Morphologic and immunophenotypic characteristics of malignant lymphomas inSIV-infected rhesus macaques

Eight cases of extranodal non-Hodgkin's lymphoma in simian immunodeficiency virus (SIV)-infected rhesus macaques, aged 4-9 years, were phenotypically and immunologically characterized, using the updated Kiel classification, i n order to determine both the differences and the similarities between thes e types of lymphoma in immunodeficient rhesus macaques (Macaca mulatta) and man. The high-grade malignant tumors were of B-cell origin, with a predile ction for extranodal growth in viscera and peliorbital tissues. Immunopheno typical characterization showed that the monkey lymphomas were similar in m any aspects to human immunodeficiency virus-associated lymphomas. The numbe r of Ki67 positive cells varied fi om case to case and ranged from 50 to 90 %. A serological screening for the simian equivalent of the Epstein-Barr vi rus (sEBV) by immunofluorescence assay revealed a prevalence of 92% of the sEBV antibodies in our cohort. The presence of Ebstein-Barr virus nuclear a ntigen (EBNA-2) could be demonstrated by immunohistochemistry in four out o f eight cases. In situ hybridization revealed the presence of small EBV-enc oded RNAs (EBER-2, EBER-2) in six of the eight cases. Further studies shoul d define the precise role of herpesvirus infection for lymphomagenesis in S IV-induced immunodeficiency.