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

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%).