV negative cervical cancers show no significant difference, except for HPV. Further studies are needed to early identify this biologically distinct group of cervical cancers.

Comparison of DNA and RNA sequencing of total nucleic acids from human cervix for metagenomics.

Although metagenomics and metatranscriptomics are commonly used to identify bacteria and viruses in human samples, few studies directly compare these strategies. We wished to compare DNA and RNA sequencing of bacterial and viral metagenomes and metatranscriptomes in the human cervix. Total nucleic acids from six human cervical samples were subjected to DNA and RNA sequencing. The effect of DNase-treatment before reverse transcription to cDNA were also analyzed. Similarities and differences in the metagenomic findings with the three different sequencing approaches were evaluated. A higher proportion of human sequences were detected by DNA sequencing (93%) compared to RNA sequencing without (76%) and with prior DNase-treatment (11%). On the contrary, bacterial sequences increased 17 and 91 times. However, the number of detected bacterial genera were less by RNA sequencing, suggesting that only a few contribute to most of the bacterial transcripts. The viral sequences were less by RNA sequencing, still twice as many virus genera were detected, including some RNA viruses that were missed by DNA sequencing. Metatranscriptomics of total cDNA provided improved detection of mainly transcribed bacteria and viruses in cervical swabs as well as detection of RNA viruses, compared to metagenomics.

Characterization of human papillomavirus type 154 and tissue tropism of gammapapillomaviruses.

The novel human papillomavirus type 154 (HPV154) was characterized from a wart on the crena ani of a three-year-old boy. It was previously designated as the putative HPV type FADI3 by sequencing of a subgenomic FAP amplicon. We obtained the complete genome by combined methods including rolling circle amplification (RCA), genome walking through an adapted method for detection of integrated papillomavirus sequences by ligation-mediated PCR (DIPS-PCR), long-range PCR, and finally by cloning of four overlapping amplicons. Phylogenetically, the HPV154 genome clustered together with members of the proposed species Gammapapillomavirus 11, and demonstrated the highest identity in L1 to HPV136 (68.6%). The HPV154 was detected in 3% (2/62) of forehead skin swabs from healthy children. In addition, the different detection sites of 62 gammapapillomaviruses were summarized in order to analyze their tissue tropism. Several of these HPV types have been detected from multiple sources such as skin, oral, nasal, and genital sites, suggesting that the gammapapillomaviruses are generalists with a broader tissue tropism than previously appreciated. The study expands current knowledge concerning genetic diversity and tropism among HPV types in the rapidly growing gammapapillomavirus genus.

Lack of methylation in the upstream region of human papillomavirus type 6 from aerodigestive tract papillomas.

Methylation of the high-risk human papillomavirus type 16 (HPV16) upstream regulatory region (URR) has been described, but whether methylation is present among low-risk HPVs is unknown. The methylation status of the HPV6 URR was analyzed in papillomas from the upper aerodigestive tract of six adult patients. All CpGs in the URR were unmethylated, from both basal/intermediate and superficial cells, suggesting that methylation is not involved in the regulation of transcription from the HPV6 URR, regardless of epithelial differentiation.