Amikacin Liposomal Inhalation Suspension (ALIS) in the treatment of Mycobacterium abscessus lung infection: a French observational experience

Background

Mycobacterium abscessus infections remain difficult to manage in both cystic fibrosis (CF) and non-CF patients and reported clinical outcomes are largely unsatisfactory. Clinical trial data are limited and no approved therapies are currently available for the management of M abscessus lung diseases. As an alternative, cohort studies may provide insightful information into the management of M abscessus pulmonary disease.

Methods

Based on a retrospective observational cohort study, we investigated the safety and efficacy of amikacin liposome inhaled suspension (ALIS) as an adjunct to a standard antibiotic regimen for M abscessus lung infection in both CF and non-CF patients. We also assessed the association of patient drug compliance with culture conversion and clinical outcomes.

Results

Twenty-six patients had long-term follow-up data available. Culture conversion was achieved in 54% (14/26) of the patients with no difference between CF and non-CF patients after an average treatment duration of 10 months. Patient treatment compliance was significantly better in the converter group compared to nonconverters with an odds ratio of 44.78 associated with good compared to poor patient compliance. Overall, 9 patients (35%) experienced an adverse event that led to treatment discontinuation.

Conclusions

ALIS appears beneficial in both CF and non-CF populations with M abscessus lung disease.

The chance of transition: strategies for multidisciplinary collaboration

Many long-term childhood cancer survivors suffer from treatment-related late effects, which may occur in any organ and include a wide spectrum of conditions. Long-term follow-up (LTFU) is recommended to facilitate early diagnosis and to ensure better health outcomes. Due to the heterogeneity of these sequelae, different specialists work together in the diagnosis and treatment of these conditions. Experts from both pediatric and internal medicine are involved in age-appropriate care by providing a transition process. Hence, LTFU of childhood cancer survivors is a prototypic example of multidisciplinary care for patients with complex needs treated in a specialized setting. International collaborations of healthcare professionals and scientists involved in LTFU of childhood cancer survivors, such as the International Guideline Harmonization Group, compile surveillance recommendations that can be clinically adopted all over the world. These global networks of clinicians and researchers make a joint effort to address gaps in knowledge, increase visibility and awareness of cancer survivorship and provide an excellent example of how progress in clinical care and scientific research may be achieved by international and multidisciplinary collaboration.

Impact of disease-modifying treatments on humoral response after COVID-19 vaccination: A mirror of the response after SARS-CoV-2 infection

Objective

To analyze the humoral response after COVID-19 vaccination in patients with multiple sclerosis (MS) according to disease-modifying treatments (DMTs) and in comparison with the humoral response after SARS-CoV-2 infection.

Methods

We included 28 MS patients with serological results after COVID-19 vaccination (Pfizer-BioNTech or Moderna ARNm) and 61 MS patients with serological results after COVID-19 (COVID-19 group) among patients followed up at the MS Center of Strasbourg, France, between January and April 2021. The primary endpoint was the IgG index according to DMTs (anti-CD20 mAb, sphingosine 1-phosphate receptor [S1PR] modulator and other treatments) and COVID-19 vaccine or COVID-19 groups.

Results

In the vaccinated MS patients, the median IgG index was lower in patients treated with anti-CD20 mAb and in patients treated with S1PR modulator compared to patients receiving other or no DMTs (4.80 [1.58–28.6], 16.5 [16.3–48.5], 1116 [434–1747] and 1272 [658–1886], respectively, P < 0.001). Similar results were found for MS patients after COVID-19.

Conclusions

Patients with MS and treated with S1PR modulators or anti-CD20 mAb had a reduced humoral response after COVID-19 vaccine.

Identification and measurement of cervical spinal cord atrophy in neuromyelitis optica spectrum disorders (NMOSD) and correlation with clinical characteristics and cervical spinal cord MRI data

INTRODUCTION

The spinal cord is one of the two main targets of neuromyelitis optica (NMO). The aim of this study was to highlight cervical spinal cord atrophy in NMO patients as compared to controls and to assess correlations between atrophy and clinical characteristics and cervical spinal cord MRI data.

METHODS

This prospective study investigated 15 patients with a diagnosis of NMOSD and 15 healthy controls. The whole cervical spinal cord was explored by MRI. The cross-sectional area (CSA) was estimate at every level of cup. This measurement was then averaged on the whole cervical spinal cord, providing a single measurement for every subject, denoted as mean CSA.

RESULTS

Mean CSA was 68.5 mm2 in the population of NMO patients and 72.8 mm2 in the population of healthy subjects. NMO patients had significantly smaller cervical spinal cord area than healthy controls (T test=0.009). Cervical spinal cord atrophy was associated with clinical signs of medullary involvement (T test=0.0006). There was a tendency toward a relation between cervical spinal cord atrophy and the Expanded Disability Status Scale (EDSS) (T test=0.07). This correlation seems statistically significant (T test<0.05) at the level of the upper cervical spinal cord (C2-C3) CONCLUSION: This study provides the first evidence of cervical spinal cord atrophy in NMOSD by studying the entire cervical spinal cord. Upper cervical spinal cord atrophy was substantially correlated to clinical disability and seems more involved in the development of clinical disability in NMOSD patients in comparison to the lower cervical spinal cord.

Atypical myelitis in patients with multiple sclerosis: Characterization and comparison with typical multiple sclerosis and neuromyelitis optica spectrum disorders

Background:

Atypical myelitis in multiple sclerosis (MS) is characterized by extensive myelitis in the longitudinal (longitudinally extensive transverse myelitis) or axial plane (transverse myelitis).

Objective:

To characterize a cohort of MS patients with atypical myelitis.

Methods:

Atypical myelitis was extracted from the French and Luxembourg MS databases and compared to two cohorts of MS patients with typical myelitis and neuromyelitis optica spectrum disorders (NMOSDs) patients with myelitis.

Results:

We enrolled 28 MS patients with atypical myelitis, 68 MS patients with typical myelitis and 119 NMOSD patients with a first episode of myelitis. MS patients with atypical myelitis were characterized by a mean age of 34.0 (±10.7) years and 64.3% were women. In 82.1% of the patients, atypical myelitis was the first episode of MS. Mean Expanded Disability Status Scale (EDSS) scores at nadir and 3–6 months after onset were 4.1 ± 2.1 and 3.3 ± 2, respectively. Differences between groups revealed a predominance of cervicothoracic myelitis and a higher level of disability in NMOSD patients. Disability in MS patients with atypical myelitis was more severe than in the MS patients with typical myelitis; 28% had already converted to progressive MS within our mean follow-up of 39.6 (±30.4) months.

Conclusion:

Atypical myelitis may be the first presentation of MS and is associated with poorer prognosis.

MON-458 Radiological Alterations Of The Hypothalamic-pituitary Region After Craniospinal Irradiation For Medulloblastoma During Childhood

Background Hypothalamic-pituitary (HP) dysfunction after craniospinal irradiation (CSI) is frequently observed in childhood brain tumor survivors (CBTS). The risk increases with higher dose and younger age at time of radiation exposure. Whether radiological alterations of the HP-region or alterations in brain volume are predictive of HP dysfunction remains unknown. Aim The aim of this (retrospective) study was to quantify radiological alterations of the HP-region in time in CBTS after CSI and to correlate these alterations to the occurrence of HP dysfunction. Methods Ninety survivors of childhood medulloblastoma (mean age at diagnosis: 8.3 years) from a previously reported nationwide cohort, treated with CSI between 2002-2012, were included. Sixty CBTS (67%) were diagnosed with HP dysfunction during follow-up (FU). All MRI scans were collected from time of diagnosis, post-neurosurgical intervention, post-radiation and 3 and 5 years of FU. Pituitary height (PH) and width (PW) were measured on mid-sagittal images. The pituitary stalk (PS) width was assessed by measuring the ratio of the PS to basilar artery (BA) on axial images on the same plane in the middle of the PS. Volume measurements of the PG (PGV) were performed. Observers were blinded for outcome of HP function. Separate analyses were performed for children < 6 years at time of CSI. All measurements were corrected for age and gender using Z-scores. Statistical analyses were performed by SPSS (General Linear Model repeated measures with Bonferroni correction). Results Mean PH (p<0.01, 95% CI [0.25, 1.27], PW (p<0.01, 95% CI [0.85-2.32], width of the PS (p<0.01, 95% CI [0.38-3.0] and PGV (p<0.05, 95% CI [0.12-1.29] declined during FU. No correlation was observed between radiological alterations in time and the presence of HP dysfunction. On a marginal trend level, an interaction effect was seen for PS/BA ratio and the presence of HP dysfunction (p= 0.097, F= 2.44). HP dysfunction occurred more frequently in CBTS treated with CSI < 6 years (71% vs 58%). Radiological alterations in this age group could also not be related to occurrence of HP dysfunction. Conclusion When compared to age and gender reference values, CBTS treated with CSI show radiological alterations of the HP region in time. Exposure to cranial irradiation in childhood seems to have a negative effect on PH, PW, width of PS and PGV. However, these effects cannot be related to the development of HP dysfunction or age at time of CRT. Prospective studies are needed to confirm these results, with systematic evaluation of the HP function in time.

[Fractures of the lower extremities in childhood : Part 2: lower leg and ankle fractures]

The treatment of pediatric patients in trauma surgery is a special situation in every aspect. For deciding on the correct treatment of fractures of the lower leg and ankle joint, various parameters, such as residual growth rate, skeletal age and height of the patient are decisive. The differences between fractures in children and adolescents are the open epiphyseal plate and the resulting residual growth. The bones of young children have a higher healing tendency and a greater potential for correction than in adolescents. Especially in the lower leg and the ankle joint, the potential for correction is decisive for the healing of fractures and for possible development of growth disorders. The limits of tolerance concerning axial malalignments and the expected spontaneous potential for correction must play an essential role for further treatment with conservative or operative therapy. This article deals with the special features of pediatric fractures of the lower leg and ankle joint.

Biopsying a spinal cord lesion: A diagnostic dilemma. Case report and review of literature

Spinal cord biopsy is a difficult procedure fraught with the risk of false-negative results or even misdiagnosis in up to 30% of cases. Differential diagnoses of spinal cord lesions include a wide range of inflammatory, infectious and neoplastic diseases. Given the importance of correctly managing these pathologies, it is crucial to avoid delays in making the correct diagnosis in order to improve the patient's outcome. We present here the case of a 21-year-old male with rapidly progressing sphincter and lower limb motor dysfunctions up to complete paraplegia with evidence of thoracic spinal cord lesion on magnetic resonance imaging. None of the blood and cerebrospinal fluid tests pointed to a diagnosis, while a first spinal cord biopsy revealed an inflammatory necrotic process. After several weeks of empirical treatments and clinical stability, the patient started having focal structural seizures that became generalized with local progression of the lesion and diffuse leptomeningeal spread on magnetic resonance imaging. A second spinal cord biopsy found a grade IV glioblastoma with H3 K27M histone mutation. Unfortunately the patient passed away before any treatment could be initiated. In this report, the authors analyze the difficulty of making the rapid, correct diagnosis of a highly malignant intrinsic spinal cord lesion, discussing also possible strategies to avoid diagnostic delays and to improve the outcome of these difficult patients.

The influence of genetic variation on late toxicities in childhood cancer survivors: A review

INTRODUCTION

The variability in late toxicities among childhood cancer survivors (CCS) is only partially explained by treatment and baseline patient characteristics. Inter-individual variability in the association between treatment exposure and risk of late toxicity suggests that genetic variation possibly modifies this association. We reviewed the available literature on genetic susceptibility of late toxicity after childhood cancer treatment related to components of metabolic syndrome, bone mineral density, gonadal impairment and hearing impairment.

METHODS

A systematic literature search was performed, using Embase, Cochrane Library, Google Scholar, MEDLINE, and Web of Science databases. Eligible publications included all English language reports of candidate gene studies and genome wide association studies (GWAS) that aimed to identify genetic risk factors associated with the four late toxicities, defined as toxicity present after end of treatment.

RESULTS

Twenty-seven articles were identified, including 26 candidate gene studies: metabolic syndrome (n = 6); BMD (n = 6); gonadal impairment (n = 2); hearing impairment (n = 12) and one GWAS (metabolic syndrome). Eighty percent of the genetic studies on late toxicity after childhood cancer had relatively small sample sizes (n < 200), leading to insufficient power, and lacked adjustment for multiple comparisons. Only four (4/26 = 15%) candidate gene studies had their findings validated in independent replication cohorts as part of their own report.

CONCLUSION

Genetic susceptibility associations are not consistent or not replicated and therefore, currently no evidence-based recommendations can be made for hearing impairment, gonadal impairment, bone mineral density impairment and metabolic syndrome in CCS. To advance knowledge related to genetic variation influencing late toxicities among CCS, future studies need adequate power, independent cohorts for replication, harmonization of disease outcomes and sample collections, and (international) collaboration.

Parsonage-Turner syndrome due to autochthonous acute genotype 3f hepatitis E virus infection in a nonimmunocompromised 55-year-old patient

Hepatitis E virus (HEV) infection is an emerging autochthonous disease in industrialized countries. Extra-hepatic manifestations, in particular neurologic manifestations, have been reported in HEV infection. Only a few cases of hepatitis E-associated Parsonage-Turner syndrome have been reported, and HEV genotypes were rarely determined. Here, we report the case of a Parsonage-Turner syndrome associated with an acute autochthonous HEV infection in a 55-year-old immunocompetent patient. HEV genomic RNA was detected in serum and cerebrospinal fluid samples (CSF), and molecular phylogenetic analysis of HEV was performed. The interest of this case lies in its detailed description notably the molecular analysis of HEV RNA isolated from serum and CSF. HEV infection should be considered in diagnostic investigations of neurologic manifestations associated with liver function perturbations.

Brainstem manifestations in neuromyelitis optica: a multicenter study of 258 patients

BACKGROUND

Neuromyelitis optica (NMO) is a severe autoimmune disease of the central nervous system characterized by spinal cord and optic nerve involvement. Brainstem manifestations have recently been described.

OBJECTIVE

To evaluate the time of occurrence, the frequency and the characteristics of brainstem symptoms in a cohort of patients with NMO according to the ethnic background and the serologic status for anti-aquaporin-4 antibodies (AQP4-abs).

METHODS

We performed a multicenter study of 258 patients with NMO according to the 2006 Wingerchuk criteria and we evaluated prospectively the frequency, the date of onset and the duration of various brainstem signs in this population.

RESULTS

Brainstem signs were observed in 81 patients (31.4%). The most frequently observed signs were vomiting (33.1%), hiccups (22.3%), oculomotor dysfunction (19.8%), pruritus (12.4%), followed by hearing loss (2.5%), facial palsy (2.5%), vertigo or vestibular ataxia (1.7%), trigeminal neuralgia (2.5%) and other cranial nerve signs (3.3%). They were inaugural in 44 patients (54.3%). The prevalence was higher in the non-Caucasian population (36.6%) than in the Caucasian population (26%) (p<0.05) and was higher in AQP4-ab-seropositive patients (32.7%) than in seronegative patients (26%) (not significant).

CONCLUSIONS

This study confirms the high frequency of brainstem symptoms in NMO with a majority of vomiting and hiccups. The prevalence of these manifestations was higher in the non Caucasian population.

Antibiotic prophylaxis for bacterial infections in afebrile neutropenic patients following chemotherapy

BACKGROUND

Bacterial infections are a major cause of morbidity and mortality in neutropenic patients following chemotherapy for malignancy. Trials have shown the efficacy of antibiotic prophylaxis in decreasing the incidence of bacterial infections, but not in reducing mortality rates.

OBJECTIVES

This review aimed to evaluate whether antibiotic prophylaxis in afebrile neutropenic patients reduced mortality when compared to placebo or no intervention.

SEARCH STRATEGY

Electronic searches on The Cochrane Cancer Network Register of Trials (2004), Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 4, 2004), MEDLINE (1966 to 2004) and EMBASE (1980 to 2004) and abstracts of conference proceedings; references of identified studies; the first author of each included trial was contacted.

SELECTION CRITERIA

RCTs or quasi-RCTs comparing different types of antibiotic prophylaxis with placebo or no intervention, or another antibiotic to prevent bacterial infections in afebrile neutropenic patients.

DATA COLLECTION AND ANALYSIS

Two authors independently appraised the quality of each trial and extracted data from the included trials. Relative risks (RR) or average differences, with their 95% confidence intervals (CI) were estimated.

MAIN RESULTS

One hundred trials (10,274 patients) performed between the years 1973 to 2004 met inclusion criteria. Antibiotic prophylaxis significantly decreased the risk for death when compared with placebo or no intervention (RR, 0.66 [95% CI 0.54 to 0.81]). The authors estimated the number needed to treat (NNT) in order to prevent 1 death from all causes as 60 (95% CI 34 to 268). Prophylaxis resulted in a significant decrease in the risk of infection-related death, RR 0.58 (95% CI 0.45 to 0.74) and in the occurrence of fever, RR 0.78 (95% CI 0.75 to 0.82). A reduction in mortality was also evident when the more recently conducted quinolone trials were analysed separately. Quinolone prophylaxis reduced the risk for all-cause mortality, RR 0.52 (95% CI, 0.37 to 0.84).

AUTHORS' CONCLUSIONS

Our review demonstrated that prophylaxis significantly reduced all-cause mortality. The most significant reduction in mortality was observed in trials assessing prophylaxis with quinolones. The benefit demonstrated in our review outweighs harm, such as adverse effects, and development of resistance, since all-cause mortality is reduced. Since most trials in our review were of patients with haematologic cancer, prophylaxis, preferably with a quinolone, should be considered for these patients.

Recombinant Mycobacterium bovis BCG producing IL-18 reduces IL-5 production and bronchoalveolar eosinophilia induced by an allergic reaction

BACKGROUND

Allergic reactions occur through the exacerbated induction of a Th2 cell type expression profile and can be prevented by agents favoring a Th1 profile. Bacillus Calmette-Guérin (BCG) is able to induce high IFN-gamma levels and has been shown to decrease experimentally induced allergy. The induction of IFN-gamma is mediated by interleukin (IL)-12 known to be secreted upon mycobacterial infections and can be enhanced by IL-18 acting in synergy with IL-12.

OBJECTIVE

We evaluated the ability of a recombinant BCG strain producing IL-18 (rBCG) to modify the Th2 type responses in a murine model of ovalbumin (OVA)-dependent allergic reaction.

METHODS

Mice were injected intraperitoneally or intranasally with OVA at days 0 and 15 and exposed to an OVA aerosol challenge at days 29, 30, 31 and 34. At days 0 and 15, two additional groups of mice received OVA together with 5 x 10(6) colony forming units of either rBCG or nonrecombinant BCG.

RESULTS

A time-course analysis of OVA-specific immunoglobulin (Ig)E, IgG1 and IgG2a levels indicated no significant difference between the three groups of mice. However, following in vitro stimulation with OVA, lymph node cells from rBCG-treated mice produced less IL-5 and more IFN-gamma than those of mice injected with nonrecombinant BCG. In addition, 48 h after the last OVA challenge, a strong reduction of bronchoalveolar eosinophilia was found in the rBCG-injected mice compared to the nontreated or nonrecombinant BCG-treated groups.

CONCLUSION

These results indicate that the production of IL-18 by rBCG may enhance the immunomodulatory properties of BCG that suppress pulmonary Th2 responses and, in particular, decrease airway eosinophilia.

Mycobacterium tuberculosis lipomannan induces apoptosis and interleukin-12 production in macrophages

The mycobacterial cell wall component lipoarabinomannan (LAM) has been described as a virulence factor of Mycobacterium tuberculosis, and modification of the terminal arabinan residues of this compound with mannose caps (producing mannosyl-capped LAM [ManLAM]) in M. tuberculosis or with phosphoinositol caps (producing phosphoinositol-capped LAM [PILAM]) in Mycobacterium smegmatis has been implicated in various functions associated with these lipoglycans. A structure-function analysis was performed by using LAMs and their biosynthetic precursor lipomannans (LMs) isolated from different mycobacterial species on the basis of their capacity to induce the production of interleukin-12 (IL-12) and/or apoptosis of macrophage cell lines. Independent of the mycobacterial species, ManLAMs did not induce IL-12 gene expression or apoptosis of macrophages, whereas PILAMs induced IL-12 secretion and apoptosis. Interestingly, uncapped LAM purified from Mycobacterium chelonae did not induce IL-12 secretion or apoptosis. Furthermore, LMs, independent of their mycobacterial origins, were potent inducers of IL-12 and apoptosis. The precursor of LM, phosphatidyl-myo-inositol dimannoside, had no activity, suggesting that the mannan core of LM was required for the activity of LM. The specific interaction of LM with Toll-like receptor 2 (TLR-2) but not with TLR-4 suggested that these responses were mediated via the TLR-2 signaling pathway. Our experiments revealed an important immunostimulatory activity of the biosynthetic LAM precursor LM. The ratio of LAM to LM in the cell wall of mycobacteria may be an important determinant of virulence, and enzymes that modify LM could provide targets for development of antituberculosis drugs and for derivation of attenuated strains of M. tuberculosis.

The M. tuberculosis antigen 85 complex and mycolyltransferase activity

AIMS

The antigen 85 complex (Ag85) from Mycobacterium tuberculosis consists of three abundantly secreted proteins (FbpA, FbpB and FbpC2) which play a key role in the pathogenesis of tuberculosis and also exhibit cell wall mycolyltransferase activity. A related protein with similarity to the Ag85 complex was recently annotated in the M. tuberculosis genome as FbpC1. An investigation was carried out to determine whether FbpC1 may also possess mycolyltransferase activity, a characteristic feature of the Ag85 complex.

METHODS AND RESULTS

Heterologous expression of FbpA, FbpC1 and FbpC2 was performed in Escherichia coli. Recombinant proteins were purified under non-denaturating conditions and used in an in vitro mycolyltransferase assay.

CONCLUSIONS

In contrast to FbpA and FbpC2, recombinant FbpC1 did not possess in vitro mycolyltransferase activity and was not recognized by two monoclonal antibodies to the native Ag85.

SIGNIFICANCE AND IMPACT OF THE STUDY

Mycolyltransferase activity is restricted to FbpA, FbpbB and FbpC2 only; the actual function of FbpC1 remains to be established.

Mammalian STAG3 is a cohesin specific to sister chromatid arms in meiosis I

Cohesins, which have been characterized in budding yeast and Xenopus, are multisubunit protein complexes involved in sister chromatid cohesion. Regulation of the interactions among different cohesin subunits and the assembly/disassembly of the cohesin complex to chromatin are key steps in chromosome segregation. We previously characterized the mammalian STAG3 protein as a component of the synaptonemal complex that is specifically expressed in germinal cells, although its function in meiosis remains unknown. Here we show that STAG3 has a role in sister chromatid arm cohesion during mammalian meiosis I. Immunofluorescence results in prophase I cells suggest that STAG3 is a component of the axial/lateral element of the synaptonemal complex. In metaphase I, STAG3 is located at the interchromatid domain and is absent from the chiasma region. In late anaphase I and the later stages of meiosis, STAG3 is not detected. STAG3 interacts with the structural maintenance chromosome proteins SMC1 and SMC3, which have been reported to be subunits of the mitotic cohesin complex. We propose that STAG3 is a sister chromatid arm cohesin that is specific to mammalian meiosis I.

Galactan biosynthesis in Mycobacterium tuberculosis. Identification of a bifunctional UDP-galactofuranosyltransferase

The cell wall of Mycobacterium tuberculosis and related genera is unique among prokaryotes, consisting of a covalently bound complex of mycolic acids, D-arabinan and D-galactan, which is linked to peptidoglycan via a special linkage unit consisting of Rhap-(1-->3)-GlcNAc-P. Information concerning the biosynthesis of this entire polymer is now emerging with the promise of new drug targets against tuberculosis. Accordingly, we have developed a galactosyltransferase assay that utilizes the disaccharide neoglycolipid acceptors beta-d-Galf-(1-->5)-beta-D-Galf-O-C(10:1) and beta-D-Galf-(1-->6)-beta-D-Galf-O-C(10:1), with UDP-Gal in conjunction with isolated membranes. Chemical analysis of the subsequent reaction products established that the enzymatically synthesized products contained both beta-D-Galf linkages ((1-->5) and (1-->6)) found within the mycobacterial cell, as well as in an alternating (1-->5) and (1-->6) fashion consistent with the established structure of the cell wall. Furthermore, through a detailed examination of the M. tuberculosis genome, we have shown that the gene product of Rv3808c, now termed glfT, is a novel UDP-galactofuranosyltransferase. This enzyme possesses dual functionality in performing both (1-->5) and (1-->6) galactofuranosyltransferase reactions with the above neoglycolipid acceptors, using membranes isolated from the heterologous host Escherichia coli expressing Rv3808c. Thus, at a biochemical and genetic level, the polymerization of the galactan region of the mycolyl-arabinogalactan complex has been defined, allowing the possibility of further studies toward substrate recognition and catalysis and assay development. Ultimately, this may also lead to a more rational approach to drug design to be explored in the context of mycobacterial infections.

BENE, a novel raft-associated protein of the MAL proteolipid family, interacts with caveolin-1 in human endothelial-like ECV304 cells

The MAL proteolipid, an integral protein present in glycolipid- and cholesterol-enriched membrane (GEM) rafts, is an element of the machinery necessary for apical sorting in polarized epithelial Madin-Darby canine kidney cells. MAL was the first member identified of an extended family of proteins that have significant overall sequence identity. In this study we have used a newly generated monoclonal antibody to investigate an unedited member of this family, named BENE, which was found to be expressed in endothelial-like ECV304 cells and normal human endothelium. Human BENE was characterized as a proteolipid protein predominantly present in GEM rafts in ECV304 cells. Coimmunoprecipitation experiments revealed that BENE interacted with caveolin-1. Confocal immunofluorescence and electron microscopic analyses indicated that BENE mainly accumulated into intracellular vesicular/tubular structures that partially colocalize with internal caveolin-1. In response to cell surface cholesterol oxidation, BENE redistributed to the dilated vesicular structures that concentrate most of the caveolin-1 originally on the cell surface. After cessation of cholesterol oxidation, a detectable fraction of the BENE molecules migrated to the plasmalemma accompanying caveolin-1 and then returned progressively to its steady state distribution. Together, these features highlight the BENE proteolipid as being an element of the machinery for raft-mediated trafficking in endothelial cells.

Biochemical characterization of acyl carrier protein (AcpM) and malonyl-CoA:AcpM transacylase (mtFabD), two major components of Mycobacterium tuberculosis fatty acid synthase II

Malonyl coenzyme A (CoA)-acyl carrier protein (ACP) transacylase (MCAT) is an essential enzyme in the biosynthesis of fatty acids in all bacteria, including Mycobacterium tuberculosis. MCAT catalyzes the transacylation of malonate from malonyl-CoA to activated holo-ACP, to generate malonyl-ACP, which is an elongation substrate in fatty acid biosynthesis. To clarify the roles of the mycobacterial acyl carrier protein (AcpM) and MCAT in fatty acid and mycolic acid biosynthesis, we have cloned, expressed, and purified acpM and mtfabD (malonyl-CoA:AcpM transacylase) from M. tuberculosis. According to the culture conditions used, AcpM was produced in Escherichia coli in two or three different forms: apo-AcpM, holo-AcpM, and palmitoylated-AcpM, as revealed by electrospray mass spectrometry. The mtfabD gene encoding a putative MCAT was used to complement a thermosensitive E. coli fabD mutant. Expression and purification of mtFabD resulted in an active enzyme displaying strong MCAT activity in vitro. Enzymatic studies using different ACP substrates established that holo-AcpM constitutes the preferred substrate for mtFabD. In order to provide further insight into the structure-function relationship of mtFabD, different mutant proteins were generated. All mutations (Q9A, R116A, H194A, Q243A, S91T, and S91A) completely abrogated MCAT activity in vitro, thus underlining the importance of these residues in transacylation. The generation and characterization of the AcpM forms and mtFabD opens the way for further studies relating to fatty acid and mycolic acid biosynthesis to be explored in M. tuberculosis. Since a specific type of FabD is found in mycobacterial species, it represents an attractive new drug target waiting to be exploited.

Expression of CCR9 beta-chemokine receptor is modulated in thymocyte differentiation and is selectively maintained in CD8(+) T cells from secondary lymphoid organs

Chemokines appear to have an important role in the seeding of lymphoid progenitors in the thymus, the regulation of the coordinated movements of the maturing T cells within this organ, and the egress of the resulting naive T cells to secondary lymphoid organs. CCR9, the specific receptor for the beta-chemokine TECK/CCL25, is selectively expressed in thymus, lymph node, and spleen. Using a specific anti-CCR9 polyclonal antibody, K629, and a semiquantitative reverse transcriptase-polymerase chain reaction procedure, a detailed study of CCR9 expression in the thymus and secondary lymphoid organs was performed. The results show that CD4(+)CD8(+) double-positive thymocytes have the highest CCR9 expression in thymus. Single-positive CD8(+) thymocytes continue to express this receptor after abandoning the thymus as mature naive T cells, as suggested by the existence of a CD8(+)CD69(low)CD62L(high) CCR9(+) cell subset. Consistent with this, CD8(+) lymphocytes from lymph nodes, spleen, and Peyer patches express a functional CCR9, as its expression correlates with migration in response to CCL25. Conversely, CD4(+) thymocytes lose CCR9 before abandoning the thymus, and CD4(+) T cells from secondary lymphoid organs also lack CCR9 expression. Analysis of CCR9 expression in thymocytes from mice of different ages showed that CCR9 levels are affected by age, as this receptor is more abundant, and its response to CCL25 is more potent in newborn animals. Collectively, these results suggest that CCR9 has a role in thymocyte development throughout murine life, with clear differences between the CD4(+) and CD8(+) lineages.

Immunostimulatory effect of IL-18-encoding plasmid in DNA vaccination against murine Schistosoma mansoni infection

In vivo delivery of DNA encoding antigens is a simple tool to induce immune responses against pathogens. This approach to vaccination also offers the possibility to codeliver plasmids encoding immunomodulatory molecules in order to drive immune responses towards optimal protective effects. In the murine model of Schistosoma mansoni infection, vaccination inducing a Th1 profile has been shown to be protective. In this study, we used a plasmid encoding the Th1-promoting cytokine IL-18, since we observed that percutaneous infection of Balb/c mice strongly induced the production of IL-18 mRNA in the skin. Intradermal injection of the IL-18-encoding plasmid prior to infection did not interfere with parasite migration through the skin although it led to a local and transient cellular infiltration. When the IL-18-encoding plasmid was codelivered with a S. mansoni glutathione S-transferase (Sm28GST)-encoding plasmid, a 30-fold increase of antigen-specific IFN-gamma secretion by spleen cells was observed in comparison to spleen cells from mice that had received only the Sm28GST-encoding plasmid. This immunostimulatory effect was related to a significant protective effect (28% reduction in egg laying and 23% reduction in worm burden) which was attributed to a cooperative effect between both plasmids. Therefore, this study shows that codelivery of an IL-18-encoding plasmid with an antigen-encoding plasmid can stimulate specific cellular responses and induce protective effects against S. mansoni infection.

The transient expression of C-C chemokine receptor 8 in thymus identifies a thymocyte subset committed to become CD4+ single-positive T cells

Developing T cells journey through the different thymic microenvironments while receiving signals that eventually will allow some of them to become mature naive T cells exported to the periphery. This maturation can be visualized by the phenotype of the developing cells. CCR8 is a ss-chemokine receptor preferentially expressed in the thymus. We have developed 8F4, an anti-mouse CCR8 mAb that is able to neutralize the ligand-induced activation of CCR8, and used it to characterize the CCR8 protein expression in the different thymocyte subsets. Taking into account the intrathymic lineage relationships, our data showed that CCR8 expression in thymus followed two transient waves along T cell maturation. The first one took place in CD4(-) CD8(-) double-negative thymocytes, which showed a low CCR8 expression, and the second wave occurred after TCR activation by the Ag-dependent positive selection in CD4(+) CD8(+) double-positive cells. From that maturation stage, CCR8 expression gradually increased as the CD4(+) cell differentiation proceeded, reaching a maximum at the CD4(+) CD8(-) single-positive stage. These CD4(+) cells expressing CCR8 were also CD69(high) CD62L(low) thymocytes, suggesting that they still needed to undergo some differentiation step before becoming functionally competent naive T cells ready to be exported from the thymus. Interestingly, no significant amounts of CCR8 protein were detectable in CD4(-) CD8(+) thymocytes. Our data showing a clear regulation of the CCR8 protein in thymus suggest a relevant role for CCR8 in this lymphoid organ, and identify CCR8 as a possible marker of thymocyte subsets recently committed to the CD4(+) lineage.

Improvement in affinity and HIV-1 neutralization by somatic mutation in the heavy chain first complementarity-determining region of antibodies triggered by HIV-1 infection

We assessed the impact of somatic hypermutation in the framework region 1 (FR1) and complementarity-determining region 1 (CDR1) of three clonally-related heavy chains from the human monovalent antigen-binding fragments Fab S19, S8 and S20 on gp120 binding and HIV-1 neutralization capacity. Nucleotide changes were introduced in the heavy chains to revert single and multiple amino acid residues, and two Fab libraries were constructed with the same light chain to express equivalent amounts of parental and reverted phage Fab. We studied the contribution of each amino acid replacement to antigen binding by calculating the frequency of phage Fab retrieval after competitive library selection on gp120. Whereas mutations in FR1 had no effect on antigen binding, somatic replacements in the CDR1 of the heavy chain (HCDR1) appeared to produce significant changes. In S19 HCDR1, somatic mutation of residue 32 reduced gp120 binding. In Fab S20, the Arg(30) and Asp(31) somatically replaced residues in HCDR1 improved antigen binding. Both of these residues are necessary to increase Fab binding to gp120; reversion of either residue alone results in a decrease in binding. The impact of these two replacements was confirmed by the greater neutralization capacity of S20 compared to the other Fab. Molecular modeling of S20 HCDR1 suggests that Arg(30) and Asp(31) are the main interaction sites for gp120, increasing antibody affinity and promoting the enhanced neutralization ability of S20. These findings are consistent with a gp120-driven process, supporting a role for affinity maturation and intraclonal evolution of HIV-1 neutralizing antibodies.

MAP kinases Erk1/2 phosphorylate sterol regulatory element-binding protein (SREBP)-1a at serine 117 in vitro

Sterol regulatory element-binding protein (SREBP)-1a is a transcription factor sensing cellular cholesterol levels and integrating gene regulatory signals mediated by MAP kinase cascades. Here we report the identification of serine 117 in SREBP-1a as the major phosphorylation site of the MAP kinases Erk1/2. This site was identified by nanoelectrospray mass spectrometry and peptide sequencing of recombinant fusion proteins phosphorylated by Erk1/2 in vitro. Serine 117 was verified as the major phosphorylation site by in vitro mutagenesis. Mutation of serine 117 to alanine abolished Erk2-mediated phosphorylation in vitro and the MAP kinase-related transcriptional activation of SREBP-1a by insulin and platelet-derived growth factor in vivo. Our data indicate that the MAP kinase-mediated effects on SREBP-1a-regulated target genes are linked to this phosphorylation site.

Identification and substrate specificity of beta -ketoacyl (acyl carrier protein) synthase III (mtFabH) from Mycobacterium tuberculosis

The long-chain alpha-alkyl-beta-hydroxy fatty acids, termed mycolic acids, which are characteristic components of the mycobacterial cell wall are produced by successive rounds of elongation catalyzed by a multifunctional (type I) fatty acid synthase complex followed by a dissociated (type II) fatty acid synthase. In bacterial type II systems, the first initiation step in elongation is the condensation of acetyl-CoA with malonyl-acyl carrier protein (ACP) catalyzed by beta-ketoacyl-ACP III (FabH). An open reading frame in the Mycobacterium tuberculosis genome (Rv0533c), now termed mtfabH, was 37.3% identical to Escherichia coli ecFabH and contained the Cys-His-Asn catalytic triad signature. However, the purified recombinant mtFabH clearly preferred long-chain acyl-CoA substrates rather than acyl-ACP primers and did not utilize acetyl-CoA as a primer in comparison to ecFabH. In addition, purified mtFabH was sensitive to thiolactomycin and resistant to cerulenin in an in vitro assay. However, mtFabH overexpression in Mycobacterium bovis BCG did not confer thiolactomycin resistance, suggesting that mtFabH may not be the primary target of thiolactomycin inhibition in vivo and led to several changes in the lipid composition of the bacilli. The data presented is consistent with a role for mtFabH as the pivotal link between the type I and type II fatty acid elongation systems in M. tuberculosis. This study opens up new avenues for the development of selective and novel anti-mycobacterial agents targeted against mtFabH.