Rhesus macaque as an animal model for hemophilia B gene therapy

We have determined the 2905 nucleotide sequence of the rhesus macaque facto r IX complementary DNA (cDNA) and found it to be greater than 95% identical to that of the human factor IX cDNA. The cDNA has a large 3' untranslated region like the human cDNA, but unlike the human cDNA has two polyadenylati on sites 224 nucleotides apart that are used for transcription of the messe nger RNA. The deduced amino acid sequence is greater than 97% identical to that of human factor IX, differing in only 11 of 461 amino acids in the com plete precursor protein. We found a single silent polymorphism in the nucle otide sequence at the third position of the codon for asparagine at positio n 167 in the secreted protein (AAC/AAT). All residues subject to posttransl ational modifications in the human protein are also found in the rhesus fac tor IX sequence. The high degree of homology between the rhesus and human f actor IX proteins suggested the possibility that the human factor IX protei n might be nonimmunogenic in the rhesus. We tested the immunogenicity of hu man factor IX in three rhesus macaques by repeated intravenous injections o f monoclonal antibody-purified. plasma-derived human factor IX over the cou rse of more than a year and assessed the recovery and half-life of the infu sed protein, as well as in vitro indicators of antihuman factor IX antibodi es. Human factor IX recovery and half-life remained unchanged over the cour se of a year in the three animals studied, and aPTT mixing studies showed n o evidence for neutralizing antihuman factor IX antibodies. An outbred, non human primate model that permits assessment of the level and duration of fa ctor IX expression as well as vector safety would complement the use of oth er (mouse and canine) hemophilia B animal models in current use for the dev elopment of gene therapy for hemophilia B. This is a US government work. Th ere are no restrictions on its use.