Removal of donor human leukocyte antigen class I proteins with papain: translation for possible whole organ practices

Transplantation. 2015 Apr;99(4):724-30. doi: 10.1097/TP.0000000000000436.


Background: Papain is a protease with potential use in transplantation because of its targeted capacity to selectively remove human leukocyte antigen (HLA) class I proteins from donor human cells. However, its proteolytic activity has not been studied under conditions suitable for use in perfusing donor organs, namely, under a temperature of 4°C and dissolution in Belzer-UW solution.

Methods: We test papain's HLA class I removing activity under recognized whole organ transplant conditions of lowered temperature. The activity of papain's substrate selectivity was tested using both a test substrate (casein) and fresh peripheral blood lymphocytes (PBLs). The activity of papain was also tested at 4°C, the temperature of whole organ storage.

Results: We found that papain at a range of concentrations is nearly as active in cleaving the test substrate in Belzer-UW solution as in distilled water. In distilled water, papain is as active in cleaving a test substrate at a temperature of 4°C as compared to its optimal temperature of 37°C, if the incubation time is extended from 10 min to 3 hr. This finding also holds true if papain is dissolved in Belzer-UW solution. In peripheral blood lymphocytes, papain cleaved off HLA class I proteins as effectively at 4°C as at 37°C, provided the incubation time was also extended to 3 hr.

Conclusion: These findings suggest that papain's targeted enzymatic cleavage of donor HLA class I has potential use in the whole organ transplant setting with retained activity at lower temperatures and when activated and dissolved in Belzer-UW solution.

MeSH terms

  • Adenosine / pharmacology
  • Allopurinol / pharmacology
  • Caseins / metabolism
  • Cold Temperature
  • Dose-Response Relationship, Drug
  • Glutathione / pharmacology
  • HLA Antigens / immunology
  • HLA Antigens / metabolism*
  • Histocompatibility / drug effects*
  • Humans
  • Immunosuppressive Agents / pharmacology*
  • Insulin / pharmacology
  • Isoantigens / immunology
  • Isoantigens / metabolism*
  • Kinetics
  • Lymphocytes / drug effects
  • Lymphocytes / enzymology
  • Lymphocytes / immunology
  • Organ Preservation Solutions / pharmacology
  • Organ Transplantation / adverse effects*
  • Papain / metabolism
  • Papain / pharmacology*
  • Raffinose / pharmacology
  • Substrate Specificity


  • Caseins
  • HLA Antigens
  • Immunosuppressive Agents
  • Insulin
  • Isoantigens
  • Organ Preservation Solutions
  • University of Wisconsin-lactobionate solution
  • Allopurinol
  • Papain
  • Glutathione
  • Adenosine
  • Raffinose