An autoantibody signature predictive for multiple sclerosis.

Although B cells are implicated in multiple sclerosis (MS) pathophysiology, a predictive or diagnostic autoantibody remains elusive. In this study, the Department of Defense Serum Repository (DoDSR), a cohort of over 10 million individuals, was used to generate whole-proteome autoantibody profiles of hundreds of patients with MS (PwMS) years before and subsequently after MS onset. This analysis defines a unique cluster in approximately 10% of PwMS who share an autoantibody signature against a common motif that has similarity with many human pathogens. These patients exhibit antibody reactivity years before developing MS symptoms and have higher levels of serum neurofilament light (sNfL) compared to other PwMS. Furthermore, this profile is preserved over time, providing molecular evidence for an immunologically active preclinical period years before clinical onset. This autoantibody reactivity was validated in samples from a separate incident MS cohort in both cerebrospinal fluid and serum, where it is highly specific for patients eventually diagnosed with MS. This signature is a starting point for further immunological characterization of this MS patient subset and may be clinically useful as an antigen-specific biomarker for high-risk patients with clinically or radiologically isolated neuroinflammatory syndromes.

A Closed-Loop Digital Health Tool to Improve Depression Care in Multiple Sclerosis: Iterative Design and Cross-Sectional Pilot Randomized Controlled Trial and its Impact on Depression Care.

BACKGROUND: People living with multiple sclerosis (MS) face a higher likelihood of being diagnosed with a depressive disorder than the general population. Although many low-cost screening tools and evidence-based interventions exist, depression in people living with MS is underreported, underascertained by clinicians, and undertreated. OBJECTIVE: This study aims to design a closed-loop tool to improve depression care for these patients. It would support regular depression screening, tie into the point of care, and support shared decision-making and comprehensive follow-up. After an initial development phase, this study involved a proof-of-concept pilot randomized controlled trial (RCT) validation phase and a detailed human-centered design (HCD) phase. METHODS: During the initial development phase, the technological infrastructure of a clinician-facing point-of-care clinical dashboard for MS management (BRIDGE) was leveraged to incorporate features that would support depression screening and comprehensive care (Care Technology to Ascertain, Treat, and Engage the Community to Heal Depression in people living with MS [MS CATCH]). This linked a patient survey, in-basket messages, and a clinician dashboard. During the pilot RCT phase, a convenience sample of 50 adults with MS was recruited from a single MS center with 9-item Patient Health Questionnaire scores of 5-19 (mild to moderately severe depression). During the routine MS visit, their clinicians were either asked or not to use MS CATCH to review their scores and care outcomes were collected. During the HCD phase, the MS CATCH components were iteratively modified based on feedback from stakeholders: people living with MS, MS clinicians, and interprofessional experts. RESULTS: MS CATCH links 3 features designed to support mood reporting and ascertainment, comprehensive evidence-based management, and clinician and patient self-management behaviors likely to lead to sustained depression relief. In the pilot RCT (n=50 visits), visits in which the clinician was randomized to use MS CATCH had more notes documenting a discussion of depressive symptoms than those in which MS CATCH was not used (75% vs 34.6%; χ21=8.2; P=.004). During the HCD phase, 45 people living with MS, clinicians, and other experts participated in the design and refinement. The final testing round included 20 people living with MS and 10 clinicians including 5 not affiliated with our health system. Most scoring targets for likeability and usability, including perceived ease of use and perceived effectiveness, were met. Net Promoter Scale was 50 for patients and 40 for clinicians. CONCLUSIONS: Created with extensive stakeholder feedback, MS CATCH is a closed-loop system aimed to increase communication about depression between people living with MS and their clinicians, and ultimately improve depression care. The pilot findings showed evidence of enhanced communication. Stakeholders also advised on trial design features of a full year long Department of Defense-funded feasibility and efficacy trial, which is now underway. TRIAL REGISTRATION: ClinicalTrials.gov NCT05865405; http://tinyurl.com/4zkvru9x.

Pragmatic phase II clinical trial to improve depression care in a real-world diverse MS cohort from an academic MS centre in Northern California: MS CATCH study protocol.

INTRODUCTION: Depression occurs in over 50% of individuals living with multiple sclerosis (MS) and can be treated using many modalities. Yet, it remains: under-reported by patients, under-ascertained by clinicians and under-treated. To enhance these three behaviours likely to promote evidence-based depression care, we engaged multiple stakeholders to iteratively design a first-in-kind digital health tool. The tool, MS CATCH (Care technology to Ascertain, Treat, and engage the Community to Heal depression in patients with MS), closes the communication loop between patients and clinicians. Between clinical visits, the tool queries patients monthly about mood symptoms, supports patient self-management and alerts clinicians to worsening mood via their electronic health record in-basket. Clinicians can also access an MS CATCH dashboard displaying patients' mood scores over the course of their disease, and providing comprehensive management tools (contributing factors, antidepressant pathway, resources in patient's neighbourhood). The goal of the current trial is to evaluate the clinical effect and usability of MS CATCH in a real-world clinical setting. METHODS AND ANALYSIS: MS CATCH is a single-site, phase II randomised, delayed start, trial enrolling 125 adults with MS and mild to moderately severe depression. Arm 1 will receive MS CATCH for 12 months, and arm 2 will receive usual care for 6 months, then MS CATCH for 6 months. Clinicians will be randomised to avoid practice effects. The effectiveness analysis is superiority intent-to-treat comparing MS CATCH to usual care over 6 months (primary outcome: evidence of screening and treatment; secondary outcome: Hospital Anxiety Depression Scale-Depression scores). The usability of the intervention will also be evaluated (primary outcome: adoption; secondary outcomes: adherence, engagement, satisfaction). ETHICS AND DISSEMINATION: University of California, San Francisco Institutional Review Board (22-36620). The findings of the study are planned to be shared through conferences and publishments in a peer-reviewed journal. The deidentified dataset will be shared with qualified collaborators on request, provision of CITI and other certifications, and data sharing agreement. We will share the results, once the data are complete and analysed, with the scientific community and patient/clinician participants through abstracts, presentations and manuscripts. TRIAL REGISTRATION NUMBER: NCT05865405.

A Closed-Loop Falls Monitoring and Prevention App for Multiple Sclerosis Clinical Practice: Human-Centered Design of the Multiple Sclerosis Falls InsightTrack.

BACKGROUND: Falls are common in people with multiple sclerosis (MS), causing injuries, fear of falling, and loss of independence. Although targeted interventions (physical therapy) can help, patients underreport and clinicians undertreat this issue. Patient-generated data, combined with clinical data, can support the prediction of falls and lead to timely intervention (including referral to specialized physical therapy). To be actionable, such data must be efficiently delivered to clinicians, with care customized to the patient's specific context. OBJECTIVE: This study aims to describe the iterative process of the design and development of Multiple Sclerosis Falls InsightTrack (MS-FIT), identifying the clinical and technological features of this closed-loop app designed to support streamlined falls reporting, timely falls evaluation, and comprehensive and sustained falls prevention efforts. METHODS: Stakeholders were engaged in a double diamond process of human-centered design to ensure that technological features aligned with users' needs. Patient and clinician interviews were designed to elicit insight around ability blockers and boosters using the capability, opportunity, motivation, and behavior (COM-B) framework to facilitate subsequent mapping to the Behavior Change Wheel. To support generalizability, patients and experts from other clinical conditions associated with falls (geriatrics, orthopedics, and Parkinson disease) were also engaged. Designs were iterated based on each round of feedback, and final mock-ups were tested during routine clinical visits. RESULTS: A sample of 30 patients and 14 clinicians provided at least 1 round of feedback. To support falls reporting, patients favored a simple biweekly survey built using REDCap (Research Electronic Data Capture; Vanderbilt University) to support bring-your-own-device accessibility-with optional additional context (the severity and location of falls). To support the evaluation and prevention of falls, clinicians favored a clinical dashboard featuring several key visualization widgets: a longitudinal falls display coded by the time of data capture, severity, and context; a comprehensive, multidisciplinary, and evidence-based checklist of actions intended to evaluate and prevent falls; and MS resources local to a patient's community. In-basket messaging alerts clinicians of severe falls. The tool scored highly for usability, likability, usefulness, and perceived effectiveness (based on the Health IT Usability Evaluation Model scoring). CONCLUSIONS: To our knowledge, this is the first falls app designed using human-centered design to prioritize behavior change and, while being accessible at home for patients, to deliver actionable data to clinicians at the point of care. MS-FIT streamlines data delivery to clinicians via an electronic health record-embedded window, aligning with the 5 rights approach. Leveraging MS-FIT for data processing and algorithms minimizes clinician load while boosting care quality. Our innovation seamlessly integrates real-world patient-generated data as well as clinical and community-level factors, empowering self-care and addressing the impact of falls in people with MS. Preliminary findings indicate wider relevance, extending to other neurological conditions associated with falls and their consequences.

Characteristics of multiple sclerosis and demyelinating disease in an Asian American population.

BACKGROUND: Race and ancestry influence the course of multiple sclerosis (MS). OBJECTIVES: Explore clinical characteristics of MS and neuromyelitis optica spectrum disorder (NMOSD) in Asian American patients. METHODS: Chart review was performed for 282 adults with demyelinating disease who self-identified as Asian at a single North American MS center. Demographics and clinical characteristics were compared to non-Asian MS patients and by region of Asian ancestry. RESULTS: Region of ancestry was known for 181 patients. Most (94.7%) preferred English, but fewer East Asian patients did (80%, p = 0.0001). South Asian patients had higher neighborhood household income (p = 0.002). Diagnoses included MS (76.2%) and NMOSD (13.8%). More patients with NMOSD than MS were East and Southeast Asian (p = 0.004). For MS patients, optic nerve and spinal cord involvement were similar across regions of ancestry. Asian MS patients were younger at symptom onset and diagnosis than non-Asian MS patients. MS Severity Scale scores were similar to non-Asian MS patients but worse among Southeast Asians (p = 0.006). CONCLUSIONS: MS severity was similar between Asian American patients and non-Asian patients. Region of ancestry was associated with differences in sociodemographics and MS severity. Further research is needed to uncover genetic, socioeconomic, or environmental factors causing these differences.

A Predictive Autoantibody Signature in Multiple Sclerosis.

Although B cells are implicated in multiple sclerosis (MS) pathophysiology, a predictive or diagnostic autoantibody remains elusive. Here, the Department of Defense Serum Repository (DoDSR), a cohort of over 10 million individuals, was used to generate whole-proteome autoantibody profiles of hundreds of patients with MS (PwMS) years before and subsequently after MS onset. This analysis defines a unique cluster of PwMS that share an autoantibody signature against a common motif that has similarity with many human pathogens. These patients exhibit antibody reactivity years before developing MS symptoms and have higher levels of serum neurofilament light (sNfL) compared to other PwMS. Furthermore, this profile is preserved over time, providing molecular evidence for an immunologically active prodromal period years before clinical onset. This autoantibody reactivity was validated in samples from a separate incident MS cohort in both cerebrospinal fluid (CSF) and serum, where it is highly specific for patients eventually diagnosed with MS. This signature is a starting point for further immunological characterization of this MS patient subset and may be clinically useful as an antigen-specific biomarker for high-risk patients with clinically- or radiologically-isolated neuroinflammatory syndromes.

Remote Observational Research for Multiple Sclerosis: A Natural Experiment.

BACKGROUND AND OBJECTIVES: Prospective, deeply phenotyped research cohorts monitoring individuals with chronic neurologic conditions, such as multiple sclerosis (MS), depend on continued participant engagement. The COVID-19 pandemic restricted in-clinic research activities, threatening this longitudinal engagement, but also forced adoption of televideo-enabled care. This offered a natural experiment in which to analyze key dimensions of remote research: (1) comparison of remote vs in-clinic visit costs from multiple perspectives and (2) comparison of the remote with in-clinic measures in cross-sectional and longitudinal disability evaluations. METHODS: Between March 2020 and December 2021, 207 MS cohort participants underwent hybrid in-clinic and virtual research visits; 96 contributed 100 "matched visits," that is, in-clinic (Neurostatus-Expanded Disability Status Scale [NS-EDSS]) and remote (televideo-enabled EDSS [tele-EDSS]; electronic patient-reported EDSS [ePR-EDSS]) evaluations. Clinical, demographic, and socioeconomic characteristics of participants were collected. RESULTS: The costs of remote visits were lower than in-clinic visits for research investigators (facilities, personnel, parking, participant compensation) but also for participants (travel, caregiver time) and carbon footprint (p < 0.05 for each). Median cohort EDSS was similar between the 3 modalities (NS-EDSS: 2, tele-EDSS: 1.5, ePR-EDSS: 2, range 0.6.5); the remote evaluations were each noninferior to the NS-EDSS within ±0.5 EDSS point (TOST for noninferiority, p < 0.01 for each). Furthermore, year to year, the % of participants with worsening/stable/improved EDSS scores was similar, whether each annual evaluation used NS-EDSS or whether it switched from NS-EDSS to tele-EDSS. DISCUSSION: Altogether, the current findings suggest that remote evaluations can reduce the costs of research participation for patients, while providing a reasonable evaluation of disability trajectory longitudinally. This could inform the design of remote research that is more inclusive of diverse participants.

Transitioning From S1P Receptor Modulators to B Cell-Depleting Therapies in Multiple Sclerosis: Clinical, Radiographic, and Laboratory Data.

BACKGROUND AND OBJECTIVES: Patients with multiple sclerosis (MS) transition from oral sphingosine-1-receptor (S1P) modulators to anti-CD20 therapies for several circumstances. Optimal timing of this transition is uncertain, given competing concerns of rebound disease activity and ensuring immune reconstitution. The objective of this study was to evaluate the relationship between inflammatory activity and the transition period from fingolimod to anti-CD20 therapies in a real-world MS cohort. METHODS: Medical records were reviewed for all patients at our center transitioning from fingolimod to rituximab or ocrelizumab between 2010 and October 2020. Time periods reviewed were the following: before fingolimod discontinuation, interval between fingolimod and anti-CD20 treatments, and after the first anti-CD20 infusion. The primary outcome was clinical relapses; MRI activity, time to absolute lymphocyte count (ALC) recovery, and infections were secondary. Clinical and demographic factors significant in univariable analyses were included in multivariable analyses. RESULTS: Transition data were available for 108 patients (68.5% women, 68.5% relapsing-remitting MS, mean age 44.6 years). The median (interquartile range) interval between fingolimod and anti-CD20 therapy was 28 (1-115.2) days. Six of 51 patients (11.8%) with intervals >1 month and 0/57 patients with shorter intervals experienced a relapse (MRI confirmed) within 6 months of fingolimod discontinuation. In the year following anti-CD20 initiation, 4/108 patients (3.7%) experienced a relapse (median 214.5 days after infusion). An additional 7% of those undergoing contrast-enhanced MRIs developed Gd+ lesions. ALC normalized following treatment switch in 89/92; the interval between treatments was unrelated to ALC recovery or infection. DISCUSSION: Delaying anti-CD20 start to monitor ALC after S1P modulator discontinuation may not be necessary and could increase rebound risk. ALC monitoring could instead occur after a rapid switch to anti-CD20 treatment.

Underutilization of physical therapy for symptomatic women with MS during and following pregnancy.

BACKGROUND: Many patients with MS continue to have symptoms of their disease even when inflammatory activity is reduced by DMTs. Although disease activity tends to be reduced during pregnancy - especially in the third trimester - women with MS can experience ongoing symptoms during pregnancy, or new ones in the immediate postpartum period, that degrade quality of life. While many MS-related and postpartum symptoms can be improved with physical therapy (PT), there are currently no guidelines on pregnancy-related rehabilitation in MS. In this analysis, we evaluated the prevalence of PT-amenable symptoms and patterns of PT referrals in a cohort of UCSF MS Clinic patients who became pregnant. METHODS: We extracted electronic medical records (EMR) data for the year before conception, during pregnancy, and year postpartum for women with MS cared for at UCSF between 09-2005 and 08-2019. This included clinical visits, MS therapies and symptoms (as defined by the National MS Society). PT and pelvic floor PT orders and notes were also extracted. RESULTS: We included 142 live birth pregnancies from 118 women. During the course of their pregnancy and within the year postpartum, 107 women (75.4%) reported at least one PT-amenable symptom. A total of 30 (28.0%) referrals were made to PT, with attendance confirmed for 10 (33.3% of referrals). Symptoms most commonly triggering a referral for PT evaluation were numbness and urinary incontinence. Falls were reported after 10 of the pregnancies; 4 resulted in a referral to PT. Forty-one women reported urinary incontinence: 11 (26.8%) were referred to PT, and 2 to pelvic floor PT. Nineteen women experienced a documented relapse during pregnancy and/or postpartum: 11 received a PT referral, and 4 attended PT. CONCLUSIONS: While women with MS recorded at least 1 PT-amenable symptom during or following 75.4% of their pregnancies, only 28% of these were referred to PT - and only a third attended PT. Of significance was the 4.9% referral rate for pelvic floor PT in postpartum women with a record of urinary incontinence. Pelvic floor PT is a mainstay of general postpartum care in many European countries. These data illustrate critical gaps in rehabilitation referral, access and use at the intersection of neurological conditions and pregnancy in a large US-based MS clinic. They lend support for quality improvement efforts to improve care pathways and for telerehabilitation innovations to reduce barriers to access and improve synergistic care between PT, MD and urologic care.

A pathogenic and clonally expanded B cell transcriptome in active multiple sclerosis.

Central nervous system B cells have several potential roles in multiple sclerosis (MS): secretors of proinflammatory cytokines and chemokines, presenters of autoantigens to T cells, producers of pathogenic antibodies, and reservoirs for viruses that trigger demyelination. To interrogate these roles, single-cell RNA sequencing (scRNA-Seq) was performed on paired cerebrospinal fluid (CSF) and blood from subjects with relapsing-remitting MS (RRMS; n = 12), other neurologic diseases (ONDs; n = 1), and healthy controls (HCs; n = 3). Single-cell immunoglobulin sequencing (scIg-Seq) was performed on a subset of these subjects and additional RRMS (n = 4), clinically isolated syndrome (n = 2), and OND (n = 2) subjects. Further, paired CSF and blood B cell subsets (RRMS; n = 7) were isolated using fluorescence activated cell sorting for bulk RNA sequencing (RNA-Seq). Independent analyses across technologies demonstrated that nuclear factor kappa B (NF-κB) and cholesterol biosynthesis pathways were activated, and specific cytokine and chemokine receptors were up-regulated in CSF memory B cells. Further, SMAD/TGF-ß1 signaling was down-regulated in CSF plasmablasts/plasma cells. Clonally expanded, somatically hypermutated IgM+ and IgG1+ CSF B cells were associated with inflammation, blood-brain barrier breakdown, and intrathecal Ig synthesis. While we identified memory B cells and plasmablast/plasma cells with highly similar Ig heavy-chain sequences across MS subjects, similarities were also identified with ONDs and HCs. No viral transcripts, including from Epstein-Barr virus, were detected. Our findings support the hypothesis that in MS, CSF B cells are driven to an inflammatory and clonally expanded memory and plasmablast/plasma cell phenotype.

A rare case of HIV CNS escape in a patient previously considered a viral controller.

Human immunodeficiency virus (HIV) ribonucleic acid (RNA) levels generally remain undetectable in the cerebrospinal fluid of people living with HIV with peripheral viral suppression. Secondary HIV central nervous system (CNS) escape refers to the rare independent replication of HIV RNA in the central nervous system despite peripheral viral suppression that occurs in the setting of a concomitant non-HIV infection. We describe here a young man with perinatal HIV infection considered a viral controller who developed secondary HIV CNS escape in the setting of a presumed fungal CNS infection.

Anti-gamma-aminobutyric acid receptor type A encephalitis: a review.

PURPOSE OF REVIEW: To systematically review the clinical features, diagnosis, and management of anti-gamma-aminobutyric acid receptor Type A (GABAA) autoimmune encephalitis with a focus on recent data. RECENT FINDINGS: In a review of published reports, we identified 50 cases of anti-GABAA receptor encephalitis with clinical features reported. The median age at presentation was 47 years old (range, 2.5 months-88 years old), 64% were adults, 36% were children and it occurred in both males and females. Eight-two percent (41/50) presented with seizures, 72% (36/50) with encephalopathy, and 58% (29/50) with both. Of those presenting with seizures, 42% developed status epilepticus during their disease course. Ninety-six percent (48/50) had MRI results reported, with 83% of these cases having abnormal findings, most commonly multifocal/diffuse cortical and subcortical T2/FLAIR hyperintense lesions without associated gadolinium enhancement. Almost one-third, 28% (14/50), had an associated malignancy detected by the time of diagnosis, 64% (9/14) of which was thymoma. Of 44 patients with outcomes reported, 80% had partial or complete recovery, whereas 20% had poor outcomes including 11% (5/44) who died. Of the 42 patients with type of treatment(s) and outcomes reported, 54% (23/42) received only first-line immunotherapy and 31% (13/42) received first-line and second-line immunotherapy. Receiving a combination of first-line and second-line immunotherapy may be associated with higher likelihood of complete recovery. When follow-up MRIs were reported, all showed improvement, and sometimes complete resolution, of T2/FLAIR hyperintensities. SUMMARY: Anti-GABAA receptor encephalitis can present across the age spectrum and should be considered in patients who present with rapidly progressive encephalopathy and/or seizures. Brain MRI often shows a distinctive pattern of multifocal cortical and subcortical T2/FLAIR hyperintense lesions, generally not typical of other known central nervous system autoantibody associated encephalitis syndromes. High clinical suspicion and early diagnosis are important given the potential for clinical improvement with immunotherapy.

GABAA receptor autoimmunity: A multicenter experience.

Objective: We sought to validate methods for detection and confirmation of GABAA receptor (R)-IgG and clinically characterize seropositive cases. Methods: Archived serum and CSF specimens (185 total) suspected to harbor GABAAR-IgG were evaluated by indirect immunofluorescence assay (IFA). Twenty-six specimens from 19 patients appeared suspicious for GABAAR-IgG positivity by IFA, based on prior reports and comparison with commercial GABAAR antibody staining. Aliquots of those specimens were tested at the University of Oxford, United Kingdom, and Euroimmun, Lubeck, Germany, for GABAAR-IgG by cell-based assays (CBAs) using HEK293-indicator cells transfected with plasmids encoding different GABAAR subunits. Results: Eight specimens (of 26 tested; 4 serums, 4 CSFs) from 5 patients were confirmed by CBA to be GABAAR-IgG positive. Patient IgGs were always reactive with α1ß3 GABAAR subunits. One more patient was identified clinically after this validation study. Median age for the 6 patients at serologic diagnosis was 44 years (range, 1-71 years), and 4 of them were male. Among the 4 for whom clinical information was available (2 treated by the authors), all had encephalitis and antiepileptic drug refractory seizures. Three out of 4 patients treated with a combination of immunotherapies had good outcomes. The fourth, recognized to have an autoimmune cause late in the clinical course, had severe permanent neurologic sequelae and brain atrophy. Conclusions: Though not as common as NMDA-R encephalitis, GABAAR encephalitis generally has a characteristic clinical-radiologic presentation and is treatable, making accurate laboratory diagnosis critical.

Aspirin is an effective pretreatment for exercise in multiple sclerosis: A double-blind randomized controlled pilot trial.

Exercise benefits multiple sclerosis (MS) patients, but exercise-induced overheating is a deterrent for many. We conducted a double-blind crossover-design placebo-controlled pilot of aspirin to increase time-to-exhaustion (TTE) and reduce exercise-induced body temperature increase. A total of 12 patients participated. At enrollment, 8 of 12 reported heat sensitivity during exercise. After 650 mg of aspirin or placebo, participants performed lower body cycle ergometer exercise test. TTE increased after aspirin compared to placebo: t(11) = 2.405, p = 0.035 (Cohen's d = 1.45). Body temperature increase after exercise with acetylsalicylic acid (ASA) was reduced by 56% in heat-sensitive patients, although limited power precluded statistical significance. Aspirin may represent an effective pretreatment for exercise in MS.

Altered architecture of substrate binding region defines the unique specificity of UDP-GalNAc 4-epimerases.

UDP-hexose 4-epimerases play a pivotal role in lipopolysaccharide (LPS) biosynthesis and Leloir pathway. These epimerases are classified into three groups based on whether they recognize nonacetylated UDP-hexoses (Group 1), both N-acetylated and nonacetylated UDP-hexoses (Group 2) or only N-acetylated UDP-hexoses (Group 3). Although the catalysis has been investigated extensively, yet a definitive model rationalizing the substrate specificity of all the three groups on a common platform is largely lacking. In this work, we present the crystal structure of WbgU, a novel UDP-hexose 4-epimerase that belongs to the Group 3. WbgU is involved in biosynthetic pathway of the unusual glycan 2-deoxy-L-altruronic acid that is found in the LPS of the pathogen Pleisomonas shigelloides. A model that defines its substrate specificity is proposed on the basis of the active site architecture. Representatives from all the three groups are then compared to rationalize their substrate specificity. This investigation reveals that the Group 3 active site architecture is markedly different from the "conserved scaffold" of the Group 1 and the Group 2 epimerases and highlights the interactions potentially responsible for the origin of specificity of the Group 3 epimerases toward N-acetylated hexoses. This study provides a platform for further engineering of the UDP-hexose 4-epimerases, leads to a deeper understanding of the LPS biosynthesis and carbohydrate recognition by proteins. It may also have implications in development of novel antibiotics and more economic synthesis of UDP-GalNAc and downstream products such as carbohydrate based vaccines.