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J Virol, February 1998, p. 1078-1084, Vol. 72, No. 2
Department of Microbiology and Immunology and
Tulane Cancer Center, Tulane Medical School, New Orleans, Louisiana
70112,1 and
Department of Molecular
Biology and Biochemistry and Cancer Research Institute, University
of California, Irvine, California 926972
Received 3 July 1997/Accepted 5 November 1997
A recombinant retrovirus, termed MoFe2-MuLV, was constructed in
which the U3 region of T-lymphomagenic Moloney murine leukemia virus
(Mo-MuLV) was replaced by that of FeLV-945, a provirus of unique long
terminal repeat (LTR) structure identified only in non-T-cell,
non-B-cell lymphomas of the domestic cat. The LTR of FeLV-945 is
unusual in that it contains only a single copy of the transcriptional
enhancer followed 25 bp downstream by a 21-bp sequence in triplicate in
tandem. Infectivity of MoFe2-MuLV was demonstrated in vitro in SC-1
cells and in vivo in neonatal NIH-Swiss mice. Tumors occurred in
MoFe2-MuLV-infected animals following a latency period of 4 to 10 months (average, 6 months). The results of Southern blot analysis of
the T-cell receptor beta locus demonstrated that all tumors were
lymphomas of T-cell origin. MoFe2-MuLV LTRs were amplified by PCR from
tumor DNA and were characterized by nucleotide sequence analysis. LTRs
from the tumors that occurred with relatively shorter latency
predominantly retained the original MoFe2-MuLV sequence intact and
unaltered. Tumors that occurred with relatively longer latency
contained LTRs that also retained the 21-bp sequence triplication
characteristic of the original virus but had acquired various
duplications of enhancer sequences. The repeated identification of
enhancer duplications in late-appearing tumors suggests that the
duplication affords a selective advantage, although apparently not in
the efficient induction of T-cell lymphoma. Proto-oncogenes known to be
targets of insertional mutagenesis in the majority of Mo-MuLV-induced tumors or in feline non-T-cell, non-B-cell lymphomas were shown not to
be rearranged in any tumor examined. Mink cell focus-inducing (MCF)
proviral DNA was readily detectable in some, but not all, tumors. The
presence or absence of MCF did not correlate with the kinetics of tumor
induction. These studies indicate that the single-enhancer,
triplication-containing FeLV LTR, typical of non-T-cell, non-B-cell
lymphomas in cats, is competent in the induction of T-cell lymphoma in
mice. The findings suggest that the mechanism of MoFe2-MuLV-mediated
lymphomagenesis may differ from that of Mo-MuLV-mediated disease,
considering the possible involvement of novel oncogenes and the
variable presence of MCF recombinants.
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Tumorigenic Potential of a Recombinant Retrovirus
Containing Sequences from Moloney Murine Leukemia Virus and Feline
Leukemia Virus
*
Corresponding author. Mailing address: Department of
Microbiology and Immunology, Tulane Medical School SL38, 1430 Tulane Ave., New Orleans, LA 70112. Phone: (504) 587-2083. Fax: (504) 588-5144. E-mail: llevy{at}tmcpop.tmc.tulane.edu.
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