HUMAN HERPESVIRUS-6 INFECTION IN RENAL-ALLOGRAFTS - RETROSPECTIVE IMMUNOHISTOCHEMICAL STUDY IN JAPANESE RECIPIENTS

This study was conducted to determine the incidence and clinical signi ficance of human herpesvirus-g (HHV-6) infection in renal allografts. A total of 105 biopsy specimens from 72 recipients were immunohistoche mically examined for the presence of HHV-6 antigen, which localized in the distal tubular epithelial cells and in a few lymphocytes infiltra ting into the interstitium. HHV-6 antigen in the tubular epithelia was detected in 63 (61.2 %) specimens. Categorically a higher incidence o f the antigen was noted in specimens of accelerated rejection (314, 75 .0 %), acute rejection (28/3, 73.7 %), and cyclosporin nephropathy (8/ 11, 72.7 %). The antigen was present and absent an almost equal number of times in the categories of chronic rejection, intraoperative and r outine protocol biopsies. Repeated biopsies were performed in six case s showing HHV-6 antigen, only one of which underwent transplant nephre ctomy due to severe chronic rejection. Single or multinucleated giant cells in distal tubuli occurred in 10 (9.5 %) specimens in a scattered manner. All of them were diagnosed as acute or chronic rejection. The giant cells showed no immunoreactivity for HHV-6, cytomegalovirus, or herpes simplex virus. These results indicate overall that HHV-6 infec tion is common in renal allografts and might be reactivated in acute r ejection or cyclosporin nephropathy. The presence of HHV-6 antigen, ho wever, does not necessarily correlate with a poor prognosis for the re nal graft nor with the occurrence of giant cells in distal tubuli.