Responses to Interferon of LM Cells Growing Continuously in the Absence of Serum and Exogenous Lipids

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SUMMARYPoly(rI). poly(rC) induces a lytic reaction in interferon-treated mouse LM cells. We have attempted to determine whether the intracellular penetration of poly(rI), poly(rC) is a prerequisite for cell lysis and to gain some insight into the pathway followed. We found that poly(rI), poly(rC) coupled to Sepharose beads was unable to generate lysis of interferon-treated cells whereas the cells underwent lysis after microinjection of poly(rI).poly(rC). Some inhibitors of endocytosis were found to inhibit the development of the lytic reaction. Lysosomotropic amines or a low temperature (19 °C) blocked endocytosis of poly(rI).poly(rC) but did not prevent its uptake. The internalization of poly(rI).poly(rC) was energy-dependent and was blocked when sodium azide and 2-deoxyglucose were added simultaneously. We conclude that poly(rI), poly(rC) is internalized and reaches an acidic compartment before triggering the lytic reaction in the cell.

Section: Discussionsupporting

confidence: 81%

Requirement for Endocytosis of Poly(rI).Poly(rC) to Generate Toxicity on Interferon-treated LM Cells

Milhaud

Silhol

Salehzada

et al. 1987

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“…Metabolic inhibitors of prostaglandin biosynthesis which block fatty acid cyclooxygenase, like indomethacin or aspirin, have been reported to inhibit the antiviral action of interferon (Pottathil et al, 1980). However, a lack of such effects on interferon action has been reported from other laboratories (Tovey et al, 1982;Milhaud et al, 1983). Mouse ~//~ interferon-resistant cells (L-1210R) which lack a functional cyclooxygenase (Chandrabose et al, 1981), have also been shown to lack receptors for this class of interferons (Aguet, 1980).…”

Section: Discussionmentioning

confidence: 99%

Antiviral Activity of Prostaglandin A on Encephalomyocarditis Virus-infected Cells: A Unique Effect Unrelated to Interferon

Ankel

Mittnacht

Jacobsen

1985

SUMMARYAntiviral effects of prostaglandins of the A series (PGAs) on Sendai, vaccinia and vesicular stomatitis viruses have previously been reported and a relationship between the antiviral actions of PGAs and interferons has been suggested. We have investigated the antiviral activity of PGAs on encephalomyocarditis (EMC) virus. Using single-cycle assays of virus replication our results indicate that PGAs only inhibit when present in the culture medium after the cells are infected, and that they are most effective during incubation periods including from 3 to 5 h post-infection. Furthermore, viral RNA synthesis is blocked in infected cells treated with PGA and, as a result, viral antigens are greatly reduced in the cytoplasm of the cells 5 h postinfection. Since the antiviral effect of PGAs is unperturbed by actinomycin D, when cellular RNA synthesis is greatly reduced, it appears unlikely that induction of new cellular proteins is the reason for the antiviral activity of PGAs. In separate experiments we were unable to demonstrate directly the induction of interferon, or of the two dsRNA-dependent enzymes, 2',5'-oligoadenylate synthetase and protein kinase, which are greatly increased in interferon-treated cells. Thus, we conclude that the antiviral activity of PGAs is unrelated to the antiviral action of interferons and involves a unique mechanism independent of cellular protein synthesis.

“…LM cells (ATCC clone CCL 1-2) and derived clones were passaged in the absence of trypsin in microbiology-grade Petri dishes as previously described (Milhaud et al, 1983). Most experiments, however, were performed in tissue culture Petri dishes where the cells attach and grow as monolayers.…”

Section: Methodsmentioning

confidence: 99%

“…In dose-response experiments, IFN and poly(rI), poly(rC) alone do not appreciably reduce cell viability, as judged by their plating efficiency, at doses up to 1000 u/ml and 5 ktg/ml, respectively. When added sequentially, however, 1000 u/ml IFN and 5 gg/ml poly(rI), poly(rC) reduce cell survival to less than 5~ (Milhaud et al, 1983).…”

Section: Isolation Of (Ifn + I C) R Variantsmentioning

confidence: 99%

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Isolation and Biological Characterization of Mouse LM Fibroblast Variants Resistant to the Cytotoxicity of Polyriboinosinic{middle dot}Polyribocytidylic Acid after Interferon Treatment

Faure

Milhaud

Laclos

et al. 1984

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SUMMARYMouse LM fibroblasts growing continuously in the absence of serum have an increased sensitivity to the cytotoxicity of poly(rI).poly(rC) after interferon (IFN) exposure. This has allowed the isolation by an enrichment procedure of several independent and stable variant clones (IFN + I. C) g which are resistant to such a treatment. One of the resistant variants has been more extensively characterized as far as IFN action and IFN production are concerned. It behaves identically to the wildtype parent except for the spontaneous release of low amounts of IF N. The target of the mutation probably resides in a late step in the development of the cytotoxic response as revealed by microinjection techniques. The (IFN + I. C) g variants characterized here thus appear different from mutants in the IFN system isolated so far.