Howard P. Charman

Wild rat type C virus: Isolation and characterization

Abstract Type C virus has been isolated for the first time from a feral rat ( Rattus rattus ). The virus exhibits general properties of rat leukemia virus (RaLV) including the RaLV-specific p30 antigen. It shows low infectivity for rat cells and no infectivity for cells of other species. Virus neutralization and interference tests indicate that the new isolate is also antigenically closely related to other RaLV strains of laboratory rat origin.

Immunologic characterization of gp70 and gp45 from Rauscher murine leukemia virus

The envelope glycoproteins gp70 and gp45 were purified from Rauscher leukemia virus and compared in radioimmunoassay and gel diffusion using antibody to the purified proteins and a cross-reactive antibody prepared against feline leukemia virus. Previous studies indicated that gp70 and gp45 had very similar polypeptide components and differed mainly in carbohydrate content. The current studies indicate that gp70 contains the major antigenic determinants of gp45, and, in addition, determinants unique to gp70. We presume that these differences involve the carbohydrate components, either directly or indirectly by influence on conformation. The major antigenic deficiencies in gp45, relative to gp70, appeared to be in interspecies reactivity.

Type D retroviruses: Occurrence of natural antibodies to Mason-Pfizer monkey virus in rhesus monkeys

Abstract Sera from rhesus monkeys maintained at three separate geographic regions were found to possess naturally occurring antibody to the Mason-Pfizer monkey virus (MPMV) major structural protein. The specificity of this reactivity was established by absorption with purified viral protein. While animals from two of these colonies were housed in association with MPMV-infected monkeys, no such prior exposure to virus-infected animals could be traced in the case of the third colony. These results in combination with the previous inability to detect full complements of MPMV genetic sequences in the cellular DNA of the normal rhesus monkeys provide evidence for horizontal transmission of MPMV. Alternatively, the present findings could reflect humoral immune response to expression of an endogenous type D retrovirus highly related to MPMV.

Multiple Distinct Antigenic Determinants Associated with Murine Type-C Virus Group-Specific Antigen

Three serologically active fragments were identified in tryptic digests of iodinated MuLV major group-specific antigen (p30). Two of these eluted in a single zone on Sephadex G-50 and agarose gels developed with guanidine·HCl with an apparent molecular weight of 11,500. Approximately one half of the radioactivity in this zone was precipitated with antiserum to a tryptic fragment (IEFP, mol. wt. 10,300) purified by isoelectric focusing. The remaining radioactivity was still precipitable by antisera to homologous and heterologous (FeLV) p30’s. A smaller fragment (mol. wt. 2,500) not found in IEFP was apparently derived from the material in this zone. Direct radioimmunoassays and inhibition tests established that species-specific and interspecific determinants were present on each fragment. The assay with the 125I-labeled small fragment was inhibited optimally with trypsinized p30 showing an increase of 130-fold in sensitivity compared to inhibition tests with intact p30.