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A "liver" antigen associated with avian erythroblastosis: binding by bentonite and precipitation with sodium dodecyl sulphate.

The properties of a complement fixing antigen, EbAg, extracted from erythroblastosis-affected chicken livers are described. The antigen in extracts freed of structural protein is strongly bound by bentonite, but not by barium sulphate. Strongly alkaline solutions of sodium dodecyl sulphate are required to release the antigen from bentonite. Acidification of the detergent solution precipitates the active solution precipitates the active protein. Extraction of heme from the acidified detergent precipitate by methyl-ethyl ketone further purifies the antigen. This acid detergent treatment eliminates the need to use bentonite as a purification step.

Adsorption↗

Comparison of genome structures among three different strains of avian erythroblastosis virus.

The genomic DNAs of two strains of avian erythroblastosis virus (AEV), AEV-R and AEV-H, were molecularly cloned in Escherichia coli using lambda Charon 16A as a vector. Comparison of the restriction maps of the cloned DNAs with that of AEV-ES4 DNA revealed that R strain is identical with ES4 strain, but totally differs from H strain. The erbB gene product of AEV-R and that of AEV-H were shown to be glycoproteins with molecular weights of 68,000 and 72,000, respectively. Nucleotide sequence analysis of the 3' part of the erbB gene showed that the erbB gene in AEV-R is 126 base pairs (bp) shorter than that in AEV-H, which might result in some difference in tumorigenicity between these viruses.

Alpharetrovirus↗

The removal of "nucleic acid" from an antigen present in the livers of chickens with erythroblastosis.

The recovery of viral antigen in a pure form from tissue can be hindered by the small amount of antigen present relative to the remaining normal tissue constituents with which the antigen may form loose associations. An antigen from the livers of chickens with erythroblastosis had earlier seemed to be associated with nucleic acid. The present work suggests that this material, which reacts with reagents for DNA and RNA but is soluble in 0.2N HClO4, is only a contaminant and not an integral part required for complete activity of the antigen. Treatment with 0.2N HClO4, together with precipitation of the active protein by 60% saturation of aqueous solutions with ammonium sulphate, removes the nucleic acid without destroying antigenicity. The procedure results in a marked degree of purification of the antigen (732-fold with respect to original liver protein) but contaminants still remain. A contaminant absorbing at 260 nm resisting extraction with 0.2N HClO4, can be partly eliminated if the solution is treated with ether-alcohol to remove lipid.

Animals↗

Variable response to a candidate cancer vaccine antigen: MHC control of the antibody response in the rat to avian erythroblastosis virus (AEV)-encoded epithelial growth factor receptor but not AEV-encoded thyroid hormones receptor.

BACKGROUND: A problem likely to be encountered in any cancer immunotherapy based on vaccination with a single protein or peptide is variation in the host response. A particularly informative example is provided by the two oncogenic proteins, one intracellular and the other extracellular, encoded by the avian erythroblastosis virus (AEV), homologs of the thyroid hormones receptor (THsR) and the epithelial growth factor receptor (EGFR), respectively. MATERIALS AND METHODS: Antibodies to these two proteins were assayed by radioimmune precipitation (RIP) in sera from MHC-congenic rats immunized by virally induced tumors. RESULTS: Among the four haplotypes tested, RT1(1) rats exhibited a significantly lower response to the EGFR homolog than the high responders RT1c and RT1u, while RT1a rat strains had an intermediate response. Analysis of the recombinant haplotype RT1ac indicated that the response is controlled, as expected, by the class II locus of the MHC. In contrast, these rat strains responded uniformly to the intracellular THsR homolog. CONCLUSIONS: These results support the hypothesis that MHC restriction of the response to self-related proteins reflects mainly a tolerance mechanism. They sound a note of warning for cancer vaccine development, and also one of positive advice. The likelihood of MHC restriction suggests that a widely applicable polyvalent vaccine should be the final aim in cancer immunotherapy. Yet, paradoxically, evidence of MHC restriction can help establish that a candidate vaccine is likely to prove effective.

Alpharetrovirus↗