Antigenic and Morphological Similarities of Progressive Pneumonia Virus, a Recently Isolated “Slow Virus” of Sheep, to Visna and Maedi Viruses

Abstract

Progressive pneumonia virus, the causative agent of a slow, pulmonary disease of Montana sheep, was shown to be antigenically related to two other slow viruses of sheep, visna and maedi. Electron microscopic examination of infected cells revealed that the virus matures by a budding process and that the budding particles as well as the mature, extracellular virions bear striking resemblances to the oncogenic ribonucleic acid (RNA) viruses. Recent findings of an RNA-dependent deoxyribonucleic acid polymerase associated with the virions of this group of slow viruses lend further support to the notion that they may tentatively be classified with the oncogenic RNA tumor viruses.

Morphological and immunological comparison of caprine arthritis encephalitis and ovine progressive pneumonia viruses

“…The two virus preparations were not pure enough to allow identification of other structural proteins, although the PPV p105 was precipitated by serum from CAEV-infected goats (see below). PPV has been shown in several reports to be virtually indistinguishable from other lentivirus isolates from sheep (8,10,15,16). The data presented here on the proteins of PPV are in agreement with earlier reports on the protein composition of the lentiviruses (8,9,13).…”

“…A great many of the budding virions were aberrant in both size and shape with many stalklike structures apparent. Such aberrant budding structures are also typical of PPV-infected cells (4,8,16,17). Figure 1B demonstrates that CAEV budding virions are very similar in appearance to type C retroviruses.…”

Maedi-visna

“…In flocks affected with zwoegerziekte, visna-like meningoencephalitis has occasionally been reported (Ressang, Stam, and de Boer, 1966). Recently viruses having properties similar to maedi and visna have also been isolated from cases of progressive pneumonia in Montana (Kennedy, Eklund, Lopez, and Hadlow, 1968;Lopes, Eklund, and Hadlow, 1970;Takemoto, Mattern, Stone, Coe, and Lavell, 1971) and from sheep of the Texel breed in West Germany and Denmark (Straub, 1970;Hoff-J0rgensen, 1971).…”

Transformation of Murine Cells by Two “Slow Viruses,” Visna Virus and Progressive Pneumonia Virus

“…Visna is the causative agent of a slow infection of the central nervous system of sheep (20, 21), whereas the "foamy" virus does not cause any known disease in monkeys. Progressive pneumonia virus (PPV), another "slow virus" which causes a slowly evolving lung disease of sheep (8), is a virus which has recently been shown to be antigenically related to visna (24) and also contains the RNA-dependent DNA polymerase (Stone and Takemoto, unpublished data).…”