Abstract

Epidemiological studies have consistently shown that posttransplant KS (PT-KS) may be either due to the reactivation of Kaposi’s sarcoma associated herpesvirus (KSHV)/human herpesvirus-8 (HHV-8) infection in solid organ recipients, or to the primary infection with the virus transmitted from the donors (1). In the latter cases, the source of viral transmission remains unknown. KSHV/HHV-8 is known to infect endothelial and lymphoid cells, but the viral tropism is likely to be broader than initially suspected. Relevant to this, in a case of disseminated acute primary KSHV/HHV-8 infection affecting a newborn, the virus could be found by in situ hybridization in the kidney, both in the glomerulo- endothelial and in the tubular epithelial cells (2). Furthermore, experiments in a transgenic mouse model have demonstrated that the kidney tubular epithelium is permissive to the KSHV/HHV-8 latency associated nuclear antigen (LANA) promoter activity and consequently to KSHV/HHV-8 latency (3). We have previously reported one case of primary infection with KSHV/HHV-8 in a renal recipient followed by the development of a disseminated PT-KS and related hemophagocytic syndrome. In the present study we used a combination of immunohistochemical and molecular methods to test the hypothesis that the donor’s kidney could represent a site of viral infection (4). Archival specimens from the formalin-fixed and paraffin embedded tissues from the donor’s kidney were available, being obtained at the time of acute renal rejection from the patient, about two months before the development of KSHV/HHV-8 related complication. Immunostaining for LANA in the kidney biopsy from both the index case (pt.1) and three KSHV/HHV-8 DNA negative recipients, showed the typical nuclear localization of the protein only in 1–3% of the epithelial cells of proximal tubules of pt.1 (Fig. 1A, 1B). To validate the detection of KSHV/HHV-8 antigen in these cells, we performed a nested polymerase chain reaction analysis of the KSHV/HHV-8 orf26 sequence in LANA positive and negative single microdissected cells, as described. KSHV/HHV-8 DNA was found only in LANA positive cells, with an amplification efficiency for ranging from 8% to 17%, as obtained in previous studies (Fig. 1.C and not shown) (1).FIGURE 1.: Micromanipulation of a LANA-positive cell from tubular epithelium of donor’s kidney biopsy from patient one. Sections of paraffin-embedded renal tissue were stained with a monoclonal antibody to the KSHV latency-associated nuclear antigen, LANA-1 (Novocastra Laboratories Ltd, Newcastle, UK), as described previously (1). LANA-1 positive cells were then isolated by microdissection. The tissue section is shown before (A) and after (B) the isolation of the cell. PCR detection of KSHV orf26 sequence in 2 of 12 samples of microdissected LANA positive cells from patient (C). MK, molecular weight marker IX; NC, negative control; PC, positive control, represented by the DNA extracted from the PT-KS.Unfortunately, the donor’s kidney biopsy was not available at the time of transplantation, so that we cannot formally prove that the kidney represented one source of viral transmission, and the possibility remains that the donor’s kidney was infected after its engraftment in the recipient, as a result of a primary infection with the virus transmitted from other sources. However, our findings provide the first evidence that the transplanted kidney may be a reservoir of KSHV/HHV-8 infection, with possible relevant clinical consequences. The lack of a gold standard in the serological assays for anti KSHV/HHV-8 antibodies represents a major obstacle to implementation of screening programs of organ donors/recipients in transplantation centers (5). If the KSHV/HHV-8 infection of epithelial or other cells in the kidney will be confirmed in a larger series of cases, a rapid immunostaining for LANA in the renal biopsies at the time of transplantation, could be an additional useful tool to assess the KSHV/HHV-8 status of potential organ donors. Patrizia Barozzi Raffaella Bosco Daniela Vallerini Leonardo Potenza Giuseppe Torelli Mario Luppi Department of Oncology and Hematology Policlinico Modena, Italy Fabio Facchetti Department of Pathology University of Brescia Brescia, Italy Giovanni Guaraldi Department of Medicine and Medical Specialties Infectious Diseases Clinic Modena, Italy Thomas F. Schulz Department of Virology Hannover Medical School Hannover, Germany

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