Characterization of enzootic nasal tumor virus capsid antigen

The RT-PCR was carried out on tumor tissue from sheep with enzootic nasal tumor (ENT), using primers designed from conserved amino acid regions of related type D retroviruses. A 591 bp PCR fragment, corresponding to 90% of the capsid antigen was cloned, sequenced and expressed in E. coli. Alignment with ovine pulmonary carcinoma (OPC) virus showed 93% nucleotide and 96% amino acid homology. No amplification occurred when DNA from ovine fetal cell line was used as template. The recombinant protein, highly expressed in prokaryotic system, reacted in immunoblot with mouse antiserum to Mason Pfizer monkey virus (MPMV) p27, as well as sera from OPC and ENT diseased animals. Preliminary application of this antigen in ELISA suggested its potential use to detect seropositive animals in infected flocks.