Unstable EBV latency drives inflammation in multiple sclerosis patient derived spontaneous B cells

Epidemiological studies have demonstrated that Epstein-Barr virus (EBV) is a known etiologic risk factor, and perhaps prerequisite, for the development of MS. EBV establishes life-long latent infection in a subpopulation of memory B cells. Although the role of memory B cells in the pathobiology of MS is well established, studies characterizing EBV-associated mechanisms of B cell inflammation and disease pathogenesis in EBV (+) B cells from MS patients are limited. Accordingly, we analyzed spontaneous lymphoblastoid cell lines (SLCLs) from multiple sclerosis patients and healthy controls to study host-virus interactions in B cells, in the context of an individual's endogenous EBV. We identify differences in EBV gene expression and regulation of both viral and cellular genes in SLCLs. Our data suggest that EBV latency is dysregulated in MS SLCLs with increased lytic gene expression observed in MS patient B cells, especially those generated from samples obtained during "active" disease. Moreover, we show increased inflammatory gene expression and cytokine production in MS patient SLCLs and demonstrate that tenofovir alafenamide, an antiviral that targets EBV replication, decreases EBV viral loads, EBV lytic gene expression, and EBV-mediated inflammation in both SLCLs and in a mixed lymphocyte assay. Collectively, these data suggest that dysregulation of EBV latency in MS drives a pro-inflammatory, pathogenic phenotype in memory B cells and that this response can be attenuated by suppressing EBV lytic activation. This study provides further support for the development of antiviral agents that target EBV-infection for use in MS.

Comparison of tracheal aspirate and bronchoalveolar lavage samples in the microbiological diagnosis of lower respiratory tract infection in pediatric patients

BACKGROUND

Bacterial cultures from tracheal aspirates (TA) and bronchoalveolar lavage (BAL) specimens can be used to assess patients with artificial airways for lower respiratory tract infections (LRTI). TA collection may be advantageous in situations of limited resources or critical illness. Literature comparing these diagnostic modalities in pediatric populations is scarce.

METHODS

Single-center, retrospective analysis of 52 pediatric patients with an artificial airway undergoing evaluation for LRTI. All patients had a TA specimen collected for semiquantitative Gram stain and culture followed by BAL within 48 h. Microbiologic diagnosis of LRTI was defined as a BAL sample with >25% neutrophils and growth of >104 colony-forming units/ml of one or more bacterial species. The test characteristics of TA were compared with these BAL results as the reference standard. Concordance in microorganism identification was also assessed.

RESULTS

Overall, 24 patients (47%) met criteria for LRTI using BAL as the diagnostic standard. TA samples positive for an isolated organism had poor sensitivity for acute LRTI when compared with BAL, regardless of semiquantitative white blood cell (WBC) count by Gram stain. Using a TA diagnostic threshold of organism growth and at least "moderate" WBC yielded a specificity of 93%. Positive predictive value was highest when an organism was identified by TA. Negative predictive value was >70% for TA samples with no WBC by semiquantitative analysis, with or without growth of an organism. Complete concordance of cultured species was 58% for all patients, with a higher rate seen among those with endotracheal tubes.

CONCLUSIONS

The role of cultures obtained by TA remains limited for the diagnosis of acute LRTI as demonstrated by the poor correlation to BAL results within our cohort. Optimal strategies for diagnosing LRTI across patient populations and airway types remain elusive.

Arresting microbiome development limits immune system maturation and resistance to infection

The transition from milk to solid food is a critical period in post-natal human development. Weaning coincides with a dramatic and rapid maturation of both the microbiome and immune system. Whether these weaning induced changes in commensal communities shape immune system development and susceptibility to enteric infection remains unknown. Here we find maturation of the microbiome during weaning is required for proper immune system development and protection against enteric infection. To this end, we developed a stable gnotobiotic mouse model of the early-life microbiome composed of a representative nine-member consortium of phylogenetically diverse microbes found pre-weaning, designated as Pediatric Community (PedsCom). PedsCom efficiently colonized germfree adult mice and was vertically transmitted to offspring. Unexpectedly, the composition of PedsCom was unaffected by the transition from a milk-based to a fiber rich solid food diet. This permitted us to study adult mice with a pre-weaning intestinal microbiome. We find that arresting intestinal microbiome maturation in PedsCom mice limited immune system development. PedsCom mice displayed decreased both peripheral regulatory T cells accumulation and Immunoglobulin A production, hallmarks of microbiota-driven immune development. Consistent with defects in maturation, adult PedsCom mice retain high susceptibility to Salmonella infection characteristic of young mice and humans. Altogether, our work illustrates how the post-weaning transition in intestinal microbiome composition is essential for normal immune maturation, and protection from enteric infection.

Supported by 1R21AI146629-01A1

CFTR-PTEN-dependent mitochondrial metabolic dysfunction promotes Pseudomonas aeruginosa airway infection

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is a tumor suppressor best known for regulating cell proliferation and metabolism. PTEN forms a complex with the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) at the plasma membrane, and this complex is known to be functionally impaired in CF. Here, we demonstrated that the combined effect of PTEN and CFTR dysfunction stimulates mitochondrial activity, resulting in excessive release of succinate and reactive oxygen species. This environment promoted the colonization of the airway by Pseudomonas aeruginosa, bacteria that preferentially metabolize succinate, and stimulated an anti-inflammatory host response dominated by immune-responsive gene 1 (IRG1) and itaconate. The recruitment of myeloid cells induced by these strains was inefficient in clearing the infection and increased numbers of phagocytes accumulated under CFTR-PTEN axis dysfunction. This central metabolic defect in mitochondrial function due to impaired PTEN activity contributes to P. aeruginosa infection in CF.

A horizontally gene transferred copper resistance locus enables survival of community acquired methicillin resistant Staphylococcus aureus USA300 in host cells

The spread of community acquired, methicillin resistant Staphylococcus aureus (CA-MRSA) is an increasing problem seen outside the healthcare setting. One such strain, CA-MRSA USA300, is epidemic in the United States. USA300 shows a heightened resistance to the innate immune system, in particular to macrophage engulfment. Two horizontally acquired genes, encoding an efflux pump (CopX) and lipoprotein (CopL), were discovered in 2 different lineages of USA300, representing CA-MRSA epidemics in North and South America. Removal of either of these genes resulted in elevated copper concentrations in the cytoplasm of S. aureus, implying a function in copper hyper-resistance. While copper is an essential part of metabolic machinery, it is toxic at high concentrations and is utilised by macrophages to kill bacteria in the phagosome. Supporting this, USA300 with functional copXL genes showed increased survival in macrophages compared to their copXL negative counterparts. Although the role of CopX as an efflux pump explains the rise in intracellular copper concentration upon its mutation, the role of the CopL lipoprotein is still unknown. Therefore, to better understand the function of CopL and how it might influence S. aureus host interaction, transcriptomic analysis is underway to identify downstream targets. This has the potential to uncover an exciting mechanism linking metal resistance to host virulence.

Asymptomatic Summertime Shedding of Respiratory Viruses

To determine rates of both symptomatic and asymptomatic infection among ambulatory adults, we collected nasopharyngeal swab specimens, demographic characteristics, and survey information from 1477 adult visitors to a New York City tourist attraction during April–July 2016. Multiplex polymerase chain reaction analysis was used to identify specimens positive for common respiratory viruses. A total of 7.2% of samples tested positive for respiratory viruses; among positive samples, 71.0% contained rhinovirus, and 21.5% contained coronavirus. Influenza virus, respiratory syncytial virus, and parainfluenza virus were also detected. Depending on symptomatologic definition, 57.7%–93.3% of positive samples were asymptomatic. These findings indicate that significant levels of asymptomatic respiratory viral shedding exist during summer among the ambulatory adult population.

1232. Phylogenomics of Enterococcus faecium From South America: Revisiting Worldwide VRE Population Structure

Background

Previous studies have suggested that the population structure of E. faecium is composed of two main clades; a commensal clade (designated clade B) and a hospital-associated clade (Clade A) that encompass most of the clinical and animal isolates. The phylogenetic analyses leading to these results have been accomplished with the notable absence of isolates from diverse geographical regions (including South America). We aimed to refine the worldwide population structure of E. faecium by including 55 representative genomes from isolates obtained from five Latin American countries recovered between 1998 and 2014.

Methods

We sequenced our 55 representative isolates and selected other 285 genomes, from public databases, obtained across different regions (36 countries), different sources (animal, commensal, and clinical strains) and a wide range of dates of isolation (1946–2017). We characterized the genomes by presence/absence of resistance, virulence and mobile elements, and of CRISPR-cas systems. We analyzed the phylogeny of the entire population, selected the genomes belonging to clade A to examine recombination patterns and performed Bayesian molecular clock analysis excluding recombinant regions.

Results

Two major clades were identified, as previously reported. However, a higher degree of variation in clade A was found. Indeed, we identified a subclade (subclade I) that diverged ~894 years ago, and clearly distinguished clinical isolates from those of animal origin (distributed among a number of smaller early-branching subclades). A further split within the clinical subclade (subclade II) that diverged around ~371 years ago was also evident. Latin American isolates were distributed within subclades I (48%) and II (42%). Isolates in “animal” branches exhibited an average recombination of 34 Kbp, where it was 5 Kbp and 21 Kbp for subclades I and II, respectively. More resistance determinants were found in subclade II (62%), followed by I (54%) and absence of cas was the norm in the clinical subclades.

Conclusion

Inclusion of E. faecium isolates from diverse geographical region supports a continuous evolution of these organisms causing human infections. Important evolutionary events seem to favor emergence of novel subclades capable to cause important morbidity and mortality.

Disclosures

J. Munita, Pfizer: Grant Investigator, Research grant. C. Arias, Merck & Co., Inc.: Grant Investigator, Research support. MeMed: Grant Investigator, Research support. Allergan: Grant Investigator, Research support.

625. Metabolic Interactions Drive Staphylococcus aureus Adaptation to the Skin

Background

Methods

Results

Conclusion

Disclosures

Mycobacterium tuberculosis Infection among Asian Elephants in Captivity

Although awareness of tuberculosis among captive elephants is increasing, antituberculosis therapy for these animals is not standardized. We describe Mycobacterium tuberculosis transmission between captive elephants based on whole genome analysis and report a successful combination treatment. Infection control protocols and careful monitoring of treatment of captive elephants with tuberculosis are warranted.

Bacterial neuraminidase facilitates mucosal infection by participating in biofilm production

Many respiratory pathogens, including Hemophilus influenzae, Streptococcus pneumoniae, and Pseudomonas aeruginosa, express neuraminidases that can cleave alpha2,3-linked sialic acids from glycoconjugates. As mucosal surfaces are heavily sialylated, neuraminidases have been thought to modify epithelial cells by exposing potential bacterial receptors. However, in contrast to neuraminidase produced by the influenza virus, a role for bacterial neuraminidase in pathogenesis has not yet been clearly established. We constructed a mutant of P. aeruginosa PAO1 by deleting the PA2794 neuraminidase locus (Delta2794) and tested its virulence and immunostimulatory capabilities in a mouse model of infection. Although fully virulent when introduced i.p., the Delta2794 mutant was unable to establish respiratory infection by i.n. inoculation. The inability to colonize the respiratory tract correlated with diminished production of biofilm, as assessed by scanning electron microscopy and in vitro assays. The importance of neuraminidase in biofilm production was further demonstrated by showing that viral neuraminidase inhibitors in clinical use blocked P. aeruginosa biofilm production in vitro as well. The P. aeruginosa neuraminidase has a key role in the initial stages of pulmonary infection by targeting bacterial glycoconjugates and contributing to the formation of biofilm. Inhibiting bacterial neuraminidases could provide a novel mechanism to prevent bacterial pneumonia.

Detection and characterization of the African citrus greening liberobacter by amplification, cloning, and sequencing of the rplKAJL-rpoBC operon

Greening disease of citrus is caused by a phloem-restricted, uncultured bacterium, recently characterized and named Liberobacter. As shown previously, a probe encoding ribosomal protein genes (rplKAJL-rpoBC operon) from an Asian liberobacter could detect all Asian liberobacter strains tested, but not African strains. Using the sequence of the rplKAJL-rpoBC operon of the Asian liberobacter strain from Poona (India), we have defined primers for PCR amplification of the equivalent genes of an African liberobacter strain. The amplified fragment was cloned in pUC18 and successfully used as a probe to detect African liberobacter strains by Southern and dot hybridizations. Sequence comparisons of the African and Asian liberobacter operons indicate that they represent two different species in the proposed genus Liberobacter.