Insights into the human gut virome by sampling a population from the Indian subcontinent

Gut virome plays an important role in human physiology but remains poorly understood. This study reports an investigation of the human gut DNA-virome of a previously unexplored ethnic population through metagenomics of faecal samples collected from individuals residing in Northern India. Analysis shows that, similar to the populations investigated earlier, majority of the identified virome belongs to bacteriophages and a smaller fraction (<20 %) consists of viruses that infect animals, archaea, protists, multiple domains or plants. However, crAss-like phages, in this population, are dominated by the genera VI, VII and VIII. Interestingly, it also reveals the presence of a virus family, Sphaerolipoviridae, which has not been detected in the human gut earlier. Viral families, Siphoviridae, Myoviridae, Podoviridae, Microviridae, Herelleviridae and Phycodnaviridae are detected in all of the analysed individuals, which supports the existence of a core virome. Lysogeny-associated genes were found in less than 10 % of the assembled genomes and a negative correlation was observed in the richness of bacterial and free-viral species, suggesting that the dominant lifestyle of gut phage is not lysogenic. This is in contrast to some of the earlier studies. Further, several hundred high-quality viral genomes were recovered. Detailed characterization of these genomes would be useful for understanding the biology of these viruses and their significance in human physiology.

High-Throughput RNA Sequencing Analysis of Plasma Samples Reveals Circulating microRNA Signatures with Biomarker Potential in Dengue Disease Progression

The circulating microRNA (miRNA) profile has been widely used for identifying potential biomarkers against viral infections. However, data on circulating microRNA expression patterns in dengue patients are scanty. Considering the impact of severity caused by dengue infection, circulating miRNA profiles in plasma of dengue patients may prove to be valuable for developing early prognostic markers for the disease severity. Here, we described an in-depth analytical study of small RNA sequencing data obtained from the plasma of 39 dengue patients. Integrating bioinformatics and in vitro studies, we identified differentially expressed miRNAs (DEMs) (log2 fold change ≥1.5, P < 0.05) associated with dengue disease progression. In comparing miRNA expression pattern with the follow-up samples, nine miRNAs were found to exhibit an altered expression that could distinguish between severe dengue and the convalescent patients. To understand the abundance and specificity of the DEMs in the context of dengue infection and disease progression, eight top-hit DEMs were further validated in the dengue virus-infected cell lines as well as in the patient's plasma and peripheral blood mononuclear cells (PBMCs) using the quantitative reverse transcription-PCR (qRT-PCR) method. Importantly, receiver operating curve analysis further confirmed that the plasma expression pattern of hsa-miR-122-5p could differentiate between different stages of dengue infection (area under the concentration-time curve [AUC] = 0.792), and dengue-negative patients with other febrile illnesses (AUC = 0.984). The in silico analysis of DEM target genes suggested an enrichment of the pathways associated with metabolism and inflammation. Our study gives a global view of miRNA expression in the plasma from dengue patients and provides a precious resource of candidate miRNAs involved in dengue infection and disease progression.IMPORTANCE Dengue virus (DENV) infection usually causes dengue fever (DF) with flu-like illness affecting infants, young children, and adults. The DF occasionally evolves into a potentially lethal complication called dengue severe (DS) leading to a rapid fall in platelet count along with plasma leakage, fluid accumulation, respiratory distress, and severe bleeding. The diverse clinical spectrum of dengue disease, as well as its significant similarity to other febrile viral illnesses, makes early identification more challenging in this high-risk group. microRNAs (miRNAs) are small (∼19 to 21 nucleotides [nt] in length), noncoding RNAs, extremely stable and easily detectable in the plasma; thus, they have potential as biomarkers for diagnosing and monitoring human diseases. This study provides a comprehensive analysis of miRNAs circulating in plasma of dengue virus-infected patients and identifies the miRNA signatures that have biomarker potential for dengue infection and disease progression.

Correlation of altered expression of a long non-coding RNA, NEAT1, in peripheral blood mononuclear cells with dengue disease progression

The association of long non-coding RNAs (lncRNAs) with dengue disease progression is currently unknown. Therefore, the present study aimed to identify lncRNAs in different categories of dengue patients and evaluate their association with dengue disease progression. Herein, we examined the expression profiles of lncRNAs and protein-coding genes between other febrile illness (OFI) and different grade of dengue patients through high-throughput RNA sequencing. We identified Nuclear Enriched Abundant Transcript 1 (NEAT1) as one of the differentially expressed lncRNAs (adjusted P ≤ 0.05 and log-fold change ≥ 2) and subsequently validated the expression by qRT-PCR. The co-expression analysis further revealed that NEAT1 and the coding gene IFI27 were highly co-expressed and negatively correlated with dengue severity. Using regression analysis, we observed that NEAT1 expression was significantly dependent on disease progression (Coefficient = -0.27750, SE Coefficient = 0.07145, and t = -3.88).Further, receiver operating characteristic (ROC) curve revealed that NEAT1 expression could discriminate DI from DS (sensitivity and specificity of 100% (95%CI: 85.69 - 97.22) and area under the curve (AUC) = 0.97). Overall, the results of this study offer the first experimental evidence demonstrating the correlation between lncRNAs and severe dengue phenotype. Monitoring NEAT1and IFI27 expression in PBMC may be useful in understanding dengue virus-induced disease progression.

RNA-Seq analysis of peripheral blood mononuclear cells reveals unique transcriptional signatures associated with disease progression in dengue patients

Patients infected with Dengue virus usually present a mild, self-limiting febrile dengue infection (DI) that occasionally leads to a potentially lethal complication, called the severe dengue (DS). The ability to identify the prognostic markers of DS could allow an improved disease intervention and management. To identify the transcriptional signatures associated with the dengue disease progression, we carried out the high-throughput sequencing of the RNA isolated from the peripheral blood mononuclear cells (PBMCs) of the dengue patients of varying severity and compared with that in the patients with other febrile illnesses (OFIs) or the healthy controls. The transcriptional signatures that discriminated the DS patients from OFI and DI patients were broadly related to the pathways involving glycine, serine, and threonine metabolisms, extracellular matrix organization, ubiquitination, and cytokines and inflammatory response. Several upregulated genes in the inflammatory process (MPO, DEFA4, ELANE, AUZ1, CTSG, OLFM4, SLC16A14, and CRISP3) that were associated with the dengue disease progression are known to facilitate leukocyte-mediated migration, and neutrophil activation and degranulation process. High activity of MPO and ELANE in the plasma samples of the follow-up and recovered dengue patients, as well as and the presence of a larger amount of cell-free dsDNA in the DS patients, suggested an association of neutrophil-mediated immunity with dengue disease progression. Careful monitoring of some of these gene transcripts, and control of the activity of proteins encoded by them, may have a great translational significance for the prognosis and management of the dengue patients.