Our group previous demonstrated a strong association between elevated plasma soluble CD13 enzyme activity and newly diagnosed extensive chronic graft-versus-host disease (cGVHD) in children. Since cytotoxic anti-CD13 antibodies have been documented after blood and marrow transplant in association with cytomegalovirus infection and cGVHD, we hypothesized soluble CD13 contributes to cGVHD pathogenesis by induction of CD13 reactive antibodies and that anti-CD13 antibodies could be additional biomarkers for newly diagnosed pediatric extensive cGVHD. Using prospectively collected plasma samples from pediatric allogeneic blood and marrow transplant subjects with cGVHD and controls without cGVHD enrolled in a large multi-institution Children's Oncology Group cGVHD therapeutic trial we evaluated whether soluble CD13 correlates with induction of anti-CD13 antibodies. We found that CD13 reactive antibodies are present in a proportion of patients after allogeneic BMT, but did not appear to correlate with the presence of soluble CD13. Anti-CD13 antibodies also did not meet our criteria as a diagnostic biomarker for cGVHD. These data are not able to confirm that induction of CD13 reactive antibodies is a mechanism for cGVHD in children nor are part of the pathogenesis of cGVHD associated with elevated soluble CD13. The exact role of CD13 in cGVHD remains to be determined.
Keywords: anti-CD13 antibodies, CD13, aminopeptidase N, biomarkers, chronic graft-versus-host disease, blood and marrow transplantation