Ylva Kai-Larsen

Uropathogenic Escherichia coli Modulates Immune Responses and Its Curli Fimbriae Interact with the Antimicrobial Peptide LL-37

Bacterial growth in multicellular communities, or biofilms, offers many potential advantages over single-cell growth, including resistance to antimicrobial factors. Here we describe the interaction between the biofilm-promoting components curli fimbriae and cellulose of uropathogenic E. coli and the endogenous antimicrobial defense in the urinary tract. We also demonstrate the impact of this interplay on the pathogenesis of urinary tract infections. Our results suggest that curli and cellulose exhibit differential and complementary functions. Both of these biofilm components were expressed by a high proportion of clinical E. coli isolates. Curli promoted adherence to epithelial cells and resistance against the human antimicrobial peptide LL-37, but also increased the induction of the proinflammatory cytokine IL-8. Cellulose production, on the other hand, reduced immune induction and hence delayed bacterial elimination from the kidneys. Interestingly, LL-37 inhibited curli formation by preventing the polymerization of the major curli subunit, CsgA. Thus, even relatively low concentrations of LL-37 inhibited curli-mediated biofilm formation in vitro. Taken together, our data demonstrate that biofilm components are involved in the pathogenesis of urinary tract infections by E. coli and can be a target of local immune defense mechanisms.

Neutrophil primary granule proteins HBP and HNP1–3 boost bacterial phagocytosis by human and murine macrophages

In acute inflammation, infiltrating polymorphonuclear leukocytes (also known as PMNs) release preformed granule proteins having multitudinous effects on the surrounding environment. Here we present what we believe to be a novel role for PMN-derived proteins in bacterial phagocytosis by both human and murine macrophages. Exposure of macrophages to PMN secretion markedly enhanced phagocytosis of IgG-opsonized Staphylococcus aureus both in vitro and in murine models in vivo. PMN secretion activated macrophages, resulting in upregulation of the Fcgamma receptors CD32 and CD64, which then mediated the enhanced phagocytosis of IgG-opsonized bacteria. The phagocytosis-stimulating activity within the PMN secretion was found to be due to proteins released from PMN primary granules; thorough investigation revealed heparin-binding protein (HBP) and human neutrophil peptides 1-3 (HNP1-3) as the mediators of the macrophage response to PMN secretion. The use of blocking antibodies and knockout mice revealed that HBP acts via beta2 integrins, but the receptor for HNP1-3 remained unclear. Mechanistically, HBP and HNP1-3 triggered macrophage release of TNF-alpha and IFN-gamma, which acted in an autocrine loop to enhance expression of CD32 and CD64 and thereby enhance phagocytosis. Thus, we attribute what may be a novel role for PMN granule proteins in regulating the immune response to bacterial infections.

Vernix caseosa as a multi-component defence system based on polypeptides, lipids and their interactions

Abstract.Vernix caseosa is a white cream-like substance that covers the skin of the foetus and the newborn baby. Recently, we discovered antimicrobial peptides/proteins such as LL-37 in vernix, suggesting host defence functions of vernix. In a proteomic approach, we have continued to characterize proteins in vernix and have identified 20 proteins, plus additional variant forms. The novel proteins identified, considered to be involved in host defence, are cystatin A, UGRP-1, and calgranulin A, B and C. These proteins add protective functions to vernix such as antifungal activity, opsonizing capacity, protease inhibition and parasite inactivation. The composition of the lipids in vernix has also been characterized and among these compounds the free fatty acids were found to exhibit antimicrobial activity. Interestingly, the vernix lipids enhance the antimicrobial activity of LL-37 in vitro, indicating interactions between lipids and antimicrobial peptides in vernix. In conclusion, vernix is a balanced cream of compounds involved in host defence, protecting the foetus and newborn against infection.

Narcolepsy patients have antibodies that stain distinct cell populations in rat brain and influence sleep patterns

Significance Narcolepsy is a chronic sleep disease with autoimmune origin. We explored occurrence of autoantibodies in narcolepsy and other sleep-related disorders (OSRDs) by screening human sera with immunohistochemistry on rat brains. Hypocretin/orexinergic neurons were not stained, but a prominent immunostaining pattern of hypothalamic melanin-concentrating hormone (MCH) and proopiomelanocortin (POMC) neurons was overrepresented in cases of narcolepsy and OSRD patients. The autoantigen was identified as the common C-terminal epitope of neuropeptide glutamic acid-isoleucine/α–melanocyte-stimulating hormone (NEI/αMSH). Purified IgGs from a patient with MCH/POMC staining injected intracerebroventricularly to rats caused disturbed sleep patterns. Also, GABAergic cortical interneurons were stained with other narcolepsy and OSRD sera. Thus, autoantibodies are frequent in patients with sleep disorders, and NEI/αMSH may be a previously unidentified autoantigen involved in pathomechanism(s). These findings indicate possible diagnostic/therapeutic targets. Narcolepsy is a chronic sleep disorder, likely with an autoimmune component. During 2009 and 2010, a link between A(H1N1)pdm09 Pandemrix vaccination and onset of narcolepsy was suggested in Scandinavia. In this study, we searched for autoantibodies related to narcolepsy using a neuroanatomical array: rat brain sections were processed for immunohistochemistry/double labeling using patient sera/cerebrospinal fluid as primary antibodies. Sera from 89 narcoleptic patients, 52 patients with other sleep-related disorders (OSRDs), and 137 healthy controls were examined. Three distinct patterns of immunoreactivity were of particular interest: pattern A, hypothalamic melanin-concentrating hormone and proopiomelanocortin but not hypocretin/orexin neurons; pattern B, GABAergic cortical interneurons; and pattern C, mainly globus pallidus neurons. Altogether, 24 of 89 (27%) narcoleptics exhibited pattern A or B or C. None of the patterns were exclusive for narcolepsy but were also detected in the OSRD group at significantly lower numbers. Also, some healthy controls exhibited these patterns. The antigen of pattern A autoantibodies was identified as the common C-terminal epitope of neuropeptide glutamic acid-isoleucine/α–melanocyte-stimulating hormone (NEI/αMSH) peptides. Passive transfer experiments on rat showed significant effects of pattern A human IgGs on rapid eye movement and slow-wave sleep time parameters in the inactive phase and EEG θ-power in the active phase. We suggest that NEI/αMSH autoantibodies may interfere with the fine regulation of sleep, contributing to the complex pathogenesis of narcolepsy and OSRDs. Also, patterns B and C are potentially interesting, because recent data suggest a relevance of those brain regions/neuron populations in the regulation of sleep/arousal.

Antimicrobial components of the neonatal gut affected upon colonization

Antimicrobial peptides (AMP) produced throughout our body are important effectors in the defense barrier of innate immunity. Here, we have analyzed antimicrobial activity and polypeptide composition of meconium versus neonatal feces to address the development of antimicrobial defense of the neonatal gut. Extracts of meconium exhibited antimicrobial activity against Bacillus megaterium, Escherichia coli, and group B streptococci (GBS) but not against the yeast Candida albicans. Extracts of neonatal feces were found to possess low activity against E. coli, GBS, and C. albicans. However, the anti-B. megaterium activity was higher in the fecal extracts than in meconium. All activities were reduced or abolished when salt was added to the antimicrobial assay. The AMP cathelicidin LL-37, α-defensin HNP-1-2, α-defensin HD 5, and lysozyme were identified in both meconium and fecal extracts. In addition, HNP-3 and a fragment of azurocidin were found in meconium, whereas the holoprotein azurocidin was detected in feces. In meconium, histones H2A and H4 were isolated and identified by their antimicrobial activity. Notably, LL-37 and lysozyme were found at significantly higher levels in feces than in meconium. Our findings reveal that meconium and feces contain AMP, acting in the defense of the neonatal gut, and may be implicated in the control of the initial colonization.

Lactose in human breast milk an inducer of innate immunity with implications for a role in intestinal homeostasis.

Postpartum, infants have not yet established a fully functional adaptive immune system and are at risk of acquiring infections. Hence, newborns are dependent on the innate immune system with its antimicrobial peptides (AMPs) and proteins expressed at epithelial surfaces. Several factors in breast milk are known to confer immune protection, but which the decisive factors are and through which manner they work is unknown. Here, we isolated an AMP-inducing factor from human milk and identified it by electrospray mass spectrometry and NMR to be lactose. It induces the gene (CAMP) that encodes the only human cathelicidin LL-37 in colonic epithelial cells in a dose- and time-dependent manner. The induction was suppressed by two different p38 antagonists, indicating an effect via the p38-dependent pathway. Lactose also induced CAMP in the colonic epithelial cell line T84 and in THP-1 monocytes and macrophages. It further exhibited a synergistic effect with butyrate and phenylbutyrate on CAMP induction. Together, these results suggest an additional function of lactose in innate immunity by upregulating gastrointestinal AMPs that may lead to protection of the neonatal gut against pathogens and regulation of the microbiota of the infant.

Somatostatin and its 2A receptor in dorsal root ganglia and dorsal horn of mouse and human: expression, trafficking and possible role in pain

BackgroundSomatostatin (SST) and some of its receptor subtypes have been implicated in pain signaling at the spinal level. In this study we have investigated the role of SST and its sst2A receptor (sst2A) in dorsal root ganglia (DRGs) and spinal cord.ResultsSST and sst2A protein and sst2 transcript were found in both mouse and human DRGs, sst2A-immunoreactive (IR) cell bodies and processes in lamina II in mouse and human spinal dorsal horn, and sst2A-IR nerve terminals in mouse skin. The receptor protein was associated with the cell membrane. Following peripheral nerve injury sst2A-like immunoreactivity (LI) was decreased, and SST-LI increased in DRGs. sst2A-LI accumulated on the proximal and, more strongly, on the distal side of a sciatic nerve ligation. Fluorescence-labeled SST administered to a hind paw was internalized and retrogradely transported, indicating that a SST-sst2A complex may represent a retrograde signal. Internalization of sst2A was seen in DRG neurons after systemic treatment with the sst2 agonist octreotide (Oct), and in dorsal horn and DRG neurons after intrathecal administration. Some DRG neurons co-expressed sst2A and the neuropeptide Y Y1 receptor on the cell membrane, and systemic Oct caused co-internalization, hypothetically a sign of receptor heterodimerization. Oct treatment attenuated the reduction of pain threshold in a neuropathic pain model, in parallel suppressing the activation of p38 MAPK in the DRGsConclusionsThe findings highlight a significant and complex role of the SST system in pain signaling. The fact that the sst2A system is found also in human DRGs and spinal cord, suggests that sst2A may represent a potential pharmacologic target for treatment of neuropathic pain.

188 Human Meconium Contains Antimicrobial Peptides/Proteins

Background: Meconium is a greenish substance that accumulates in the fetal intestines and is expelled after birth. After the transition from a sterile environment to a world full of microbes, the newborn baby needs to be protected against microbial invasion. Since the adaptive immunity of the newborn is immature, the neonate must rely on its innate immunity. Antimicrobial peptides/proteins are effector molecules of the innate immune system and form a chemical barrier at epithelial surfaces that prevent infection.Aim: To screen for antimicrobial activities in meconium extracts and to isolate and characterise the components giving rise to these activities.Methods: Meconium from 12 newborns was collected and peptides/proteins were extracted. Antimicrobial activities were measured with an inhibition zone assay. Bactericidal components were isolated utilizing cationic and reverse-phased chromatographies and identification of peptides/proteins was performed with N-terminal sequence analysis, peptide mass fingerprinting, mass spectrometry and immunodetection.Results: Antimicrobial activities were detected against Group B Streptococci (GBS), Bacillus megaterium (Bm11), Escherichia coli (D21), but not against Candida albicans. The antimicrobial activity against GBS, Bm11 and D21 was salt sensitive, where high salt concentration diminished the activity. After treatment of the extracts with pepsin, the activity against Bm11 decreased, indicating that a part of the activity is derived from peptides/proteins. In several extracts, lysozyme was detected. So far, we have identified five antimicrobial peptides; the cathelicidin LL-37 and four alpha-defensins, the human neutrophil peptides 1, 2 and 3 (HNP1–3) and human defensin 5 (HD-5). Furthermore, two histones, i.e. H2A and H4, were isolated and found to exhibit antibacterial activity.Conclusions: These results suggest that meconium exhibit protective function against microbes in the gastrointestinal tract of the foetus and the newborn baby.