Further characterization of a herpesvirus‐positive orang‐utan cell line and comparative aspects of in vitro transformation with lymphotropic old world primate herpesviruses

Abstract
An orang‐utan (Pongo pygmaeus) suspension line, CP81, was shown to lack myeloid markers of lysozyme activity and phagocytosis but to be positive for lymphocytic N‐alkaline phosphatase activity, and to release a B‐cell‐tropic herpesvirus. This herpesvirus, termed Herpesvirus pongo, had 30‐40% DNA homology with EBV and was present at 2‐3 genome copies per CP‐81 cell. Gibbon lymphocytes transformed by H. pongo, Epstein‐Barr virus (EBV), and H. papio (of baboon, Papio hamadryas, origin) were found to be virus antigen‐positive B cells. Gibbon lymphocytes transformed by H. pongo and EBV and transplanted to nude mice by the intracranial (IC) route (had a 75% and a 45% success rate, respectively), while transplants of similar cells transformed by H. papio were only 10% successful. None of these lines transplanted subcutaneously (SC) nor manifested a high degree of colony formation in 0.33% agarose (⩽0.5%), Gibbon lymphocytes transformed by H. pongo were hypodiploid while those transformed by EBV or H. papio were diploid. CP‐81 cells themselves could be transplanted both IC (100%) and SC (70%) and showed a relatively high degree of colony formation in agarose (6.4‐7.6%). B95‐8 cells (marmoset, Saguinus oedipus‐EBV) could be transplanted IC (66%) but not SC and had a low but significant ability to grow in agarose (1.6%).594S (baboon, P. hamadryas‐H. papio) cells could be transplanted IC (25%) but not SC, and grew to very low levels in agarose (0.1%).