[23, 24] Initial studies describing the encephalitogenic potential of MOG35–55 made use

of the human MOG sequences[10] whereas later studies reported the pathogenic potential of mouse sequences. In the initial studies the search for encephalitogenic epitopes was not performed systematically as we have reported for Biozzi ABH and SJL mice.[3] Rather, immunodominant T-cell epitopes in mice were examined based on T-cell responses to hMOG peptides in people with MS. Although this study revealed the pathogenic potential of MOG35–55 in C57BL/6 mice, it failed to identify U0126 datasheet other T-cell and B-cell epitopes and, more crucially, failed to reveal other encephalitogenic epitopes recognizing sequences in mMOG. Here, we show that

systematic screening revealed novel B-cell and T-cell peptide epitopes within recombinant mMOG representing the extracellular immunoglobulin-like domain. For example in both WT and MOG-deficient mice ELISA studies revealed that antibodies CH5424802 order raised in mice immunized with rmMOG recognized epitopes within sequence 1–82. Whether the antibody responses to these individual peptides are pathogenic remains to be determined. In addition the use of 15 mer and 23 mer MOG peptides specifically performed to take into account any misalignments that may interfere with antigen-processing and so T-cell activation, revealed two new B-cell epitopes MOG113–127 and filipin MOG148–162. Only MOG113–127 corresponded with a new encephalitogenic T-cell epitope for C57BL/6 mice and this may be a dominant epitope, although further studies will need to examine whether this epitope is generated during the natural processing of MOG protein. Currently the lack of sufficient quantities of purified native

MOG from control human or mouse or indeed MS myelin, precludes such studies. That both T-cell responses to MOG113–127 and MOG120–134 were encephalitogenic suggests a minimal encephalitogenic epitope residing in residues MOG120–127. One factor possibly contributing to the failure to identify other encephalitogenic epitopes in mice, rodents and monkeys is the use of human peptide sequences. Human MOG differs from mouse, rat and marmoset MOG at several residues, including a proline for serine substitution at position 42 (see Supplementary material, Table S1).[25] In C57BL/6 mice human MOG35–55 is only weakly encephalitogenic, and a proline substitution in rat MOG at position 42 was reported to severely attenuate EAE.[26] As well as differences in peptide sequences, the conformation of the rhMOG protein used for immunization also strongly influences the presence of conformational antibodies. This is in contrast to myelin basic protein, in which the native protein and the recombinant protein behave antigenically similarly, indicating that native antigen strongly influences antibody and T-cell responses.