Conversion Predictors of Clinically Isolated Syndrome to Multiple Sclerosis in Mexican Patients: A Prospective Study.

BACKGROUND: Clinically Isolated Syndrome (CIS) is the first clinical episode suggestive of Clinical Definite Multiple Sclerosis (CDMS). There are no reports on possible predictors of conversion to CDMS in Mexican mestizo patients. AIM OF THE STUDY: To investigate immunological markers, clinical and paraclinical findings, and the presence of herpesvirus DNA to predict the transition from CIS to CDMS in Mexican patients. METHODS: A single-center prospective cohort study was conducted with newly diagnosed patients with CIS in Mexico between 2006 and 2010. Clinical information, immunophenotype, serum cytokines, anti-myelin protein immunoglobulins, and herpes viral DNA were determined at the time of diagnosis. RESULTS: 273 patients diagnosed with CIS met the enrolment criteria; after 10 years of follow-up, 46% met the 2010 McDonald criteria for CDMS. Baseline parameters associated with conversion to CDMS were motor symptoms, multifocal syndromes, and alterations of somatosensory evoked potentials. The presence of at least one lesion on magnetic resonance imaging was the main factor associated with an increased risk of conversion to CDMS (RR 15.52, 95% CI 3.96-60.79, p = 0.000). Patients who converted to CDMS showed a significantly lower percentage of circulating regulatory T cells, cytotoxic T cells, and B cells, and the conversion to CDMS was associated with the presence of varicella-zoster virus and herpes simplex virus 1 DNA in cerebrospinal fluid and blood. CONCLUSION: There is scarce evidence in Mexico regarding the demographic and clinical aspects of CIS and CDMS. This study shows several predictors of conversion to CDMS to be considered in Mexican patients with CIS.

Interaction of HLA Class II rs9272219 and TMPO rs17028450 (Arg690Cys) Variants Affects Neuromyelitis Optica Spectrum Disorder Susceptibility in an Admixed Mexican Population.

Neuromyelitis Optica Spectrum Disorder (NMOSD) is a demyelinating autoimmune disease of the central nervous system, more prevalent in individuals of non-European ancestry. Few studies have analyzed genetic risk factors in NMOSD, and HLA class II gene variation has been associated NMOSD risk in various populations including Mexicans. Thymopoietin (TMPO) has not been tested as a candidate gene for NMOSD or other autoimmune disease, however, experimental evidence suggests this gene may be involved in negative selection of autoreactive T cells and autoimmunity. We thus investigated whether the missense TMPO variant rs17028450 (Arg630Cys, frequent in Latin America) is associated with NMOSD, and whether this variant shows an interaction with HLA-class II rs9272219, previously associated with NMOSD risk. A total of 119 Mexican NMOSD patients, 1208 controls and 357 Native Mexican individuals were included. The HLA rs9272219 "T" risk allele frequency ranged from 21 to 68%, while the rs17028450 "T" minor allele frequency was as high as 18% in Native Mexican groups. Both rs9272219 and rs17028450 were significantly associated with NMOSD risk under additive models (OR = 2.48; p = 8 × 10-10 and OR = 1.59; p = 0.0075, respectively), and a significant interaction between both variants was identified with logistic regression models (p = 0.048). Individuals bearing both risk alleles had an estimated 3.9-fold increased risk of NMOSD. To our knowledge, this is the first study reporting an association of TMPO gene variation with an autoimmune disorder and the interaction of specific susceptibility gene variants, that may contribute to the genetic architecture of NMOSD in admixed Latin American populations.

T-Cell Response against Varicella Zoster Virus in Patients with Multiple Sclerosis during Relapse and Remission.

An association between varicella zoster virus (VZV) and multiple sclerosis (MS) has been reported in Mexican populations. The aim of this study was to compare the response of T cells from MS patients, during relapse and remission, to in vitro stimulation with VZV, adenovirus (AV) and Epstein-Barr virus (EBV). Proliferation and cytokine secretion of T cells from 29 relapsing-remitting MS patients and 38 healthy controls (HC) were analyzed by flow cytometry after stimulating with VZV, AV or EBV. IgG and IgM levels against VZV and EBV were quantified using Enzyme-Linked Immunosorbent Assay. Relapsing MS patients showed a higher percentage of responding CD4+ and CD8+ T cells against VZV compared to AV. In HC and remitting MS patients, proliferation of CD4+ T cells was higher when stimulated with VZV as compared to EBV. Moreover, T cells isolated from remitting patients secreted predominantly Th1 cytokines when cell cultures were stimulated with VZV. Finally, high concentration of anti-VZV IgG was found in sera from patients and controls. The results support previous studies of an VZV-MS association in the particular population studied and provide additional information about the possible role of this virus in the pathogenesis of MS.

The presence of herpes simplex-1 and varicella zoster viruses is not related with clinical outcome of Bell's Palsy.

Bell's Palsy is the most frequent acute neuropathy of cranial nerves; it has been associated in various reports to herpes viruses. In a prospective study we searched the presence of DNA from five herpes viruses (HSV-1 and 2, VZV, EBV and HHV-6) in 79 patients at the acute phase of Bell's Palsy. Results were related with various parameters; age, gender and clinical outcome. We found the significant presence (p˂0.001) of HSV-1 and VZV in 39% and 42% of patients. However, a large percentage of cases were negative. When comparisons were made between subgroups according to gender and age no differences were found with viral findings nor with clinical outcome of palsy, which was of clinical remission in most cases (78%). Our results suggest that herpes viruses might participate in the complex mechanisms of autoimmunity of Bell's Palsy but not as determinant etiological element.

Native American ancestry significantly contributes to neuromyelitis optica susceptibility in the admixed Mexican population.

Neuromyelitis Optica (NMO) is an autoimmune disease with a higher prevalence in non-European populations. Because the Mexican population resulted from the admixture between mainly Native American and European populations, we used genome-wide microarray, HLA high-resolution typing and AQP4 gene sequencing data to analyze genetic ancestry and to seek genetic variants conferring NMO susceptibility in admixed Mexican patients. A total of 164 Mexican NMO patients and 1,208 controls were included. On average, NMO patients had a higher proportion of Native American ancestry than controls (68.1% vs 58.6%; p = 5 × 10-6). GWAS identified a HLA region associated with NMO, led by rs9272219 (OR = 2.48, P = 8 × 10-10). Class II HLA alleles HLA-DQB1*03:01, -DRB1*08:02, -DRB1*16:02, -DRB1*14:06 and -DQB1*04:02 showed the most significant associations with NMO risk. Local ancestry estimates suggest that all the NMO-associated alleles within the HLA region are of Native American origin. No novel or missense variants in the AQP4 gene were found in Mexican patients with NMO or multiple sclerosis. To our knowledge, this is the first study supporting the notion that Native American ancestry significantly contributes to NMO susceptibility in an admixed population, and is consistent with differences in NMO epidemiology in Mexico and Latin America.

Herpes viruses in optic neuritis: Similar to Bell's palsy.

OBJECTIVE: Optic Neuritis (ON) might unfold either as a single intracranial neuritis or as multiple sclerosis, a widespread demyelinating disorder. Different herpes viruses have been proposed as potential participants in the etiology of multiple sclerosis (MS). To analyze the potential presence of herpes viruses in blood and subarachnoid area at the time of ON and contrast the findings according to long-term evolution either as intracranial neuritis or as progression to multiple sclerosis. PATIENTS AND METHODS: In a prospective investigation we searched the presence of DNA from 5 herpes viruses (HSV-1, HSV-2, VZV, EBV and HHV6) in CSF and blood lymphocytes from 54 patients with ON, patients were followed 62 ±â€¯3 months; those who developed MS were separated from those with ephemeral ON. Long-term prognosis of ON was related to DNA findings. RESULTS: As compared with controls, DNA from HSV-1 was significantly more frequent in CSF and blood from cases with ON; VZV and HSV-2 were found only in CSF; EBV was found only in blood samples (p < 0.006). CONCLUSIONS: Our results point out the potential participation of HSV, VZV and EBV in ON; suggesting the intervention of various herpes viruses as triggering agents of autoimmunity. However, the number of positive cases was minor than negative cases. Also, our results suggest that the etiological mechanisms in ON could be similar to those of neuritis of the facial nerve (Bell's palsy).

Varicella-Zoster Virus in Cerebrospinal Fluid at Relapses of Multiple Sclerosis is Infective in Vitro.

BACKGROUND: We have reported the presence of varicella-zoster virus (VZV) DNA and viral particles in the cerebrospinal fluid (CSF) of multiple sclerosis (MS) patients during exacerbation. It is not known whether these viruses are infective. AIM: To determine whether the VZV found in CSF of MS patients in exacerbation phase are infective. METHODS: VZV found in CSF of MS patients was quantified by qPCR. Vero E6 cell cultures were incubated with CSF of five MS cases positive for VZV DNA, containing herpes-like viral particles. Propagated virus harvested from these cultures were used to infect new VeroE6 cells. Localization of an immediate-early and a late structural VZV proteins was monitored by confocal microscopy after 72 h. CSF from five non-inflammatory neurological (NIN) patients were used as controls. RESULTS: A cytopathic effect was found in cultured cells inoculated with CSF from MS patients. Both, structural VZV glycoprotein (gB) and immediate-early VZV protein (IE62) were detected in Vero E6 cultures inoculated with samples from all five MS cases. CSF from control patients produced no effect on Vero E6 cells. CONCLUSION: When present in the CSF at relapses of MS, VZV is infective under in vitro conditions.

Occasional presence of herpes viruses in synovial fluid and blood from patients with rheumatoid arthritis and axial spondyloarthritis.

Viral agents have been suspected as participants of immune-mediated disorders. In the case of rheumatic diseases, the synovial joint cavity represents a secluded area of inflammation which could harbor etiological agents. We analyzed by polymerase chain reaction the possible presence of DNA from various herpes viruses in blood and synovial fluid from patients with either rheumatoid arthritis (n = 18), axial spondyloarthritis (n = 11), or osteoarthritis (n = 8). Relevant findings were as follows: DNA from varicella zoster virus was found in synovial fluid but not in blood mononuclear cells from 33 % of patients with rheumatoid arthritis and in 45 % of patients with axial spondyloarthritis but not in patients with osteoarthritis. Also, DNA from herpes simplex viruses 1 and 2 was found both in the blood and in the synovial fluid from 33 % of patients with rheumatoid arthritis. Our results indicate the occasional presence of DNA from herpes viruses in patients with rheumatoid arthritis or with axial spondyloarthritis. However, these findings might represent a parallel epiphenomenon of viral activation associated either with immunosuppressive therapy or with primary immune disturbances, rather than the etiological participation of herpes viruses in these disorders.

Genomewide admixture study in Mexican Mestizos with multiple sclerosis.

BACKGROUND: Multiple sclerosis (MS) is a complex immune-mediated disease. It has been suggested that genetic factors could explain differences in the prevalence among ethnic groups. To know whether genetic ancestry is a potential risk factor for MS in Mexican patients and to identify candidate genes for the susceptibility to the disease we conducted an initial trial of genome-wide analysis. METHODS: 29 patients with diagnosis of definitive MS and 132 unrelated healthy controls were genotyped using the Affymetrix human 6.0 array. After QC procedures, ancestry determination and a preliminary case-control association study were performed. RESULTS: We identified significant differences in the European ancestry proportion between MS cases and controls (33.1 vs. 25.56, respectively; p=0.0045). Imputation analysis in the MHC region on chromosome 6 showed a signal with a significant level (p<0.00005) on the HLA-DRB region. Additionally, a preliminary association analysis highlighted the ASF1B as novel candidate gene participating in MS. CONCLUSION: Our data suggest that European ancestry is a risk factor to develop MS in Mexican Mestizo population. Conversely, indigenous ancestry of Asian origin seems to confer protection. Further studies with more MS cases are needed to confirm these findings.

Molecular detection and prognostic value of epithelial markers mRNA expression in peripheral blood of advanced non-small cell lung cancer patients.

BACKGROUND: Few studies, have evaluated the prognostic impact of the quantification of mRNA expression levels in advanced non-small cell lung cancer (NSCLC). OBJECTIVE: The aim of this work was to quantify mRNA expression levels in peripheral blood through three epithelial markers in patients with stages IIIB and IV in NSCLC. METHODS: Seventy advanced NSCLC patients and ten healthy controls were included. All patients received platinum-based chemotherapy in first line treatment. Peripheral blood was obtained of each participant and mRNA expression levels present in circulating cells were quantified by molecular techniques (RT-PCR) using three epithelial markers: cytokeratin (CK)-18, CK-19 and Carcinoembryonic-Antigen (CEA). The expression levels were quantified from a standard curve using the cDNA obtained from A549 cells. Registered in ClinicalTrials.gov (NCT01052818). RESULTS: We found a significant statistical correlation between levels of CK-18, CK-19 and CEA mRNA. mRNA expression levels were lower in patients who present three or less metastasis; higher CEA mRNA expression was associated a worse progression-free survival to platinum-based chemotherapy and overall survival. CONCLUSION: RNA expression of CEA by RT-PCR is useful as a prognostic marker in advanced NSCLC.

Vitamin A increases nerve growth factor and retinoic acid receptor beta and improves diabetic neuropathy in rats.

All-trans retinoic acid (ATRA) promotes the endogenous expression of both nerve growth factor (NGF) and retinoic acid receptor beta (RAR-ß). We have previously shown that the administration of ATRA partly reverts the damage induced by diabetic neuropathy (DN). In this investigation, we evaluated the effects of vitamin A, a commercial, inexpensive compound of retinoic acid, on the therapy of DN. A total of 70 rats were randomized into 4 groups. Group A was the control, and groups B, C, and D received a total dose of 60 mg/kg streptozotocin intraperitoneally. When signs of DN developed, groups C and D were treated either with vitamin A (20,000 IU) or with ATRA 25 mg/kg for 60 days. Plasma glucose, contents of NGF, thermal and nociceptive tests, and RAR-ß expression were evaluated. All diabetic rats developed neuropathy. The treatment with vitamin A and ATRA reverted similarly the sensorial disturbances, which was associated with increased contents of NGF and RAR-ß expression. Our results indicate that the administration of vitamin A has the same therapeutic effect as ATRA on peripheral neuropathy and suggest its potential therapeutic use in patients with diabetes.

Sunlight exposure and multiple sclerosis in a tropical country.

OBJECTIVE: We analysed past and current sun exposure in multiple sclerosis (MS) patients as compared with matched controls in Mexico, a country with tropical climate. METHODS: In a case-controlled study that include 83 MS patients and 166 matched controls, we inquired about sunlight exposure in two different periods: during adolescence and during the immediate past 5 years. Indicators were: exposure on quotidian and weekend outdoor activities with direct sunlight contact as expressed on frequency by mean number of days, daytime (morning, noon, afternoon), number of hours, visits to sunny places, and use of sunblocking agents. Additional elements were socioeconomic status, skin colour, and antecedent of varicella infection during childhood. RESULTS: MS patients showed a larger proportion of white skin. MS patients had more sunlight exposure during adolescence (80% versus 60%, P = 0·002); this tendency prevailed on current indicators (46% versus 30%, P = 0·02). However, current exposure on weekends (10% versus 22%, P = 0·02) and visits to the beach (64% versus 98%, P = 0·002) were lower in MS than in controls. DISCUSSION: Mexico gets more sunlight through the year than areas with high incidence of MS; nevertheless, its prevalence has greatly increased over the last decades, making it a relevant emerging disease. Our results indicate that in a tropical country, there is no association between sunlight exposure and the risk to develop MS, given the immunological effects of sunlight exposure either through UV radiation or vitamin D metabolism.

The participation of varicella zoster virus in relapses of multiple sclerosis.

OBJECTIVE: Recent studies have documented the apparent participation of varicella zoster virus (VZV) in the etiopathogenesis of multiple sclerosis (MS). The present study aimed to corroborate the possible presence of VZV during exacerbations of MS. DESIGN: Fifty-three patients with definite MS were included; of them, 31 were studied during the first week of a clinical relapse, whereas 16 were studied during remission; 6 patients with progressive MS were also studied. Genes from 5 herpes viruses: varicella zoster, herpes simplex 1 and 2, Epstein-Barr and herpes 6 were studied by polymerase chain reaction in cerebrospinal fluid and in peripheral blood mononuclear cells (PBMC). As controls 21 patients with inflammatory or functional neurological disorders were included. RESULTS: DNA from varicella zoster virus was found in the CSF from all MS patients studied during relapse (100%) and in the PBMC from 28 of them (90%). However, VZV DNA was found in the CSF only in 5 MS patients studied during remission (31%) and in the PBMC from 3 of them (19%). VZV DNA was also found, but in lower amounts, in the CSF (83%) and PBMC (33%) from patients with progressive MS. In contrast, VZV was not found either in CSF or in PBMC from controls. Results from the other herpes viruses tested were similar in MS patients and in controls. CONCLUSIONS: Our results corroborate the conspicuous, but ephemeral presence of VZV during relapses of MS and support the idea of VZV involvement in the etiopathogenesis of MS. Recent epidemiological and molecular studies as well as reports of severe VZV infections triggered by specifically induced immunosuppression during therapy of MS give additional support to this potential association.

Retinoic acid reduces solvent-induced neuropathy and promotes neural regeneration in mice.

In humans, exposure to organic solvents (OS) is frequent in work activities or as a recreational inhalant, inducing severe neuropathy (secondary to demyelization of peripheral nerves). We have previously shown that all-trans retinoic acid (ATRA) increases local content of neural growth factor (NGF), improving peripheral neuropathy of diverse origins. In this study, we evaluated the effect of ATRA on OS-induced peripheral neuropathy in experimental mice. Two simultaneous experiments were performed. The first one aimed to evaluate ATRA for the prevention of damage induced by OS, the second to test ATRA as an OS-induced neuropathy treatment. Nociceptive threshold latency and NGF concentration in serum and in peripheral nerves were determined. Morphological changes and evidence of sciatic nerve regeneration were evaluated. Mice exposed to OS developed neuropathy and axonal degeneration. ATRA diminished the effects of OS inhalation on sensorial changes and nerve morphology. Treatment with ATRA reversed sensorial and nerve morphological changes of OS-induced neuropathy, and this was associated with increased contents of NGF. Similar to previous experiences on diabetic and toxic neuropathy, ATRA reduced and partially reversed the peripheral neuropathy caused by OS exposure. These favorable effects apparently are due to local production of NGF induced by neural regeneration in response to the administration of retinoic acid.

Epidemiology of varicella in Mexico.

BACKGROUND: The epidemiological patterns of varicella-zoster virus (VZV) infection, which are strongly associated with climate, are characterized by more frequent infections occurring among children in temperate regions than in the tropics. In temperate regions, varicella exhibits a seasonal cyclic behavior in which the number of cases increases significantly during the winter and spring seasons, further supporting the role of environmental factors in disease transmission. However, the underlying mechanisms responsible for this distinctive behavior are not fully understood. In Mexico, information regarding the epidemiology of varicella is scarce, and the distribution of VZV infection has not been analyzed. OBJECTIVES: In this article we investigate the epidemiological patterns of varicella in Mexico and their relationship with different environmental and demographic factors. STUDY DESIGN: A retrospective study was conducted using the data reported by the National Center of Epidemiological Surveillance and Disease Control. The overall varicella incidence was calculated and associated with temperature, overcrowding, age, gender and population density. RESULTS: The epidemiology of varicella showed an intriguing pattern, in which warmer regions were characterized by higher incidences than in temperate regions. Young children were the most affected age group. There was no correlation between varicella incidence and overcrowding or population density. CONCLUSIONS: The epidemiology of varicella in Mexico significantly departs from the characteristic patterns observed in other tropical latitudes, with some features resembling those commonly associated with temperate regions.

Varicella zoster virus in progressive forms of multiple sclerosis.

OBJECTIVE: The apparent association between varicella zoster virus (VZV) and multiple sclerosis (MS) has been described. In patients with relapse/remission (R/R) MS we have found high loads of VZV DNA in lymphocytes and in cerebrospinal fluid (CSF), as well as abundant viral particles in CSF visualized by electron microscopy at the time of relapse. Both, the molecular and the ultrastructural evidence of VZV became negative in the same patients at the time of remission. METHODS: In the present study we analyzed the presence of VZV in patients with progressive forms of MS; DNA from VZV was searched by real-time PCR in blood lymphocytes and in CSF of 20 patients with progressive MS. Ultrastructural study searching for viral particles in CSF was made with transmission electron microscopy. RESULTS: VZV DNA was found in the CSF from 65% of cases with progressive MS- and VZV-like viral particles were found in 30% of these patients. Nonetheless, the amount of DNA and the number of viral particles were lower than those that have been found in MS patients with R/R at the time of relapse, but higher than those found during remission. CONCLUSION: Similar to findings in patients with R/R MS, VZV might be associated to progressive MS, but in minor quantity. In these cases, the virus may produce a chronic, relentless infection or trigger a process of immune-mediated demyelination.

Association of a history of varicella virus infection with multiple sclerosis.

OBJECTIVE: To analyze the association of a previous history of varicella virus infection with multiple sclerosis (MS) and its subtypes. MATERIAL AND METHODS: We performed a case-control study including 126 cases and 157 controls. Subjects were divided into subgroups according to MS subtype and the history of varicella virus infection along with other variables was assessed. RESULTS: History of varicella zoster virus (VZV) infection was positive in 42% of controls and 66% of MS cases (p

All-trans retinoic acid induces nerve regeneration and increases serum and nerve contents of neural growth factor in experimental diabetic neuropathy.

Local diminution of the neural growth factor (NGF) contributes to the apparition of diabetic neuropathy. All-trans retinoic acid (RA) increases the expression of neural growth factor and its receptor participating in translation pathways. This study evaluates RA as a treatment of diabetic neuropathy: 120 mice were assigned randomly to 4 groups. Group A (n = 30) was taken as control; group B (n = 30) received 50 mg/kg intraperitoneal streptozotocin (STZ); group C (n = 30) received STZ, and after diabetic neuropathy developed, they were treated with subcutaneous RA 20 mg/kg daily during 60 days; and group D (n = 30) only received RA. Plasma glucose, thermosensitive tests, serum, and the nerve contents of NGF were measured in all animals. Evaluation by electron microscopy was performed in search of morphologic changes secondary to neuropathy and nerve regeneration. Diabetic mice had an increased threshold to pain. Treatment with RA in diabetic mice reverted changes in sensitivity as compared with diabetic mice that received placebo (P < 0.001). No differences in pain threshold among controls, RA, and diabetes mellitus (DM) + RA groups were found. Glucose levels were not affected by the treatment with RA. NGF diminished significantly in the sciatic nerve in diabetic mice as compared with controls and with the RA group. Animals with DM + RA had a significant increase of NGF in nerves as compared with the other groups. RA also regressed the ultrastructural changes induced by diabetes that showed increased neural regeneration. RA can revert functional and ultrastructural changes and induce neural regeneration after the establishment of diabetic neuropathy, possibly because of the increased of NGF concentrations in nerve terminals.

Varicella-zoster virus in cerebrospinal fluid at relapses of multiple sclerosis.

OBJECTIVE: Recent studies in peripheral blood mononuclear cells (PBMCs) have indicated that exacerbations of multiple sclerosis (MS) could be associated with the reactivation of latent varicella-zoster virus (VZV). METHODS: Ultrastructural observations for viral particles were made by electron microscopy in cerebrospinal fluid (CSF) from 15 MS patients during relapse, 19 MS patients during remission, and 28 control subjects. Initial findings were reproduced in a confirmation cohort. In addition, DNA from VZV was quantified by real-time polymerase chain reaction in PBMCs and CSF from a large number of MS patients (n = 78). RESULTS: We found by electron microscopy the presence of abundant viral particles identical to VZV in CSF obtained from MS patients within the first few days of an acute relapse. In contrast, viral particles were not seen in CSF samples from MS patients in remission or from neurological control subjects. Also, DNA from VZV was present in CSF and in PBMCs during relapse, disappearing in most patients during remission. The mean viral load was 542 times greater in CSF at relapse than in CSF at remission and 328 times greater in CSF at relapse than in PBMCs at relapse. INTERPRETATION: The ultrastructural finding of viral particles identical to VZV, together with the simultaneous presence of large quantities of DNA from VZV in the subarachnoid space, almost restricted to the periods of exacerbation, as well as its steady diminution and eventual disappearance from clinical relapse to clinical remission are surprising and constitute the strongest evidence to support the participation of VZV in the pathogenesis of MS.

Varicella-zoster virus at relapses of multiple sclerosis.

The possible participation of different herpes viruses was studied during exacerbations of multiple sclerosis (MS). We searched for the presence of DNA from the following herpes viruses: varicella zoster virus (VZV), herpes-simplex viruses 1 and 2; Epstein-Barr virus (EBV) and human herpes-virus-6 (HHV6) in mononuclear cells from patients with MS during relapse (n = 40), MS during remission (n = 131) and controls (n = 125). Additionally, immune cells containing viral antigens were quantified by flow cytometry, and VZV load was determined by real time PCR in 2 MS patients at various times during relapse and remission. DNA from VZV was found in 95% of MS patients during relapse and in 17% during remission; all controls were negative; by contrast, DNA from HHV6 was found in 24% of MS patients during relapse and in 2% during remission; DNA from herpes simplex viruses was not found in any subject; and DNA from EBV was found in a similar percentage of subjects from all groups. Sequential quantification of VZV-load showed a curve that increased during relapse and disappeared at remission. Also, VZV antigens were found inside a large number of immune cells from MS patients during relapse as compared with MS patients on remission and controls. In the typical forms of VZV infection, varicella and herpes-zoster, DNA from VZV is found in mononuclear cells exclusively during brief periods at the beginning of the active infection, but not during latency; thus, the conspicuous presence of VZV during relapses of MS may indicate a period of active infection and suggests the participation of VZV in the pathogenesis of MS.