Characterization of some isolates of newly recovered avian sarcoma virus

Area of Science:

• Virology
• Molecular Biology
• Oncology

Background:

• Avian sarcoma viruses (ASVs) are retroviruses known to cause tumors in chickens.
• Transformation-defective (td) mutants of Rous sarcoma virus (RSV) have deletions in the viral oncogene, src.
• Previously, a recovered ASV (rASV) was isolated from tumors induced by td mutants.

Purpose of the Study:

• To further characterize the biological and biochemical properties of newly recovered avian sarcoma viruses (rASV).
• To investigate the genetic basis for the recovery of sarcoma virus activity from transformation-defective mutants.

Main Methods:

• Cocultivation of tumor cells with chicken embryo fibroblasts and tissue homogenization to obtain high titers of rASV.
• Analysis of viral growth characteristics, subgroup specificity, and structural protein electrophoresis.
• Molecular hybridization using src-specific complementary DNA (cDNAsrc) to assess genetic information in viral RNA.

Main Results:

• Most rASV isolates exhibited non-defective replication and characteristics similar to the parental Schmidt-Ruppin strain of RSV, subgroup A (SR-RSV-A).
• rASV genomic RNA was larger than parental td RNA and indistinguishable in size from SR-RSV-A.
• Molecular hybridization revealed that rASV had regained significant portions of the src gene absent in the td mutants.

Conclusions:

• The recovered avian sarcoma viruses (rASV) have reacquired genetic information, specifically within the src gene, that was deleted in the transformation-defective mutants.
• The generation of rASV likely involves a genetic recombination or interaction between the transformation-defective virus and host cell genetic material.
• These findings provide insights into viral evolution and oncogene restoration mechanisms.