Autogenous immunity to endogenous RNA tumor virus: reactivity of natural immune sera to antigenic determinants of several biologically distinct murine leukemia viruses

Abstract

Sera from normal (C57BL/6XC3H/Anf)F1(B6C3F1) mice reacted with several biologically distinct murine leukemia virus(es) (MuLV) by radioimmune precipitation assays with the use of purified tritiated leucine-labeled virus. The reactivities of this natural antibody to viral envelope antigens of two laboratory strains (Rauscher and Moloney) and two endogenous mouse C-type viruses (AKR and BALB:virus-2) were further analyzed and compared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Similar patterns of antibody reactivities to AKR MuLV and the two member viruses of the Friend-Moloney-Rauscher group were found. Three major antigenic determinants of the virus envelope, gp71, gp43, and p15, were recognized by and precipitated natural antibody. In all viruses examined, normal B6C3F1 sera precipitated comparable amounts of gp71 and gp43. However, compared with the other viruses, the amount of p15 (relative to the glycoproteins) precipitating from BALB:virus-2 was significantly lower. This appears to be due to a lesser amount of p15 on the xenotropic virus. While heterologous antisera to purified gp71 and p15 of MuLV reacted to a certain degree with rhabdomyosarcoma virus 114 and rat leukemia virus, natural mouse antibody did not. These results suggest that MuLV have common antigenic determinants recognized by natural antibody, and that the reactivities of natural antibody in an autogenous immune response are restrictive in contrast to immune antibody produced in a heterologous host.