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Pro-inflammatory signaling mediated by Toll-like receptor 4 (TLR4)/myeloid differentiation-2 (MD-2) complex plays a crucial role in the instantaneous protection against infectious challenge and largely contributes to recovery from Gram-negative infection. Activation of TLR4 also boosts the adaptive immunity which is implemented in the development of vaccine adjuvants by application of minimally toxic TLR4 activating ligands. The modulation of pro-inflammatory responses via the TLR4 signaling pathway was found beneficial for management of acute and chronic inflammatory disorders including asthma, allergy, arthritis, Alzheimer disease pathology, sepsis, and cancer. The TLR4/MD-2 complex can recognize the terminal motif of Gram-negative bacterial lipopolysaccharide (LPS)-a glycophospholipid lipid A. Although immense progress in understanding the molecular basis of LPS-induced TLR4-mediated signaling has been achieved, gradual, and predictable TLR4 activation by structurally defined ligands has not yet been attained. We report on controllable modulation of cellular pro-inflammatory responses by application of novel synthetic glycolipids-disaccharide-based lipid A mimetics (DLAMs) having picomolar affinity for TLR4/MD-2. Using crystal structure inspired design we have developed endotoxin mimetics where the inherently flexible β(1 → 6)-linked diglucosamine backbone of lipid A is replaced by a conformationally restricted α,α-(1↔1)-linked disaccharide scaffold. The tertiary structure of the disaccharide skeleton of DLAMs mirrors the 3-dimensional shape of TLR4/MD-2 bound E. coli lipid A. Due to exceptional conformational rigidity of the sugar scaffold, the specific 3D organization of DLAM must be preserved upon interaction with proteins. These structural factors along with specific acylation and phosphorylation pattern can ensure picomolar affinity for TLR4 and permit efficient dimerization of TLR4/MD-2/DLAM complexes. Since the binding pose of lipid A in the binding pocket of MD-2 (±180°) is crucial for the expression of biological activity, the chemical structure of DLAMs was designed to permit a predefined binding orientation in the binding groove of MD-2, which ensured tailored and species-independent (human and mice) TLR4 activation. Manipulating phosphorylation and acylation pattern at the sugar moiety facing the secondary dimerization interface allowed for adjustable modulation of the TLR4-mediated signaling. Tailored modulation of cellular pro-inflammatory responses by distinct modifications of the molecular structure of DLAMs was attained in primary human and mouse immune cells, lung epithelial cells and TLR4 transfected HEK293 cells., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Heine, Adanitsch, Peternelj, Haegman, Kasper, Ittig, Beyaert, Jerala and Zamyatina.)

Background: Sex differences in cognitive functioning have long been recognized in schizophrenia patients and healthy controls (HC). However, few studies have focused on patients with an at-risk mental state (ARMS) for psychosis. Thus, the aim of the present study was to investigate sex differences in neurocognitive performance in ARMS patients compared with HC., Methods: The data analyzed in this study were collected within the multicenter European Gene-Environment Interactions study (11 centers). A total of 343 ARMS patients (158 women) and 67 HC subjects (33 women) were included. All participants completed a comprehensive neurocognitive battery. Linear mixed effects models were used to explore whether sex differences in cognitive functioning were present in the total group (main effect of sex) and whether sex differences were different for HC and ARMS (interaction between sex and group)., Results: Women performed better in social cognition, speed of processing, and verbal learning than men regardless of whether they were ARMS or HC. However, only differences in speed of processing and verbal learning remained significant after correction for multiple testing. Additionally, ARMS patients displayed alterations in attention, current IQ, speed of processing, verbal learning, and working memory compared with HC., Conclusions: Findings indicate that sex differences in cognitive functioning in ARMS are similar to those seen between healthy men and women. Thus, it appears that sex differences in cognitive performance may not be specific for ARMS, a finding resembling that in patients with schizophrenic psychoses.

Objectives: Brain-derived neurotrophic factor (BDNF) is involved in numerous cognitive processes. Since cognitive deficits are a core feature of psychotic disorders, the investigation of BDNF levels in psychosis and their correlation with cognition has received increased attention. However, there are no studies investigating BDNF levels in individuals with an at-risk mental state (ARMS) for psychosis. Hence, the aims of the present study were: (1) assessing peripheral BDNF levels across different (potential) stages of psychosis; (2) investigating their association with cognition. Methods: Plasma and serum BDNF levels and neuropsychological performance were assessed in 16 ARMS, six first-episode psychosis (FEP), and 11 chronic schizophrenia (CS) patients. Neuropsychological assessment covered intelligence, verbal memory, working memory, attention and executive functioning. Results: Both plasma and serum BDNF levels were highest in CS, intermediate in FEP and lowest in ARMS. Multiple regression analysis revealed a significant positive association of plasma BDNF levels with planning ability across all groups. Conclusions: The lower peripheral BDNF levels in ARMS compared to FEP and CS might point towards an important drop of this neurotrophin prior to the onset of frank psychosis. The associations of peripheral BDNF with planning-abilities match previous findings.

Aim: Ultrahigh risk (UHR) criteria, consisting of brief limited intermittent psychotic symptoms (BLIPS), attenuated psychotic symptoms (APS) and genetic risk and deterioration (GRD) syndrome are the most widely used criteria for assessing the clinical high-risk state for psychosis (CHR-P). The Basel Screening Instrument for Psychosis (BSIP) includes a further risk category, the unspecific risk category (URC). However, little is known about the predictive power of this risk category compared to other risk categories., Methods: Two hundred CHR-P patients were detected as part of the Früherkennung von Psychosen (FePsy) study using the BSIP. Transition to psychosis was assessed in regular intervals for up to 7 years., Results: Patients meeting only the URC criterion (n = 40) had a significantly lower risk of transition to psychosis than the UHR group (including BLIPS, APS and GRD) (HR 0.19 [0.05; 0.80] (P = 0.024). Furthermore, the URC only risk group had a lower transition risk than the APS without BLIPS group (P = 0.015) and a trendwise lower risk than the BLIPS group (P = 0.066). However, despite the lower transition risk in the URC only group, there were still two patients (5%) in this group with a later transition to psychosis., Conclusions: The URC includes patients who have a lower risk of transition than those included by the UHR categories and thereby increases the sensitivity of the BSIP. This offers the possibility of a stratified intervention, with these subjects receiving low intensity follow-up and treatment., (© 2018 John Wiley & Sons Australia, Ltd.)

Background: Research on patients at clinical high risk (CHR) for psychosis has so far mainly focused on those with transition to frank psychosis (CHR-T patients). However, the majority of CHR patients do not transition (CHR-NT patients) and relatively little information is available on their clinical and functional outcome., Methods: We conducted a systematic review on clinical and functional long-term outcome of CHR-NT patients. Studies were included if they had an average follow-up period of at least 24 months and reported on long-term outcome of CHR-NT patients in one or more of the following domains: (non-)remission from CHR, prevalence of clinical symptoms and/or clinical diagnoses (axis I and II), and psychosocial functioning., Results: Ten publications from seven different single or multicenter studies with average follow-up durations of 2-7.5 years could be included. At the last follow-up assessment 28-71% of CHR-NT patients were not remitted from their CHR and 22-82% still had at least one clinical diagnosis. Approximately half of CHR-NT patients presented with poor psychosocial outcome at 2-year and 6-year follow-up., Conclusions: The results suggest that, in the long-term, the majority of CHR-NT patients are not in full clinical remission and seem to suffer from one or more clinical disorders and psychosocial impairments. Since relatively few studies could be identified, further research is required to better understand the trajectories and clinical needs of CHR-NT patients., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Aim: Gender differences in the current symptomatology of patients with psychotic disorders have previously been described in the literature. However, it has not yet been investigated whether gender differences exist in the very first self-perceived signs or symptoms of illness onset. The aim of this study was to investigate this aspect in at-risk mental state (ARMS) and first-episode psychosis (FEP) patients., Methods: ARMS and FEP were recruited via the early detection of psychosis (FePsy) clinic Basel, Switzerland. The Basel Interview for Psychosis (BIP) was used to retrospectively assess the first 3 self-perceived signs and symptoms at illness onset. Differences between gender and patient groups on single item and symptom cluster levels were analysed using logistic regression models., Results: One-hundred-thirty six ARMS (91 men, 45 women) and 89 FEP patients (63 men, 26 women) could be recruited for this study. On a single item level, women more frequently reported "unusual anxiety, fears" and men (at a trend level) "social withdrawal" as being among their 3 first self-perceived symptoms, independent of diagnostic group. On the symptom cluster level, women more frequently reported "increased worrying/anxiety" and (sub-threshold) "hallucinations", independent of diagnostic group. Problems with "thinking, concentration" were reported more frequently by men in the ARMS group only., Conclusion: Our results suggest that only few and relatively small gender differences exist in the first self-perceived signs and symptoms. While men initially mainly notice negative/cognitive symptoms, women first notice (sub-threshold) positive and affective symptoms., (© 2017 John Wiley & Sons Australia, Ltd.)

Background: Gender differences in symptomatology in chronic schizophrenia and first episode psychosis patients have often been reported. However, little is known about gender differences in those at risk of psychotic disorders. This study investigated gender differences in symptomatology, drug use, comorbidity (i.e. substance use, affective and anxiety disorders) and global functioning in patients with an at-risk mental state (ARMS) for psychosis., Methods: The sample consisted of 336 ARMS patients (159 women) from the prodromal work package of the EUropean network of national schizophrenia networks studying Gene-Environment Interactions (EU-GEI; 11 centers). Clinical symptoms, drug use, comorbidity and functioning were assessed at first presentation to an early detection center using structured interviews., Results: In unadjusted analyses, men were found to have significantly higher rates of negative symptoms and current cannabis use while women showed higher rates of general psychopathology and more often displayed comorbid affective and anxiety disorders. No gender differences were found for global functioning. The results generally did not change when corrected for possible cofounders (e.g. cannabis use). However, most differences did not withstand correction for multiple testing., Conclusions: Findings indicate that gender differences in symptomatology and comorbidity in ARMS are similar to those seen in overt psychosis and in healthy controls. However, observed differences are small and would only be reliably detected in studies with high statistical power. Moreover, such small effects would likely not be clinically meaningful., (Copyright © 2019. Published by Elsevier Masson SAS.)

Negative symptoms and neurocognitive performance have been reported to be negatively associated in patients with emerging psychosis. However, most previous studies focused on patients with frank psychosis and did not differentiate between subdomains of negative symptoms. Hence, we aimed to elucidate the specific relationship between negative symptoms and cognitive functioning in patients at clinical high risk (CHR) for psychosis. Data from 154 CHR patients collected within the prospective Früherkennung von Psychosen (FePsy) study were analyzed. Negative symptoms were assessed with the Scale for the Assessment of Negative Symptoms (SANS) and cognitive functioning with an extensive neuropsychological test battery. Regression analyses revealed significant negative associations between negative symptoms and cognitive functioning, particularly in the domains of nonverbal intelligence and verbal fluency. When analyzing each negative symptom domain separately, alogia and asociality/anhedonia were significantly negatively associated with nonverbal intelligence and alogia additionally with verbal fluency. Overall, our results in CHR patients are similar to those reported in patients with frank psychosis. The strong negative association between verbal fluency and negative symptoms may be indicative of an overlap between these constructs. Verbal fluency might have a strong influence on the clinical impression of negative symptoms (particularly alogia) and vice versa., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Background: Patients with an at-risk mental state (ARMS) for psychosis and patients with attention-deficit/hyperactivity disorder (ADHD) have many overlapping signs and symptoms and hence can be difficult to differentiate clinically. The aim of this study was to investigate whether the differential diagnosis between ARMS and adult ADHD could be improved by neuropsychological testing., Methods: 168 ARMS patients, 123 adult ADHD patients and 109 healthy controls (HC) were recruited via specialized clinics of the University of Basel Psychiatric Hospital. Sustained attention and impulsivity were tested with the Continuous Performance Test, verbal learning and memory with the California Verbal Learning Test, and problem solving abilities with the Tower of Hanoi Task. Group differences in neuropsychological performance were analyzed using generalized linear models. Furthermore, to investigate whether adult ADHD and ARMS can be correctly classified based on the pattern of cognitive deficits, machine learning (i.e. random forests) was applied., Results: Compared to HC, both patient groups showed deficits in attention and impulsivity and verbal learning and memory. However, in adult ADHD patients the deficits were comparatively larger. Accordingly, a machine learning model predicted group membership based on the individual neurocognitive performance profile with good accuracy (AUC = 0.82)., Conclusions: Our results are in line with current meta-analyses reporting that impairments in the domains of attention and verbal learning are of medium effect size in adult ADHD and of small effect size in ARMS patients and suggest that measures of these domains can be exploited to improve the differential diagnosis between adult ADHD and ARMS patients., (Copyright © 2018 Elsevier Masson SAS. All rights reserved.)

Objectives: Patients with schizophrenia often experience subtle disturbances in several domains of information processing-so-called basic symptoms (BS). BS are already present before onset of frank psychosis and can be assessed by interviews but also by the self-administered Frankfurt Complaint Questionnaire (FCQ). We investigated the factor structure, reliability, and predictive validity for transition to psychosis of the FCQ, comparing previously proposed factor solutions containing 1, 2, 4, and 10 factors., Methods: Confirmatory factor analysis was used in a sample of 117 at-risk mental state and 92 first-episode psychosis participants of the Basel FePsy (early detection of psychosis) study., Results: Although all factor models fitted to the data, the 2- or 4-factor solutions performed best among the models that used at least half of the FCQ items, suggesting the covariance between FCQ items is best explained by 2 to 4 underlying factors. No FCQ-scale predicted transition to psychosis., Conclusion: We could confirm a 2- to 4-factor structure of the FCQ in a sample of at-risk mental state and first-episode psychosis patients using confirmatory factor analysis. Contrary to interview-assessed cognitive-perceptive BS, self-assessed BS do not seem to improve prediction of psychosis. This result reinforces reports of poor correspondence between interview- and questionnaire-assessed BS., (Copyright © 2017 John Wiley & Sons, Ltd.)

Background: Verbal learning and memory are impaired not only in patients with a first episode of psychosis (FEP) but also-to a lower extent-in those with an at-risk mental state for psychosis (ARMS). However, little is known about the specific nature of these impairments. Hence, we aimed to study learning and memory processes in ARMS and FEP patients by making use of structural equation modelling., Methods: Verbal learning was assessed with the California Verbal Learning Test (CVLT) in 98 FEP patients, 126 ARMS patients and 68 healthy controls (HC) as part of the Basel early detection of psychosis (FePsy) study. The four-factorial CFA model of Donders was used to estimate test performance on latent variables of the CVLT and growth curve analysis was used to model the learning curve. The latter allows disentangling initial recall, which is strongly determined by attentional processes, from the learning rate., Results: The CFA model revealed that ARMS and FEP patients were impaired in Attention Span, Learning Efficiency and Delayed Memory and that FEP patients were additionally impaired in Inaccurate Memory. Additionally, ARMS-NT, but not ARMS-T, performed significantly worse than HC on Learning Efficiency. The growth curve model indicated that FEP patients were impaired in both initial recall and learning rate and that ARMS patients were only impaired in the learning rate., Conclusions: Since impairments were more pronounced in the learning rate than the initial recall, our results suggest that the lower scores in the CVLT reported in previous studies are more strongly driven by impairments in the rate of learning than by attentional processes.

Aim: Despite the large scientific debate concerning potential stigmatizing effects of identifying an individual as being in an at-risk mental state (ARMS) for psychosis, studies investigating this topic from the subjective perspective of patients are rare. This study assesses whether ARMS individuals experience stigmatization and to what extent being informed about the ARMS is experienced as helpful or harmful., Methods: Eleven ARMS individuals, currently participating in the follow-up assessments of the prospective Basel Früherkennung von Psychosen (FePsy; English: Early Detection of Psychosis) study, were interviewed in detail using a semistructured qualitative interview developed for this purpose. Data were analysed using Interpretative Phenomenological Analysis., Results: Most individuals experiencing first symptoms reported sensing that there was 'something wrong with them' and felt in need of help. They were relieved that a specific term was assigned to their symptoms. The support received from the early detection centre was generally experienced as helpful. Many patients reported stigmatization and discrimination that appeared to be the result of altered behaviour and social withdrawal due to the prepsychotic symptoms they experienced prior to contact with the early detection clinic., Conclusions: The results suggest that early detection services help individuals cope with symptoms and potential stigmatization rather than enhancing or causing the latter. More emphasis should be put on the subjective experiences of those concerned when debating the advantages and disadvantages of early detection with regard to stigma. There was no evidence for increased perceived stigma and discrimination as a result of receiving information about the ARMS., (© 2015 Wiley Publishing Asia Pty Ltd.)

Aim: Research findings on the correlations between self-rating and observer-rating of schizophrenic psychopathology are inconsistent and have rarely considered first-episode psychosis (FEP) and at-risk mental state (ARMS) for psychosis patients. This study investigates these correlations in ARMS and FEP patients and how they are moderated by disease stage and gender., Methods: In the Basel Früherkennung von Psychosen (FePsy) study, positive and negative psychotic and affective symptoms were rated in 126 ARMS and 94 FEP patients using two observer- and three self-rating scales. The agreement between self-rating and observer-rating and the moderating influence of disease stage and gender was quantified using Pearson correlation and multiple regression models., Results: Correlations between self- and observer-rated subscales covering the same symptom dimension were low and mostly non-significant except for one correlation of positive and one of negative symptoms. There was no moderating influence of disease stage and gender on the correlations between self-rating and observer-rating except for one higher association in positive symptoms in FEP compared to ARMS and in women compared to men. However, these significant interaction effects did not withstand correction for multiple testing., Conclusions: This study suggests that the agreement between self-rating and observer-rating in FEP and ARMS patients is rather low, similar across symptom dimensions, and only partially dependent on disease stage and gender. However, low correlations between self-rating and observer-rating do not necessarily indicate that these patients have difficulties reporting their symptoms. They could also have occurred because the scales did not exactly cover the same symptom dimensions., (© 2015 Wiley Publishing Asia Pty Ltd.)

Background: Hyperprolactinemia is a known side effect of antipsychotics. In recent reports it has also been shown in antipsychotic-naïve at-risk mental state (ARMS) and first-episode psychosis (FEP) patients. Prolactin is not only involved in reproduction and lactation, but is also synthesized in response to stress. As stress is thought to play an important role in the onset and relapse of schizophrenia, the aim of this study was to further elucidate the influence of prolactin in emerging psychosis., Methods: The data analysed in this study were collected within the prospective Früherkennung von Psychosen (FePsy) study. Blood sample collection took place under standardized conditions between 8 and 10am after an overnight fast and 30minutes of rest. All patients were antipsychotic-naïve and did not take any prolactin influencing medication., Results: Our sample consisted of 116 antipsychotic-naïve ARMS and 49 FEP patients. Hyperprolactinemia was shown in 32% of ARMS and 35% of FEP patients. After correction for the normal biological variation between the sexes, we still found higher average prolactin levels in female than in male patients (β=0.42; t=2.47; p=0.01) but no difference in prolactin levels between ARMS and FEP patients (β=-0.05; t=-0.30; p=0.76). The survival analysis revealed no significant predictive value for prolactin levels to predict transition to psychosis., Conclusion: Our findings support a possible role of prolactin in emerging psychosis and it could be speculated that stress, which can induce hyperprolactinemia, has a stronger effect on women than on men in emerging psychosis., (Copyright © 2017. Published by Elsevier B.V.)

Background: Converging evidence indicates that neural oscillations coordinate activity across brain areas, a process which is seemingly perturbed in schizophrenia. In particular, beta (13-30 Hz) and gamma (30-50 Hz) oscillations were repeatedly found to be disturbed in schizophrenia and linked to clinical symptoms. However, it remains unknown whether abnormalities in current source density (CSD) and lagged phase synchronization of oscillations across distributed regions of the brain already occur in patients with an at-risk mental state (ARMS) for psychosis., Methods: To further elucidate this issue, we assessed resting-state EEG data of 63 ARMS patients and 29 healthy controls (HC). Twenty-three ARMS patients later made a transition to psychosis (ARMS-T) and 40 did not (ARMS-NT). CSD and lagged phase synchronization of neural oscillations across brain areas were assessed using eLORETA and their relationships to neurocognitive deficits and clinical symptoms were analyzed using linear mixed-effects models., Results: ARMS-T patients showed higher gamma activity in the medial prefrontal cortex compared to HC, which was associated with abstract reasoning abilities in ARMS-T. Furthermore, in ARMS-T patients lagged phase synchronization of beta oscillations decreased more over Euclidian distance compared to ARMS-NT and HC. Finally, this steep spatial decrease of phase synchronicity was most pronounced in ARMS-T patients with high positive and negative symptoms scores., Conclusions: These results indicate that patients who will later make the transition to psychosis are characterized by impairments in localized and synchronized neural oscillations providing new insights into the pathophysiological mechanisms of schizophrenic psychoses and may be used to improve the prediction of psychosis., (© The Author 2014. Published by Oxford University Press on behalf of the Maryland Psychiatric Research Center. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Modification of the Lipid A phosphates by positively charged appendages is a part of the survival strategy of numerous opportunistic Gram-negative bacteria. The phosphate groups of the cystic fibrosis adapted Burkholderia Lipid A are abundantly esterified by 4-amino-4-deoxy-β-L-arabinose (β-L-Ara4N), which imposes resistance to antibiotic treatment and contributes to bacterial virulence. To establish structural features accounting for the unique pro-inflammatory activity of Burkholderia LPS we have synthesised Lipid A substituted by β-L-Ara4N at the anomeric phosphate and its Ara4N-free counterpart. The double glycosyl phosphodiester was assembled by triazolyl-tris-(pyrrolidinyl)phosphonium-assisted coupling of the β-L-Ara4N H-phosphonate to α-lactol of β(1→6) diglucosamine, pentaacylated with (R)-(3)-acyloxyacyl- and Alloc-protected (R)-(3)-hydroxyacyl residues. The intermediate 1,1'-glycosyl-H-phosphonate diester was oxidised in anhydrous conditions to provide, after total deprotection, β-L-Ara4N-substituted Burkholderia Lipid A. The β-L-Ara4N modification significantly enhanced the pro-inflammatory innate immune signaling of otherwise non-endotoxic Burkholderia Lipid A., (© 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.)

Background: Although several instruments have been developed to identify patients with an at-risk mental state (ARMS) for psychosis and first episode of psychosis (FEP), up to now there were no instruments for a detailed assessment of risk factors and indicators of emerging psychosis and the temporal development of psychiatric symptoms over the whole life span in these patients. We therefore developed the Basle Interview for Psychosis (BIP). The aim of this study is to describe the development of the BIP and to report about its psychometric properties., Methods: The BIP is a comprehensive semi-structured interview that was developed for the Basel early detection of psychoses (FePsy) study. Its items were derived from the most important risk factors and indicators of psychosis described in the literature and from several existing instruments. It contains the following six sections: 1) social and physical development and family, 2) signs and symptoms, 3) vulnerability, 4) help-seeking behavior, 5) illness insight, 6) evaluation of the interview. To estimate the inter-rater reliabilities of the items of sections 2 and 3, 20 interviews were conducted and rated by 8 well-trained raters. The factorial structure of the BIP section "signs and symptoms" was explored in a sample of 120 ARMS and 77 FEP patients. On the basis of the discovered factorial structure, we created new subscales and assessed their reliabilities and validities., Results: Of the 153 studied items of sections 2 and 3, 150 (98 %) were rated with sufficiently high agreement (inter-rater reliability > 0.4). The items of section "signs and symptoms" could be grouped into 5 subscales with predominantly good to very good internal consistencies, homogeneities, and discriminant and convergent validities. Predictive validities could be demonstrated for the subscales "Positive Psychotic Symptoms", "Disturbance of Thinking" and the total score., Discussion: The BIP is the first interview for comprehensively assessing risk factors and indicators of emerging psychosis and the temporal development of psychiatric symptoms over the whole life span, which has been validated in ARMS and FEP patients. We could show that the BIP has excellent psychometric properties., (© Georg Thieme Verlag KG Stuttgart · New York.)

The endotoxic portion of lipopolysaccharide (LPS), a glycophospholipid Lipid A, initiates the activation of the Toll-like Receptor 4 (TLR4)-myeloid differentiation factor 2 (MD-2) complex, which results in pro-inflammatory immune signaling. To unveil the structural requirements for TLR4·MD-2-specific ligands, we have developed conformationally restricted Lipid A mimetics wherein the flexible βGlcN(1→6)GlcN backbone of Lipid A is exchanged for a rigid trehalose-like αGlcN(1↔1)αMan scaffold resembling the molecular shape of TLR4·MD-2-bound E. coli Lipid A disclosed in the X-ray structure. A convergent synthetic route toward orthogonally protected αGlcN(1↔1)αMan disaccharide has been elaborated. The α,α-(1↔1) linkage was attained by the glycosylation of 2-N-carbamate-protected α-GlcN-lactol with N-phenyl-trifluoroacetimidate of 2-O-methylated mannose. Regioselective acylation with (R)-3-acyloxyacyl fatty acids and successive phosphorylation followed by global deprotection afforded bis- and monophosphorylated hexaacylated Lipid A mimetics. αGlcN(1↔1)αMan-based Lipid A mimetics (α,α-GM-LAM) induced potent activation of NF-κB signaling in hTLR4/hMD-2/CD14-transfected HEK293 cells and robust LPS-like cytokines expression in macrophages and dendritic cells. Thus, restricting the conformational flexibility of Lipid A by fixing the molecular shape of its carbohydrate backbone in the "agonistic" conformation attained by a rigid αGlcN(1↔1)αMan scaffold represents an efficient approach toward powerful and adjustable TLR4 activation.

We here describe the NMR analysis of an intact lipopolysaccharide (LPS, endotoxin) in water with 1,2-dihexanoyl-sn-glycero-3-phosphocholine as detergent. When HPLC-purified rough-type LPS of Capnocytophaga canimorsus was prepared, (13)C,(15)N labeling could be avoided. The intact LPS was analyzed by homonuclear ((1)H) and heteronuclear ((1)H,(13)C, and (1)H,(31)P) correlated one- and two-dimensional NMR techniques as well as by mass spectrometry. It consists of a penta-acylated lipid A with an α-linked phosphoethanolamine attached to C-1 of GlcN (I) in the hybrid backbone, lacking the 4'-phosphate. The hydrophilic core oligosaccharide was found to be a complex hexasaccharide with two mannose (Man) and one each of 3-deoxy-d-manno-oct-2-ulosonic acid (Kdo), Gal, GalN, and l-rhamnose residues. Position 4 of Kdo is substituted by phosphoethanolamine, also present in position 6 of the branched Man(I) residue. This rough-type LPS is exceptional in that all three negative phosphate residues are "masked" by positively charged ethanolamine substituents, leading to an overall zero net charge, which has so far not been observed for any other LPS. In biological assays, the corresponding isolated lipid A was found to be endotoxically almost inactive. By contrast, the intact rough-type LPS described here expressed a 20,000-fold increased endotoxicity, indicating that the core oligosaccharide significantly contributes to the endotoxic potency of the whole rough-type C. canimorsus LPS molecule. Based on these findings, the strict view that lipid A alone represents the toxic center of LPS needs to be reassessed., (© 2014 by The American Society for Biochemistry and Molecular Biology, Inc.)

Recognition of the lipopolysaccharide (LPS), a major component of the outer membrane of Gram-negative bacteria, by the Toll-like receptor 4 (TLR4)-myeloid differentiation factor 2 (MD-2) complex is essential for the control of bacterial infection. A pro-inflammatory signaling cascade is initiated upon binding of membrane-associated portion of LPS, a glycophospholipid Lipid A, by a coreceptor protein MD-2, which results in a protective host innate immune response. However, activation of TLR4 signaling by LPS may lead to the dysregulated immune response resulting in a variety of inflammatory conditions including sepsis syndrome. Understanding of structural requirements for Lipid A endotoxicity would ensure the development of effective anti-inflammatory medications. Herein, we report on design, synthesis, and biological activities of a series of conformationally confined Lipid A mimetics based on β,α-trehalose-type scaffold. Replacement of the flexible three-bond β(1→6) linkage in diglucosamine backbone of Lipid A by a two-bond β,α(1↔1) glycosidic linkage afforded novel potent TLR4 antagonists. Synthetic tetraacylated bisphosphorylated Lipid A mimetics based on a β-GlcN(1↔1)α-GlcN scaffold selectively block the LPS binding site on both human and murine MD-2 and completely abolish lipopolysaccharide-induced pro-inflammatory signaling, thereby serving as antisepsis drug candidates. In contrast to their natural counterpart lipid IVa, conformationally constrained Lipid A mimetics do not activate mouse TLR4. The structural basis for high antagonistic activity of novel Lipid A mimetics was confirmed by molecular dynamics simulation. Our findings suggest that besides the chemical structure, also the three-dimensional arrangement of the diglucosamine backbone of MD-2-bound Lipid A determines endotoxic effects on TLR4.

Capnocytophaga canimorsus is a usual member of dog's mouths flora that causes rare but dramatic human infections after dog bites. We determined the structure of C. canimorsus lipid A. The main features are that it is penta-acylated and composed of a "hybrid backbone" lacking the 4' phosphate and having a 1 phosphoethanolamine (P-Etn) at 2-amino-2-deoxy-d-glucose (GlcN). C. canimorsus LPS was 100 fold less endotoxic than Escherichia coli LPS. Surprisingly, C. canimorsus lipid A was 20,000 fold less endotoxic than the C. canimorsus lipid A-core. This represents the first example in which the core-oligosaccharide dramatically increases endotoxicity of a low endotoxic lipid A. The binding to human myeloid differentiation factor 2 (MD-2) was dramatically increased upon presence of the LPS core on the lipid A, explaining the difference in endotoxicity. Interaction of MD-2, cluster of differentiation antigen 14 (CD14) or LPS-binding protein (LBP) with the negative charge in the 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo) of the core might be needed to form the MD-2 - lipid A complex in case the 4' phosphate is not present.