No Retroviremia or Pathology in Long-Term Follow-Up of Monkeys Exposed to a Murine Amphotropic Retrovirus

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Abstract
Four monkeys were exposed to a retroviral vector and replication-competent murine amphotropic retrovirus in a bone marrow transplantation/gene transfer protocol (Kantoff et al., 1987). We have studied these animals 2 and 3 years post-transplantation and did not detect replicating virus in serum, peripheral blood mononuclear cells, or bone marrow cells. Amphotropic envelope sequences could not be detected in blood or bone marrow cells by Southern blotting or the polymerase chain reaction. Antibodies directed against the p30 and gp70 viral antigens were detected by Western blot and immunoprecipitation. The animals remain alive and well. Our findings suggest that primates can clear murine amphotropic retroviruses even when exposure occurs during a time of severe immunosuppression. With the onset of human gene therapy clinical trials, it is important to acquire data that contribute to an understanding of the safety of retroviral-mediated gene transfer. Cornetta et al. provide 3-year follow-up data on monkeys that had been exposed (at a time when they were severely immune compromised) to a retroviral vector preparation that contained a contaminating infectious murine retrovirus.