Free kappa light chains in cerebrospinal fluid as a biomarker to assess risk conversion to multiple sclerosis.

BACKGROUND: Multiple sclerosis (MS) initiates with a first attack or clinically isolated syndrome (CIS). The importance of an early treatment in MS leads to the search, as soon as possible, for novel biomarkers which can predict conversion from CIS to MS. OBJECTIVE: The purpose of this study was to assess the predictive value of the kappa index ([Formula: see text] index), using kappa free light light chains ([Formula: see text]FLCs) in cerebrospinal fluid (CSF), for the conversion of CIS patients to MS, and compare its accuracy with other parameters used in clinical practice. METHODS: FLC levels were analysed in CSF from 176 patients: 70 as control group, 77 CIS, and 29 relapsing-remitting MS. FLC levels were quantified by nephelometry. RESULTS: [Formula: see text] Index sensitivity and specificity (93.1%; 95.7%) was higher than those from the immunoglobulin G (IgG) index (75.9%; 94.3%), and lower than those from oligoclonal IgG bands (OCGBs) (96.5%; 98.6%). The optimal cut-off for [Formula: see text] index was 10.62. Most of the CIS patients with [Formula: see text] index >10.62 presented OCGBs, IgG index >0.56 and fulfilled magnetic resonance imaging (MRI) criteria. CONCLUSION: CIS patients above [Formula: see text] index cut-off of 10.62 present 7.34-fold risk of conversion to MS than CIS below this value. The [Formula: see text] index correlated with positive OCGBs, IgG index above 0.56 and MRI criteria.

Assessment of the reproducibility of oligoclonal IgM band detection for its application in daily clinical practice.

BACKGROUND: The presence of oligoclonal IgM bands (OCMB) in cerebrospinal fluid (CSF) is an unfavourable prognostic marker in multiple sclerosis. There is no commercial test to investigate OCMB status. However, a sensitive and specific isoelectrofocusing (IEF) and western blot method was described. We aimed to study the inter-centre reproducibility of this technique, a necessary condition for a reliable test to be incorporated into clinical practice. METHODS: The presence of OCMB was analysed by IEF and western blot with prior reduction of pentameric IgM. We assayed the reproducibility of this test in a blinded multicentre study performed in 13 university hospitals. Paired-CSF and serum samples from 52 neurological patients were assayed at every centre. RESULTS: Global analysis rendered a concordance of 89.8% with a kappa value of 0.71. CONCLUSION: These data indicate that OCMB detection by means of IEF and western blot with IgM reduction shows a good interlaboratory reproducibility and thus can be used in daily clinical setting.

Utility of oligoclonal IgG band detection for MS diagnosis in daily clinical practice.

An early and accurate diagnosis of multiple sclerosis (MS) is very important, since it allows early treatment initiation, which reduces the activity of the disease. Oligoclonal IgG band (OCGB) detection is a good ancillary tool for MS diagnosis. However, it was argued that its usefulness was limited by the high interlaboratory variability. In the last years, different techniques for OCGB detection have appeared. We performed a blinded aleatorized multicenter study in 19 Spanish hospitals to assess the accuracy and reproducibility of OCGB detection in this new scenario. We studied cerebrospinal fluid (CSF) and serum samples from 114 neurological patients. Every hospital contributed to the study with triplicated pairs of CSF and serum samples of six patients and analyzed 18 different samples. Global analysis rendered a sensitivity of 92.1%, a specificity of 95.1% and a Kappa value of 0.81. This shows that current techniques for OCGB detection have good accuracy and a high interlaboratory reproducibility and thus, represent a good tool for MS diagnosis. When we analyzed separately the different techniques used for OCGB detection, the highest concordance was observed in western blot with alkaline phosphatase detection (kappa=0.91). This indicates that high sensitivity techniques improve the reproducibility of this assay.

Arg113His mutation of vanishing white matter is not present in multiple sclerosis.

Vanishing white matter (VWM) is a childhood leukoencephalopathy with central hypomyelination, white matter rarefaction, and cystic degeneration. Adult onset, variable phenotype, and high frequency characterize Arg113His mutation caused by G338A polymorphism associated with VWM. A patient with trauma-associated onset, and clinical features compatible with multiple sclerosis (MS), was homozygous for G338A mutation of eukaryotic translation initiation factor (eIF2B5). The authors checked a cohort of 101 MS patients, including 19 with head/neck trauma-associated onset, and failed to find the mutation, described above, in MS chromosomes. Our report does not exclude the presence in MS chromosomes of other mutations in the eIF2B gene family.

Critical residues of Chlamydomonas reinhardtii ferredoxin for interaction with nitrite reductase and glutamate synthase revealed by site-directed mutagenesis.

Incubation of wild-type ferredoxin (Fd) with Chlamydomonas reinhardtii crude extract in the presence of a carboxyl activator resulted in the formation of a unique 1:1 covalent complex with nitrite reductase. However, glutamate synthase was able to form two covalent complexes of Fd: GOGAT with 1:1 and 2:1 stoichiometries. These complexes were functional only when reduced methyl viologen was used as electron donor. Kinetic studies of complex formation suggested the presence of two Fd-binding domains with similar affinity for Fd in the glutamate synthase molecule. Using site-directed mutagenesis with recombinant Fd, we have shown that Fd-Glu91 is directly involved in Fd interaction with glutamate synthase and nitrite reductase. Moreover, a negative core of residues in the alpha1 helix of Fd was also critical in binding the enzymes. These data highlight the analogy in the Fd-binding sites of nitrite reductase and glutamate synthase, which may compete for the electrons coming from the photosynthetic chain.

Homology predicted structure and functional interaction of ferredoxin from the eukaryotic alga Chlamydomonas reinhardtii with nitrite reductase and glutamate synthase.

Ferredoxin (Fd) from Chlamydomonas reinhardtii is composed of 94 amino-acid residues and a [2Fe-2S] cluster. The homology modelling technique has been used to predict the tertiary structure of C. reinhardtii Fd. The overall structure shows the typical fifth-stranded beta-grasp plus two additional beta-sheets and three alpha-helices. Site-directed mutagenesis of recombinant Fd has allowed us to obtain four point mutants and one double mutant--all mutations being located in the short alpha-helix at the carboxy-terminal segment as well as a triple mutant affected on helix alpha1. Crosslinking studies and measurement of enzymatic activities reveal that the residues changed are critical for the interaction of Fd with glutamate synthase (GOGAT) and nitrite reductase (NiR). Potentiometric analyses of the Fd mutants show that the replacement of glutamate in position 91 drastically changes the redox potential value (70 mV), thereby suggesting that such a glutamate can modulate the reactivity of Fd towards its reaction partners. According to results herein presented, the reported mutations modify the electrostatic interactions within the complex formed between Fd and GOGAT or NiR.