Contributions
Abstract: P435
Type: Poster
Abstract Category: Pathology and pathogenesis of MS - Immunology
Introduction: Intrathecally synthesized IgG of multiple sclerosis (MS) patients carry somatic mutations compatible with an antigen-driven and T cell mediated immune response, but the target antigens remain unknown. Based on proof-of-principle experiments we have postulated that mutated fragments of immunoglobulin molecules are presented as antigens to the T cells, and thereby sustain the immune response. The immense diversity of the IgG repertoire has so far precluded further studies. The complete immunoglobulin heavy-chain variable (IGHV) transcriptome can now be established by next generation sequencing (NGS), and the ability of the immunoglobulins to stimulate T cells can be predicted based on their amino acid sequences and the human leukocyte antigen (HLA) makeup of each patient.
Methods: IGVH transcriptomes (complementarity determining region 3 (CDR3) and framework region 3) from blood and CSF of 11 MS patients and 6 controls with other neurological diseases (OIND) were identified by high throughput sequencing. The binding affinities of deduced IgG peptides to HLA class II molecules, the likelihood of protease (cathepsin S) cleavage, and the stimulating potential of their T cell exposed motifs (TCEM) were calculated in silico.
Results: Among the 2,151,776 recovered transcripts, we discovered two distinct patterns of TCEM utilization in blood vs CSF when computing pairwise correlations. Moreover, IGVH transcripts from CSF exhibited two different TCEM patterns in MS vs OIND patients. This suggests a selection of different TCEM in CSF of patients with MS compared to OIND. Further we found an IGHV4 predominance in the CNS of MS patients that was associated with a significantly higher likelihood of cleavage with cathepsin S than the other IGVH classes (p< 0,05, Tukey-Kramer HSD). Reiterative mutation resulting in a high recurrence of TCEM that otherwise only appears elsewhere in the IGHV occurs in the CDR3 region of both MS and OIND patients.
Conclusion: Bioinformatic prediction analysis suggests that intrathecally synthesized IgG carry hypervariable regions which can be presented on HLA class II and stimulate T cells, and that cathepsin S cleavage contributes to a preferential use of IGVH4 in CSF of MS patients.
Disclosure: Rune A. Høglund: nothing to disclose.
Robert D.Bremel holds equity in EigenBio LLC, responsible for the biostatistics algorithms used in this project.
Trygve Holmøy has received speakers honoraria from Biogen, Genzyme, Novartis and Merck-Serono.
Andreas Lossius has received speaker honoraria from Genzyme and Fisher Scientific.
Jorunn Johansen: nothing to disclose.
Harlan Robins: nothing to disclose.
Abstract: P435
Type: Poster
Abstract Category: Pathology and pathogenesis of MS - Immunology
Introduction: Intrathecally synthesized IgG of multiple sclerosis (MS) patients carry somatic mutations compatible with an antigen-driven and T cell mediated immune response, but the target antigens remain unknown. Based on proof-of-principle experiments we have postulated that mutated fragments of immunoglobulin molecules are presented as antigens to the T cells, and thereby sustain the immune response. The immense diversity of the IgG repertoire has so far precluded further studies. The complete immunoglobulin heavy-chain variable (IGHV) transcriptome can now be established by next generation sequencing (NGS), and the ability of the immunoglobulins to stimulate T cells can be predicted based on their amino acid sequences and the human leukocyte antigen (HLA) makeup of each patient.
Methods: IGVH transcriptomes (complementarity determining region 3 (CDR3) and framework region 3) from blood and CSF of 11 MS patients and 6 controls with other neurological diseases (OIND) were identified by high throughput sequencing. The binding affinities of deduced IgG peptides to HLA class II molecules, the likelihood of protease (cathepsin S) cleavage, and the stimulating potential of their T cell exposed motifs (TCEM) were calculated in silico.
Results: Among the 2,151,776 recovered transcripts, we discovered two distinct patterns of TCEM utilization in blood vs CSF when computing pairwise correlations. Moreover, IGVH transcripts from CSF exhibited two different TCEM patterns in MS vs OIND patients. This suggests a selection of different TCEM in CSF of patients with MS compared to OIND. Further we found an IGHV4 predominance in the CNS of MS patients that was associated with a significantly higher likelihood of cleavage with cathepsin S than the other IGVH classes (p< 0,05, Tukey-Kramer HSD). Reiterative mutation resulting in a high recurrence of TCEM that otherwise only appears elsewhere in the IGHV occurs in the CDR3 region of both MS and OIND patients.
Conclusion: Bioinformatic prediction analysis suggests that intrathecally synthesized IgG carry hypervariable regions which can be presented on HLA class II and stimulate T cells, and that cathepsin S cleavage contributes to a preferential use of IGVH4 in CSF of MS patients.
Disclosure: Rune A. Høglund: nothing to disclose.
Robert D.Bremel holds equity in EigenBio LLC, responsible for the biostatistics algorithms used in this project.
Trygve Holmøy has received speakers honoraria from Biogen, Genzyme, Novartis and Merck-Serono.
Andreas Lossius has received speaker honoraria from Genzyme and Fisher Scientific.
Jorunn Johansen: nothing to disclose.
Harlan Robins: nothing to disclose.