PORCINE ENDOGENOUS RETROVIRUS SIGNIFICANTLY CONTRIBUTES PEPTIDE EPITOPES FOR SLA AND HLA CLASS I MOLECULES: IMPLICATIONS FOR XENOTRANSPLANTATION.

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PORCINE ENDOGENOUS RETROVIRUS SIGNIFICANTLY CONTRIBUTES PEPTIDE EPITOPES FOR SLA AND HLA CLASS I MOLECULES: IMPLICATIONS FOR XENOTRANSPLANTATION.
Sabarinathan Ramachandran Ph.D , Andres Jaramillo Ph.D , William Chapman M.D and T. Mohanakumar . St Louis MO, Washington University School of Medicine, 63110, Department of Surgery .

Introduction: Porcine endogenous retroviruses (PERV) have been shown to infect human cells in vitro and in vivo raising concerns regarding safety of xenotransplantation. However, in patients exposed to porcine tissues no PERV infection was observed. This may be due to natural anti-Gala1-3Gal antibodies or cellular immunity.
Aim: This study was designed to determine whether human CD8+ cytotoxic T lymphocytes (CTL) could be generated against human/porcine MHC class I-restricted PERV-derived peptides and to identify the immunodominant PERV-derived peptides.
Methods: Human CD8+ CTLs were generated using PAEC (SLA^z/z), envelope peptide pulsed T2 cells or PERV-infected 293 cells as stimulators. Peptides were eluted from immunoaffinity purified SLA class I molecules on PAEC, fractionated by RP-HPLC and analyzed by mass spectrometer. The peptide-/ PERV specific cytotoxicity and frequency of resulting CD8+ CTLs was analyzed by chromium release and IFN-γ ELISPOT assays.
Results: Sequencing of fractions that resored recognition and lysis of peptide depled PAEC identified them to be derived from Tat (AHQDPLPEQP) and endogenous transcription factor(PQKPFVT). CTLs generated against envelope peptide pulsed T2 cells were able to lyse peptide pulsed T2 and PERV infected human cells (32.27%) but not uninfected 293 cells. Cytotoxicity and IFN-γ ELISPOT assays demonstrated that ~70% of CTL were against one of the immunodominant Env-5 PERV-peptide.
Conclusions: PERV derived peptides are presented naturally by porcine and human HLA class I molecules following PERV infection. CD8+ CTL responses elicited against PERV epitopes may play an important role in containment of PERV infection of human cells.