Expression of natural antibodies against endogenous and horizontally transmitted macaque retroviruses in captive primates

Abstract

To determine the prevalence of retrovirus antibodies in captive primate populations and to identify factors that influence antibody responses, we analyzed sera from seven geographically separated primate colonies for antibodies to the genetically [baboon endogenous virus (BaEV), squirrel monkey retrovirus (SMRV), and macaque endogenous viruses (MMC-1 and MAC-1)] and horizontally [Mason Pfizer monkey virus (MPMV) and gibbon ape lymphoma virus (GaLV)] transmitted primate retroviruses. Antibodies were detected with a solid-phase radioimmunoassay in which iodinated staphylococal protein A is used for precipitation of immunoglobulins. Naturally occurring antibodies to MPMV were found in sera of Macaca mulatta from seven geographically separated primate colonies and in the sera of three different macaque species. The predominant reactivity of these natural sera was directed against antigens shared by MPMV, BaEV, and SMRV. Several of these sera were found to have MPMV-neutralizing activity. Antibodies to the endogenous Macaca mulatta virus, MMC-1, were found in three species of macaques and in Macaca mulatta sera from five of the seven colonies tested. These positive sera were directed predominantly against a 69,000 molecular weight protein and against determinants shared by both MMC-1 and MAC-1, an endogenous virus of Macaca arctoides. Antibody expression to MMC-1 appears to be both sex and age related, whereas antibody expression to MPMV in the same monkey population was not.