Let Me Upgrade You: Impact of Mobile Genetic Elements on Enterococcal Adaptation and Evolution.

Enterococci are Gram-positive bacteria that have evolved to thrive as both commensals and pathogens, largely due to their accumulation of mobile genetic elements via horizontal gene transfer (HGT). Common agents of HGT include plasmids, transposable elements, and temperate bacteriophages. These vehicles of HGT have facilitated the evolution of the enterococci, specifically Enterococcus faecalis and Enterococcus faecium, into multidrug-resistant hospital-acquired pathogens. On the other hand, commensal strains of Enterococcus harbor CRISPR-Cas systems that prevent the acquisition of foreign DNA, restricting the accumulation of mobile genetic elements. In this review, we discuss enterococcal mobile genetic elements by highlighting their contributions to bacterial fitness, examine the impact of CRISPR-Cas on their acquisition, and identify key areas of research that can improve our understanding of enterococcal evolution and ecology.

Bacteriophage Resistance Alters Antibiotic-Mediated Intestinal Expansion of Enterococci.

Enterococcus faecalis is a human intestinal pathobiont with intrinsic and acquired resistance to many antibiotics, including vancomycin. Nature provides a diverse and virtually untapped repertoire of bacterial viruses, or bacteriophages (phages), that could be harnessed to combat multidrug-resistant enterococcal infections. Bacterial phage resistance represents a potential barrier to the implementation of phage therapy, emphasizing the importance of investigating the molecular mechanisms underlying the emergence of phage resistance. Using a cohort of 19 environmental lytic phages with tropism against E. faecalis, we found that these phages require the enterococcal polysaccharide antigen (Epa) for productive infection. Epa is a surface-exposed heteroglycan synthesized by enzymes encoded by both conserved and strain-specific genes. We discovered that exposure to phage selective pressure favors mutation in nonconserved epa genes both in culture and in a mouse model of intestinal colonization. Despite gaining phage resistance, epa mutant strains exhibited a loss of resistance to cell wall-targeting antibiotics. Finally, we show that an E. faecalisepa mutant strain is deficient in intestinal colonization, cannot expand its population upon antibiotic-driven intestinal dysbiosis, and fails to be efficiently transmitted to juvenile mice following birth. This study demonstrates that phage therapy could be used in combination with antibiotics to target enterococci within a dysbiotic microbiota. Enterococci that evade phage therapy by developing resistance may be less fit at colonizing the intestine and sensitized to vancomycin, preventing their overgrowth during antibiotic treatment.

Clinical interventions that influence vaginal birth after cesarean delivery rates: Systematic Review & Meta-Analysis.

BACKGROUND: To systematically review the literature on clinical interventions that influence vaginal birth after cesarean (VBAC) rates. METHODS: We searched Ovid Medline, Ovid Embase, Wiley Cochrane Library, CINAHL via EBSCOhost; and Ovid PsycINFO. Additional studies were identified by searching for clinical trial records, conference proceedings and dissertations. Limits were applied for language (English and French) and year of publication (1985 to present). Two reviewers independently screened comparative studies (randomized or non-randomized controlled trials, and observational designs) according to a priori eligibility criteria: women with prior cesarean sections; any clinical intervention or exposure intended to increase the VBAC rate; any comparator; and, outcomes reporting VBAC, uterine rupture and uterine dehiscence rates. One reviewer extracted data and a second reviewer verified for accuracy. Meta-analysis was conducted using Mantel-Haenszel (random effects model) relative risks (VBAC rate) and risk differences (uterine rupture and dehiscence). Two reviewers independently conducted methodological quality assessments using the Mixed Methods Appraisal Tool (MMAT). RESULTS: Twenty-nine studies (six trials and 23 cohorts) examined different clinical interventions affecting rates of vaginal deliveries among women with a prior cesarean delivery (CD). Methodological quality was good overall for the trials; however, concerns among the cohort studies regarding selection bias, comparability of groups and outcome measurement resulted in higher risk of bias. Interventions for labor induction, with or without cervical ripening, included pharmacologic (oxytocin, prostaglandins, misoprostol, mifepristone, epidural analgesia), non-pharmacologic (membrane sweep, amniotomy, balloon devices), and combined (pharmacologic and non-pharmacologic). Single studies with small sample sizes and event rates contributed to most comparisons, with no clear differences between groups on rates of VBAC, uterine rupture and uterine dehiscence. CONCLUSIONS: This systematic review evaluated clinical interventions directed at increasing the rate of vaginal delivery among women with a prior CD and found low to very low certainty in the body of evidence for cervical ripening and/or labor induction techniques. There is insufficient high-quality evidence to inform optimal clinical interventions among women attempting a trial of labor after a prior CD.

Gut Microbiome Composition Predicts Infection Risk During Chemotherapy in Children With Acute Lymphoblastic Leukemia.

Background: Myelosuppression-related infections remain important causes of morbidity and mortality in children with acute lymphoblastic leukemia (ALL). Methods: By analyzing fecal samples collected at diagnosis and after each of the initial 3 phases of chemotherapy, we evaluated the role of gut microbiota in predicting infections in 199 children with newly diagnosed ALL. The bacterial 16S rRNA gene was analyzed by high-depth sequencing to determine the diversity and composition of the microbiome. Results: After the induction and reinduction I phases of chemotherapy, microbial diversity decreased significantly relative to the prechemotherapy value. After chemotherapy, the relative abundance of certain bacterial taxa (eg, Bacteroidetes) decreased significantly, whereas that of other taxa (eg, Clostridiaceae and Streptococcaceae) increased. A baseline gut microbiome characterized by Proteobacteria predicted febrile neutropenia. Adjusting for the chemotherapy phase and ALL risk level, Enterococcaceae dominance (relative abundance ≥30%) predicted significantly greater risk of subsequent febrile neutropenia and diarrheal illness, whereas Streptococcaceae dominance predicted significantly greater risk of subsequent diarrheal illness. Conclusions: In children undergoing therapy for newly diagnosed ALL, the relative abundance of Proteobacteria before chemotherapy initiation predicts development of febrile neutropenia, and domination of the gut microbiota by Enterococcaceae or Streptococcaceae at any time during chemotherapy predicts infection in subsequent phases of chemotherapy. Clinical Trial Registration: NCT00549848.

A descriptive analysis of non-Cochrane child-relevant systematic reviews published in 2014.

BACKGROUND: Consumers, clinicians, policymakers and researchers require high quality evidence to guide decision-making in child health. Though Cochrane systematic reviews (SRs) are a well-established source of evidence, little is known about the characteristics of non-Cochrane child-relevant SRs. To complement published descriptions of Cochrane SRs, we aimed to characterize the epidemiologic, methodological, and reporting qualities of non-Cochrane child-relevant SRs published in 2014. METHODS: English-language child-relevant SRs of quantitative primary research published outside the Cochrane Library in 2014 were eligible for this descriptive analysis. A research librarian searched MEDLINE, CINAHL, Web of Science, and PubMed in August 2015. A single reviewer screened articles for inclusion; a second verified the excluded studies. Reviewers extracted: general characteristics of the review; included study characteristics; methodological approaches. We performed univariate analyses and presented the findings narratively. RESULTS: We identified 1598 child-relevant SRs containing a median (IQR) 19 (11, 33) studies. These originated primarily from high-income countries (n = 1247, 78.0%) and spanned 47 of the 53 Cochrane Review Groups. Most synthesized therapeutic (n = 753, 47.1%) or epidemiologic (n = 701, 43.8%) evidence. Though 39.3% (n = 628) of SRs included evidence related to children only, few were published in pediatric-specific journals (n = 283, 17.7%). Reporting quality seemed poor based on the items we assessed; few reviews mentioned an a-priori protocol (n = 246, 15.4%) or registration (n = 111, 6.9%), and only 23.4% (n = 374) specified a primary outcome. Many SRs relied solely on evidence from non-RCTs (n = 796, 49.8%). Less than two-thirds (n = 953, 59.6%) appraised the quality of included studies and assessments of the certainty of the body of evidence were rare (n = 102, 6.4%). CONCLUSIONS: Child-relevant Cochrane SRs are a known source of high quality evidence in pediatrics. There exists, however, an abundance of evidence from non-Cochrane SRs that may be complementary. Our findings show that high-quality non-Cochrane SRs may not be practical nor easy for knowledge users to find. Improvements are needed to ensure that evidence syntheses published outside of the Cochrane Library adhere to the high standard of conduct and reporting characteristic of Cochrane SRs.

Glucocorticoids for croup in children.

BACKGROUND: Glucocorticoids are commonly used for croup in children. This is an update of a Cochrane Review published in 1999 and previously updated in 2004 and 2011. OBJECTIVES: To examine the effects of glucocorticoids for the treatment of croup in children aged 0 to 18 years. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (the Cochrane Library, Issue 2, 2018), which includes the Cochrane Acute Respiratory Infections Group's Specialised Register, Ovid MEDLINE Epub Ahead of Print, In-Process & Other Non-Indexed Citations and Ovid MEDLINE (1946 to 3 April 2018), and Embase (Ovid) (1996 to 3 April 2018, week 14), and the trials registers ClinicalTrials.gov (3 April 2018) and the World Health Organization International Clinical Trials Registry Platform (ICTRP, 3 April 2018). We scanned the reference lists of relevant systematic reviews and of the included studies. SELECTION CRITERIA: We included randomised controlled trials (RCTs) that investigated children aged 0 to 18 years with croup and measured the effects of glucocorticoids, alone or in combination, compared to placebo or another pharmacologic treatment. The studies needed to report at least one of our primary or secondary outcomes: change in croup score; return visits, (re)admissions or both; length of stay; patient improvement; use of additional treatments; and adverse events. DATA COLLECTION AND ANALYSIS: One author extracted data from each study and another verified the extraction. We entered the data into Review Manager 5 for meta-analysis. Two review authors independently assessed risk of bias for each study using the Cochrane 'Risk of bias' tool and the certainty of the body of evidence for the primary outcomes using the GRADE approach. MAIN RESULTS: We added five new RCTs with 330 children. This review now includes 43 RCTs with a total of 4565 children. We assessed most (98%) studies as at high or unclear risk of bias. Compared to placebo, glucocorticoids improved symptoms of croup at two hours (standardised mean difference (SMD) -0.65, 95% confidence interval (CI) -1.13 to -0.18; 7 RCTs; 426 children; moderate-certainty evidence), and the effect lasted for at least 24 hours (SMD -0.86, 95% CI -1.40 to -0.31; 8 RCTs; 351 children; low-certainty evidence). Compared to placebo, glucocorticoids reduced the rate of return visits or (re)admissions or both (risk ratio 0.52, 95% CI 0.36 to 0.75; 10 RCTs; 1679 children; moderate-certainty evidence). Glucocorticoid treatment reduced the length of stay in hospital by about 15 hours (mean difference -14.90, 95% CI -23.58 to -6.22; 8 RCTs; 476 children). Serious adverse events were infrequent. Publication bias was not evident. Uncertainty remains with regard to the optimal type, dose, and mode of administration of glucocorticoids for reducing croup symptoms in children. AUTHORS' CONCLUSIONS: Glucocorticoids reduced symptoms of croup at two hours, shortened hospital stays, and reduced the rate of return visits to care. Our conclusions have changed, as the previous version of this review reported that glucocorticoids reduced symptoms of croup within six hours.

Adjunct clinical interventions that influence vaginal birth after cesarean rates: systematic review.

BACKGROUND: Rates of cesarean deliveries have been increasing, and contributes to the rising number of elective cesarean deliveries in subsequent pregnancies with associated maternal and neonatal risks. Multiple guidelines recommend that women be offered a trial of labor after a cesarean (TOLAC). The objective of the study is to systematically review the literature on adjunct clinical interventions that influence vaginal birth after cesarean (VBAC) rates. METHODS: We searched Ovid Medline, Ovid Embase, Wiley Cochrane Library, CINAHL via EBSCOhost; and Ovid PsycINFO. Additional studies were identified by searching for clinical trial records, conference proceedings and dissertations. Limits were applied for language (English and French) and year of publication (1985 to present). Two reviewers independently screened comparative studies (randomized or non-randomized controlled trials, and observational designs) according to a priori eligibility criteria: women with prior cesarean sections; any adjunct clinical intervention or exposure intended to increase the VBAC rate; any comparator; and, outcomes reporting changes in TOLAC or VBAC rates. One reviewer extracted data and a second reviewer verified for accuracy. Two reviewers independently conducted methodological quality assessments using the Mixed Methods Appraisal Tool (MMAT). RESULTS: Twenty-three studies of overall moderate to good methodological quality examined adjunct clinical interventions affecting TOLAC and/or VBAC rates: system-level interventions (three studies), provider-level interventions (three studies), guidelines or information for providers (seven studies), provider characteristics (four studies), and patient-level interventions (six studies). Provider-level interventions (opinion leader education, laborist, and obstetrician second opinion for cesarean sections) and provider characteristics (midwifery antenatal care, physicians on night float call schedules, and deliveries by family physicians) were associated with increased rates of VBAC. Few studies employing heterogeneous designs, sample sizes, interventions and comparators limited confidence in the effects. Studies of system-level and patient-level interventions, and guidelines/information for providers reported mixed findings. CONCLUSIONS: Limited evidence indicates some provider-level interventions and provider characteristics may increase rates of attempted and successful TOLACs and/or VBACs, whereas other adjunct clinical interventions such as system-level interventions, patient-level interventions, and guidelines/information for healthcare providers show mixed findings.

Convergent impact of vaccination and antibiotic pressures on pneumococcal populations.

Streptococcus pneumoniae is a remarkably adaptable and successful human pathogen, playing dual roles of both asymptomatic carriage in the nasopharynx and invasive disease including pneumonia, bacteremia, and meningitis. Efficacious vaccines and effective antibiotic therapies are critical to mitigating morbidity and mortality. However, clinical interventions can be rapidly circumvented by the pneumococcus by its inherent proclivity for genetic exchange. This leads to an underappreciated interplay between vaccine and antibiotic pressures on pneumococcal populations. Circulating populations have undergone dramatic shifts due to the introduction of capsule-based vaccines of increasing valency imparting strong selective pressures. These alterations in population structure have concurrent consequences on the frequency of antibiotic resistance profiles in the population. This review will discuss the interactions of these two selective forces. Understanding and forecasting the drivers of antibiotic resistance and capsule switching are of critical importance for public health, particularly for such a genetically promiscuous pathogen as S. pneumoniae.

Staphylococcus aureus oleate hydratase produces ligands that activate host PPARα.

Commensal gut bacteria use oleate hydratase to release a spectrum of hydroxylated fatty acids using host-derived unsaturated fatty acids. These compounds are thought to attenuate the immune response, but the underlying signaling mechanism(s) remain to be established. The pathogen Staphylococcus aureus also expresses an oleate hydratase and 10-hydroxyoctadecanoic acid (h18:0) is the most abundant oleate hydratase metabolite found at Staphylococcal skin infection sites. Here, we show h18:0 stimulates the transcription of a set of lipid metabolism genes associated with the activation of peroxisome proliferator activated receptor (PPAR) in the RAW 264.7 macrophage cell line and mouse primary bone marrow-derived macrophages. Cell-based transcriptional reporter assays show h18:0 selectively activates PPARα. Radiolabeling experiments with bone marrow-derived macrophages show [1-14C]h18:0 is not incorporated into cellular lipids, but is degraded by ß-oxidation, and mass spectrometry detected shortened fragments of h18:0 released into the media. The catabolism of h18:0 was >10-fold lower in bone marrow-derived macrophages isolated from Ppara -/- knockout mice, and we recover 74-fold fewer S. aureus cells from the skin infection site of Ppara -/- knockout mice compared to wildtype mice. These data identify PPARα as a target for oleate hydratase-derived hydroxy fatty acids and support the existence of an oleate hydratase-PPARα signaling axis that functions to suppress the innate immune response to S. aureus.

An enterococcal phage protein inhibits type IV restriction enzymes involved in antiphage defense.

The prevalence of multidrug resistant (MDR) bacterial infections continues to rise as the development of antibiotics needed to combat these infections remains stagnant. MDR enterococci are a major contributor to this crisis. A potential therapeutic approach for combating MDR enterococci is bacteriophage (phage) therapy, which uses lytic viruses to infect and kill pathogenic bacteria. While phages that lyse some strains of MDR enterococci have been identified, other strains display high levels of resistance and the mechanisms underlying this resistance are poorly defined. Here, we use a CRISPR interference (CRISPRi) screen to identify a genetic locus found on a mobilizable plasmid from Enterococcus faecalis involved in phage resistance. This locus encodes a putative serine recombinase followed by a Type IV restriction enzyme (TIV-RE) that we show restricts the replication of phage phi47 in vancomycin-resistant E. faecalis. We further find that phi47 evolves to overcome restriction by acquiring a missense mutation in a TIV-RE inhibitor protein. We show that this inhibitor, termed type IV restriction inhibiting factor A (tifA), binds and inactivates diverse TIV-REs. Overall, our findings advance our understanding of phage defense in drug-resistant E. faecalis and provide mechanistic insight into how phages evolve to overcome antiphage defense systems.

A 44-Nucleotide Region in the Chikungunya Virus 3' UTR Dictates Viral Fitness in Disparate Host Cells.

We previously reported that deletion of a 44-nucleotide element in the 3' untranslated region (UTR) of the Chikungunya virus (CHIKV) genome enhances the virulence of CHIKV infection in mice. Here, we find that while this 44-nucleotide deletion enhances CHIKV fitness in murine embryonic fibroblasts in a manner independent of the type I interferon response, the same mutation decreases viral fitness in C6/36 mosquito cells. Further, the fitness advantage conferred by the UTR deletion in mammalian cells is maintained in vivo in a mouse model of CHIKV dissemination. Finally, SHAPE-MaP analysis of the CHIKV 3' UTR revealed this 44-nucleotide element forms a distinctive two-stem-loop structure that is ablated in the mutant 3' UTR without altering additional 3' UTR RNA secondary structures.

Evolution of a small phage protein overcomes antiphage defense in Enterococcus faecalis.

The prevalence of multidrug resistant (MDR) bacterial infections continues to rise as the development of new antibiotics needed to combat these infections remains stagnant. MDR enterococci, which are a common cause of hospital-acquired infections, are emerging as one of the major contributors to this crisis. A potential therapeutic approach for combating MDR enterococci is bacteriophage (phage) therapy, which entails the use of lytic viruses to infect and kill pathogenic bacteria. While phages that lyse some strains of MDR enterococci have been identified, other strains display high levels of phage resistance and the mechanisms underlying this resistance are unknown. Here, we use a CRISPR interference (CRISPRi) screen to identify a genetic locus found on a mobilizable plasmid from vancomycin-resistant Enterococcus faecalis involved in phage resistance. This locus encodes a putative serine recombinase followed by a Type IV restriction enzyme (TIV-RE) and we show that this enzyme is sufficient to restrict the replication of the lytic phage in E. faecalis. We further find that phages can evolve to overcome restriction by acquiring a missense mutation in a novel TIV-RE inhibitor protein encoded by many enterococcal phages. We show that this inhibitor, which we have named anti-restriction-factor A (arfA), directly binds to and inactivates diverse TIV-REs. Overall, our findings significantly advance our understanding of phage defense in drug-resistant E. faecalis and provide mechanistic insight into how phages can evolve to overcome antiphage defense systems.

Genetically distant bacteriophages select for unique genomic changes in Enterococcus faecalis.

The human microbiota harbors diverse bacterial and bacteriophage (phage) communities. Bacteria evolve to overcome phage infection, thereby driving phage evolution to counter bacterial resistance. Understanding how phages select for genetic alterations in medically relevant bacteria is important as phages become established biologics for the treatment of multidrug-resistant (MDR) bacterial infections. Before phages can be widely used as standalone or combination antibacterial therapies, we must obtain a deep understanding of the molecular mechanisms of phage infection and how host bacteria alter their genomes to become resistant. We performed coevolution experiments using a single Enterococcus faecalis strain and two distantly related phages to determine how phage pressure impacts the evolution of the E. faecalis genome. Whole-genome sequencing of E. faecalis following continuous exposure to these two phages revealed mutations previously demonstrated to be essential for phage infection. We also identified mutations in genes previously unreported to be associated with phage infection in E. faecalis. Intriguingly, there was only one shared mutation in the E. faecalis genome that was selected by both phages tested, demonstrating that infection by two genetically distinct phages selects for diverse variants. This knowledge serves as the basis for the continued study of E. faecalis genome evolution during phage infection and can be used to inform the design of future therapeutics, such as phage cocktails, intended to target MDR E. faecalis.

Technology-assisted title and abstract screening for systematic reviews: a retrospective evaluation of the Abstrackr machine learning tool.

BACKGROUND: Machine learning tools can expedite systematic review (SR) processes by semi-automating citation screening. Abstrackr semi-automates citation screening by predicting relevant records. We evaluated its performance for four screening projects. METHODS: We used a convenience sample of screening projects completed at the Alberta Research Centre for Health Evidence, Edmonton, Canada: three SRs and one descriptive analysis for which we had used SR screening methods. The projects were heterogeneous with respect to search yield (median 9328; range 5243 to 47,385 records; interquartile range (IQR) 15,688 records), topic (Antipsychotics, Bronchiolitis, Diabetes, Child Health SRs), and screening complexity. We uploaded the records to Abstrackr and screened until it made predictions about the relevance of the remaining records. Across three trials for each project, we compared the predictions to human reviewer decisions and calculated the sensitivity, specificity, precision, false negative rate, proportion missed, and workload savings. RESULTS: Abstrackr's sensitivity was > 0.75 for all projects and the mean specificity ranged from 0.69 to 0.90 with the exception of Child Health SRs, for which it was 0.19. The precision (proportion of records correctly predicted as relevant) varied by screening task (median 26.6%; range 14.8 to 64.7%; IQR 29.7%). The median false negative rate (proportion of records incorrectly predicted as irrelevant) was 12.6% (range 3.5 to 21.2%; IQR 12.3%). The workload savings were often large (median 67.2%, range 9.5 to 88.4%; IQR 23.9%). The proportion missed (proportion of records predicted as irrelevant that were included in the final report, out of the total number predicted as irrelevant) was 0.1% for all SRs and 6.4% for the descriptive analysis. This equated to 4.2% (range 0 to 12.2%; IQR 7.8%) of the records in the final reports. CONCLUSIONS: Abstrackr's reliability and the workload savings varied by screening task. Workload savings came at the expense of potentially missing relevant records. How this might affect the results and conclusions of SRs needs to be evaluated. Studies evaluating Abstrackr as the second reviewer in a pair would be of interest to determine if concerns for reliability would diminish. Further evaluations of Abstrackr's performance and usability will inform its refinement and practical utility.

Screening for chlamydia and/or gonorrhea in primary health care: protocol for systematic review.

BACKGROUND: Chlamydia trachomatis and Neisseria gonorrhoeae are the most commonly reported sexually transmitted infections in Canada. Existing national guidance on screening for these infections was not based on a systematic review, and recommendations as well as implementation considerations (e.g., population groups, testing and case management) should be explicit and reflect the quality of evidence. The aim of this systematic review is to synthesize research on screening for these infections in sexually active individuals within primary care. We will also review evidence on how people weigh the relative importance of the potential outcomes from screening, rated as most important by the Canadian Task Force on Preventive Health Care (CTFPHC) with input from patients and stakeholders. METHODS: We have developed a peer-reviewed strategy to comprehensively search MEDLINE, Embase, Cochrane Library, CINAHL, and PsycINFO for English and French literature published 1996 onwards. We will also search trial registries and conference proceedings, and mine references lists. Screening, study selection, risk of bias assessments, and quality of findings across studies (for each outcome) will be independently undertaken by two reviewers with consensus for final decisions. Data extraction will be conducted by one reviewer and checked by another for accuracy and completeness. The CTFPHC and content experts will provide input for decisions on study design (i.e., when and whether to include uncontrolled studies for screening effectiveness) and for interpretation of the findings. DISCUSSION: The results section of the review will include a description of all studies, results of all analyses, including planned subgroup and sensitivity analyses, and evidence profiles and summary of findings tables incorporating assessment based on Grading of Recommendations Assessment, Development and Evaluation (GRADE) methods to communicate our confidence in the estimates of effect. We will compare our findings to others and discuss limitations of the review and available literature. The findings will be used by the CTFPHC-supplemented by consultations with patients and stakeholders and from other sources on issues of feasibility, acceptability, costs/resources, and equity-to inform recommendations on screening to support primary health care providers in delivering preventive care. SYSTEMATIC REVIEW REGISTRATION: International Prospective Register of Systematic Reviews (PROSPERO), registration number CRD42018100733.

Astrovirus Pathogenesis.

Astroviruses are a major cause of diarrhea in the young, elderly, and the immunocompromised. Since the discovery of human astrovirus type 1 (HAstV-1) in 1975, the family Astroviridae has expanded to include two more human clades and numerous mammalian and avian-specific genotypes. Despite this, there is still little known about pathogenesis. The following review highlights the current knowledge of astrovirus pathogenesis, and outlines the critical steps needed to further astrovirus research, including the development of animal models of cell culture systems.

Astrovirus Biology and Pathogenesis.

Astroviruses are nonenveloped, positive-sense single-stranded RNA viruses that cause gastrointestinal illness. Although a leading cause of pediatric diarrhea, human astroviruses are among the least characterized enteric RNA viruses. However, by using in vitro methods and animal models to characterize virus-host interactions, researchers have discovered several important properties of astroviruses, including the ability of the astrovirus capsid to act as an enterotoxin, disrupting the gut epithelial barrier. Improved animal models are needed to study this phenomenon, along with the pathogenesis of astroviruses, particularly in those strains that can cause extraintestinal disease. Much like for other enteric viruses, the current dogma states that astroviruses infect in a species-specific manner; however, this assumption is being challenged by growing evidence that these viruses have potential to cross species barriers. This review summarizes these remarkable facets of astrovirus biology, highlighting critical steps toward increasing our understanding of this unique enteric pathogen.

Obesity Outweighs Protection Conferred by Adjuvanted Influenza Vaccination.

UNLABELLED: Obesity is a risk factor for developing severe influenza virus infection, making vaccination of utmost importance for this high-risk population. However, vaccinated obese animals and adults have decreased neutralizing antibody responses. In these studies, we tested the hypothesis that the addition of either alum or a squalene-based adjuvant (AS03) to an influenza vaccine would improve neutralizing antibody responses and protect obese mice from challenge. Our studies demonstrate that adjuvanted vaccine does increase both neutralizing and nonneutralizing antibody levels compared to vaccine alone. Although obese mice mount significantly decreased virus-specific antibody responses, both the breadth and the magnitude of the responses against hemagglutinin (HA) and neuraminidase (NA) are decreased compared to the responses in lean mice. Importantly, even with a greater than fourfold increase in neutralizing antibody levels, obese mice are not protected against influenza virus challenge and viral loads remain elevated in the respiratory tract. Increasing the antigen dose affords no added protection, and a decreasing viral dose did not fully mitigate the increased mortality seen in obese mice. Overall, these studies highlight that, while the use of an adjuvant does improve seroconversion, vaccination does not fully protect obese mice from influenza virus challenge, possibly due to the increased sensitivity of obese animals to infection. Given the continued increase in the global obesity epidemic, our findings have important implications for public health. IMPORTANCE: Vaccination is the most effective strategy for preventing influenza virus infection and is a key component for pandemic preparedness. However, vaccines may fail to provide optimal protection in high-risk groups, including overweight and obese individuals. Given the worldwide obesity epidemic, it is imperative that we understand and improve vaccine efficacy. No work to date has investigated whether adjuvants increase the protective capacity of influenza vaccines in the obese host. In these studies, we show that adjuvants increased the neutralizing and nonneutralizing antibody responses during vaccination of lean and obese mice to levels considered "protective," and yet, obese mice still succumbed to infection. This vulnerability is likely due to a combination of factors, including the increased susceptibility of obese animals to develop severe and even lethal disease when infected with very low viral titers. Our studies highlight the critical public health need to translate these findings and better understand vaccination in this increasing population.