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An array of murine leukemia virus-related elements is transmitted and expressed in a primate recipient of retroviral
D F Purcell1, C M Broscius, E F Vanin
1Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Abstract:
Direct RNA-PCR analyses of T-cell lymphomas that developed in rhesus macaques during a gene transfer experiment revealed the presence of several different recombinant murine leukemia viruses (MuLV). Most prominent was the expected MuLV recombinant, designated MoLTRAmphoenv in which the amphotropic env of the helper packaging virus was joined to the long terminal repeat (LTR) of the Moloney MuLV-derived vector. This retrovirus does not exist in nature. An additional copy of the core enhancer acquired from the vector LTR may have augmented the replicative properties of MoLTRAmphoenv MuLV in several different rhesus cell types compared with the prototype amphotropic MuLV4070A. Unexpectedly, at least two types of mink cell focus-forming MuLV elements, arising from endogenous retroviral sequences expressed in the murine packaging cell line, were also transmitted and highly expressed in one of the macaques. Furthermore, murine virus-like VL-30 sequences were detected in the rhesus lymphomas, but these were not transcribed into RNA. The unanticipated presence of an array of MuLV-related structures in a primate gene transfer recipient demands ever-vigilant scrutiny for the existence of transmissible retroviral elements and replication-competent viruses possessing altered tropic or growth properties in packaging cells producing retroviral vectors.
Insights
Gene transfer in macaques unexpectedly generated novel recombinant murine leukemia viruses (MuLV), including MoLTRAmphoenv and mink cell focus-forming MuLV. This highlights the need for vigilance against transmissible retroviral elements in gene therapy.
Area of Science:
- Retroviral research
- Gene therapy safety
- Primate virology
Background:
- Gene transfer experiments utilize viral vectors to deliver genetic material.
- Murine leukemia viruses (MuLV) are commonly used in research but can pose risks.
- Rhesus macaques are a model organism for studying gene transfer and retroviral infections.
Purpose of the Study:
- To investigate the presence and nature of retroviral elements in T-cell lymphomas that developed in rhesus macaques post-gene transfer.
- To characterize the recombinant murine leukemia viruses (MuLV) identified in the study subjects.
- To assess the implications of these findings for the safety of gene transfer technologies.
Main Methods:
- Direct RNA-PCR analysis of T-cell lymphoma tissues from rhesus macaques.
- Sequencing and characterization of identified recombinant MuLV elements.
- Comparison of viral properties with prototype MuLV strains.
Main Results:
- Discovery of several distinct recombinant MuLV, including a novel MoLTRAmphoenv (amphotropic env joined to Moloney MuLV LTR).
- Evidence of augmented replicative properties of MoLTRAmphoenv MuLV in macaque cells.
- Unexpected transmission and high expression of mink cell focus-forming MuLV elements from the murine packaging cell line.
- Detection of non-transcribed murine virus-like VL-30 sequences in lymphomas.
Conclusions:
- The study identified unexpected and potentially replication-competent MuLV-related structures in a primate gene transfer recipient.
- Findings underscore the critical need for rigorous screening of packaging cell lines and retroviral vectors for transmissible elements.
- Enhanced scrutiny is required to detect replication-competent viruses with altered tropic or growth properties in gene therapy applications.