As a natural environment for human-microbiota interactions, healthy mucus houses a remarkably stable and diverse microbial community. Maintaining this microbiota is essential to human health, both to support the commensal bacteria that perform a wide array of beneficial functions and to prevent the outgrowth of pathogens. However, how the host selects and maintains a specialized microbiota remains largely unknown. In this viewpoint, we propose several strategies by which mucus may regulate the composition and function of the human microbiota and discuss how compromised mucus barriers in disease can give rise to microbial dysbiosis.
SARS‐CoV‐2 mortality has been extensively studied in relation to host susceptibility. How sequence variations in the SARS‐CoV‐2 genome affect pathogenicity is poorly understood. Starting in October 2020, using the methodology of genome‐wide association studies (GWAS), we looked at the association between whole‐genome sequencing (WGS) data of the virus and COVID‐19 mortality as a potential method of early identification of highly pathogenic strains to target for containment. Although continuously updating our analysis, in December 2020, we analyzed 7548 single‐stranded SARS‐CoV‐2 genomes of COVID‐19 patients in the GISAID database and associated variants with mortality using a logistic regression. In total, evaluating 29,891 sequenced loci of the viral genome for association with patient/host mortality, two loci, at 12,053 and 25,088 bp, achieved genome‐wide significance (p values of 4.09e−09 and 4.41e−23, respectively), though only 25,088 bp remained significant in follow‐up analyses. Our association findings were exclusively driven by the samples that were submitted from Brazil (p value of 4.90e−13 for 25,088 bp). The mutation frequency of 25,088 bp in the Brazilian samples on GISAID has rapidly increased from about 0.4 in October/December 2020 to 0.77 in March 2021. Although GWAS methodology is suitable for samples in which mutation frequencies varies between geographical regions, it cannot account for mutation frequencies that change rapidly overtime, rendering a GWAS follow‐up analysis of the GISAID samples that have been submitted after December 2020 as invalid. The locus at 25,088 bp is located in the P.1 strain, which later (April 2021) became one of the distinguishing loci (precisely, substitution V1176F) of the Brazilian strain as defined by the Centers for Disease Control. Specifically, the mutations at 25,088 bp occur in the S2 subunit of the SARS‐CoV‐2 spike protein, which plays a key role in viral entry of target host cells. Since the mutations alter amino acid coding sequences, they potentially imposing structural changes that could enhance viral infectivity and symptom severity. Our analysis suggests that GWAS methodology can provide suitable analysis tools for the real‐time detection of new more transmissible and pathogenic viral strains in databases such as GISAID, though new approaches are needed to accommodate rapidly changing mutation frequencies over time, in the presence of simultaneously changing case/control ratios. Improvements of the associated metadata/patient information in terms of quality and availability will also be important to fully utilize the potential of GWAS methodology in this field.
Simulating native mucus with model systems such as gels made from reconstituted mucin or commercially available polymers presents experimental advantages including greater sample availability and reduced inter- and intradonor heterogeneity. Understanding whether these gels reproduce the complex physical and biochemical properties of native mucus at multiple length scales is critical to building relevant experimental models, but few systematic comparisons have been reported. Here, we compared bulk mechanical properties, microstructure, and biochemical responses of mucus from different niches, reconstituted mucin gels (with similar pH and polymer concentrations as native tissues), and commonly used commercially available polymers. To evaluate gel properties across these length scales, we used small-amplitude oscillatory shear, single-particle tracking, and microaffinity chromatography with small analytes. With the exception of human saliva, the mechanical response of mucin gels was qualitatively similar to that of native mucus. The transport behavior of charged peptides through native mucus gels was qualitatively reproduced in gels composed of corresponding isolated mucins. Compared to native mucus, we observed substantial differences in the physicochemical properties of gels reconstituted from commercially available mucins and the substitute carboxymethylcellulose, which is currently used in artificial tear and saliva treatments. Our study highlights the importance of selecting a mucus model system guided by the length scale relevant to the scientific investigation or disease application.
Human microbiome composition is closely tied to health, but how the host manages its microbial inhabitants remains unclear. One important, but understudied, factor is the natural host environment: mucus, which contains gel-forming glycoproteins (mucins) that display hundreds of glycan structures with potential regulatory function. Leveraging a tractable culture-based system to study how mucins influence oral microbial communities, we found that mucin glycans enable the coexistence of diverse microbes, while resisting disease-associated compositional shifts. Mucins from tissues with unique glycosylation differentially tuned microbial composition, as did isolated mucin glycan libraries, uncovering the importance of specific glycan patterns in microbiome modulation. We found that mucins shape microbial communities in several ways: serving as nutrients to support metabolic diversity, organizing spatial structure through reduced aggregation, and possibly limiting antagonism between competing taxa. Overall, this work identifies mucin glycans as a natural host mechanism and potential therapeutic intervention to maintain healthy microbial communities.
Modulation of mucus production by the human ecto- and endo-cervical epithelium by steroid hormones and associated interactions with commensal microbiome play a central role in the physiology and pathophysiology of the female reproductive tract. However, most of our knowledge about these interactions is based on results from animal studies or in vitro models that fail to faithfully mimic the mucosal environment of the human cervix. Here we describe microfluidic organ-on-a-chip (Organ Chip) models of the human cervical mucosa that recreate the cervical epithelial-stromal interface with a functional epithelial barrier and produce abundant mucus that has compositional, biophysical, and hormone-responsive properties similar to the living cervix. Use of continuous fluid flow promoted ecto-cervical differentiation, whereas use of periodic flow including periods of stasis stimulated endo-cervical specialization. Similar results with minor differences were obtained using epithelial cells isolated from three donors each from a different ethnic background (African American, Hispanic, and Caucasian). When the endo-Cervix Chips were co-cultured with living Lactobacillus crispatus and Gardnerella vaginalis bacterial communities to respectively mimic the effects of human host interactions with optimal (healthy) or non-optimal (dysbiotic) microbiome, significant differences in tissue innate immune responses, barrier function, cell viability, and mucus composition were detected reminiscent of those observed in vivo. Thus, human Cervix Chips provide a physiologically relevant experimental in vitro model to study cervical mucus physiology and its role in human host-microbiome interactions as well as a potential preclinical testbed for development of therapeutic interventions to enhance women's health.
SARS-CoV-2 mortality has been extensively studied in relationship to a patient’s predisposition to the disease. However, how sequence variations in the SARS-CoV-2 genome affect mortality is not understood. To address this issue, we used a whole-genome sequencing (WGS) association study to directly link death of SARS-CoV-2 patients with sequence variation in the viral genome. Specifically, we analyzed 3,626 single stranded RNA-genomes of SARS-CoV-2 patients in the GISAID database (Elbe and Buckland-Merrett, 2017; Shu and McCauley, 2017) with reported patient’s health status from COVID-19, i.e. deceased versus non-deceased. In total, evaluating 28,492 loci of the viral genome for association with patient/host mortality, two loci, 12,053bp and 25,088bp, achieved genome-wide significance (p-values of 1.24e-12, and 1.24e-26, respectively). Mutations at 25,088bp occur in the S2 subunit of the SARS-CoV-2 spike protein, which plays a key role in viral entry of target host cells. Additionally, mutations at 12,053bp are within the ORF1ab gene, in a region encoding for the protein nsp7, which is necessary to form the RNA polymerase complex responsible for viral replication and transcription. Both mutations altered amino acid coding sequences, potentially imposing structural changes that could enhance viral infectivity and symptom severity, and may be important to consider as targets for therapeutic development.
SARS-CoV-2 mortality has been extensively studied in relationship to a patient's predisposition to the disease. However, how sequence variations in the SARS-CoV-2 genome affect mortality is not understood. To address this issue, we used a whole-genome sequencing (WGS) association study to directly link death of SARS-CoV-2 patients with sequence variation in the viral genome. Specifically, we analyzed 3,626 single stranded RNA-genomes of SARS-CoV-2 patients in the GISAID database (Elbe and Buckland-Merrett, 2017; Shu and McCauley, 2017) with reported patient’s health status from COVID-19, i.e. deceased versus non-deceased. In total, evaluating 28,492 loci of the viral genome for association with patient/host mortality, two loci, 12,053bp and 25,088bp, achieved genome-wide significance (p-values of 1.24e-12, and 1.24e-26, respectively). Mutations at 25,088bp occur in the S2 subunit of the SARS-CoV-2 spike protein, which plays a key role in viral entry of target host cells. Additionally, mutations at 12,053bp are within the ORF1ab gene, in a region encoding for the protein nsp7, which is necessary to form the RNA polymerase complex responsible for viral replication and transcription. Both mutations altered amino acid coding sequences, potentially imposing structural changes that could enhance viral infectivity and symptom severity, and may be important to consider as targets for therapeutic development.
Limited access to public health insurance may negatively impact patient care for migrant Australians particularly those in remote hospital settings. This may reflect language and other social barriers including not insignificantly, apprehension of cost and fear of subsequent reprisal. This case reports the experience of a 26-year-old Malaysian female who presented to an emergency department with suspicion of ectopic pregnancy. Background: Globally, Australia is a major immigration target. Population data from 2020 estimate over 7.6 million migrants currently living within our borders, with many in regional or remote rural centres [1]. Access to effective healthcare is often impacted by demographic and social challenges unique to this population which include affordability and economic limitations, cultural bias and vulnerability, language barriers and alienation from the Australian Medicare system [2]. The latter, a Commonwealth government program, provides Australian citizens and selected temporary visa holders, access to a wide range of health services including hospital and outpatient treatment, pharmaceuticals and diagnostic services without cost or with subsidy by way of the Medical Benefits Schedule [3]. Patients not able to share in this scheme, may be left isolated or unfairly biased when issues of health crisis or routine self-assessment arise. We present a case report of a 26-year-old female migrant of Malaysian origin, who presented acutely to a public hospital emergency department with suspected acute abdomen. She had limited understanding of English and had no Medicare entitlement. Whilst we were able to provide care for this young woman, our ability to do so was significantly hindered by these barriers, a dilemma not uncommon in remote rural practice. It highlights the inequalities of a healthcare system that at times can have little reserve or capacity to encompass the needs of patients with cultural or social demographics that may segregate or displace them from the general population. This is all the more poignant when it occurs in a setting of limited resource and vulnerability and it demonstrates the importance of shared language skills, compliance, and a culturally sensitive and inclusive healthcare environment.
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