Diseases caused by mutations in ORAI1 and STIM1.

Ca(2+) release-activated Ca(2+) (CRAC) channels mediate a specific form of Ca(2+) influx called store-operated Ca(2+) entry (SOCE) that contributes to the function of many cell types. CRAC channels are composed of ORAI1 proteins located in the plasma membrane, which form its ion-conducting pore. ORAI1 channels are activated by stromal interaction molecule (STIM) 1 and STIM2 located in the endoplasmic reticulum. Loss- and gain-of-function gene mutations in ORAI1 and STIM1 in human patients cause distinct disease syndromes. CRAC channelopathy is caused by loss-of-function mutations in ORAI1 and STIM1 that abolish CRAC channel function and SOCE; it is characterized by severe combined immunodeficiency (SCID)-like disease, autoimmunity, muscular hypotonia, and ectodermal dysplasia, with defects in sweat gland function and dental enamel formation. The latter defect emphasizes an important role of CRAC channels in tooth development. By contrast, autosomal dominant gain-of-function mutations in ORAI1 and STIM1 result in constitutive CRAC channel activation, SOCE, and increased intracellular Ca(2+) levels that are associated with an overlapping spectrum of diseases, including nonsyndromic tubular aggregate myopathy (TAM) and York platelet and Stormorken syndromes. The latter two syndromes are defined, besides myopathy, by thrombocytopenia, thrombopathy, and bleeding diathesis. The fact that myopathy results from both loss- and gain-of-function mutations in ORAI1 and STIM1 highlights the importance of CRAC channels for Ca(2+) homeostasis in skeletal muscle function. The cellular dysfunction and clinical disease spectrum observed in mutant patients provide important information about the molecular regulation of ORAI1 and STIM1 proteins and the role of CRAC channels in human physiology.

Emergence of vaccine-derived polioviruses, Democratic Republic of Congo, 2004-2011.

Polioviruses isolated from 70 acute flaccid paralysis patients from the Democratic Republic of Congo (DRC) during 2004-2011 were characterized and found to be vaccine-derived type 2 polioviruses (VDPV2s). Partial genomic sequencing of the isolates revealed nucleotide sequence divergence of up to 3.5% in the viral protein 1 capsid region of the viral genome relative to the Sabin vaccine strain. Genetic analysis identified at least 7 circulating lineages localized to specific geographic regions. Multiple independent events of VDPV2 emergence occurred throughout DRC during this 7-year period. During 2010-2011, VDPV2 circulation in eastern DRC occurred in an area distinct from that of wild poliovirus circulation, whereas VDPV2 circulation in the southwestern part of DRC (in Kasai Occidental) occurred within the larger region of wild poliovirus circulation.

Infectious and noninfectious triggers in Guillain-Barré syndrome.

Guillain-Barré syndrome (GBS) is the commonest cause of acquired flaccid paralysis in the world and regarded by many as the prototype for postinfectious autoimmunity. Here the authors consider both infectious and noninfectious triggers of GBS and determine where possible what immunological mechanisms may account for this association. In approximately two-thirds of cases, an infectious trigger is reported in the weeks that lead up to disease onset, indicating that the host's response to infection must play an important role in disease pathogenesis. The most frequently identified bacteria, Campylobacter jejuni, through a process known as molecular mimicry, has been shown to induce cross-reactive anti-ganglioside antibodies, which can lead to the development of axonal-type GBS in some patients. Whether this paradigm can be extended to other infectious organisms or vaccines remains an important area of research and has public health implications. GBS has also been reported rarely in patients with underlying systemic diseases and immunocompromised states and although the exact mechanism is yet to be established, increased susceptibility to known infectious triggers should be considered most likely.

Marked hypotonia in an infant of a mother with Devic disease.

A full-term female neonate was born with severe hypotonia and weakness. Her mother had been treated for neuromyelitis optica (Devic disease) for 6 years. Her previous son, born 10 years earlier and before she developed the disease, also had marked hypotonia that gradually improved over several weeks. A suspicion of neonatal myasthenia gravis arose, as a search of the literature revealed the occasional detection of anti-acetylcholine receptor antibodies in patients with Devic disease. A neostigmine test was mildly positive in the baby, but anti-acetylcholine receptor antibodies were elevated. Aquaporin 4 antibodies typical of neuromyelitis optica were not detected in the infant. Because of clinical deterioration, intravenous immunoglobulin was administered with substantial improvement. Anti-acetylcholine antibodies were markedly elevated in the mother's serum, although she showed no clinical signs of myasthenia gravis. It is very likely that her previous baby also had unrecognized transient myasthenia gravis.

Leukocyte and complement activation by GM1-specific antibodies is associated with acute motor axonal neuropathy in rabbits.

Acute motor axonal neuropathy (AMAN) in humans is associated with the presence of GM1-specific antibodies. Immunization of rabbits with GM1-containing ganglioside mixtures, purified GM1, or Campylobacter jejuni lipo-oligosaccharide exhibiting a GM1-like structure elicits GM1-specific antibodies, but axonal polyneuropathy only occurs in a subset of animals. This study aimed to dissect the molecular basis for the variable induction of AMAN in rabbits. Therefore, we analyzed the pro-inflammatory characteristics of GM1-specific antibodies in plasma samples from ganglioside-immunized rabbits with and without neurological deficits. GM1-specific plasma samples from all rabbits with AMAN were capable of activating both complement and leukocytes, in contrast to none of the plasma samples from rabbits without paralysis. Furthermore, GM1-specific IgG-mediated activation of leukocytes was detected before the onset of clinical signs. These data suggest that AMAN only occurs in rabbits that develop GM1-specific antibodies with pro-inflammatory properties.

Pediatric macrophagic myofasciitis associated with motor delay.

BACKGROUND: Macrophagic myofasciitis (MMF) is a rare inflammatory myopathy characterized by accumulation of perifascicular macrophages without muscle fiber necrosis. Few sporadic pediatric cases have been described, and MMF is recognized as a possible reaction to intramuscular injections of aluminum-containing vaccines. The association of MMF and motor delay is unclear in the pediatric population. We report the clinical evaluation and follow-up of 4 young children with MMF and review of 4 cases previously reported of sporadic, pediatric MMF to better determine the possible association of sporadic MMF in children presenting with motor delay. PATIENTS AND METHODS: Described our 4 case reports in which we observed children presenting for evaluation of motor delay with unrevealing clinical and laboratory evaluations for common causes of motor delay and histopathological evaluations consistent with macrophagic myofasciitis. Muscle data was obtained by quadriceps muscle biopsy. RESULTS: Clinical presentations were similar in all children and were characterized by motor delay, hypotonia, and failure to thrive with an unrevealing evaluation for central nervous system disease, congenital, and mitochondrial myopathies. CONCLUSIONS: Our cases and those previously reported in the literature demonstrate MMF should be considered in the evaluation of children with failure to thrive, hypotonia, and muscle weakness, as clinical outcome appears to be favorable.

Immune status to polioviruses in the child population of Romania between 2002-2005 as indicated by serological investigation in cases of acute flaccid paralysis (AFP) and facial paralysis (FP) and its use as a "national reference value" to evaluate the vaccination coverage in particular groups of healthy children.

Although the European region is polio free since 2002, the risk of importation from endemic regions remains present and a high level of population immunity must be maintained. In Romania during the period 2002-2005, 101 FP cases, 91 AFP cases and 29 healthy contacts (living in groups with low social and sanitary status, relatively low vaccination coverage named "at risk") could have been investigated serologically. Antibody prevalences for poliovirus types 1, 2, and 3 were: 97.2%, 98% and 81.2% for FP cases; 96.7%, 94.5% and 85.7% for AFP cases, and 85.7%, 82.1% and 53% for the group of healthy children at risk. The risk of the emergence and spread of cVDPVs remains present especially in "at risk" groups with the gaps in immunity, even in countries where indigenous wild polioviruses have already been eradicated.

Inclusion body myositis: clinical, morphological, physiological and laboratory findings in 18 cases.

Eighteen consecutive patients with inclusion body myositis (IBM) were studied. The mean age of onset of symptoms was 60 years. A typical clinical pattern with insidious onset of muscle weakness in knee extensors and finger flexors combined with dysphagia was observed. Serial measurements of the maximal voluntary muscle strength revealed a mean loss of muscle strength of 1.4% per month. Two of the cases had common variable immunodeficiency, and three cases had reduced levels of the IgG3 subclass. Treatment with prednisone resulted in a temporary improvement of muscle function in three patients. No positive effect of azathioprine or cyclosporine A could be documented. The results show that IBM may be associated with immunodeficiency, and that prednisone treatment may temporarily improve the clinical signs. The results from our studies on the progression of the muscle weakness may provide basis for future studies on treatment of IBM.

Linkage between the frequency of muscular weakness and loci that regulate immune responsiveness in murine experimental myasthenia gravis.

Mice immunized with acetylcholine receptor (AChR) purified from Torpedo californica form anti-AChR antibodies and often develop muscular weakness and flaccid paralysis closely resembling the human disease myasthenia gravis. This condition, termed experimental myasthenia gravis (EMG), is strain dependent in that the frequency of paralysis is much greater in some strains than in others. Differences in the frequency of EMG might result from differences in the immune system or the neuromuscular junction. In these studies, we have identified two loci, the major histocompatibility complex (H-2) region on chromosome 17 and the region that contains the structural genes for the constant region of immunoglobulin heavy chains (IgCH region) on chromosome 12, which significantly effect the probability with which a mouse immunized with T. californica AChR can be expected to become paralyzed. One genotype (H-2b, Ig-1b) correlated with high susceptibility to EMG in four strains with three dissimilar backgrounds. These studies demonstrate that susceptibility to EMG is a heritable trait determined by at least two distinct loci that are linked to regions of the mouse genome that regulate immune responsiveness.

Peripheral neuropathy and benign IgG paraproteinaemia.

Three patients with peripheral neuropathy and an associated benign IgG paraproteinaemia are described. No direct immunological evidence for an aetiological role of the paraprotein was found, and the implications of this are discussed.