Quantification of CSF and serum levels and intrathecal synthesis of anti-EBV antibodies in patients with multiple sclerosis and with other neurological disorders.

Purpose: Epidemiological studies suggest that Multiple Sclerosis (MS) pathogenesis could be related to an infection superimposed on a predisposing genetic background. Epstein-Barr virus (EBV) is currently considered to be the most plausible candidate for MS autoimmunity since seroepidemiological studies have demonstrated that EBV seropositivity is more frequent in MS than in controls whereas the risk of developing MS is increased by the presence of elevated serum levels of EBV-specific antibodies and a history of EBV-induced mononucleosis. In addition, high concentrations of anti-EBV antibodies have been found in CSF and blood of MS patients. Considering these observations, the aim of our study was to investigate CSF and serum levels and the presence of an intrathecal synthesis of anti-EBV IgG in MS and controls. Materials and methods: We measured by ELISA technique cerebrospinal fluid (CSF) and serum levels of anti-EBV IgG in 80 relapsing-remitting (RR) MS patients grouped according to clinical and Magnetic Resonance Imaging (MRI) evidence of disease activity. Eighty-six patients with other inflammatory neurological disorders (OIND) and 67 with non-inflammatory neurological disorders (NIND) served as neurological controls. Anti-EBV nuclear antigen-1 (EBNA-1) and anti viral capsid antigen (VCA) IgG levels were expressed as arbitrary units and quantitative intrathecal synthesis of anti-EBNA and anti-VCA IgG was determined by Antibody Specific Index (ASI). After checking data for normality, statistical analysis was performed by Kruskal-Wallis test, followed by Mann-Whitney U test, to compare mean values among the various groups of patients. Chi-square test (χ2) was used to compare the patient group percentages. Bonferroni correction was utilized for multiple comparisons. Results: Detectable levels of CSF and serum anti-EBNA-1 IgG and serum anti-VCA IgG were equally represented in MS, OIND and NIND, whereas measurable CSF concentrations anti-VCA IgG were more frequent in OIND than in MS (p < 0.0001) and NIND (p < 0.001) and equivalent in MS and NIND. CSF and serum mean levels of anti-EBNA-1 IgG were different among the groups of patients examined (p < 0.02 and p < 0.001, respectively). While CSF mean values were higher in MS than in NIND (p < 0.02), serum mean concentrations were greater in MS than in OIND and NIND (p < 0.001 and p < 0.02, respectively). CSF and serum mean levels of anti-VCA IgG were also different among the patient groups analyzed (p < 0.0001 and p < 0.05, respectively). CSF mean values were more elevated in OIND than in MS (p < 0.0001) and NIND (p < 0.02), whereas serum mean titers were increased in OIND than in MS (p < 0.05). In addition, serum mean levels of anti-VCA IgG were more prominent in MRI inactive than in MRI active MS (p < 0.0001). ASI values suggestive of an intrathecal synthesis of anti-EBNA-1 and of anti-VCA IgG were present in a small proportion of MS (6.3% and 2.5%, respectively), OIND (3.5% in both cases) and NIND (1.5 and 0%, respectively), without any significant differences among the various group explored. Conclusions: These findings do not seem to support a crucial role of an intrathecal humoral immune response to EBV in MS pathogenesis. However, the altered anti-EBV antibody production detected in MS for CSF anti-EBNA-1 IgG and serum anti-VCA IgG remains to be clarified. On the other hand, elevated CSF levels of anti-VCA IgG found in OIND are probably blood-derived because they are related to the more frequent occurrence of blood-brain barrier dysfunction. Work supported by FISM (2008-R-12) and by Programma di ricerca Regione-Università 2007-2009.