Role of modified Widal test in the diagnosis of enteric fever

OBJECTIVES

To evaluate the diagnostic specificity of modified Widal for recent infection in comparison with conventional Widal test.

METHOD

Modified widal test was simultaneously done along with conventional Widal test in serum samples obtained from 50 bacteriologically positive cases of Salmonella typhi infection as well as 50 healthy individuals.

RESULTS

A four-fold difference in the titres was noticed in the 50 sera of the test group and no charge in the titres of the control group. The early rising O antibodies which are predominantly IgM in nature. These are due to recent infection and are inactivated by 2-mercaptoethanol. On the other hand H is a mixture of IgG and IgM hence IgM portion gets inactivated giving rise to fall in titre. By inactivating IgM antibodies in modified Widal test, the agglutination would be brought about only by specific IgG while in the conventional Widal test agglutination is due to specific IgG and IgM. The difference in the titres indicates specific IgM class of antibodies which is the hallmark of recent infection.

CONCLUSION

If conventional Widal test and modified Widal test are simultaneously done, one can be definite about the diagnosis of enteric fever.

The use of Irradiated Allografts in Posterior Spinal Fusion for Healed Tubercular Kyphosis in Children

Post-tubercular spinal kyphosis in children is not only cosmetically unacceptable but functionally disabling as well, as with the progression of the deformity there is a very significant risk of late onset paraplegia. We present our preliminary results in a prospective study of 12 cases of healed post-tubercular kyphosis in children treated with isolated posterior spinal fusion using irradiated allografts and autogenous cancellous grafts.The study included 12 patients of healed post-tubercular kyphosis documented by clinical, radiological and haematological criteria, with >2 spine at risk signs radiologically. The mean age was 7 years. In situ posterior spinal fusion with irradiated allografts and autogenous cancellous bone graft without any instrumentation was done for all the patients. The total follow-up is 5 years (mean 2.8 years).Eight patients (66%) showed a correction of the kyphosis, 3 patients (25%) were static and only 1 patient showed worsening of the deformity. Eleven patients had sound fusion and 1 patient had good fusion but a pseudoarthrosis at the lower vertebral level.Good posterior fusion was achieved because of the judicious use of morcellised, irradiated cancellous allografts with autogenous cancellous grafts. The proposed mechanism of correction is selective anterior column growth vis-à-vis posterior fused mass leading to gradual self-correction and remodelling.Conclusion. In situ posterior spinal fusion with irradiated allografts is a simple, safe, easily reproducible, less morbid surgical procedure with good results which may alter the long term disability of the patients.

Magnetic resonance arthrography in recurrent anterior shoulder instability as compared to arthroscopy: a prospective comparative study

AIM

To evaluate the accuracy of magnetic resonance (MR) arthrographic imaging in the diagnosis of glenoid labral and ligament tears in recurrent shoulder instability.

SETTINGS AND DESIGN

Prospective, comparative study at a tertiary care centre.

MATERIAL AND METHODS

Patients with three or more episodes of anterior shoulder dislocation were enrolled in the study. They were subjected to magnetic resonance arthrography (MRA) for delineation of abnormalities. The findings obtained at MRA were compared with those found at arthroscopy and surgical exploration.

RESULTS

MRA detected glenoid tears in all 22 patients with 20 (90%) patients having antero-inferior tears, 3 (14%) patients had superior labral involvement and 2 (10%) patients had posterior labral abnormality. On arthroscopy, antero-inferior, superior and posterior labral tear were found in 21 (95%), 5 (22%) and 7 (32%) patients respectively. MRA showed a sensitivity of 95%, and a specificity of 100% for the detection of the antero-inferior labral tears. The sensitivity of MRA for the detection of superior, middle and inferior glenohumeral ligament tear was 83%, 80% and 86% with a specificity of 100%, 71% and 93% respectively. MRA was 100% sensitive for the detection of rotator cuff injuries and detection of bony lesions like Hill-Sach's and bony Bankart's lesion.

CONCLUSIONS

MRA is a sensitive and specific modality for evaluation of anterior shoulder instability.

Association studies of cytosolic phospholipase A2 polymorphisms and schizophrenia among two independent family-based samples

An association between the cytosolic phospholipase A2 locus (cPLA2) and schizophrenia has been reported using two polymorphic DNA markers. In an attempt to replicate these results, two independent family-based samples were ascertained from the United States and India (86 and 159 families, respectively). No significant associations were detected in either sample.

Electroanatomically guided catheter ablation of ventricular tachycardias causing multiple defibrillator shocks

With conventional techniques, RF catheter ablation is difficult in patients with unstable VT or with multiple VTs. The feasibility of RF catheter ablation guided by three-dimensional electroanatomic mapping technique in patients whose implanted ICD continued to deliver multiple shocks due to VT despite use of antiarrhythmic medications was assessed in 19 patients (15 men, 4 women; mean age [+/- SD] 70+/-7 years). All had a prior history of MI and subsequently had received an ICD due to VT. During the 12-week preablation period, these patients received 31+/-15 shocks (range 4-62 shocks) due to refractory monomorphic VTs. An electroanatomic mapping technique using the CARTO system was performed to delineate scar tissue. RF catheter ablation was then performed at appropriate sites identified by pace mapping and by substrate mapping. Seventeen patients were on amiodarone at the time of ablation. Twenty-seven VTs were documented clinically, and 45 were induced during electrophysiological evaluation. Of the 45 tachycardias induced, 38 VTs were targeted for ablation. Catheter ablation was performed during sinus rhythm in 31 episodes and during VT in 7 episodes. During a mean follow-up of 26+/-8 weeks (range 18-48 weeks), 13 (66%) patients had no recurrence of VT (P < 0.0001) and antiarrhythmic drugs were discontinued or the number of medications reduced in 17 patients (P < 0.0001). Electroanatomic mapping is helpful in identifying sites for catheter ablation in highly symptomatic patients with refractory VT associated with myocardial scarring.

Contribution of vascular endothelial growth factor in the neovascularization process during the pathogenesis of herpetic stromal keratitis

This report analyzes the role of vascular endothelial growth factor (VEGF)-induced angiogenesis in the immunoinflammatory lesion stromal keratitis induced by ocular infection with herpes simplex virus (HSV). Our results show that infection with replication-competent, but not mutant, viruses results in the expression of VEGF mRNA and protein in the cornea. This a rapid event, with VEGF mRNA detectable by 12 h postinfection (p.i.) and proteins detectable by 24 h p.i. VEGF production occurred both in the virus-infected corneal epithelium and in the underlying stroma, in which viral antigens were undetectable. In the stroma, VEGF was produced by inflammatory cells; these initially were predominantly polymorphonuclear leukocytes (PMN), but at later time points both PMN and macrophage-like cells were VEGF producers. In the epithelium, the major site of VEGF-expressing cells in early infection, the infected cells themselves were usually negative for VEGF. Similarly, in vitro infection studies indicated that the cells which produced VEGF were not those which expressed virus. Attesting to the possible role of VEGF-induced angiogenesis in the pathogenesis of herpetic stromal keratitis were experiments showing that VEGF inhibition with mFlt(1-3)-immunoglobulin G diminished angiogenesis and the severity of lesions after HSV infection. These observations are the first to evaluate VEGF-induced angiogenesis in the pathogenesis of stromal keratitis. Our results indicate that the control of angiogenesis represents a useful adjunct to therapy of herpetic ocular disease, an important cause of human blindness.

Bystander activation involving T lymphocytes in herpetic stromal keratitis

Herpes simplex virus infection of mouse corneas can lead to the development of an immunopathological lesion, termed herpetic stromal keratitis (HSK). Such lesions also occur in TCR-transgenic mice backcrossed to SCID (TgSCID) that are unable to mount detectable HSV-specific immune responses. The present study demonstrates that lesion expression in such mice depends on continuous viral replication, whereas in immunocompetent mice, lesions occurred even if virus replication was terminated at 4 days after infection. The continuous replication in TgSCID mice was considered necessary to produce an activating stimulus to CD4(+) T cells that invade the cornea. Lesions in TgSCID were resistant to control by cyclosporin A, but were inhibited by treatment with rapamycin. This result was interpreted to indicate that T cell activation involved a non-TCR-mediated cytokine-driven bystander mechanism. Bystander activation was also shown to play a role in HSK lesions in immunocompetent mice. Accordingly, in immunocompetent DO11.10 mice, lesions were dominated by KJ1.26(+) OVA-specific CD4(+) T cells that were unreactive with HSV. In addition, KJ1.26(+) HSV nonimmune cells parked in ocularly infected BALB/c mice were demonstrable in HSK lesions. These results provide insight for the choice of new strategies to manage HSK, an important cause of human blindness.

Type I Monteggia fracture dislocation associated with ipsilateral distal radial epiphyseal injury

SUMMARY

Ipsilateral elbow and wrist injuries are rare in children. We present a previously undescribed case of a Bado Type I Monteggia fracture with a Salter-Harris Type II epiphyseal injury of the distal radius. A satisfactory result was achieved but required surgical intervention. Complete diagnostic evaluation is imperative to avoid missed injuries and achieve satisfactory outcome.

Ventricular fibrillation sensing and detection by implantable defibrillators: is one better than the others? A prospective, comparative study

INTRODUCTION

We prospectively compared the performance of the sensing and detection systems of three leading defibrillator manufacturers: Medtronic, Guidant, and Ventritex.

METHODS AND RESULTS

Ventricular fibrillation signal was digitally recorded during defibrillator implantation and subsequently played back sequentially to a Medtronic Micro Jewel II 7223Cx, a Guidant MINI II 1762, and a Ventritex Cadet V-115C. The devices were programmed for single-zone detection, at nominal settings. Rate cutoff was set at 320 msec (185/min for the MINI). We analyzed 253 episodes from 47 patients. Median undersensing was 0%, 2.1%, and 5.3% for the Jewel, MINI, and Cadet, respectively (P < 0.001 for each paired comparison). Detection time was 4.1 +/- 1.6 seconds, 3.4 +/- 1.6 seconds, and 4.3 +/- 2.2 seconds for the Jewel, MINI, and Cadet, respectively (P < 0.001 between MINI-Jewel and MINI-Cadet; P < 0.01 between Jewel-Cadet). Delayed detection (detection time longer than the mean of all observations + 2 SD) occurred in 3 (1.2%), 7 (2.8%), and 18 (7.1%) episodes for the Jewel, MINI, and Cadet, respectively. Performance for all devices was worse when the short-separation integrated bipolar lead was used and when the episode followed a failed high-energy shock.

CONCLUSION

Statistically significant differences were seen in sensing and detection performance among the devices and device/lead combinations during ventricular fibrillation. These differences are related to specific features of the respective devices and should be taken into account during clinical practice, as well as in future device development.

Lymphotoxin alpha-/- mice develop functionally impaired CD8+ T cell responses and fail to contain virus infection of the central nervous system

Recent observations have indicated that viral persistence and tumor spreading could occur because of effector function-defective CD8(+) T cells. Although chronic exposure to Ag, lack of CD4 help, and epitope dominance are suggested to interfere with CTL differentiation, mechanisms underlying the defective effector function remain obscure. We demonstrate in this report that lymphotoxin alpha-deficient mice develop CD8(+) T cells at normal frequencies when infected with HSV or immunized with OVA Ag but show impaired cytotoxic and cytokine-mediated effector functions resulting in enhanced susceptibility to HSV-induced encephalitis. Although these cells display near normal levels of perforin and Fas ligand, they remain largely at a naive state as judged by high expression of CD62 ligand and failure to up-regulate activation or memory markers. In particular, these CD8(+) T cells revealed inadequate expression of the IL-12 receptor, thus establishing a link between CTL differentiation and LTalpha possibly through regulation of IL-12 receptor. Viruses and tumors could evade immunity by targeting the same pathway.

Electroanatomic mapping to identify breakthrough sites in recurrent typical human flutter

The accuracy of conventional techniques in localizing previous radiofrequency (RF) ablation sites and thus breakthrough sites of recurrent atrial flutter is somewhat limited. We investigated the role of electroanatomic mapping for identifying breakthrough sites or "gaps" at the tricuspid annulus and inferior vena cava (IVC)/eustachian ridge isthmus to help RF ablation in patients with recurrent typical flutter. Twelve patients (8 men, 4 women, age 63 +/- 10 years) with recurrent typical atrial flutter were included in the study. An electroanatomic mapping system (CARTO) was used to create a voltage map and activation and propagation patterns in the right atrium. Detailed voltage, activation, and propagation mapping of the tricuspid annulus and IVC/eustachian ridge isthmus allowed precise identification of gaps in all 12 patients at the tricuspid annulus (eight sites), IVC ridges (two sites), mid-isthmus region (one site), and tricuspid annulus and IVC ridges (one site). Radiofrequency energy directed at these sites eliminated atrial flutter in all 12 patients, confirmed by noninducibility of atrial flutter and demonstration of conduction block during atrial pacing on either side of the lesion lines. During a mean follow-up of 14.8 +/- 3.5 months (range 8-19 months), paroxysmal atrial flutter recurred in only one patient and was subsequently treated with amiodarone, although this had been ineffective prior to ablation. Electroanatomic mapping can precisely identify gaps in the lesion line responsible for breakthrough of recurrent typical atrial flutter at the tricuspid annulus and at the IVC/eustachian ridge isthmus. These sites can be targeted with RF ablation with a high degree of success.

Chemokines in autoimmune diseases

Autoimmune diseases like multiple sclerosis (MS) and insulin-dependent diabetes (IDD) are believed to be mediated by pathogenic CD4+ autoreactive T cells which mediate selective destruction of specific host cells. Interrupting the trafficking of such T cells from host circulation to the sites of pathology, such as the central nervous system in the case of MS and the pancreas in the case of IDD, potentially offers a novel opportunity for therapeutic intervention in these diseases. The following summarizes our evolving thoughts on the role of the chemokine network in MS and IDD, and focuses on the chemokine receptor CXCR3 as a potential target for impeding T-cell-mediated destruction in these disease settings.

Localization of soluble major histocompatibility class II-peptide complexes on T cell surface

Affinity purified major histocompatibility (MHC)-peptide complexes are heterodimeric cell surface glycoproteins and are known to recognize antigen-specific CD4(+) T cell receptors (TCRs). In general, the affinity of MHC-peptide complexes to TCRs are considered very low with a K(D) of 5 x 10(-5) M and, therefore, stabilization of these complexes on T cell surface was not reported earlier. This could be due to (1) incomplete occupancy of MHC molecules with antigenic peptides, (2) variability of the binding constant of peptides to MHC molecules, (3) presence of endogenously bound peptides in MHC preparations, or (4) a combination of these. Using well-characterized HLA-DR2 complex loaded with a high affinity immunodominant epitope analog from human myelin basic protein (MBP), which shows release of gamma-IFN by specific stimulation of transformed human T cell clone (SS8T). The present report demonstrates a method for the localization of bound MHC class II-peptide complexes on T cell surface by backscatter electron imaging using in-lens Field Emission Scanning Electron Microscopy (FESEM). The localization is specific to the complex recognized by the TCR on MHC class II (DR2) and MBP peptide restricted human T cells.

Nonhydrolyzable diubiquitin analogues are inhibitors of ubiquitin conjugation and deconjugation

A series of nonhydrolyzable ubiquitin dimer analogues has been synthesized and evaluated as inhibitors of ubiquitin-dependent processes. Dimer analogues were synthesized by cross-linking ubiquitin containing a terminal cysteine (G76C) to ubiquitin containing cysteine at position 11 ((76-11)Ub(2)), 29 ((76-29)Ub(2)), 48 ((76-48)Ub(2)), or 63 ((76-63)Ub(2)). A head-to-head dimer of cysteine G76C ((76-76)Ub(2)) served as a control. These analogues are mimics of the different chain linkages observed in natural polyubiquitin chains. All analogues showed weak inhibition toward the catalytic domain of UCH-L3 and a UBP pseudogene. In the absence of ubiquitin, isopeptidase T was inhibited only by the dimer linked through residue 29. In the presence of 0.5 microM ubiquitin, isopeptidase T was inhibited by several of the dimer analogues, with the (76-29)Ub(2) dimer exhibiting a K(i) of 1.8 nM. However, USP14, the human homologue of yeast Ubp6, was not inhibited at the concentrations tested. Some analogues of ubiquitin dimer also acted as selective inhibitors of conjugation and deconjugation of ubiquitin catalyzed by reticulocyte fraction II. (76-76)Ub(2) and (76-11)Ub(2) did not inhibit the conjugation of ubiquitin, while (76-29)Ub(2), (76-48)Ub(2), and (76-63)Ub(2) were potent inhibitors of conjugation. This specificity is consistent with the known ability of cells to form K29-, K48-, and K63-linked polyubiquitin chains. While (76-11)Ub(2), (76-29)Ub(2), and (76-63)Ub(2) inhibited release of ubiquitin from a pool of total conjugates, (76-48)Ub(2) and (76-76)Ub(2) showed no significant inhibition. Isopeptidase T was shown to specifically disassemble two conjugates (assumed to be di- and triubiquitin with masses of 26 and 17 kDa) formed in the reticulocyte lysate system. This activity was inhibited differentially by all dimer analogues. The inhibitor selectivity for deconjugation of the 26 and 17 kDa conjugates was similar to that observed for isopeptidase T. The observations suggest that these two conjugated proteins of the reticulocyte lysate are specific substrates for isopeptidase T in lysates.

NADPH oxidase activation increases the sensitivity of intracellular Ca2+ stores to inositol 1,4,5-trisphosphate in human endothelial cells

Many stimuli that activate the vascular NADPH oxidase generate reactive oxygen species and increase intracellular Ca(2+), but whether NADPH oxidase activation directly affects Ca(2+) signaling is unknown. NADPH stimulated the production of superoxide anion and H(2)O(2) in human aortic endothelial cells that was inhibited by the NADPH oxidase inhibitor diphenyleneiodonium and was significantly attenuated in cells transiently expressing a dominant negative allele of the small GTP-binding protein Rac1, which is required for oxidase activity. In permeabilized Mag-indo 1-loaded cells, NADPH and H(2)O(2) each decreased the threshold concentration of inositol 1,4,5-trisphosphate (InsP(3)) required to release intracellularly stored Ca(2+) and shifted the InsP(3)-Ca(2+) release dose-response curve to the left. Concentrations of H(2)O(2) as low as 3 microm increased the sensitivity of intracellular Ca(2+) stores to InsP(3) and decreased the InsP(3) EC(50) from 423.2 +/- 54.9 to 276.9 +/- 14. 4 nm. The effect of NADPH on InsP(3)-stimulated Ca(2+) release was blocked by catalase and by diphenyleneiodonium and was not observed in cells lacking functional Rac1 protein. Thus, NADPH oxidase-derived H(2)O(2) increases the sensitivity of intracellular Ca(2+) stores to InsP(3) in human endothelial cells. Since Ca(2+)-dependent signaling pathways are critical to normal endothelial function, this effect may be of great importance in endothelial signal transduction.

[Ca(2+)](i) oscillation frequency regulates agonist-stimulated NF-kappaB transcriptional activity

In nonexcitable cells, stimulation by high agonist concentrations typically produces a biphasic increase in cytosolic Ca(2+) ([Ca(2+)](i)). This response is characterized by a transient initial increase because of intracellular Ca(2+) release followed by a sustained elevation which varies in amplitude depending on the nature of the stimulus. In contrast, low-level stimulation often evokes oscillatory changes in [Ca(2+)](i). The specific information provided by repetitive [Ca(2+)](i) spikes appears to be encoded in the frequency rather than in the amplitude of [Ca(2+)](i) oscillations. The specific, membrane-permeable inositol 1,4, 5-trisphosphate (Ins-1,4,5-P(3)) receptor blocker Xestospongin C (XeC, 2-20 microM) was used to affect [Ca(2+)](i) signaling in human aortic endothelial cells (HAEC) during an established response to low-level (1 microM) histamine stimulation. XeC produced a dose-dependent decrease in the frequency of [Ca(2+)](i) oscillations during histamine stimulation without affecting oscillation amplitude. Histamine stimulated a 14-fold increase in NF-kappaB-chloramphenicol acetyltransferase reporter gene activity that was dose-dependently decreased by XeC. Thus, during low-level agonist stimulation, [Ca(2+)](i) oscillation frequency regulates nuclear transcription in HAEC.

Driving safety among patients with neurocardiogenic (vasovagal) syncope

Neurocardiogenic syncope is one of the most common causes of syncope. However, the important issue of driving related injury due to syncope in this population is not well defined. Risk of injury due to syncope while driving and driving behavior was evaluated in 155 consecutive patients (92 women and 63 men; mean age 49 +/- 19 years) with history of syncope in whom hypotension and syncope or presyncope could be provoked during head-up tilt testing. Patients with syncope and positive head-up tilt table test were treated with pharmacological therapy. All participants were asked to fill out a detailed questionnaire regarding any driving related injuries and their driving behavior before tilt table testing and during follow-up. Prior to head-up tilt testing two patients had syncope while driving, and one of these patients had syncope related injury during driving. The mean duration of syncopal episodes was 50 +/- 14 months (range 12-72 months). Of the 155 patients, 52 (34%) had no warning prior to syncope, while 103 (6%) had warning symptoms such as dizziness prior to their clinical syncope. Following a diagnosis of neurocardiogenic syncope established by head-up tilt testing, six patients stopped driving on their own. During a median follow-up of 22 months recurrent syncope occurred in five (3.2%) patients. No patient had syncope or injury during driving. In conclusion, syncope and injury while driving in patients with neurocardiogenic syncope is rare. The precise mechanism of this is unclear but may be related to posture during driving. Consensus among the medical community will be needed to provide specific guidelines in these patients.

Peptide binding inhibits aggregation of soluble MHC class II in solution

Affinity-purified major histocompatability complex (MHC) class II molecules are known to bind antigenic peptide in vitro. This peptide-bound MHC class II is known to undergo a change in structure upon stable binding of antigenic peptide. Previous results from our, and other laboratories, have suggested a relationship between MHC class II structure and peptide association that enables class II to enter into a stable conformation upon peptide binding. In this report we describe that stable binding of high-affinity antigenic peptide to MHC class II molecule results in transition of aggregated purified MHC class II proteins to a stable heterodimeric state. Such transition was demonstrated by using purified human HLA-DR2 class II molecule and high-affinity myelin basic protein (MBP) 83-102)Y83 peptide. Highly aggregated purified DR2 (high molecular weight; HMW) was first separated from heterodimer (low molecular weight: LMW) in the presence of 50-fold molar excess of MBP(83-102)Y83 peptide. We then show that the aggregated HMW preparation can be successfully converted into a stable dimer by further incubation with MBP(83-102)Y83 and changing various binding parameters such as pH, temperature, reducing agent, and peptide concentrations. Under optimized conditions, the highly aggregated inactive DR2 molecules can be completely loaded with the antigenic peptide. The transformed heterodimers with bound peptide prepared by this method are biologically active, as shown by their ability to induce the production of gamma-interferon by SS8T-transformed human T cells. These results suggest that in solution, MHC class II molecules may be aggregated in the absence of bound peptide. Such aggregated MHC class II molecules can be converted to stable and biologically active heterodimers in the presence of high-affinity antigenic peptide.

Sudden cardiac death

SCD continues to be an important cause of death and morbidity. Despite expanding insight into the mechanisms causing SCD, the population at high risk is not being effectively identified. Although there is still much to do in the management phase of SCD (predicting the efficacy of various therapies), recent clinical trials have helped define the relative risks and benefits of therapies in preventing SCD. Trials are underway to determine whether treating other patient populations, including asymptomatic patients after MI, will improve survival rate. The approach to reducing mortality rate will always be multifaceted; primary prevention of coronary artery disease and prompt salvage of jeopardized myocardium are 2 important aspects of this approach. In addition to interventions for MI, such as myocardial revascularization when indicated, simple and easily administered therapies that are likely to remain the most effective prophylactic interventions are aspirin, ACE inhibitors, beta-blockers, and cholesterol-lowering agents. However, the MADIT and AVID data clearly demonstrate a role for ICD therapy in a subgroup of patients who have VT/VF and are at risk of cardiac arrest. Even though the absolute magnitude of benefit associated with ICDs is still to be determined, the AVID study and other recent reports provide convincing evidence that patients who have VT/VF fare better with ICDs than with antiarrhythmic drug therapy. For the high-risk population described in this article, in addition to aggressive anti-ischemic and heart failure therapy, ICDs are now a mainstay of life-saving treatment. Still to be surmounted is the challenge of identifying patients who have nonischemic substrates and of providing them with the appropriate therapy. Guided by genetic studies and new insight into the mechanisms of such problems as congenital long QT syndrome, life-saving and life-enhancing therapies may soon be available for the management of SCD.

Synthesis and kinetics of cyclization of MHC class II-derived cyclic peptide vaccine for diabetes

Conformationally constrained cyclic peptides are known to be better vaccines because of their ability to mimic the native structure of a protein against which an immune response is sought. To test the hypothesis of using conformationally constrained, disease-associated, MHC-derived peptides as vaccines for the prevention of type I diabetes, a 22 amino acid nonobese diabetic(NOD) mouse MHC class II-derived synthetic peptide was cyclized by the formation of end-to-end disulfide bonds and used to prevent diabetes and insulitis in NOD mice. The peptide was synthesized by Fmoc chemistry and cyclized using two methods: a commercially available cyclizing resin (Ekathiox) and air oxidation. When a 10 m excess of resin was used, the Ekathiox yielded a substantial amount of cyclic peptide with few or no side reactions. The kinetics of cyclization by air oxidation at different temperatures indicated that increasing both temperature and pH decreased the cyclization time significantly. Air oxidation at pH 10 at 37-55 degrees C yielded the desired product within 2 h.