A Chlamydia pneumoniae-specific peptide induces experimental autoimmune encephalomyelitis in rats

It has been reported recently that the bacterial respiratory pathogen Chlam ydia pneumoniae is present in the cerebrospinal fluid of a subset of multip le sclerosis (MS) patients. However, it is not known whether this organism is a causative agent of MS, or merely an opportunistic pathogen that takes advantage of a disease process initiated by some other means. We report ide ntification of a 20-mer peptide from a protein specific to C. pneumoniae wh ich shares a 7-aa motif with a critical epitope of myelin basic protein, a major CNS Ag targeted by the autoimmune response in MS. This bacterial pept ide induces a Th1 response accompanied by severe clinical and histological experimental autoimmune encephalomyelitis in Lewis rats, a condition closel y reflective of many aspects of MS. Studies with peptide analogues suggest that different populations of encephalitogenic T cells are activated by the C. pneumoniae and myelin basic protein Ags. Mild experimental autoimmune e ncephalomyelitis was also observed when rats were immunized with sonicated C. pneumoniae in CFA.