Oncornavirus-Like Particles in Squirrel Monkey (Saimiri sciureus) Placenta and Placenta Culture2

Abstract

Oncornavirus-like particles similar in morphology to type D particles were observed in 1 of 2 squirrel monkey (Saimiri sciureus) placentas. Intracytoplasmic type A particles, immature virus particles, and mature viruses with eccentric or occasionally centric nucleoids were associated with placental syncytiotrophoblasts. A spike layer typical of type B viruses was not detected in viral envelopes. Onvornaviruses, identical to those previously isolated from squirrel monkey tissues and similar to Mason-Pfizer monkey virus, were seen in cultures derived from the virus-positive squirrel monkey placenta cocultivated with a mink lung culture. The major morphologic difference between the in vivo and the in vitro squirrel monkey virus was in the nucleoid position of mature virus particles.

Ultrastructural Characterization of Endogenous Retroviral Particles Isolated from Normal Human Placentas1

“…Numerous electron microscopic (EM) studies have described the presence of "virus-like" particles in thin sections of human and primate placental chorionic villous tissue [1][2][3][4][5][6][7][8]. These reports connected endogenous retroviral (ERV) particle expression with placental syncytiotrophoblast, particularly in regions associated with cytotrophoblast depletion.…”

Human Teratocarcinomas Cultured in vitro Produce Unique Retrovirus-like Viruses

“…However, all attempts (including our own) to grow placenta-derived particles in tissue culture have failed. Subsequently, retroviruses have also been detected in the placentas of non-human primates (Ahmed et al, 1974;Benveniste et al, 1974;Kalter et al, 1973Kalter et al, b, 1975Schidlovsky & Ahmed, 1973;Seman et al, 1975 ;Smith et al, 1977) and of other mammals (Gardner, 1971 ;Gross et al, 1975;Hsiung et al, 1974;.…”