Use of the MHC Associated Peptide Proteomic (MAPPs) assay to understand clinical outcomes associated with the use of Factor VIII in the treatment of Hemophilia A

The immune response to protein-therapeutics (immunogenicity) is an important safety and efficacy concern during drug development and regulation. Non-clinical assays that can be used in the early stages of clinical development and to identify at-risk individuals and sub-populations in the clinic are an important unmet need. The so-called MHC Associated Peptide Proteomic (MAPPs) assay directly identifies peptides derived from a protein of interest on a donor’s MHC-II proteins. Here we have applied this technique to address several questions related to the use Factor VIII (FVIII) replacement therapy, in the treatment of hemophilia A. Over a dozen FVIII products are marketed but most fall into 3 categories: (i) Purified from human plasma (PD-FVIII). (ii) Full-length FVIII manufactured using recombinant DNA technology (FL-rFVIII). (iii) A truncated, beta-domain deleted rFVIII (BDD-rFVIII). We investigated whether there are differences in the FVIII peptides found on the MHC-II proteins of the same individual when incubated with products from the 3 classes. Our principal findings are as follows:
The number of unique FVIII peptides isolated, average length of peptides and range of peptide length were comparable for MHC proteins immunoprecipitated from cells from hemophilia A patients and healthy donors.
When cells from the same donor was exposed to FL-rFVIII in the presence and absence of PD-VWF, fewer peptides were recovered in the absence of PD-VWF; FVIII peptides not recovered in the presence of VWF map regions of VWF-FVIII interaction.
When dendritic cells from the same donor were incubated with FL-rFVIII or PD-FVII (both in the presence of PD-VWF); fewer FVIII peptides were recovered from the PD-FVIII. The peptides not recovered in the PD-FVIII did not map to the locations of FVIII-VWF interactions.
For each donor, FVIII peptides identified by the MAPPs assay exhibited affinities for that donor’s MHC variants which was orders of magnitude higher than the affinities of all overlapping peptides from FVIII and VWF, or when compared to a million random peptides obtained from the human proteome.

Zuben Sauna is a Principal Investigator and a Reviewer at the US Food and Drug Administration. His research interests lie in understanding the pharmacogenetic basis of the immune response to proteins used in therapeutic interventions as these affect efficacy and safety. His laboratory exploits a combination of computational, in vitro and ex vivo approaches to understand why some individuals and/or sub-populations develop immune responses while others do not. His work has published extensively in high impact journals such as Nature Biotechnology, Nature Medicine, Science, Science Translational Medicine and Nature Reviews Genetics. He received his Ph.D. from Poona University, India with subsequent training at the National Cancer Institute, Bethesda, USA.