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Background: While John Cunningham virus (JCV) is known to cause neuronal damage in progressive multifocal leukoencephalopathy (PML) among natalizumab-treated MS patients, its association with axonal loss in non-PML conditions remains unclear., Methods: In a cohort of 128 natalizumab-treated MS patients, serum neurofilament (sNfL) levels and JCV antibody titres were measured., Results: Among 128 patients (mean age = 38.4 years, 71.9% female), 51 (40%) were JCV positive. NfL levels increased by 15.3% for JCV index <0.7 (95% confidence interval [CI] = 0.963-1.381), by 18.6% for index 0.7-1.5 (95% CI = 1.009-1.394) and by 21.1% for index >1.5 (95% CI = 1.040-1.409) compared to JCV negative patients., Conclusion: These findings indicate a potential link between JCV burden and neuroaxonal degeneration in natalizumab-treated MS patients., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: G.D.C., M.P., T.C., F.S., B.C., A.H., and R.G. report no disclosures. VM has received honoraria for activities with Biogen, Merck, Bayer, TEVA and Sanofi-Genzyme as a speaker. L.M. has received honoraria for speaking in scientific meetings and for advisory board from Biogen TEVA, Sanofi-Genzyme, and Merck. R.F. has received honoraria for speaker activities from Biogen, Merck, Novartis, Roche and Teva. L.L. has received honoraria for consulting services and/or speaking activity from Biogen, Novartis and Excemed. G.C. has received personal compensation for consulting services and/or speaking activities from Novartis, Teva, Sanofi, Sanofi-Genzyme, Merck, Biogen, Excemed, Serono Symposia International Foundation, Roche, Almirall, Receptos, Celgene and Forward Pharma.

Introduction: One strategy to mitigate progressive multifocal leukoencephalopathy (PML) risk is to switch to other highly effective disease-modifying therapies (DMTs). However, the optimal switch DMT following natalizumab (NTZ) discontinuation is yet to be determined., Objective: The objective of the study is to determine the most effective and tolerable DMTs to switch to following NTZ discontinuation due to John Cunningham virus (JCV) antibody positivity., Methods: This is a multicenter observational cohort study that included all stable relapsing-remitting multiple sclerosis (MS) patients who were treated with NTZ for at least 6 months before switching therapy due to JCV antibody positivity., Results: Of 321 patients, 255 switched from NTZ to rituximab/ocrelizumab, 52 to fingolimod, and 14 to alemtuzumab, with higher annualized relapse rate (ARR) in fingolimod switchers (0.193) compared with rituximab/ocrelizumab or alemtuzumab (0.028 and 0.032, respectively). Fingolimod switchers also had increased disability progression ( p = 0.014) and a higher proportion developed magnetic resonance imaging (MRI) lesions compared with rituximab/ocrelizumab (62.9% vs. 13.0%, p < 0.001, and 66.6% vs. 24.0%, p < 0.001, respectively). Mean drug survival favored rituximab/ocrelizumab or alemtuzumab over fingolimod ( p < 0.001)., Conclusion: Our study shows superior effectiveness of rituximab/ocrelizumab and alemtuzumab compared with fingolimod in stable patients switching from NTZ due to JC virus antibody positivity., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: M.Z. has received honoraria for lectures from Biologix, Biogen, Janssen, Hikma Pharmaceuticals, Novartis, Merck, Roche, and Sanofi-Genzyme. She received travel grants from Novartis, Merck, and Roche and a research grant from Biogen. She received two research grants from Biogen, one research grant from Merck, and two research grants from MENACTRIMS. She has no conflict of interest related to this study. B.Y. has received speaker honoraria from Bayer, Biogen, Merck, Novartis, Roche, and Sanofi; research grants from Bayer, Biogen, Merck, Novartis, and Pfizer; and advisory board honoraria from Bayer, Biogen, Merck, Novartis, Roche, and Sanofi. He has no conflict of interest related to this study. A.A.-A. has received honoraria from Novartis, Sanofi, Biologix, Merck, Roche, Biogen, and Bayer. He serves on the scientific advisory boards of Novartis, Merck, and Roche. He has no conflict of interest related to this study. R.G. has received research grant from Roche and advisory board honoraria from Biogen, Hikma, Merck, Roche, and Sanofi. He has no conflict of interest related to this study. S.M. received a MENACTRIMS clinical research grant (2020) but has no conflict of interest related to this study. R.A.-R., S.F.A., S.K., N.E.-A., A.A.-M., J.A.-K., A.C., J.I., N.S., J.M., F.M.R.H.M., A.A.-H., P.S., H.D., and F.B. declare that there is no conflict of interest.

Background: The coronavirus disease 2019 (COVID-19) pandemic offered an epidemiological opportunity to evaluate if isolation and masking affected John Cunningham (JC) virus transmission., Objective: This study aimed to assess the proportion of natalizumab-treated patients who converted to a positive anti-JCV antibody serostatus before and during the pandemic., Methods: Data from TYSABRI Outreach: Unified Commitment to Health (TOUCH) for 22,375 US patients treated with natalizumab with anti-JCV antibody records were assessed in epochs annually from 2017 to 2022., Results: Pre-pandemic anti-JCV antibody serostatus change was observed for 7.4%-7.7%. During the first and second years of the pandemic, 7.3% and 7.2% of patients' serostatus changed, respectively., Conclusion: The proportion of patients with anti-JCV antibody serostatus change did not significantly differ during the first 2 years of the pandemic compared with prior years. In contrast to seasonal influenza, masking and social distancing had no discernable effect on JCV serostatus change., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: S.C.K. reports consulting or advisory work with Biogen, EMD Serono, Genentech, Genzyme/Sanofi, Novartis, Octave, and TG Therapeutics; nonpromotional speaking with Biogen, EMD Serono, and Genentech; grant and research support from Biogen, Bristol Myers Squibb (BMS), Novartis, and Sanofi. S.S., F.H., J.S., T.J.K., K.W., and R.L.A. are the employees of and may hold stock and/or stock options in Biogen.

Background: Anti-John Cunningham virus (JCV) serology has been studied with varying results concerning longitudinal changes., Objectives and Methods: Results from 17 published natalizumab-treated multiple sclerosis (MS) patient cohorts were analyzed with common parameters and subsequently verified in two large independent cohorts with 722 and 499 patients from Germany and the United States., Results: Published studies and the verification showed (1) a mean of 10.80% sero-negative patients presented with sero-status change to positivity per year; (2) patients, who sero-convert to index values <0.9, convert from near the threshold and have a high probability of reverting with time; (3) patients, who convert to index values >0.9, start with low index values; (4) while JCV sero-positive patients with low index values sometimes revert to sero-negativity, patients with high index values almost never revert; and (5) the conversion rate of natalizumab-treated patients is three to four times higher than the biological conversion by age., Conclusion: JCV sero-conversion was comparable using standardized parameters and indicates influence of natalizumab on JCV immune control. Converters to low index values are probably consistently infected with JCV with varying low levels of activity, in line with their low risk to develop progressive multifocal leukoencephalopathy (PML). Patients with high index values rarely revert back to sero-negativity.

Background: Natalizumab, a treatment used in multiple sclerosis (MS), is associated with cases of progressive multifocal leukoencephalopathy (PML)., Objective: We describe two cases of PML in related but not genetically apparented natalizumab-treated MS patients who are stepsisters. Reported cases/outcomes: While Patient 1 developed PML, Patient 2 was on natalizumab and had contacts with Patient 1. Patient 2 was diagnosed with PML 5 months after Patient 1., Conclusion: The clinical and temporal data highly suggest that there was JC virus (JCV) transmission from one patient to the other with development of PML as primo-infection in Patient 2.

Background: Natalizumab treatment is associated with progressive multifocal leukoencephalopathy (PML) development. Treatment duration, prior immunosuppressant use, and JCV serostatus are currently used for risk stratification, but PML incidence stays high. Anti-JCV antibody index and L-selectin (CD62L) have been proposed as additional risk stratification parameters., Objective: This study aimed at verifying and integrating both parameters into one algorithm for risk stratification., Methods: Multicentric, international cohorts of natalizumab-treated MS patients were assessed for JCV index (1921 control patients and nine pre-PML patients) and CD62L (1410 control patients and 17 pre-PML patients)., Results: CD62L values correlate with JCV serostatus, as well as JCV index values. Low CD62L in natalizumab-treated patients was confirmed and validated as a biomarker for PML risk with the risk factor "CD62L low" increasing a patient's relative risk 55-fold (p < 0.0001). Validation efforts established 86% sensitivity/91% specificity for CD62L and 100% sensitivity/59% specificity for JCV index as predictors of PML. Using both parameters identified 1.9% of natalizumab-treated patients in the reference center as the risk group., Conclusions: Both JCV index and CD62L have merit for risk stratification and share a potential biological relationship with implications for general PML etiology. A risk algorithm incorporating both biomarkers could strongly reduce PML incidence., (© The Author(s), 2015.)

Background: Anti-JC virus antibody status is a risk factor for progressive multifocal leukoencephalopathy after natalizumab treatment in multiple sclerosis. Previous studies have used a cross-sectional approach to conclude that the presence and duration of natalizumab treatment does not influence anti-JCV Ab seropositivity., Objectives: Using a longitudinal approach, we measured change in anti-JCV Ab results after natalizumab treatment., Methods: Anti-JCV Ab results (n = 1154) from the second-generation STRATIFY JCV™ DxSelect™ test were analysed from an observational cohort of MS patients on natalizumab (n = 485; n = 340 with repeat testing; n = 657 repeat tests on natalizumab)., Results: Across sequential paired tests, seroconversion rate was greater than seroreversion rate (40/364 (11.0%) versus 18/293 (6.1%); p < 0.05). Moreover, anti-JCV Ab index increased across longitudinal paired tests (mA-B 0.102; paired t(656) = 5.0; p < 0.0001). This magnitude of Ab level increase far exceeds that expected due to increasing age alone., Conclusion: Our data suggest that natalizumab therapy is associated with a significant and substantial increase in anti-JCV Ab index over time. Further work should focus on the underlying mechanisms of this phenomenon, and the clinical relevance to risk stratification., (© The Author(s), 2015.)

The presence of anti-John Cunningham Virus (JCV) antibodies is a risk factor for the development of progressive multifocal leukoencephalopathy (PML) in MS patients treated with natalizumab. It has been suggested that an increase in serum anti-JCV antibody index precedes the development of PML. We here describe extensive longitudinal serum anti-JCV antibody indexes of four MS patients who developed PML. Anti-JCV antibodies were measured using the STRATIFY JCV™DxSelect™ test. All four patients had rather stable high anti-JCV antibody indexes in all samples obtained before developing PML. Possibly caused by reaching the saturation level of the assay, no increase in anti-JCV antibody indexes was seen just before the diagnosis of PML. This study confirms that high serum anti-JCV antibody indexes precede natalizumab-associated PML., (© The Author(s), 2015.)

The use of natalizumab has likely been limited by its association with progressive multifocal leukoencephalopathy (PML), an infection caused by the human polyomavirus John Cunningham (JC). Three factors were recently identified that contribute to the overall risk of natalizumab-associated PML: (1) Positive serostatus for anti-JCV antibodies, (2) prior use of immunosuppressants, and (3) duration of natalizumab therapy. This risk stratification algorithm has not led to a reduction in the incidence of PML in natalizumab-treated patients with multiple sclerosis between April 2010 and February 2014. This observation may appear perplexing, as treatment duration and JCV serostatus are modifiable risk factors. Potential reasons for the lack of success of companion diagnostics that determine the overall risk of natalizumab-associated PML are discussed., (© The Author(s), 2014.)

Background: The lack of prospective trial data comparing certain multiple sclerosis (MS) therapies could be addressed with observational research., Objective: The objective of this paper is to investigate outcomes of natalizumab versus fingolimod treatment in an MS cohort using a novel method of patient selection., Methods: We reviewed entries from our clinic's database for all relapsing-remitting MS patients started on fingolimod and natalizumab where JCV serology was used to determine treatment. We analyzed each group for time to first relapse and in a second analysis, time to first relapse or gadolinium-enhancing lesion., Results: Sixty-nine patients on natalizumab and 36 on fingolimod met our inclusion criteria and had adequate follow-up for analysis. The baseline clinical characteristics at the time of treatment switch were similar. With a mean follow-up of 1.5 years for both treatment groups, there was a trend favoring natalizumab in time to first relapse, although this was not statistically significant (2.20 (0.87, 5.55) p = 0.095). There was a significant difference in the secondary outcome, time to relapse or gadolinium-enhancing lesion (2.31 (1.03, 5.17) p = 0.041), favoring natalizumab. Adjusted analyses favored natalizumab for both outcomes (p < 0.05)., Conclusion: This work employed an observational study design where treatment allocation by JCV serology allowed for treatment groups with well-balanced characteristics., (© The Author(s), 2014.)

Aim: The objectives of this study were to evaluate the rate of JC virus (JCV) seroconversion/seroreversion in a French cohort of multiple sclerosis (MS) patients receiving natalizumab (NTZ), describe the characteristics of this population, identify risk factors for JCV seropositivity and analyse the additional value of quantitative JCV serology results in this context., Methods: MS patients from two French MS centres, whose JCV serological status in 2011 while receiving NTZ was known (n=357; first-generation enzyme-linked immunosorbent assay (ELISA) test (Gen1)), were proposed for inclusion in this study. We evaluated the rate of JCV seroconversion over a period of one year with a second-generation ELISA test (Gen2; n=303) and analysed the quantitative results. Multivariate analysis was performed to identify risk factors for JCV seropositivity., Results: Among the patients with Gen2 JCV serology (n=303) that had been JCV-seronegative one year before (n=165), the rate of JCV seroconversion was 26.67% (44/165). We observed a higher proportion of anti-JCV antibody seroconverters (14.5%) than expected (≤3%) but also increasing index values of anti-JCV antibody over time., Conclusion: Our data suggest that JCV reactivation occurs during NTZ therapy and leads to an increase in the anti-JCV antibodies titre, thus making them more easily detectable by the second-generation ELISA test., (© The Author(s) 2013.)

JCV serologic status is used to determine PML risk in natalizumab-treated patients. Given two cases of natalizumab-associated PML in JCV sero-negative patients and two publications that question the false negative rate of the JCV serologic test, clinicians may question whether our understanding of PML risk is adequate. Given that there is no gold standard for diagnosing previous JCV exposure, the test characteristics of the JCV serologic test are unknowable. We propose a model of PML risk in JCV sero-negative natalizumab patients. Using the numbers of JCV sero-positive and -negative patients from a study of PML risk by JCV serologic status (sero-positive: 13,950 and sero-negative: 11,414), we apply a range of sensitivities and specificities in order calculate the number of JCV-exposed but JCV sero-negative patients (false negatives). We then apply a range of rates of developing PML in sero-negative patients to calculate the expected number of PML cases. By using the binomial function, we calculate the probability of a given number of JCV sero-negative PML cases. With this model, one has a means to establish a threshold number of JCV sero-negative natalizumab-associated PML cases at which it is improbable that our understanding of PML risk in JCV sero-negative patients is adequate.

JC virus (JCV) is an opportunistic virus known to cause progressive multifocal leukoencephalopathy. Anti-JC virus (Anti-JCV) antibody prevalence in a large, geographically diverse, multi-national multiple sclerosis (MS) cohort was compared in a cross-sectional study. Overall, anti-JCV antibody prevalence was 57.6%. Anti-JCV antibody prevalence in MS patients ranged from approximately 47% to 68% across these countries: Norway, 47.4%; Denmark, 52.6%; Israel, 56.6%; France, 57.6%; Italy, 58.3%; Sweden, 59.0%; Germany, 59.1%; Austria, 66.7% and Turkey, 67.7%. Prevalence increased with age (from 49.5% in patients < 30 years of age to 66.5% in patients ≥ 60 years of age; p < 0.0001 comparing all age categories), was lower in females than in males (55.8% versus 61.9%; p < 0.0001) and was not affected by prior immunosuppressant or natalizumab use.

Background: The StratifyJCV® test is a qualitative assay to classify MS patients as anti-JC virus (JCV) antibody positive or negative. Quantification of anti-JCV antibody levels in serum and cerebrospinal fluid (CSF) of multiple sclerosis (MS) patients might add to the progressive multifocal leukoencephalopathy (PML) risk assessment., Objective: The objective of this study is to test sera of patients in a quantitative anti-JCV antibody assay, and to compare the results with preexisting data from the StratifyJCV® test., Methods: Sera of a total of 175 MS patients and matched non-MS-controls were tested for anti-JCV antibodies using glutathione S-transferase-tagged-VP1 as antigen. Antibody reactivity was quantified in arbitrary units using human immunoglobulin as standard., Results: The comparison of our assay with StratifyJCV® showed good inter-assay agreement (kappa 0.6), and strong correlation for antibody reactivity (r (2) = 0.94). Discordant samples had low-reactive positivity, and a higher proportion (13% vs. 4%) tested positive in the StratifyJCV® test only., Conclusions: The method presented is a tool for the reliable quantification of anti-JCV antibodies, which demonstrates good agreement with results from StratifyJCV®. In contrast to StratifyJCV®, we pre-adsorbed all of the sera with BK virus (BKV) VP1 protein to reduce cross-reactivity. This step may account for a higher species-specificity of our assay. As such, our assay might be a promising additional tool for PML risk assessment.

Objective: Natalizumab, a highly effective treatment for multiple sclerosis (MS) and Crohn's disease, is associated with progressive multifocal leukoencephalopathy (PML). Upon suspicion or diagnosis of PML, plasma exchange (PLEX) is performed to remove natalizumab from the circulation, allowing immune reconstitution of the central nervous system. Since PLEX may also remove other circulating antibodies, we examined the effects of PLEX on serum immunoglobulin (IgG) and anti-JC virus (JCV) antibody levels in MS patients with and without PML., Methods: Serum samples from 12 natalizumab-treated patients without PML collected before, during and after PLEX were tested for IgG isotypes using a commercial assay, and for anti-JCV antibodies using a two-step enzyme-linked immunosorbent assay. Five natalizumab-treated PML patients who underwent PLEX were also tested for anti-JCV antibodies., Results: PLEX produced a two- to three-fold reduction in all IgG isotypes. Among patients without PML, 42% (five of 12 patients) had detectable anti-JCV antibodies before PLEX; in these patients, anti-JCV antibodies were reduced approximately two- to five-fold, with levels returning to 50-100 percent of baseline two weeks after the final PLEX. The five PML patients, all of whom had detectable anti-JCV antibodies before PLEX, experienced similar reductions in anti-JCV antibody levels following PLEX., Conclusions: Our results indicate that PLEX effectively removes circulating antibodies; however, levels of endogenous anti-JCV antibody, unlike exogenously administered natalizumab, were replenished relatively quickly following PLEX. While interpretation of anti-JCV antibody levels during or within two weeks after PLEX may be problematic, humoral JCV immunity is not abolished by PLEX and antibody levels are rapidly restored.

Clinical and/or neuroimaging evidence of disease reactivation has been described in multiple sclerosis (MS) patients after a break from natalizumab. Whether fingolimod might be a therapeutic option following natalizumab needs to be evaluated. Twenty-two relapsing remitting MS patients having JC virus antibodies (JCVAb+) in serum were shifted from natalizumab to fingolimod after a three-month washout period. Neurological evaluation with the Expanded Disability Status Scale (EDSS) was performed monthly for a mean follow-up period of nine months. In 20/22 patients, brain magnetic resonance imaging (MRI) was obtained within one month after therapy initiation. Disease reactivation was observed in 11/22 (50%) patients: clinical relapses in six patients (four patients within the first month of therapy) and MRI activity in a further five patients (three patients within the first month of therapy). Clinical and/or MRI signs suggestive of disease rebound were observed in three patients. Our data indicate that fingolimod does not exert clinical activity quickly enough to stop MS reactivation after a break from natalizumab.

Multifocal progressive leukoencephalopathy (PML) is associated with JC virus (JCV) seropositivity, past immunosuppression, and natalizumab treatment for two years or more. The aim of our study was to investigate the rate of treatment discontinuation after stratifying for the three risk factors in a group of 104 natalizumab-treated patients with relapsing-remitting multiple sclerosis. We investigated JCV serological status in our population. We then divided patients into groups according to their PML risk. Treatment indication was reassessed. Of the patients, 64 (61.5%) were JCV seropositive. Amongst seropositive patients on natalizumab for 2 years or more, 10 had received immunosuppression (group A), and 38 had not (group B). After an informed and shared decision-making process, 6/10 (60%) from group A compared with 9/38 (23.7%) from group B discontinued treatment (p=0.027). In groups A and B, discontinuation also depended upon doctors' views (p=0.019, group A; p=0.010, group B) and clinical outcomes (p=0.021, group A). No-one from low-intermediate risk groups discontinued. The decision to discontinue natalizumab treatment is complex, even when clear PML risk rates are described. Clinical outcomes and doctors' idiosyncrasies play a crucial part in patients' final choice.

Background: Long-term therapy with natalizumab increases the risk of progressive multifocal leukoencephalopathy (PML)., Objectives: We present a patient study through therapy, the diagnosis of PML (after 29 infusions), plasma exchange (PE) and development of immune reconstitution inflammatory syndrome (IRIS)., Methods: Routine diagnostics, magnetic resonance imaging (MRI), immunological status (flow cytometry, T-cell migration assays and T-cell repertoire analysis), and brain biopsy with immunohistological analysis., Results: CD49d decreased after 12 months of treatment. At PML diagnosis, CD49d expression and migratory capacity of T cells was low and peripheral T-cell receptor (TCR) complexity showed severe perturbations. The distribution of peripheral monocytes changed from CCR5+ to CCR7+. After PE some changes reverted: CD49d increased and overshot earliest levels, migratory capacities of T cells recovered and peripheral TCR complexity increased. With no clinical, routine laboratory or cerebrospinal fluid (CSF) changes, MRI 2 months after PE demonstrated progressive lesion development. Brain histopathology confirmed the presence of infiltrates indicative of IRIS without clinical signs, immunologically accompanied by CCR7/CCR5 recovery of peripheral monocytes., Conclusion: Natalizumab-associated immunological changes accompanying PML were reversible after PE; IRIS can occur very late, remain asymptomatic and be elusive to CSF analysis. Our study may provide insights into the changes under treatment with natalizumab associated with JC virus control.

Objective: 1) To determine whether JC virus (JCV) DNA was present in the cerebrospinal fluid (CSF) and blood from patients with multiple sclerosis (MS) in comparison with controls and 2) to find out if our clinical material, based on presence of JCV DNA, included any patient at risk for progressive multifocal leukoencephalopathy (PML)., Methods: The prevalence of JCV DNA was analyzed in CSF and plasma from 217 patients with MS, 86 patients with clinically isolated syndrome (CIS), and 212 patients with other neurological diseases (OND). In addition, we analyzed CSF cells, the first report of JCV DNA in CSF cells in a single sample, and peripheral blood cells in a subgroup of MS (n = 49), CIS (n = 14) and OND (n = 53)., Results: A low copy number of JCV DNA was detected in one MS cell free CSF sample and in one MS CSF cell samples. None of these had any signs of PML or developed this disease during follow-up. In addition, two OND plasma samples were JCV DNA positive, whereas all the other samples had no detectable virus., Conclusion: A low copy number of JCV DNA may occasionally be observed both in MS and other diseases and may occur as part of the normal biology of JC virus in humans. This study does not support the hypothesis that patients with MS would be at increased risk to develop PML, and consequently screening of CSF as a measurable risk for PML is not useful.