Retrovirus-encoded transformation-specific polyproteins: expression coordinated with malignant phenotype in cells...

Area of Science:

• Virology
• Oncology
• Immunology

Background:

• Feline sarcoma virus (FeSV) induces a transformation-associated polyprotein, gag-x, in nonproductively transformed cells.
• The expression and immunological significance of gag-x in feline cells were previously unclear.

Purpose of the Study:

• To investigate the expression of gag-x protein in feline cells.
• To determine if cats produce antibodies against the transformation-specific portion of gag-x.
• To correlate gag-x expression with the malignant phenotype.

Main Methods:

• Western blot analysis to detect gag-x protein.
• Immunofluorescence assays to detect antibodies against gag-x and FOCMA.
• Analysis of gag-x expression in FeSV-transformed feline fibroblasts and melanoma cells.

Main Results:

• The gag-x protein is expressed in feline cells, irrespective of feline leukemia helper virus (FeLV) presence.
• Cats generate humoral antibodies recognizing the transformation-specific (x) region of gag-x.
• These antibodies cross-react with feline oncornavirus-associated cell membrane antigen (FOCMA).
• Indistinguishable gag-x proteins were found in FeSV-transformed cat fibroblasts and melanoma cells, correlating with malignancy.

Conclusions:

• The gag-x protein is a virus-related transformation marker expressed in feline cells.
• The humoral immune response to gag-x suggests its role in FeSV-induced oncogenesis.
• Transformation-related proteins may have pleiotropic functions when virally introduced.