Intrathecal production of Chlamydia pneumoniae-specific high-affinity antibodies is significantly associated to a subset of multiple sclerosis patients with progressive forms

The purpose of this study was to provide further insight into the effective relevance of the association between Chlamydia pneumoniae and MS. We evaluated by ELISA technique cerebrospinal fluid (CSF) and serum levels of anti-C. Pneumoniae IgG in 46 relapsing-remitting (RR), 14 secondary progressive (SP) and 11 primary progressive (PP) MS patients grouped according to clinical and Magnetic Resonance Imaging (MRI) evidence of disease activity. Fifty-one patients with other inflammatory neurological disorders (OIND) and 52 with non-inflammatory neurological disorders (NIND) were used as controls. A C. pneumoniae-specific intrathecal IgG synthesis as detected by the relative specific index was present in a small proportion of MS (17%), OIND (22%) and NIND (2%) patients and was significantly more frequent in NIS and in OIND than in NIND (p < 0.001) and in SP and PP NIS than in RR NIS patients (p < 0.02). Among the patients with C. pneumoniae-specific intratecally produced antibodies, CSF high-affinity anti-C. pneumoniae IgG were found in the majority of SP or PP MS, occasionally in OIND, but not in RR NIS and NIND patients. These findings confirm that the presence of a humoral immune response to C pneumoniae within the central nervous system (CNS) is not selectively restricted to MS, but is shared by several inflammatory neurological conditions. In addition, our results suggest that an intrathecal production of C. pneumoniae-specific high-affinity IgG can occur in a subset of patients with NIS progressive forms in which a C. pneumoniae brain chronic persistent infection may play an important pathogenetic role.