Skunks have gene sequences in their cellular DNA related to squirrel monkey retrovirus: transmission between species of a new world primate endogenous type D retrovirus

Exchange of genetic sequences of long terminal repeat and the env gene by a promiscuous primate type D retrovirus

Squirrel monkey retrovirus (SMRV) is a New World primate type D retrovirus. It was shown that SMRV-related sequences could be detected in another New World species, the skunk. It was further suggested that SMRV and an Old World primate type C retrovirus, baboon endogenous virus (BaEV), may have exchanged their env gene sequences. In this study, we sought to understand which sequences were exchanged between the genomic DNAs of SMRV and skunk. We also sought to determine the sequences exchanged between SMRV and BaEV. Here, we demonstrate that the long terminal repeat of SMRV is present in the skunk genome. We also show, by nucleotide sequence analysis, that the env gene that encodes the p15E glycoprotein of BaEV was most likely transduced from the corresponding gene of a primate type D retrovirus. Our results demonstrate that SMRV is a promiscuous virus with its pol gene homologous to the pol genes of type A, type B and avian type C viruses and a portion of its env gene homologous to the env genes of primate type C retroviruses. However, the primer binding sequence is unique to type D retroviruses. These kinds of recombination are likely to occur more than once in the evolution of retroviruses. The promiscuous nature of retroviruses and the recent incidence of unintended retroviral integration into a gene therapy patient underscore the importance of understanding how retroviral sequences are recombined among themselves and how they are integrated into the mammalian genome.

Distribution of endogenous type B and type D sheep retrovirus sequences in ungulates and other mammals

The jaagsiekte sheep retrovirus (JSRV), which appears to be a type B/D retrovirus chimera, has been incriminated as the cause of ovine pulmonary carcinoma. Recent studies suggest that the sequences related to this virus are found in the genomes of normal sheep and goats. To learn whether there are breeds of sheep that lack the endogenous viral sequences and to study their distribution among other groups of mammals, we surveyed several domestic sheep and goat breeds, other ungulates, and various mammal groups for sequences related to JSRV. Probes prepared from the envelope (SU) region of JSRV and the capsid (CA) region of a Peruvian type D virus related to JSRV were used in Southern blot hybridization with genomic DNA followed by low- and high-stringency washes. Fifteen to 20 CA and SU bands were found in all members of the 13 breeds of domestic sheep and 6 breeds of goats tested. There were similar findings in 6 wild Ovis and Capra genera. Within 22 other genera of Bovidae including domestic cattle, and 7 other families of Artiodactyla including Cervidae, there were usually a few CA or SU bands at low stringency and rare bands at high stringency. Among 16 phylogenetically distant genera, there were generally fewer bands hybridizing with either probe. These results reveal wide-spread phylogenetic distribution of endogenous type B and type D retroviral sequences related to JSRV among mammals and argue for further investigation of their potential role in disease.

Characterization of exogenous type D retrovirus from a fibroma of a macaque with simian AIDS and fibromatosis

A novel type D retrovirus was isolated by cocultivation of explants of fibromatous tissue from a rhesus monkey (Macaca mulatta) with immunodeficiency and retroperitoneal fibromatosis. This type D virus, isolated from a macaque with simian acquired immunodeficiency syndrome (SAIDS-D/Washington), is exogenous and is partially related to the Mason-Pfizer and the langur monkey type D viruses. The SAiDS-D virus can be distinguished from all other primate retroviruses by antigenicity and molecular hybridization. Nucleic acid hybridization studies reveal that the origin of the SAIDS-D isolate may reside in Old World monkey (subfamily Colobinae) cellular DNA.

Efficient isolation of endogenous rhesus retrovirus from trophoblast

An examination of various rhesus monkey (Macaca mulatta) organs has shown a preference for type C viral antigen expression in the placenta. Separate cocultivations of isolated trophoblasts from 10 rhesus monkey placentas with cell lines from heterologous mammalian species led to rapid isolation of type C rhesus retrovirus in 4 of 10 cases. These four retrovirus isolates have been designated MMC-2 through MMC-5. Five of the remaining six sets of cocultivations grew simian foamy virus and were discontinued. Distinction of these viral isolates from the initial rhesus isolate (MMC-1) and the previous isolate from the stumptail monkey, Macaca arctoides (MAC-1), could be made by liquid DNA hybridization, although not by limited restriction endonuclease digestion. Both MAC-1 and MMC-1 were obtained in single long-term cocultivation experiments (over 7 months). The present isolates MMC-2 through MMC-5 were detected in 2 to 5 weeks. Consequently, primary trophoblast cells represent a useful differentiated cell type for isolation of infectious retrovirus from this primate species.