Replication of Lactate Dehydrogenase-elevating Virus in Macrophages: 1. Evidence for Cytocidal Replication

Abstract

SUMMARYCultures of starch-elicited peritoneal mouse macrophages in medium containing macrophage growth factor (MGF) were infected with lactate dehydrogenaseelevating virus (LDV) and, after various times in culture, LDV production was monitored as a function of time by infectivity titrations in mice, by measuring [3H]uridine incorporation into LDV RNA and extracellular LDV, by autoradiographic analysis of the proportion of productively infected cells and by electron microscopy. Regardless of the age of the cultures when infected with LDV, only a small proportion of the macrophages (generally between 3 and 20% of the total) became productively infected after a primary infection; maximum virus RNA synthesis and virus production occurred during the first 24 h after infection and then decreased precipitously. Productively infected macrophages could be readily recognized in electron micrographs of 24-h infected macrophage cultures and in sections of spleens from 24-h infected mice by characteristic morphological alterations. These consisted of formation of clusters of double-membrane vesicles with a diameter of 100 to 300 ~m, budding of nucleocapsids into vesicles with single membranes and accumulation of mature virions in these vesicles. One to 4 days later, however, such cells were no longer found in infected cultures or spleens of infected mice and superinfection did not restimulate LDV replication. Cultures established with macrophages from 1-day LDV-infected mice also did not support LDV replication. We conclude that LDV replication in cultures or mice is limited to a single cycle in a subpopulation of macrophages and that infection leads to cell death and rapid phagocytosis of the dead cells by the resistant, uninfected macrophages.

Replication of lactate dehydrogenase-elevating virus in cells infected with murine leukaemia viruses in vitro

“…Cells or cell lines other than macrophages which are permissive for LDV in vitro have not yet been detected despite extensive study (Stueckemann et al, 1982;Rowson & Mahy, 1985): The cells employed in this study also failed to support LDV infection and replication unless these cells had been infected with ecotropic MuLV. Infection by LDV was observed in various ecotropic MuLV-infected cells, but the extent of infection varied cons!derably from virus strain to strain and from cell line to cell line.…”

“…The susceptibility Of mice to the disease increased with age and immune suppressive treatments (Duffey et al, 1976;Martinez et al, 1980). The target cells for LDV are macrophages, and no permissive cells or cell lines other than macrophages have yet been found (Stueckemann et al, 1982). Whereas in the spinal cord of paralysed mice, LDV was shown to infect and replicate in motor neurons and other CNSspecific cells, no replication has been observed in the CNS of disease-resistant mice (Kascsak et al, 1983;Stroop & Brinton, 1983).…”

Neonatal Infection of Mice With Lactate Dehydrogenase-elevating Virus Results in Suppression of Humoral Antiviral Immune Response but does not Alter the Course of Viraemia or the Polyclonal Activation of B Cells and Immune Complex Formation

“…(Porter & Porter, 1971 ;Inada & Mims, 1985;Chan et al, 1989), these findings being consistent with the cytocidal nature of LDV replication in macrophages (Plagemann & Moennig, 1992). Similarly, LDV-infected cells have been detected in sections of the spleen by in situ hybridization and by electron microscopy at 1 day p.i., but not at later times (Stueckemann et al, 1982a;Chan et al, 1989) and the same applies to the detection of LDV genomic and subgenomic mRNAs in the spleens by using Northern hybridization analysis (Contag & Plagemann, 1989;Kuo et al, 1992). Thus, little is known about the site of LDV replication during chronic infection.…”

“…Cultures of peritoneal macrophages were prepared and infected with about 500 IDa0 of LDV-P/cell as described previously (Stueckemann et al, 1982a).…”

Sequences of 3' end of genome and of 5' end of open reading frame 1a of lactate dehydrogenase-elevating virus and common junction motifs between 5' leader and bodies of seven subgenomic mRNAs

“…2d). However, such a structure would explain the apparent smoothness of the surface of LDV virions (Brinton-Darnell & Plagemann, 1975;Stueckemann et al, 1982) and perhaps the finding that antibodies neutralize LDV infectivity only very inefficiently . The EAV ORF 5 protein also possesses three similar potential membranespanning segments, but after cleavage of the signal peptide possesses an external N-terminal segment of about 75 amino acids with one carbohydrate side-chain (den Boon et al, 1991;de Vries et al, 1992).…”