A mutation in the interferon-gamma-receptor gene and susceptibility to mycobacterial infection

BACKGROUND

Genetic differences in immune responses may affect susceptibility to mycobacterial infection, but no specific genes have been implicated in humans. We studied four children who had an unexplained genetic susceptibility to mycobacterial infection and who appeared to have inherited the same recessive mutation from a common ancestor.

METHODS

We used microsatellite analysis, immunofluorescence studies, and sequence analysis to study the affected patients, unaffected family members, and normal controls.

RESULTS

A genome search using microsatellite markers identified a region on chromosome 6q in which the affected children were all homozygous for eight markers. The gene for interferon-gamma receptor 1 maps to this region. Immunofluorescence studies showed that the receptor was absent on leukocytes from the affected children. Sequence analysis of complementary DNA for the gene for interferon-gamma receptor 1 revealed a point mutation at nucleotide 395 that introduces a stop codon and results in a truncated protein that lacks the transmembrane and cytoplasmic domains.

CONCLUSIONS

Four children with severe mycobacterial infections had a mutation in the gene for interferon-gamma receptor 1 that leads to the absence of receptors on cell surfaces and a functional defect in the up-regulation of tumor necrosis factor alpha by macrophages in response to interferon-gamma. The interferon-gamma pathway is important in the response to intracellular pathogens such as mycobacteria.

A molecular pathway determining left-right asymmetry in chick embryogenesis

While significant progress has been made in understanding the molecular events underlying the early specification of the antero-posterior and dorso-ventral axes, little information is available regarding the cellular or molecular basis for left-right (LR) differences in animal morphogenesis. We describe the expression patterns of three genes involved in LR determination in chick embryos: activin receptor IIa, Sonic hedgehog (Shh), and cNR-1 (related to the mouse gene nodal). These genes are expressed asymmetrically during and after gastrulation and regulate the expression of one another in a sequential pathway. Moreover, manipulation of the sidedness of either activin protein or Shh expression alters heart situs. Together, these observations identify a cascade of molecular asymmetry in that determines morphological LR asymmetry in the chick embryo.

Dysfunction of endothelial protein C activation in severe meningococcal sepsis

BACKGROUND

Impairment of the protein C anticoagulation pathway is critical to the thrombosis associated with sepsis and to the development of purpura fulminans in meningococcemia. We studied the expression of thrombomodulin and the endothelial protein C receptor in the dermal microvasculature of children with severe meningococcemia and purpuric or petechial lesions.

METHODS

We assessed the integrity of the endothelium and the expression of thrombomodulin and the endothelial protein C receptor in biopsy specimens of purpuric lesions from 21 children with meningococcal sepsis (median age, 41 months), as compared with control skin-biopsy specimens.

RESULTS

The expression of endothelial thrombomodulin and of the endothelial protein C receptor was lower in the patients with meningococcal sepsis than in the controls, both in vessels with thrombosis and in vessels without thrombosis. On electron microscopical examination, the endothelial cells were generally intact in both thrombosed and nonthrombosed vessels. Plasma thrombomodulin levels in the children with meningococcal sepsis (median, 6.4 ng per liter) were higher than those in the controls (median, 3.6 ng per liter; P=0.002). Plasma levels, protein C antigen, protein S antigen, and antithrombin antigen were lower than those in the controls. In two patients treated with unactivated protein C concentrate, activated protein C was undetectable at the time of admission, and plasma levels remained low.

CONCLUSIONS

In severe meningococcal sepsis, protein C activation is impaired, a finding consistent with down-regulation of the endothelial thrombomodulin-endothelial protein C receptor pathway.

Recombinant bactericidal/permeability-increasing protein (rBPI21) as adjunctive treatment for children with severe meningococcal sepsis: a randomised trial. rBPI21 Meningococcal Sepsis Study Group

BACKGROUND

Endotoxin is a primary trigger of the inflammatory processes that lead to shock, multiorgan failure, and purpura fulminans in meningococcal sepsis. Bactericidal/permeability-increasing protein (BPI) is a natural protein, stored within the neutrophil granules, that binds to and neutralises the effects of endotoxin in vitro, in laboratory animals, and in humans. To establish whether a recombinant 21-kDa modified fragment of human BPI (rBPI21), containing the active antimicrobial and endotoxin-neutralising moiety, would decrease death and long-term disability from meningococcal sepsis, we did a randomised, double-blind, placebo-controlled trial of rBPI21 in children with severe meningococcal sepsis.

METHODS

We enrolled children (2 weeks to 18 years of age) presenting to 22 centres in the UK and the USA with a clinical picture suggestive of meningococcal sepsis, and with evidence of severe disease. Children were randomly assigned rBPI21 (2 mg/kg over 30 min followed by 2 mg/kg over 24 h) or placebo (0.2 mg/mL human albumin solution) in addition to conventional medical therapy. Primary outcome variables were mortality, amputations, and change in paediatric overall performance category (POPC) from before illness to day 60. Analysis was by intention to treat.

FINDINGS

Of 1287 patients screened, 892 were excluded, including 57 patients who died or who met criteria for imminent death before receiving the study drug. 190 patients received rBPI21, and 203 placebo. 34 (8.7%) of 393 patients died during the study: 14 (7.4%) in the rBPI21 group and 20 (9.9%) in the placebo group (odds ratio 1.31 [95% CI 0.62-2.74], p=0.48). Compared with patients randomised to placebo, fewer patients treated with rBPI21 had multiple severe amputations (six of 190 [3.2%] vs 15 of 203 [7.4%], odds ratio 2.47 [0.94-6.51], p=0.067), and more had a functional outcome similar to that before illness (as measured by the POPC scale) at day 60 (136 of 176 [77.3%] vs 126 of 190 [66.3%], p=0.019).

INTERPRETATION

Because most deaths occurred in the interval between identification of patients and study drug administration, the mortality rate in the placebo group was substantially lower than predicted. The trial was therefore underpowered to detect significant differences in mortality. However, patients receiving rBPI21 had a trend towards improved outcome in all primary outcome variables. Given the excellent severity match between placebo and rBPI21 groups at study entry, the results overall indicate that rBPI21 is beneficial in decreasing complications of meningococcal disease.

Association of mutations in mannose binding protein gene with childhood infection in consecutive hospital series

OBJECTIVE

To determine the extent to which mutations in the mannose binding protein gene predispose to childhood infection.

DESIGN

Clinical details and genotype of mannose binding protein determined in consecutive children attending a paediatric department.

SETTING

Inner city hospital paediatric service in London.

SUBJECTS

617 children attending hospital between October 1993 and August 1995.

MAIN OUTCOME MEASURE

Infection as the cause for attendance or admission in relation to mutations in the mannose binding protein gene.

RESULTS

The prevalence of mutations in the mannose binding protein gene in children with infection (146/345) was about twice that in children without infection (64/272) (P < 0.0001). Increased susceptibility to infection was found in both heterozygotic and homozygotic children. 13 out of 17 children homozygotic for variant alleles presented with strikingly severe infections, including 6 with septicaemia.

CONCLUSIONS

The findings suggest that mutations in the mannose binding protein gene are an important risk factor for infections in children. Screening for such mutations should be included in the investigation of severe or frequent infections.

The amino acid sequence of a major nonimmunoglobulin component of some amyloid fibrils

The complete amino acid sequence of a protein, acid soluble fraction, (ASF) which constitutes up to 50% of amyloid fibrils from a patient with familial Mediterranean fever has been obtained. Partial amino acid sequences of three other proteins from patients with secondary amyloidosis were identical in the regions studied except for an alanine-valine interchange in one. The ASF contains no cysteine, does not resemble any known immunoglobulin, and has not been detected as yet in myeloma-associated amyloid.

Association of variants of the gene for mannose-binding lectin with susceptibility to meningococcal disease. Meningococcal Research Group

BACKGROUND

The reasons why meningococcal disease develops in only a small proportion of individuals carrying the causative bacteria are unknown. Differences in host responses to bacterial colonisation are thought to be involved, since people with deficiencies in the terminal components of the complement pathway, or of properdin, are susceptible to meningococcal disease. We postulate that genetic variants of mannose-binding lectin (MBL), a plasma opsonin that initiates another pathway of complement activation, might similarly cause susceptibility to meningococcal disease.

METHODS

The frequency of variants of the MBL gene was ascertained in children with meningococcal disease and controls from two independent studies; one hospital-based (194 patients and 272 controls [patients with non-infectious disorders]), and one community-based (72 patients and 110 controls [healthy individuals]), by means of PCR and restriction-enzyme digestion, with confirmation by DNA sequencing.

FINDINGS

The proportion of people homozygous for MBL-variant alleles was higher in patients with meningococcal disease than in controls in the hospital study (15 [7.7%] vs four [1.5%]; odds ratio 6.5 [95% CI 2.0-27.2]) and in the community study (six [8.3%] vs three [2.7%]; 4.5 [0.9-29.1]). The population attributable fraction of cases attributable to MBL variants (homozygous and heterozygous) was 32%.

INTERPRETATION

The MBL pathway is a critical determinant of meningococcal-disease susceptibility, and genetic variants of MBL might account for a third of all disease cases.

Partial interferon-gamma receptor 1 deficiency in a child with tuberculoid bacillus Calmette-Guérin infection and a sibling with clinical tuberculosis

Complete interferon-gamma receptor 1 (IFNgammaR1) deficiency has been identified previously as a cause of fatal bacillus Calmette-Guérin (BCG) infection with lepromatoid granulomas, and of disseminated nontuberculous mycobacterial (NTM) infection in children who had not been inoculated with BCG. We report here a kindred with partial IFNgammaR1 deficiency: one child afflicted by disseminated BCG infection with tuberculoid granulomas, and a sibling, who had not been inoculated previously with BCG, with clinical tuberculosis. Both responded to antimicrobials and are currently well without prophylactic therapy. Impaired response to IFN-gamma was documented in B cells by signal transducer and activator of transcription 1 nuclear translocation, in fibroblasts by cell surface HLA class II induction, and in monocytes by cell surface CD64 induction and TNF-alpha secretion. Whereas cells from healthy children responded to even low IFN-gamma concentrations (10 IU/ml), and cells from a child with complete IFNgammaR1 deficiency did not respond to even high IFN-gamma concentrations (10,000 IU/ml), cells from the two siblings did not respond to low or intermediate concentrations, yet responded to high IFN-gamma concentrations. A homozygous missense IFNgR1 mutation was identified, and its pathogenic role was ascertained by molecular complementation. Thus, whereas complete IFNgammaR1 deficiency in previously identified kindreds caused fatal lepromatoid BCG infection and disseminated NTM infection, partial IFNgammaR1 deficiency in this kindred caused curable tuberculoid BCG infection and clinical tuberculosis.

The diagnostic accuracy of ex vivo MRI for human atherosclerotic plaque characterization

Recent evidence indicates that the type of atherosclerotic plaque, rather than the degree of obstruction to flow, is an important determinant of the risk of cardiovascular complications. In previous work, the feasibility of using MRI for the characterization of plaque components was shown. This study extends the previous work to all the plaque components and shows the accuracy of this method. Twenty-two human carotid endarterectomy specimens underwent ex vivo MRI and histopathological examination. Sixty-six cross sections were matched between MRI and histopathology. In each cross section, the presence or absence of plaque components were prospectively identified on the MRI images. The overall sensitivity and specificity for each tissue component were very high. Calcification and fibrocellular tissue were readily identified. Lipid core was also identifiable. However, thrombus was the plaque component for which MRI had the lowest sensitivity. A semiautomated algorithm was created to identify all major atherosclerotic plaque components. MRI can characterize carotid artery plaques with a high level of sensitivity and specificity. Application of these results in the clinical setting may be feasible in the near future.

PNPLA3 has retinyl-palmitate lipase activity in human hepatic stellate cells

Retinoids are micronutrients that are stored as retinyl esters in the retina and hepatic stellate cells (HSCs). HSCs are key players in fibrogenesis in chronic liver diseases. The enzyme responsible for hydrolysis and release of retinyl esters from HSCs is unknown and the relationship between retinoid metabolism and liver disease remains unclear. We hypothesize that the patatin-like phospholipase domain-containing 3 (PNPLA3) protein is involved in retinol metabolism in HSCs. We tested our hypothesis both in primary human HSCs and in a human cohort of subjects with non-alcoholic fatty liver disease (N = 146). Here we show that PNPLA3 is highly expressed in human HSCs. Its expression is regulated by retinol availability and insulin, and increased PNPLA3 expression results in reduced lipid droplet content. PNPLA3 promotes extracellular release of retinol from HSCs in response to insulin. We also show that purified wild-type PNPLA3 hydrolyzes retinyl palmitate into retinol and palmitic acid. Conversely, this enzymatic activity is markedly reduced with purified PNPLA3 148M, a common mutation robustly associated with liver fibrosis and hepatocellular carcinoma development. We also find the PNPLA3 I148M genotype to be an independent (P = 0.009 in a multivariate analysis) determinant of circulating retinol-binding protein 4, a reliable proxy for retinol levels in humans. This study identifies PNPLA3 as a lipase responsible for retinyl-palmitate hydrolysis in HSCs in humans. Importantly, this indicates a potential novel link between HSCs, retinoid metabolism and PNPLA3 in determining the susceptibility to chronic liver disease.

4G/5G promoter polymorphism in the plasminogen-activator-inhibitor-1 gene and outcome of meningococcal disease. Meningococcal Research Group

BACKGROUND

Intravascular coagulation with infarction of skin, digits, and limbs is a characteristic feature of meningococcal sepsis. Children with meningococcal sepsis have higher than normal concentrations of plasminogen activator inhibitor 1 (PAI-1) in plasma. Combined with the widespread venous thrombosis, this finding suggests an impairment of fibrinolysis. A common functional insertion/deletion (4G/5G) polymorphism exists in the promoter region of the PAI-1 gene. We tested the hypothesis that children with the 4G/4G genotype produce higher concentrations of PAI-1, develop more severe coagulopathy, and are at greater risk of death during meningococcal sepsis.

METHODS

The relation between meningococcal disease outcome, PAI-1 concentration, and PAI-1 genotype was investigated in 175 children with meningococcal disease (37 from Rotterdam, the Netherlands, and 138 from London, UK) and 226 controls (137 from Rotterdam, 89 from London). PAI-1 concentrations in plasma were measured by ELISA, and the 4G/5G PAI-1 polymorphism was detected by PCR and hybridisation.

FINDINGS

Concentrations of PAI-1 on admission correlated with presentation (sepsis or meningitis) and outcome. The median PAI-1 concentration in children who died was substantially higher than that in survivors (2448 [IQR 1115-3191] vs 370 [146-914] ng/mL; p<0.0001). Patients with the 4G/4G genotype had significantly higher PAI-1 concentrations than those with the 4G/5G or 5G/5G genotype (1051 [550-2440] vs 436 [198-1225] ng/mL; p=0.03), and had an increased risk of death (relative risk 2.0 [1.0-3.8] for the two cohorts combined, and 4.8 [1.8-13] for the London cohort).

INTERPRETATION

A genetic predisposition to produce high concentrations of PAI-1 is associated with poor outcome of meningococcal sepsis. This finding suggests that impaired fibrinolysis is an important factor in the pathophysiology of meningococcal sepsis.

Variation in the tumor necrosis factor-alpha gene promoter region may be associated with death from meningococcal disease

Tumor necrosis factor-alpha (TNF-alpha) plays a central role in the pathophysiology of sepsis. Levels of TNF-alpha are directly correlated with severity in meningococcal disease (MD). A polymorphism in the promoter region of the TNF-alpha gene is associated with differences in the secretion of TNF-alpha. The TNF2 allele is associated with higher constitutive and inducible levels of TNF-alpha secretion than is the TNF1 allele. To investigate whether possession of the TNF2 allele is associated with severity in MD, the frequency of TNF1 and TNF2 alleles in 98 children with MD was compared. There were more deaths among children who had the TNF2 allele (P = .03; relative risk [RR], 2.5; 95% confidence interval [CI], 1.1-5.7) than in those who did not. There was also an increased risk of severe disease in children with the TNF2 allele (P = .02; RR, 1.6; 95% CI, 1.1-2.3). Possession of the TNF2 allele predisposes to a worse outcome in children with meningococcal infection.

Patatin-like phospholipase domain-containing 3 (PNPLA3) I148M (rs738409) affects hepatic VLDL secretion in humans and in vitro

BACKGROUND & AIMS

The robust association between non-alcoholic fatty liver disease (NAFLD) and the genetic variant I148M (rs738409) in PNPLA3 has been widely replicated. The aim of this study was to investigate the effect of the PNPLA3 I148M mutation on: (1) hepatic secretion of very low density lipoproteins (VLDL) in humans; and (2) secretion of apolipoprotein B (apoB) from McA-RH 7777 cells, which secrete VLDL-sized apoB-containing lipoproteins.

METHODS

VLDL kinetics was analyzed after a bolus infusion of stable isotopes in 55 overweight/obese men genotyped for the PNPLA3 I148M variant. Intracellular lipid content, apoB secretion and glycerolipid metabolism were studied in McA-RH 7777 cells overexpressing the human 148I wild type or 148M mutant PNPLA3 protein.

RESULTS

In humans, carriers of the PNPLA3 148M allele had increased liver fat compared to 148I homozygotes, and kinetic analysis showed a relatively lower secretion of the large, triglyceride-rich VLDL (VLDL(1)) in 148M carriers vs. 148I homozygotes for the same amount of liver fat. McA-RH 7777 cells overexpressing the 148M mutant protein showed a higher intracellular triglyceride content with a lower apoB secretion and fatty acid efflux, compared to cells overexpressing the 148I wild type protein. The responses with 148M matched those observed in cells expressing the empty vector, indicating that the mutation results in loss of function.

CONCLUSIONS

We have shown that PNPLA3 affects the secretion of apoB-containing lipoproteins both in humans and in vitro and that the 148M protein is a loss-of-function mutation. We propose that PNPLA3 148M promotes intracellular lipid accumulation in the liver by reducing the lipidation of VLDL.

Evidence of hypoxic areas within the arterial wall in vivo

The anoxemia theory of atherosclerosis states that an imbalance between the demand and supply of oxygen in the arterial wall is a key factor for the development of atherosclerotic lesions. Direct in vitro and in situ measurements have shown that PO2 is decreased in the more deeply situated parts of the media, but the degree of hypoxia in vivo or the distribution of hypoxia along the arterial tree is not known. For this reason, we have developed a method for the detection of hypoxia in the arterial wall in vivo by using a hypoxia marker, 7-(4'-(2-nitroimidazol-1-yl)-butyl)-theophylline, that may be visualized by immunofluorescence. In the present study, we have used this method in rabbits with experimentally induced atherosclerosis. Our results indicate that zones of hypoxia occur at depth in the atherosclerotic plaque. The mechanism was probably an impaired oxygen diffusion capacity due to the thickness of the lesion, together with high oxygen consumption by the foam cells. Thus, we have for the first time demonstrated that hypoxia actually does exist in the arterial wall in vivo, lending support to the anoxemia theory of atherosclerosis.

Immunologic studies of the major nonimmunoglobulin protein of amyloid. I. Identification and partial characterization of a related serum component

Antisera have been prepared against the major nonimmunoglobulin component of secondary and familial Mediterranean fever (FMF) associated amyloid which has been called A component or acid soluble fraction (ASF). The antisera were shown to be monospecific for ASF by precipitation of (125)I-labeled antigen and gave a reaction of identity with four different ASF preparations. The antisera were able to detect a circulating component in human serum that migrated in the alpha1-globulin region. This circulating component gave a line of identity with degraded ASF by double immunodiffusion. 57 normal sera and 89 sera from patients with diseases known to be frequently associated with amyloidosis were tested by immunodiffusion for the circulating ASF component. 7% of normal sera and 50-80% of the pathologic sera had elevated amounts of this component. Absorption studies showed that all normal sera probably have small amounts of this component while cord sera do not have detectable amounts. This component was partially purified and was shown to be slightly larger than albumin. The relation of the circulating component to the acid soluble fraction of amyloid is discussed.

Reduction in case fatality rate from meningococcal disease associated with improved healthcare delivery

BACKGROUND AND AIMS

The case fatality rate from meningococcal disease (MD) has remained relatively unchanged in the post antibiotic era, with 20-50% of patients who develop shock still dying. In 1992 a new paediatric intensive care unit (PICU) specialising in MD was opened. Educational information was disseminated to local hospitals, and a specialist transport service was established which delivered mobile intensive care. The influence of these changes on mortality of children with MD was investigated.

METHODS

A total of 331 consecutive children with meningococcal disease admitted to the PICU between 1992 and 1997 were studied. Severity of the disease on admission was assessed using the paediatric risk of mortality (PRISM) score. Logistic regression analysis was used to correct for clinical severity, age, and sex; death was the outcome, and year of admission, a temporal trend variable, was the primary exposure.

RESULTS

The case fatality rate fell year on year (from 23% in 1992/93 to 2% in 1997) despite disease severity remaining largely unchanged. After adjustment for age, sex, and disease severity, the overall estimate for improvement in the odds of death was 59% per year (odds ratio for the yearly trend 0.41).

CONCLUSIONS

A significant improvement in outcome for children admitted with MD to a PICU has occurred in association with improvements in initial management of patients with MD at referring hospitals, use of a mobile intensive care service, and centralisation of care in a specialist unit.

Familial disseminated atypical mycobacterial infection in childhood: a human mycobacterial susceptibility gene?

Inherited defects in specific components of the immune system have provided many clues to the immunological mechanisms underlying resistance to microbial infection. We report a familial immune defect predisposing to disseminated atypical mycobacterial infection in childhood. 6 children with disseminated atypical mycobacterial infection and no recognised form of immunodeficency were identified. Four, including two brothers, come from a village in Malta, and two are brothers of Greek Cypriot origin. They presented with fever, weight loss, lymphadenopathy, and hepatosplenomegaly. They had anaemia and an acute phase response. A range of different mycobacteria (Mycobacterium fortuitum, M chelonei, and four strains of M avium intracellulare complex) were isolated. Treatment with multiple antibiotics failed to eradicate the infection, although treatment with gamma interferon was associated with improvement. Three have died and the surviving children have chronic infection. Tumour necrosis factor-alpha production in response to endotoxin and gamma-interferon was found to be defective in affected patients and their parents. T-cell proliferative responses to mycobacterial and recall antigens were reduced in parents of affected children and gamma-interferon production was diminished in the affected patients and their parents. Clinical and immunological features suggest that these patients are phenotypically similar to Lsh/Ity/Bcg susceptible mice. Understanding of this defect may provide insights into the mechanisms responsible for susceptibility to mycobacteria.

Gap junctions are involved in the early generation of left-right asymmetry

Invariant left-right asymmetry of the visceral organs is a fundamental feature of vertebrate embryogenesis. While a cascade of asymmetrically expressed genes has been described, the embryonic mechanism that orients the left-right axis relative to the dorsoventral and anteroposterior axes (a prerequisite for asymmetric gene expression) is unknown. We propose that this process involves dorsoventral differences in cell-cell communication through gap junctions composed of connexin proteins. Global modulation of gap junctional states in Xenopus embryos by pharmacological agents specifically induced heterotaxia involving mirror-image reversals of heart, gut, and gall bladder. Greatest sensitivity was observed between st. 5 and st. 12, well before the onset of organogenesis. Moreover, heterotaxia was also induced following microinjection of dominant negative and wild-type connexin mRNAs to modify the endogenous dorsoventral difference in junctional communication. Heterotaxia was induced by either blocking gap junction communication (GJC) dorsally or by introducing communication ventrally (but not the reverse). Both connexin misexpression and exposure to GJC-modifying drugs altered expression of the normally left-sided gene XNR-1, demonstrating that GJC functions upstream of XNR-1 in the pathway that patterns left-right asymmetry. Finally, lineage analysis to follow the progeny of microinjected cells indicated that they generally do not contribute the asymmetric organs. Together with the early sensitivity window, this suggests that GJC functions as part of a fundamental, early aspect of left-right patterning. In addition, we show that a potential regulatory mutation in Connexin43 is sufficient to cause heterotaxia. Despite uncertainty about the prevalence of the serine364 to proline substitution reported in human patients with laterality defects, the mutant protein is both a mild hypomorph and a potent antimorph as determined by the effect of its expression on left-right patterning. Taken together, our data suggest that endogenous dorsoventral differences in GJC within the early embryo are needed to consistently orient left-right asymmetry.

Left/right patterning signals and the independent regulation of different aspects of situs in the chick embryo

Recently, a pathway of genes which are part of a cascade regulating the side on which the heart forms during chick development was characterized (M. Levin et al., 1995, Cell 82, 1-20). Here we extend these previous studies, showing that manipulation of at least one member of the cascade, Sonic hedgehog (Shh), can affect the situs of embryonic rotation and of the gut, in addition to the heart. Bilateral expression of Shh, which is normally found exclusively on the left, does not result in left isomerism (a bilaterally symmetrical embryo having two left sides) nor in a complete situs inversus phenotype. Instead, misexpression of Shh on the right side of the node, which in turn leads to bilateral nodal expression, produces a heterotaxia-like condition, where different aspects of laterality are determined independently. Heart situs has previously been shown to be altered by ectopic Shh and activin. However, the most downstream gene identified in the LR pathway, nodal, had not been functionally linked to heart laterality. We show that ectopic (right-sided) nodal expression is able to affect heart situs, suggesting that the randomization of heart laterality observed in Shh and activin misexpression experiments is a result of changes in nodal expression and that nodal is likely to regulate heart situs endogenously. The first defined asymmetric signal in the left-right patterning pathway is Shh, which is initially expressed throughout Hensen's node but becomes restricted to the left side at stage 4(+). It has been hypothesized that the restriction of Shh expression may be due to repression by an upstream activin-like factor. The involvement of such an activin-like factor on the right side of Hensen's node was suggested because ectopic activin protein is able to repress Shh on the left side of the node, as well as to induce ectopic expression of a normally right-sided marker, the activin receptor cAct-RIIa. Here we provide further evidence in favor of this model. We find that a member of this family, Activin betaB, is indeed expressed asymmetrically, only on the right side of Hensen's node, at the correct time for it to be the endogenous asymmetric activin signal. Furthermore, we show that application of follistatin-loaded beads eliminates the asymmetry in Shh expression, consistent with an inhibition of an endogenous member of the activin-BMP superfamily. This combined with the previous data on exogenous activin supports the model that Activin betaB functions in the chick embryo to initiate Shh asymmetry. While these data extend our understanding of the early signals which establish left-right asymmetry, they leave unanswered the interesting question of how the bilateral symmetry of the embryo is initially broken to define a consistent left-right axis. Analysis of spontaneous chick twins suggests that, whatever the molecular mechanism, left-right patterning is unlikely to be due to a blastodermal prepattern but rather is initiated in a streak-autonomous manner.

Ectopic lipid storage and insulin resistance: a harmful relationship

Obesity increases the risk of metabolic diseases, including insulin resistance and type 2 diabetes, as well as cardiovascular disease. In addition to lipid accumulation in adipose tissue, obesity is associated with increased lipid storage in ectopic tissues, such as skeletal muscle and liver. Furthermore, lipid accumulation in the heart may result in cardiac dysfunction and heart failure. It has recently been demonstrated that intracellular lipid accumulation in ectopic tissues leads to pathological responses and impaired insulin signalling. Here, we will review the current understanding of how lipid storage and lipid droplet physiology affect the risk of developing metabolic diseases.

CSF and MRI findings in patients with acute herpes zoster

OBJECTIVE

To explore MRI and CSF findings in patients with herpes zoster (HZ) and to correlate the findings with clinical manifestations of the disease.

METHODS

Fifty immunocompetent patients (mean age, 59 years; range, 17 to 84 years) with HZ of fewer than 18 days duration participated. None had clinical signs of meningeal irritation, encephalitis, or myelitis. In 42 patients (84%), the symptoms constituted pain and rash only. Six patients (12%) had motor paresis, and three patients (6%) had ocular complications. One to three CSF samples were obtained from 46 patients (the first sampling taken 1 to 18 days from onset of rash), and 16 patients (all with either trigeminal or cervical HZ) underwent MRI of the brain. The clinical follow-up continued at least 3 months.

RESULTS

CSF was abnormal in 28/46 patients (61%): pleocytosis (range, 5 to 1,440 microL) was detected in 21, elevated protein concentration in 12, varicella zoster virus (VZV) DNA in 10, and immunoglobulin G antibody to VZV in 10. These changes were more common in patients with acute complications, although they did not predict development of postherpetic neuralgia (PHN). In 9/16 patients (56%), MRI lesions attributable to HZ were seen in the brainstem and cervical cord. At 3 months, 5/9 patients (56%) with abnormal MRI had PHN, whereas none of the 7 patients with no HZ-related lesions on MRI had any remaining pain.

CONCLUSIONS

Subclinical extension of viral inflammation into the CNS occurs commonly in HZ. This finding may have implications for treatment of HZ and prevention of various associated complications.

Effect of aerosolization on culturability and viability of gram-negative bacteria

Estimations of the bacterial content of air can be more easily made now than a decade ago, with colony formation the method of choice for enumeration of airborne bacteria. However, plate counts are subject to error because bacteria exposed to the air may remain viable yet lose the ability to form colonies, i.e., they become viable but nonculturable. If airborne bacteria exhibit this phenomenon, colony formation data will significantly underestimate the bacterial populations in air samples. The objective of the study reported here was to determine the effect of aerosolization on viability and colony-forming ability of Serratia marcescens, Klebsiella planticola, and Cytophaga allerginae. A collision nebulizer was used to spray bacterial suspensions into an aerosol chamber, after which duplicate samples were collected in all-glass impingers over a 4-h period. Humidity was maintained at ca. 20 to 25%, and temperature was maintained at 20 to 22 degrees C for each of two replicate trials per microorganism. Viability was determined by using a modified direct viable count method, employing nalidixic acid or aztreonam and p-iodonitrotetrazolium violet (INT). Cells were stained with acridine orange and observed by epifluorescence microscopy to enumerate total and viable cells. Viable cells were defined as those elongating in the presence of antibiotic and/or reducing INT. CFU were determined by plating on tryptic soy agar and R2A agar. It was found that culture techniques did not provide an adequate description of the bacterial burdens of indoor air (i.e., less than 10% of the aerosolized bacteria were capable of forming visible colonies). It is concluded that total cell count procedures provide a better approximation of the number of bacterial cells in air and that procedures other than plate counting are needed to enumerate bacteria in aerosol samples, especially if the public health quality of indoor air is to be estimated.

Management of Kawasaki disease

Kawasaki disease (KD) is an acute self-limiting inflammatory disorder, associated with vasculitis, affecting predominantly medium-sized arteries, particularly the coronary arteries. In developed countries KD is the commonest cause of acquired heart disease in childhood. The aetiology of KD remains unknown, and it is currently believed that one or more as yet unidentified infectious agents induce an intense inflammatory host response in genetically susceptible individuals. Genetic studies have identified several susceptibility genes for KD and its sequelae in different ethnic populations, including FCGR2A, CD40, ITPKC, FAM167A-BLK and CASP3, as well as genes influencing response to intravenous immunoglobulin (IVIG) and aneurysm formation such as FCGR3B, and transforming growth factor (TGF) β pathway genes. IVIG and aspirin are effective therapeutically, but recent clinical trials and meta-analyses have demonstrated that the addition of corticosteroids to IVIG is beneficial for the prevention of coronary artery aneurysms (CAA) in severe cases with highest risk of IVIG resistance. Outside of Japan, however, clinical scores to predict IVIG resistance perform suboptimally. Furthermore, the evidence base does not provide clear guidance on which corticosteroid regimen is most effective. Other therapies, including anti-TNFα, could also have a role for IVIG-resistant KD. Irrespective of these caveats, it is clear that therapy that reduces inflammation in acute KD, improves outcome. This paper summarises recent advances in the understanding of KD pathogenesis and therapeutics, and provides an approach for managing KD patients in the UK in the light of these advances.

Left-right asymmetry determination in vertebrates

A distinctive and essential feature of the vertebrate body is a pronounced left-right asymmetry of internal organs and the central nervous system. Remarkably, the direction of left-right asymmetry is consistent among all normal individuals in a species and, for many organs, is also conserved across species, despite the normal health of individuals with mirror-image anatomy. The mechanisms that determine stereotypic left-right asymmetry have fascinated biologists for over a century. Only recently, however, has our understanding of the left-right patterning been pushed forward by links to specific genes and proteins. Here we examine the molecular biology of the three principal steps in left-right determination: breaking bilateral symmetry, propagation and reinforcement of pattern, and the translation of pattern into asymmetric organ morphogenesis.