Occludin, caveolin-1, and Alix form a multi-protein complex and regulate HIV-1 infection of brain pericytes.

HIV-1 enters the brain by altering properties of the blood-brain barrier (BBB). Recent evidence indicates that among cells of the BBB, pericytes are prone to HIV-1 infection. Occludin (ocln) and caveolin-1 (cav-1) are critical determinants of BBB integrity that can regulate barrier properties of the BBB in response to HIV-1 infection. Additionally, Alix is an early acting endosomal factor involved in HIV-1 budding from the cells. The aim of the present study was to evaluate the role of cav-1, ocln, and Alix in HIV-1 infection of brain pericytes. Our results indicated that cav-1, ocln, and Alix form a multi-protein complex in which they cross-regulate each other's expression. Importantly, the stability of this complex was affected by HIV-1 infection. Modifications of the complex resulted in diminished HIV-1 infection and alterations of the cytokine profile produced by brain pericytes. These results identify a novel mechanism involved in HIV-1 infection contributing to a better understanding of the HIV-1 pathology and the associated neuroinflammatory responses.

Evidence of disulfide bond scrambling during production of an antibody-drug conjugate.

Antibody-drug conjugates (ADCs) that are formed using thiol-maleimide chemistry are commonly produced by reactions that occur at or above neutral pHs. Alkaline environments can promote disulfide bond scrambling, and may result in the reconfiguration of interchain disulfide bonds in IgG antibodies, particularly in the IgG2 and IgG4 subclasses. IgG2-A and IgG2-B antibodies generated under basic conditions yielded ADCs with comparable average drug-to-antibody ratios and conjugate distributions. In contrast, the antibody disulfide configuration affected the distribution of ADCs generated under acidic conditions. The similarities of the ADCs derived from alkaline reactions were attributed to the scrambling of interchain disulfide bonds during the partial reduction step, where conversion of the IgG2-A isoform to the IgG2-B isoform was favored.

Rapid, automated characterization of disulfide bond scrambling and IgG2 isoform determination.

Human antibodies of the IgG2 subclass exhibit complex inter-chain disulfide bonding patterns that result in three structures, namely A, A/B, and B. In therapeutic applications, the distribution of disulfide isoforms is a critical product quality attribute because each configuration affects higher order structure, stability, isoelectric point, and antigen binding. The current standard for quantification of IgG2 disulfide isoform distribution is based on chromatographic or electrophoretic techniques that require additional characterization using mass spectrometry (MS)-based methods to confirm disulfide linkages. Detailed characterization of the IgG2 disulfide linkages often involve MS/MS approaches that include electrospray ionization or electron-transfer dissociation, and method optimization is often cumbersome due to the large size and heterogeneity of the disulfide-bonded peptides. As reported here, we developed a rapid LC-MALDI-TOF/TOF workflow that can both identify the IgG2 disulfide linkages and provide a semi-quantitative assessment of the distribution of the disulfide isoforms. We established signature disulfide-bonded IgG2 hinge peptides that correspond to the A, A/B, and B disulfide isoforms and can be applied to the fast classification of IgG2 isoforms in heterogeneous mixtures.

Combined functions of two RRMs in Dead-end1 mimic helicase activity to promote nanos1 translation in the germline.

Dead-end1 (Dnd1) expression is restricted to the vertebrate germline where it is believed to activate translation of messenger RNAs (mRNAs) required to protect and promote that unique lineage. Nanos1 is one such germline mRNA whose translation is blocked by a secondary mRNA structure within the open reading frame (ORF). Dnd1 contains a canonical RNA recognition motif (RRM1) in its N-terminus but also contains a less conserved RRM2. Here we provide a mechanistic picture of the nanos1 mRNA-Dnd1 interaction in the Xenopus germline. We show that RRM1, but not RRM2, is required for binding nanos1. Similar to the zebrafish homolog, Xenopus Dnd1 possesses ATPase activity. Surprisingly, this activity appears to be within the RRM2, different from the C-terminal region where it is found in zebrafish. More importantly, we show that RRM2 is required for nanos1 translation and germline survival. Further, Dnd1 functions as a homodimer and binds nanos1 mRNA just downstream of the secondary structure required for nanos1 repression. We propose a model in which the RRM1 is required to bind nanos1 mRNA while the RRM2 is required to promote translation through the action of ATPase. Dnd1 appears to use RRMs to mimic the function of helicases.

Genome-Wide Association Study in Craniosynostosis Condition Using Innovative Systematic Bioinformatic Analysis Tools and Techniques: Future Prospective and Clinical Practice.

BACKGROUND: Craniosynostosis (CS) conditions are included with the premature fusion of one or more multiple cranial sutures. As the second leading and most common craniofacial anomaly and orofacial clefts globally. Syndromic and nonsyndromic CS (NSCS) occur as a part of a genetic syndrome unlike Apert, Crouzon, Pfeiffer, Muenke, and Saethre-Chotzen syndromes. Approximately, 90% of the cases of CS arises from NSCS group and it is now a great challenge for the researcher and neurosurgeon for Indian-origin children, a great burden worldwide. MATERIAL AND METHODS: Study design: Prospective study of analysis sequence pattern on CS and NSCS from January 2007 to 2018 was carried out.Inclusion criteria: Diagnosed cases in syndromic and NSCS patients between 3 months and 14 years of age either preoperative or postoperative were included in the study of both groups (syndromic and NSCS).Exclusion criteria: Patients with primary microcephaly (secondary CS), postural plagiocephaly, incomplete data, no visual perception, and who were lost to follow-up, and who had no interest to participate the study were excluded from the study.Bioinformatic analysis: We have performed systematic bioinformatic analysis for all responsible genes by combining with using through the GeneDecks, Gene Runner, DAVID, and STRING databases.Genes testing: FGF family genes, MSX genes, such as Irf6, TP63, Dlx2, Dlx5, Pax3, Pax9, Bmp4, Tgf-beta2, and Tgf-beta3 were found to be involved in Cleft lip and cleft palate (CL/P), and Fgfr2, Fgfr1, Fgfr3, and TWIST, MSX, MSX1, 2 were found to be involved in both the groups of CS (SCS + NSCS). RESULTS: FGFR, MSX, Irf6, TP63, Dlx2, Dlx5, Pax3, Pax9, Bmp4, Tgf-beta2, and Tgf-beta3 demonstrated and find out that in CL/P, and Fgfr2, Fgfr1, Fgfr3, and Twist1 had accurate sequence data with more than accuracy of 95% reported with proper order with additional anomalies CS through newly developed tools. CONCLUSION: Newly developed techniques of GeneDecks, Gene Runner, DAVID, and STRING databases gave better picture to analyze the larger population, patients (SCS + NSCS) with complex genetic, maternal, parental age, environmental, and stochastic factors contributing to NSCS networking, signaling, and pathways involvement. This bioinformatic tools analyzed better prediction of CS and NSCS sequences guiding us the newer invention modalities of pattern of screening and further development of recent future application.

Influence of disulfide bond isoforms on drug conjugation sites in cysteine-linked IgG2 antibody-drug conjugates.

Cysteine-linked antibody-drug conjugates (ADCs) produced from IgG2 monoclonal antibodies (mAbs) are more heterogeneous than ADCs generated from IgG1 mAbs, as IgG2 ADCs are composed of a wider distribution of molecules, typically containing 0 - 12 drug-linkers per antibody. The three disulfide isoforms (A, A/B, and B) of IgG2 antibodies confer differences in solvent accessibilities of the interchain disulfides and contribute to the structural heterogeneity of cysteine-linked ADCs. ADCs derived from either IgG2-A or IgG2-B mAbs were compared to better understand the role of disulfide isoforms on attachment sites and distribution of conjugated species. Our characterization of these ADCs demonstrated that the disulfide configuration affects the kinetics of disulfide bond reduction, but has minimal effect on the primary sites of reduction. The IgG2-A mAbs yielded ADCs with higher drug-to-antibody ratios (DARs) due to the easier reduction of its interchain disulfides. However, hinge-region cysteines were the primary conjugation sites for both IgG2-A and IgG2-B mAbs.

Structural Basis for the Bidirectional Activity of Bacillus nanoRNase NrnA.

NanoRNAs are RNA fragments 2 to 5 nucleotides in length that are generated as byproducts of RNA degradation and abortive transcription initiation. Cells have specialized enzymes to degrade nanoRNAs, such as the DHH phosphoesterase family member NanoRNase A (NrnA). This enzyme was originally identified as a 3' → 5' exonuclease, but we show here that NrnA is bidirectional, degrading 2-5 nucleotide long RNA oligomers from the 3' end, and longer RNA substrates from the 5' end. The crystal structure of Bacillus subtilis NrnA reveals a dynamic bi-lobal architecture, with the catalytic N-terminal DHH domain linked to the substrate binding C-terminal DHHA1 domain via an extended linker. Whereas this arrangement is similar to the structure of RecJ, a 5' → 3' DHH family DNase and other DHH family nanoRNases, Bacillus NrnA has gained an extended substrate-binding patch that we posit is responsible for its 3' → 5' activity.

Posttreatment PET/CT Rather Than Interim PET/CT Using Deauville Criteria Predicts Outcome in Pediatric Hodgkin Lymphoma: A Prospective Study Comparing PET/CT with Conventional Imaging.

Data about the significance of 18F-FDG PET at interim assessment and end of treatment in pediatric Hodgkin lymphoma (HL) are limited. Methods: Patients (≤18 y) with HL were prospectively evaluated with contrast-enhanced CT (CECT) and PET combined with low-dose CT (PET/CT) at baseline, after 2 cycles of chemotherapy, and after completion of treatment. Revised International Working Group (RIW) criteria and Deauville 5 point-scale for response assessment by PET/CT were used. All patients received doxorubicin (Adriamycin), bleomycin, vinblastine, dacarbazine chemotherapy along with involved-field radiotherapy (25 Gy) for early stage (IA, IB, and IIA) and advanced stage (IIB-IV) with bulky disease. Results: Of the 57 enrolled patients, median follow-up was 81.6 mo (range, 11-97.5 mo). Treatment decisions were based on CECT. At baseline, PET/CT versus CECT identified 67 more disease sites; 23 patients (40.3%) were upstaged and of them in 9 patients (39%) upstaging would have affected treatment decision; notably none of these patients relapsed. The specificity of interim PET/CT based on RIW criteria (61.5%) and Deauville criteria (91.4%) for predicting relapse was higher than CECT (40.3%) (P = 0.03 and P < 0.0001, respectively). Event-free survival based on interim PET/CT (RIW) response was 93.3 ± 4.1 versus 89.6 ± 3.8 (positive vs. negative scan, respectively; P = 0.44). The specificity of posttreatment PET/CT (Deauville) was 95.7% versus 76.4% by CECT (P = 0.006). Posttreatment PET/CT (Deauville) showed significantly inferior overall survival in patients with positive scan versus negative scan results (66.4 ± 22.5 vs. 94.5 ± 2.0, P = 0.029). Conclusion: Interim PET/CT has better specificity, and use of Deauville criteria further improves it. Escalation of therapy based on interim PET in pediatric HL needs further conclusive evidence to justify its use. Posttreatment PET/CT (Deauville) predicts overall survival and has better specificity in comparison to conventional imaging.

Adaptation to Stressors by Systemic Protein Amyloidogenesis.

The amyloid state of protein organization is typically associated with debilitating human neuropathies and is seldom observed in physiology. Here, we uncover a systemic program that leverages the amyloidogenic propensity of proteins to regulate cell adaptation to stressors. On stimulus, cells assemble the amyloid bodies (A-bodies), nuclear foci containing heterogeneous proteins with amyloid-like biophysical properties. A discrete peptidic sequence, termed the amyloid-converting motif (ACM), is capable of targeting proteins to the A-bodies by interacting with ribosomal intergenic noncoding RNA (rIGSRNA). The pathological ß-amyloid peptide, involved in Alzheimer's disease, displays ACM-like activity and undergoes stimuli-mediated amyloidogenesis in vivo. Upon signal termination, elements of the heat-shock chaperone pathway disaggregate the A-bodies. Physiological amyloidogenesis enables cells to store large quantities of proteins and enter a dormant state in response to stressors. We suggest that cells have evolved a post-translational pathway that rapidly and reversibly converts native-fold proteins to an amyloid-like solid phase.

Preliminary Experience with Yttrium-90-labelled Rituximab (Chimeric Anti CD-20 Antibody) in Patients with Relapsed and Refractory B Cell Non-Hodgkins Lymphoma.

BACKGROUND AND OBJECTIVES: The aim of the study is to evaluate the therapeutic efficacy and safety of Yttrium- 90 radiolabelled chimeric anti CD20 antibody-Rituximab in the treatment of patients with relapsed/ refractory B cell Non-Hodgkins Lymphoma (NHL). METHODS: Twenty patients with relapsed/refractory CD20+ NHL in progressive state were included in the study. These patients had undergone a median of 2 (range 2-5) prior standard chemotherapy ± immunotherapy regimens. All the patients received rituximab 250 mg/m2 on days 1 and 8, and either 14 MBq/kg (0.4 mCi/kg) or 11 MBq/kg (0.3 mCi/kg) of Y-90 Rituximab on day 8 (maximum dose, 32 mCi) depending upon their platelet count. The patients were observed for systemic toxicity and response for at least 12 weeks after therapy. RESULTS: No acute adverse effects were observed after the administration of 90Y-Rituximab. Overall response rate (ORR) was 45% of which complete response (CR) was observed in 2 patients, stable disease in 1 patient and partial response in 6 patients. The therapy was well tolerated with grade IV thrombocytopenia, neutropenia and anemia observed in 3, 4 and 2 patients respectively. CONCLUSION: 90Y-Rituximab therapy is safe and well tolerated in high risk extensively pretreated NHL patients. Toxicity is primarily hematologic, transient and reversible.

Creating a chimeric clathrin heavy chain that functions independently of yeast clathrin light chain.

Clathrin facilitates vesicle formation during endocytosis and sorting in the trans-Golgi network (TGN)/endosomal system. Unlike in mammals, yeast clathrin function requires both the clathrin heavy (CHC) and clathrin light (CLC) chain, since Chc1 does not form stable trimers without Clc1. To further delineate clathrin subunit functions, we constructed a chimeric CHC protein (Chc-YR) , which fused the N-terminus of yeast CHC (1-1312) to the rat CHC residues 1318-1675, including the CHC trimerization region. The novel CHC-YR allele encoded a stable protein that fractionated as a trimer. CHC-YR also complemented chc1Δ slow growth and clathrin TGN/endosomal sorting defects. In strains depleted for Clc1 (either clc1Δ or chc1Δ clc1Δ), CHC-YR, but not CHC1, suppressed TGN/endosomal sorting and growth phenotypes. Chc-YR-GFP (green fluorescent protein) localized to the TGN and cortical patches on the plasma membrane, like Chc1 and Clc1. However, Clc1-GFP was primarily cytoplasmic in chc1Δ cells harboring pCHC-YR, indicating that Chc-YR does not bind yeast CLC. Still, some partial phenotypes persisted in cells with Chc-YR, which are likely due either to loss of CLC recruitment or chimeric HC lattice instability. Ultimately, these studies have created a tool to examine non-trimerization roles for the clathrin LC.

Reversible acetylation on Lys501 regulates the activity of RNase II.

RNase II, a 3' to 5' processive exoribonuclease, is the major hydrolytic enzyme in Escherichia coli accounting for ∼90% of the total activity. Despite its importance, little is actually known about regulation of this enzyme. We show here that one residue, Lys501, is acetylated in RNase II. This modification, reversibly controlled by the acetyltransferase Pka, and the deacetylase CobB, affects binding of the substrate and thus decreases the catalytic activity of RNase II. As a consequence, the steady-state level of target RNAs of RNase II may be altered in the cells. We also find that under conditions of slowed growth, the acetylation level of RNase II is elevated and the activity of RNase II decreases, emphasizing the importance of this regulatory process. These findings indicate that acetylation can regulate the activity of a bacterial ribonuclease.

How RNase R Degrades Structured RNA: ROLE OF THE HELICASE ACTIVITY AND THE S1 DOMAIN.

RNase R, a ubiquitous 3' exoribonuclease, plays an important role in many aspects of RNA metabolism. In contrast to other exoribonucleases, RNase R can efficiently degrade highly structured RNAs, but the mechanism by which this is accomplished has remained elusive. It is known that RNase R contains an unusual, intrinsic RNA helicase activity that facilitates degradation of duplex RNA, but how it stimulates the nuclease activity has also been unclear. Here, we have made use of specifically designed substrates to compare the nuclease and helicase activities of RNase R. We have also identified and mutated several residues in the S1 RNA-binding domain that are important for interacting with duplex RNA and have measured intrinsic tryptophan fluorescence to analyze the conformational changes that occur upon binding of structured RNA. Using these approaches, we have determined the relation of the RNA helicase, ATP binding, and nuclease activities of RNase R. This information has been combined with a structural analysis of RNase R, based on its homology to RNase II, whose structure has been determined, to develop a detailed model that explains how RNase R digests structured RNA and how this differs from its action on single-stranded RNA.

Novel mutation detection of fibroblast growth factor receptor 1 (FGFR1) gene, FGFR2IIIa, FGFR2IIIb, FGFR2IIIc, FGFR3, FGFR4 gene for craniosynostosis: A prospective study in Asian Indian patient.

BACKGROUND: Craniosynostosis (CS) syndrome is an autosomal dominant condition classically combining craniosynostosis and non-syndromic craniosynostosis with digital anomalies of the hands and feet. The majority of cases are caused by heterozygous mutations in the third immunoglobulin-like domain (IgIII) of FGFR2, whilst a larger number of cases can be attributed to mutations outside this region of the protein. AIMS: To find out the FGFR1, FGFR2, FGFR3 and FGFR4 gene in craniosynostosis syndrome. SETTINGS AND DESIGN: A hospital based prospective study. MATERIALS AND METHODS: Prospective analysis of clinical records of patients registered in CS clinic from December 2007 to January 2015 was done in patients between 4 months to 13 years of age. We have performed genetic findings in a three generation Indian family with Craniosynostosis syndrome. RESULTS: We report for the first time the clinical and genetic findings in a three generation Indian family with Craniosynostosis syndrome caused by a heterozygous missense mutation, Thr 392 Thr and ser 311 try, located in the IgII domain of FGFR2. FGFR 3 and 4 gene basis syndrome was eponymously named. Genetic analysis demonstrated that 51/56 families to be unrelated. In FGFR3 gene 10/TM location of 1172 the nucleotide changes C>A, Ala 391 Glu 19/56 and Exon-19, 5q35.2 at conserved linker region the changes occurred pro 246 Arg in 25/56 families. CONCLUSIONS: Independent genetic origins, but phenotypic similarities in the 51 families add to the evidence supporting the theory of selfish spermatogonial selective advantage for this rare gain-of-function FGFR2 mutation.

Diagnostic utility of fluorodeoxyglucose positron emission tomography/computed tomography in pyrexia of unknown origin.

PURPOSE OF THE STUDY: The present study was undertaken to evaluate the diagnostic utility of fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (F-18 FDG PET/CT) in patients presenting as pyrexia of unknown origin (PUO). MATERIALS AND METHODS: Forty-seven patients (31 males and 16 females; mean age of 42.7 ± 19.96 years) presenting as PUO to the Department of Medicine at the All India Institute of Medical Sciences, New Delhi over a period of 2 years underwent F-18 FDG PET/CT. PET / CT was considered supportive when its results correlated with the final definitive diagnosis. Final diagnosis was made on the basis of combined evaluation of history, clinical findings, investigations, and response to treatment. RESULTS: Thirty-five PET/CT studies (74.5%) were positive. However, only 18 (38.3%) were supportive of the final diagnosis. In three patients (6.4%), PET/CT was considered diagnostic as none of the other investigations including contrast-enhanced computed tomography of chest and abdomen, and directed tissue sampling could lead to the final diagnosis. All these three patients were diagnosed as aortoarteritis. CONCLUSION: Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography is an important emerging modality in the workup of PUO. It supported the final diagnosis in 38% of our patients and was diagnostic in 6.4% of patients. Thus, PET/CT should only be considered as second-line investigation for the diagnostic evaluation of PUO; especially in suspected noninfectious inflammatory disorders.

The Helicase Activity of Ribonuclease R Is Essential for Efficient Nuclease Activity.

RNase R, which belongs to the RNB family of enzymes, is a 3' to 5' hydrolytic exoribonuclease able to digest highly structured RNA. It was previously reported that RNase R possesses an intrinsic helicase activity that is independent of its ribonuclease activity. However, the properties of this helicase activity and its relationship to the ribonuclease activity were not clear. Here, we show that helicase activity is dependent on ATP and have identified ATP-binding Walker A and Walker B motifs that are present in Escherichia coli RNase R and in 88% of mesophilic bacterial genera analyzed, but absent from thermophilic bacteria. We also show by mutational analysis that both of these motifs are required for helicase activity. Interestingly, the Walker A motif is located in the C-terminal region of RNase R, whereas the Walker B motif is in its N-terminal region implying that the two parts of the protein must come together to generate a functional ATP-binding site. Direct measurement of ATP binding confirmed that ATP binds only when double-stranded RNA is present. Detailed analysis of the helicase activity revealed that ATP hydrolysis is not required because both adenosine 5'-O-(thiotriphosphate) and adenosine 5'-(ß,γ-imino)triphosphate can stimulate helicase activity, as can other nucleoside triphosphates. Although the nuclease activity of RNase R is not needed for its helicase activity, the helicase activity is important for effective nuclease activity against a dsRNA substrate, particularly at lower temperatures and with more stable duplexes. Moreover, competition experiments and mutational analysis revealed that the helicase activity utilizes the same catalytic channel as the nuclease activity. These findings indicate that the helicase activity plays an essential role in the catalytic efficiency of RNase R.

Human DNA Exonuclease TREX1 Is Also an Exoribonuclease That Acts on Single-stranded RNA.

3' repair exonuclease 1 (TREX1) is a known DNA exonuclease involved in autoimmune disorders and the antiviral response. In this work, we show that TREX1 is also a RNA exonuclease. Purified TREX1 displays robust exoribonuclease activity that degrades single-stranded, but not double-stranded, RNA. TREX1-D200N, an Aicardi-Goutieres syndrome disease-causing mutant, is defective in degrading RNA. TREX1 activity is strongly inhibited by a stretch of pyrimidine residues as is a bacterial homolog, RNase T. Kinetic measurements indicate that the apparent Km of TREX1 for RNA is higher than that for DNA. Like RNase T, human TREX1 is active in degrading native tRNA substrates. Previously reported TREX1 crystal structures have revealed that the substrate binding sites are open enough to accommodate the extra hydroxyl group in RNA, further supporting our conclusion that TREX1 acts on RNA. These findings indicate that its RNase activity needs to be taken into account when evaluating the physiological role of TREX1.

The role of 18F fluorodeoxyglucose positron emission tomography (18F-FDG-PET) in children with rheumatic carditis and chronic rheumatic heart disease.

BACKGROUND: We report the use of positron emission tomography (PET) using 18F-FDG for the diagnosis of carditis in children with rheumatic heart disease (RHD). MATERIAL AND METHODS: Thirty-six children aged 6-17 years (seventeen males and nineteen females) with isolated rheumatic significant mitral regurgitation (MR) underwent FDG-PET scanning of the heart after fasting for 6 h within a period of 2 years. They were divided into two groups based on Jones criteria - acute rheumatic carditis and chronic RHD. Age- and gender-matched twelve children who underwent whole body ¹8F-FDG-PET scan for routine PET scan for oncological evaluation was taken as controls. Nineteen patients had active carditis and 17 were chronic RHD cases. RESULTS: All 12 controls and all 17 cases with chronic RHD with MR showed diffuse uptake pattern. Of the 19 active cases, 14 showed ¹8F-FDG uptake in the myocardium, 5 did not show any uptake. Thus the finding of no uptake pattern on ¹8F-FDG-PET scan had a sensitivity of 26% but positive predictive value of 100% for acute carditis cases. This study describes the ¹8F-FDG-PET uptake pattern in children with RHD and in 12 age-matched control subjects in the fasting state. Those with chronic RHD with MR showed diffuse myocardial uptake pattern similar to that of the control group. Patients with active carditis showed mixed results; the majority showed diffuse uptake pattern. CONCLUSION: In view of its poor sensitivity, ¹8F-FDG-PET is not recommended as a routine imaging modality for the diagnosis of rheumatic carditis.

Utility of FDG-PET-CT scanning in assessing the extent of disease activity and response to treatment in sarcoidosis.

BACKGROUND: Radionuclide imaging modalities have increasingly been evaluated in the assessment of organ involvement in sarcoidosis. Fluoro-deoxyglucose positron emission tomography-computed tomography (FDG-PET-CT) scanning has received increasing attention in the recent years. The aim of our study was to evaluate the utility of FDG-PET-CT in determining the extent of organ involvement and disease activity in patients of sarcoidosis and to assess its utility in the evaluation of response to therapy. The secondary objective was to compare the agreement between clinical, radiological (HRCT) and metabolic indices (FDG-PET-CT) of disease activity. MATERIALS AND METHODS: This was a prospective observational study conducted between March 2007 and December 2008 at a tertiary care referral center in north India. Twenty-five symptomatic and histopathologically proven cases of sarcoidosis underwent FDG-PET-CT scanning at baseline and a follow-up scan in 21 patients at 6-9 months post-treatment with glucocorticoids. RESULTS: FDG-PET-CT scan detected metabolic disease activity in 24 of the 25 patients with clinically active sarcoidosis. It also demonstrated many clinically inapparent sites of disease activity. Complete or partial metabolic response was seen in 17 of the 21 patients in whom a follow-up scan was available. Substantial degree of agreement was found between the metabolic response and the radiological response, whereas moderate agreement was found between clinical and metabolic responses. CONCLUSIONS: FDG-PET-CT scanning is a useful imaging modality to assess disease activity, extent of disease involvement and response to treatment in clinically active sarcoidosis. There is substantial agreement between the HRCT and metabolic parameters of disease activity. Further, large sample size studies are proposed in order to identify the subset of patients who are likely to benefit the most from this sensitive modality of imaging, especially in developing countries where the cost of the procedure is an important concern.