Understanding the microbial basis of body odor in pre-pubescent children and teenagers.

BACKGROUND: Even though human sweat is odorless, bacterial growth and decomposition of specific odor precursors in it is believed to give rise to body odor in humans. While mechanisms of odor generation have been widely studied in adults, little is known for teenagers and pre-pubescent children who have distinct sweat composition from immature apocrine and sebaceous glands, but are arguably more susceptible to the social and psychological impact of malodor. RESULTS: We integrated information from whole microbiome analysis of multiple skin sites (underarm, neck, and head) and multiple time points (1 h and 8 h after bath), analyzing 180 samples in total to perform the largest metagenome-wide association study to date on malodor. Significant positive correlations were observed between odor intensity and the relative abundance of Staphylococcus hominis, Staphylococcus epidermidis, and Cutibacterium avidum, as well as negative correlation with Acinetobacter schindleri and Cutibacterium species. Metabolic pathway analysis highlighted the association of isovaleric and acetic acid production (sour odor) from enriched S. epidermidis (teen underarm) and S. hominis (child neck) enzymes and sulfur production from Staphylococcus species (teen underarm) with odor intensity, in good agreement with observed odor characteristics in pre-pubescent children and teenagers. Experiments with cultures on human and artificial sweat confirmed the ability of S. hominis and S. epidermidis to independently produce malodor with distinct odor characteristics. CONCLUSIONS: These results showcase the power of skin metagenomics to study host-microbial co-metabolic interactions, identifying distinct pathways for odor generation from sweat in pre-pubescent children and teenagers and highlighting key enzymatic targets for intervention.

Influenza A Virus Facilitates Its Infectivity by Activating p53 to Inhibit the Expression of Interferon-Induced Transmembrane Proteins.

Human influenza virus (IAV) are among the most common pathogens to cause human respiratory infections. A better understanding on interplay between IAV and host factors may provide clues for disease prevention and control. While many viruses are known to downregulate p53 upon entering the cell to reduce the innate host antiviral response, IAV infection is unusual in that it activates p53. However, it has not been clear whether this process has proviral or antiviral effects. In this study, using human isogenic p53 wild-type and p53null A549 cells generated from the CRISPR/Cas9 technology, we observed that p53null cells exhibit significantly reduced viral propagation when infected with influenza A virus (strain A/Puerto Rico/8/1934 H1N1). Genome-wide microarray analysis revealed that p53 regulates the expression of a large set of interferon-inducible genes, among which the interferon-induced transmembrane family members IFITM1, IFITM2, and IFITM3 were most significantly downregulated by the expression of p53. Knockdown of interferon-induced transmembrane proteins (IFITMs) by short interfering RNAs enhanced influenza virus infectivity in p53null A549 cells, while overexpressed IFITMs in A549 cells blocked virus entry. Intriguingly, regulation of IFITMs by p53 is independent of its transcriptional activity, as the p53 short isoform Δ40p53 recapitulates IFITM regulation. Taken together, these data reveal that p53 activation by IAV is an essential step in maintaining its infectivity. This novel association between human p53 and the broad spectrum antiviral proteins, the IFITMs, demonstrates a previous mechanism employed by influenza virus to enhance its propagation via p53 inhibition of IFITMs.

Identification of Slug and SOX7 as transcriptional repressors binding to the hepatitis B virus core promoter.

BACKGROUND & AIMS: The Hepatitis B Virus (HBV) may gain entry into non-liver cells but does not actively replicate in them. We investigated the possibility that these cells possess mechanisms that block HBV core promoter (HBVCP) transcription, specifically absent in liver cells, which together with other liver-specific mechanisms, such as sodium-taurocholate cotransporting polypeptide-mediated entry, enable liver cells to effectively produce HBV. METHODS: Liver and non-liver cell lines were screened for their capacity to activate the HBVCP and synthesize pre-genomic RNA (pgRNA). Transcription regulators differentially expressed between cells with active or inactive HBVCP were determined by human transcriptome array. Slug (SNAI2) and SRY-related HMG box 7 (SOX7) transcriptional repressors were identified and shown to bind specifically to the HBVCP by electrophoretic mobility shift assay. The resultant inhibitory effect on HBVCP transcription was validated using luciferase reporter and assays for pgRNA, HBcAg and cccDNA accumulation in cells with HBV replicon and HBV infection models. To further confirm their specific activity, short peptide mimetics generated from Slug zinc-finger domains and SOX7 HMG-box were generated. RESULTS: The HBVCP was found to be active in liver and selected non-liver cells. These cells have low/negligible expression of Slug and SOX7, which inhibit HBVCP transcription specifically by binding at the pgRNA initiator site and competitively displacing hepatocyte nuclear factor 4α, respectively. Overexpression of Slug and/or SOX7 specifically reduced HBVCP transcription, significantly diminishing pgRNA synthesis, HBcAg and cccDNA accumulation in HBV-infected primary human hepatocytes. Similar results were obtained with Slug and SOX7 stapled peptides individually, which were even more potent in combination. CONCLUSIONS: Slug and SOX7 are transcriptional repressors that bind specifically to the HBVCP. Their absence or weak expression in liver cells contribute to the favorable host environment for the active and efficient production of HBV. LAY SUMMARY: Hepatitis B virus (HBV) replication occurs efficiently in human liver because of the specificity of viral uptake receptors and presence of numerous liver-enriched transcription activators. Herein, we show that the specific lack of transcriptional inhibitory mechanisms in liver cells also contribute to effective HBV production. HBV replication is kept low in non-liver cells as transcriptional repressors Slug and SRY-related HMG box 7 (SOX7) actively bind to the transcriptional initiator and displace transcription activators, respectively, within the HBV core promoter.

Unique Allelic eQTL Clusters in Human MHC Haplotypes.

The control of gene regulation within the major histocompatibility complex (MHC) remains poorly understood, despite several expression quantitative trait loci (eQTL) studies revealing an association of MHC gene expression with independent tag-single nucleotide polymorphisms (SNPs). MHC haplotype variation may exert a greater effect on gene expression phenotype than specific single variants. To explore the effect of MHC haplotype sequence diversity on gene expression phenotypes across the MHC, we examined the MHC transcriptomic landscape at haplotype-specific resolution for three prominent MHC haplotypes (A2-B46-DR9, A33-B58-DR3, and A1-B8-DR3) derived from MHC-homozygous B-lymphoblastoid cell lines (B-LCLs). We demonstrate that MHC-wide gene expression patterns are dictated by underlying haplotypes, and identify 36 differentially expressed genes. By mapping these haplotype sequence variations to known eQTL, we provide evidence that unique allelic combinations of eQTL, embedded within haplotypes, are correlated with the level of expression of 17 genes. Interestingly, the influence of haplotype sequence on gene expression is not homogenous across the MHC. We show that haplotype sequence polymorphisms within or proximate to HLA-A, HLA-C, C4A, and HLA-DRB regions exert haplotype-specific gene regulatory effects, whereas the expression of genes in other parts of the MHC region are not affected by the haplotype sequence. Overall, we demonstrate that MHC haplotype sequence diversity can impact phenotypic outcome via the alteration of transcriptional variability, indicating that a haplotype-based approach is fundamental for the assessment of trait associations in the MHC.

Intrahaplotypic Variants Differentiate Complex Linkage Disequilibrium within Human MHC Haplotypes.

Distinct regions of long-range genetic fixation in the human MHC region, known as conserved extended haplotypes (CEHs), possess unique genomic characteristics and are strongly associated with numerous diseases. While CEHs appear to be homogeneous by SNP analysis, the nature of fine variations within their genomic structure is unknown. Using multiple, MHC-homozygous cell lines, we demonstrate extensive sequence conservation in two common Asian MHC haplotypes: A33-B58-DR3 and A2-B46-DR9. However, characterization of phase-resolved MHC haplotypes revealed unique intra-CEH patterns of variation and uncovered 127 single nucleotide variants (SNVs) which are missing from public databases. We further show that the strong linkage disequilibrium structure within the human MHC that typically confounds precise identification of genetic features can be resolved using intra-CEH variants, as evidenced by rs3129063 and rs448489, which affect expression of ZFP57, a gene important in methylation and epigenetic regulation. This study demonstrates an improved strategy that can be used towards genetic dissection of diseases.

CLEVER: A general design tool for combinatorial libraries.

CLEVER is a computational tool designed to support the creation, manipulation, enumeration, and visualization of combinatorial libraries. The system also provides a summary of the diversity, coverage, and distribution of selected compound collections. When deployed in conjunction with large-scale virtual screening campaigns, CLEVER can offer insights into what chemical compounds to synthesize, and, more importantly, what not to synthesize. In this chapter, we describe how CLEVER is used and offer advice in interpreting the results.

TAP Hunter: a SVM-based system for predicting TAP ligands using local description of amino acid sequence.

BACKGROUND: Selective peptide transport by the transporter associated with antigen processing (TAP) represents one of the main candidate mechanisms that may regulate the presentation of antigenic peptides to HLA class I molecules. Because TAP-binding preferences may significant impact T-cell epitope selection, there is great interest in applying computational techniques to systematically discover these elements. RESULTS: We describe TAP Hunter, a web-based computational system for predicting TAP-binding peptides. A novel encoding scheme, based on representations of TAP peptide fragments and composition effects, allows the identification of variable-length TAP ligands using SVM as the prediction engine. The system was rigorously trained and tested using 613 experimentally verified peptide sequences. The results showed that the system has good predictive ability with area under the receiver operating characteristics curve (AROC) ≥0.88. In addition, TAP Hunter is compared against several existing public available TAP predictors and has showed either superior or comparable performance. CONCLUSIONS: TAP Hunter provides a reliable platform for predicting variable length peptides binding onto the TAP transporter. To facilitate the usage of TAP Hunter to the scientific community, a simple, flexible and user-friendly web-server is developed and freely available at http://datam.i2r.a-star.edu.sg/taphunter/.