Acellular materials of xenogenic origin are used worldwide as xenografts, and 
phase I trials of viable pig pancreatic islets are currently being performed. 
However, limited information is available on transmission of porcine endogenous 
retrovirus (PERV) after xenotransplantation and on the long-term immune response 
of recipients to xenoantigens. We analyzed the blood of burn patients who had 
received living pig-skin dressings for up to 8 wk for the presence of PERV as 
well as for the level and nature of their long term (maximum, 34 y) immune 
response against pig Ags. Although no evidence of PERV genomic material or 
anti-PERV Ab response was found, we observed a moderate increase in anti-αGal 
Abs and a high and sustained anti-non-αGal IgG response in those patients. Abs 
against the nonhuman sialic acid Neu5Gc constituted the anti-non-αGal response 
with the recognition pattern on a sialoglycan array differing from that of burn 
patients treated without pig skin. These data suggest that anti-Neu5Gc Abs 
represent a barrier for long-term acceptance of porcine xenografts. Because 
anti-Neu5Gc Abs can promote chronic inflammation, the long-term safety of living 
and acellular pig tissue implants in recipients warrants further evaluation.