Project Details


Friend spleen focus-forming virus (SFFV) is a potent pathogenic
agent, which causes extensive proliferation of spleen cells shortly
after infection, leading to the rapid development of
erythroleukemia. Genetic evidence strongly implicates the env
gene of this virus as the major pathogenic determinant of these
viruses. The SFFV env gene is defective in comparison to its
normal MuLV counterpart, and its gene products are not
incorporated into viral particles and thus cannot be involved in
viral replication. These facts make SFFV an ideal system for
elucidating the functional roles of retroviral env genes in
leukemogenesis. We have recently shown that the mature SFFV
env gene product, gp65, is efficiently secreted from cells, and we
have found that partially purified preparations of gp65 stimulate
the proliferation of erythroid progenitor cells in in vitro cultures.
These results suggest that gp65 may be the molecule responsible
for the pathogenicity of these viruses. In order to test this
hypothesis, we propose to extend our studies of gp65 in the
following ways. We will purify gp65 to homogeneity and test the biological
activities of the purified material. Further biochemical studies of
gp65 will be performed, including amino- and carboxy-terminal
sequencing and the complete characterization of the post-
translational modifications of this molecule and identification of
their sites of attachment. Site-specific mutations will be
introduced into molecularly cloned genomes of SFFV and MuLVs
by oligonucleotide-directed mutagenesis, in order to determine
the functional roles of the SFFV-specific structural features in
the biological activities of these proteins, and in the
pathogenicity of these viruses. Monoclonal antibodies and site-
specific antisera will be prepared against different domains of
gp65. The active site of gp65 will be identified by examining the
effects of such antibodies on the in vitro and in vivo biological
activities of this molecule. The effect of the regulatory Fv-2
gene on the response of hematopoietic cells to gp65 will be
determined as an additional test of the biological specificity of
the proliferative activity of this molecule. Finally, gp65 binding
assays will be developed, and cell surface receptors for gp65
isolated and characterized, in order to study the role of these
molecules in viral leukemogenesis.
Effective start/end date4/1/876/30/87


  • National Institutes of Health


  • Medicine(all)

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