Antiviral activity of prostaglandin A on encephalomyocarditis virus-infected cells: a unique effect unrelated to interferon

Beneficial role of bioactive lipids in the pathobiology, prevention, and management of HBV, HCV and alcoholic hepatitis, NAFLD, and liver cirrhosis: A review

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HBV, HBC, and alcoholic and non-alcoholic fatty liver disease lead to liver cirrhosis.

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All these are inflammatory conditions with PUFA deficiency state.

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HBV, HCV, and alcohol inhibit PUFA metabolism.

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PUFAs and their metabolites have anti-viral and cytoprotective actions.

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PUFAs and vitamin C may be of benefit in NAFLD, AFLD, and liver cirrhosis.

It has been suggested that hepatitis B virus (HBV)- and hepatitis C virus (HCV)-induced hepatic damage and cirrhosis and associated hypoalbuminemia, non-alcoholic fatty liver disease (NAFLD), and alcoholic fatty liver disease (AFLD) are due to an imbalance between pro-inflammatory and anti-inflammatory bioactive lipids. Increased tumour necrosis factor (TNF)-α production induced by HBV and HCV leads to a polyunsaturated fatty acid (PUFA) deficiency and hypoalbuminemia. Albumin mobilizes PUFAs from the liver and other tissues and thus may aid in enhancing the formation of anti-inflammatory lipoxins, resolvins, protectins, maresins and prostaglandin E1 (PGE1) and suppressing the production of pro-inflammatory PGE2. As PUFAs exert anti-viral and anti-bacterial effects, the presence of adequate levels of PUFAs could inactivate HCV and HBV and prevent spontaneous bacterial peritonitis observed in cirrhosis. PUFAs, PGE1, lipoxins, resolvins, protectins, and maresins suppress TNF-α and other pro-inflammatory cytokines, exert cytoprotective effects, and modulate stem cell proliferation and differentiation to promote recovery following hepatitis, NAFLD and AFLD. Based on this evidence, it is proposed that the administration of albumin in conjunction with PUFAs and their anti-inflammatory products could be beneficial for the prevention of and recovery from NAFLD, hepatitis and cirrhosis of the liver. NAFLD is common in obesity, type 2 diabetes mellitus, and metabolic syndrome, suggesting that even these diseases could be due to alterations in the metabolism of PUFAs and other bioactive lipids. Hence, PUFAs and co-factors needed for their metabolism and albumin may be of benefit in the prevention and management of HBV, HCV, alcoholic hepatitis and NAFLD, and liver cirrhosis.

Multiple APOBEC3 restriction factors for HIV-1 and one Vif to rule them all

Several members of the APOBEC3 family of cellular restriction factors provide intrinsic immunity to the host against viral infection. Specifically, APOBEC3DE, APOBEC3F, APOBEC3G, and APOBEC3H haplotypes II, V, and VII provide protection against HIV-1Δvif through hypermutation of the viral genome, inhibition of reverse transcription, and inhibition of viral DNA integration into the host genome. HIV-1 counteracts APOBEC3 proteins by encoding the viral protein Vif, which contains distinct domains that specifically interact with these APOBEC3 proteins to ensure their proteasomal degradation, allowing virus replication to proceed. Here, we review our current understanding of APOBEC3 structure, editing and non-editing mechanisms of APOBEC3-mediated restriction, Vif-APOBEC3 interactions that trigger APOBEC3 degradation, and the contribution of APOBEC3 proteins to restriction and control of HIV-1 replication in infected patients.

Induction of heat-shock protein 70 by prostaglandin A₁ inhibits HIV-1 Vif-mediated degradation of APOBEC3G

Previous studies have demonstrated that cyclopentenone prostaglandins (cyPGs) inhibit human immunodeficiency virus type 1 (HIV-1) replication in various cell types. This antiviral activity has been associated with the induction of heat-shock protein 70 (HSP70) in infected cells. We investigated a new role of prostaglandin A₁ (PGA₁) in the replication of HIV-1 in non-permissive cells. Because overexpression of HSP70 blocks the viral infectivity factor (Vif)-mediated degradation of APOBEC3G (A3G) via the ubiquitin-proteasome pathway, we examined the effects of PGA₁ on A3G and HIV-1 replication. The induction of HSP70 synthesis by PGA₁ blocked Vif-mediated A3G degradation and enhanced the incorporation of A3G into both wild-type and Vif-deficient viruses. Furthermore, we determined the viral titer of HIV-1 particles produced from PGA₁-treated 293T cells. The induction of HSP70 synthesis by PGA₁ significantly reduced the viral titer in the presence of A3G. Additionally, the p24 Gag antigen levels were dramatically reduced in non-permissive cells treated once or repeatedly with PGA₁. Thus, we showed that PGA₁ inhibits HIV-1 replication, at least in part, by blocking Vif-mediated A3G degradation.

Lipid metabolism modulation by the P2X7 receptor in the immune system and during the course of infection: new insights into the old view

For decades, scientists have described numerous protein pathways and functions. Much of a protein's function depends on its interactions with different partners, and those partners can change depending on the cell type or system. The P2X7 receptor (P2X7R) is one such multifunctional protein that is related to multiple partners and signaling pathways. The relationship between P2X7R and different enzymes involved in lipid metabolism represents a relatively new field in P2X7R research. This field of research began in epithelial cells and currently includes immune and nervous cells. The P2X7R-lipid metabolism pathway is related to many biological functions of P2X7R, such as cell death and pathogen clearance, and this signaling pathway may be involved in many functions that are dependent on bioactive lipids. In the present review, we will attempt to summarize data related to the P2X7R-lipid metabolism pathway, focusing on signaling pathways and their biological relevance to the immune system and infection.

PGJ2 antagonizes NF-kappaB-induced HIV-1 LTR activation in colonic epithelial cells

Intestinal epithelial cells play an important role in early stages of HIV-1 infection and long-term persistence of the virus. Here we determined the mechanism that regulates HIV-1 activation via prostaglandin J(2) (PGJ(2)) in Caco-2 cells. We showed that treatment of Caco-2 cells with PGJ(2) decreased the infectivity of a luciferase reporter virus, pHXB-luc, as well as HIV production following infection of cells with a X4-tropic virus by antagonizing sodium butyrate, a cellular activator known to induce HIV-1 transcription. Transfection of intestinal epithelial cells such as Caco-2, HT-29 and SW620 cells with full-length HIV-1 LTR (pLTR-luc) revealed that PGJ(2) reduced HIV-1 LTR-mediated reporter gene activity. The involvement of NF-kappaB in the PGJ(2)-dependent down-regulation of HIV-1 transcription was further assessed using the kappaB-regulated luciferase-encoding vectors. In Caco-2 cells, PGJ(2) decreased IKK activity, resulting in reduced NF-kappaB translocation to the nucleus. Since sodium butyrate has been associated with a chronic stress response in AIDS patients, our results suggest that addition of PGJ(2) in the environment of infected intestinal epithelial cells could reduce HIV-1 transcription.

Reduction of phospholipase D activity during coxsackievirus infection

During enterovirus infection, host cell membranes are rigorously rearranged and modified. One ubiquitously expressed lipid-modifying enzyme that might contribute to these alterations is phospholipase D (PLD). Here, we investigated PLD activity in coxsackievirus-infected cells. We show that PLD activity is not required for efficient coxsackievirus RNA replication. Instead, PLD activity rapidly decreased upon infection and upon ectopic expression of the viral 3A protein, which inhibits the PLD activator ADP-ribosylation factor 1. However, similar decreases were observed during infection with coxsackieviruses carrying defective mutant 3A proteins. Possible causes for the reduction of PLD activity and the biological consequences are discussed.

Biochemistry of prostaglandins A

This review considers modern concepts on the structural-functional properties and antiproliferative, antitumor, and antiviral effects of cyclopentenone prostaglandins A and mechanisms underlying their actions. Possible directions of pharmacological application of these compounds and their analogs are discussed.

Cyclopentenone prostaglandins: new insights on biological activities and cellular targets

The cyclopentenone prostaglandins PGA2, PGA1, and PGJ2 are formed by dehydration within the cyclopentane ring of PGE2, PGE1, and PGD2. PGJ2 is metabolized further to yield Delta(12)-PGJ(2) and 15-deoxy-Delta(12,14)-PGJ(2) (15d-PGJ(2)). Various compounds within the cyclopentenone prostaglandin family possess potent anti-inflammatory, anti-neoplastic, and anti-viral activity. Most actions of the cyclopentenone prostaglandins do not appear to be mediated by binding to G-protein coupled prostanoid receptors. Rather, the bioactivity of these compounds results from their interaction with other cellular target proteins. 15-deoxy-Delta(12,14)-PGJ(2) is a high affinity ligand for the nuclear receptor PPARgamma and modulates gene transcription by binding to this receptor. Other activities of the cyclopentenone prostaglandins are mediated by the reactive alpha,beta-unsaturated carbonyl group located in the cyclopentenone ring. The transcription factor NF-kappaB and its activating kinase are key targets for the anti-inflammatory activity of 15d-PGJ2, which inhibits NF-kappaB-mediated transcriptional activation by PPARgamma-dependent and independent molecular mechanisms. Other cyclopentenone prostaglandins, such as Delta(7)-PGA1 and Delta(12)-PGJ2, have strong anti-tumor activity. These compounds induce cell cycle arrest or apoptosis of tumor cells depending on the cell type and treatment conditions. We review here recent progress in understanding the mechanisms of action of the cyclopentenone prostaglandins and their possible use as therapeutic agents.

Inhibition by prostaglandin PGA1 on the multiplication of influenza virus is a dose-dependent effect

Cyclopentenone prostaglandins (PGs), are strong inhibitors of the multiplicative cycle of a wide variety of enveloped RNA and DNA viruses. Their antiviral activity is generally associated with alterations in the synthesis or maturation of specific virus proteins. In this report, we describe the effect of cyclopentenone PGA1 on the replication of influenza A virus Ulster 73 in LLC-MK2 cells. PGA1 was found to inhibit viral replication in a dose-dependent fashion and virus particle yield was reduced at a PGA1 concentration, which did not suppress protein synthesis in mock-infected cells. The kinetic of late viral protein synthesis was delayed in PGA1-treated cells till 10 h post-infection; after that period, viral polypeptide synthesis appeared to be similar in PGA1-treated as well as untreated cells both infected by Ulster 73 virus. This finding suggests that PGA1 might interfere with one or more events in the viral multiplicative cycle such as protein synthesis and assembly, correct insertion of virus polypeptides into the cell membrane and, or maturation of Ulster 73 virion particles. In particular, inhibition of viral replication in LLC-MK2 cells by PGA1 is accompanied by the induction of a cellular polypeptide of 70K molecular weight. We identified this cell protein as a heat shock protein (HSP) related to the inducible isoform of HSP 70, a polypeptide of 72K molecular weight. Induction of this polypeptide by PGA1 was found to be dose-dependent and a substantial accumulation could be seen at a PGA1 concentration that did not inhibit cell protein synthesis in uninfected cells. HSP 70 synthesis started after the beginning of PGA1 treatment and remained at the same level for at least 10 h, leading us to hypothesize that the delay of production of late Ulster 73 proteins could be the consequence of HSP 70 synthesis. These results suggest that HSP 70 could play a role in the antiviral activity of cyclopentenone PGA1 in LLC-MK2 cells.

INHIBITION OF MAYARO VIRUS REPLICATION BY PROSTAGLANDIN A1 IN Aedes albopictus CELLS

Prostaglandin A1 (PGA1) inhibits Mayaro virus replication in Aedes albopictus cells at nontoxic doses to uninfected cells. At 10 µg/ml, PGA1 decreases virus production by 90%. The presence of PGA1 during virus adsorption, with no treatment after infection, reduces virus yield by 41%. Antiviral activity is observed even when treatment starts at one or two hours post-infection. However, in cells pre-treated with PGA1 during 24 hours, virus replication is not impaired. Thus, events ocurring during initial stages of infection and after virus adsorption and penetration must be the target of PGA1 action. SDS-PAGE analysis of 35S-methionine labelled proteins shows that PGA1 inhibits the synthesis of viral proteins and induces the synthesis of polypeptides with molecular weight of 70 kDa, 57 kDa and 23 kDa. In cells pre-treated with actinomycin D the induction of those proteins is suppressed. In addition, actinomycin D treatment prevents PGA1antiviral activity, indicating that PGA1-induced stress proteins are probably involved in this mechanism.

Synergistic effects of triterpenic compounds with prostaglandin A1 on vaccinia virus infected L929 cells

Triterpenic compounds, such as glycyrrhizic acid (GRa) and carbenoxolone (CBX), have a synergistic effect with prostaglandin A1 on the inhibition of vaccinia virus (VV) replication in L929 cells. The fractional inhibitory concentration (FIC) values for GRa and CBX were 0.5 and 0.25, respectively. In the supernatant of triterpene treated cells, increased production of some prostaglandins was shown, whilst cell-associated prostaglandins and prostaglandins of the A series were only slightly influenced by the presence of triterpenes. From these findings there is no evidence that prostaglandin production and metabolism could be involved in the antiviral activity of triterpenes.

Antiviral activity of cyclopentenone prostanoids

Cyclopentenone prostanoids inhibit virus replication by turning on an intracellular defence response that involves the induction of cytoprotective heat-shock proteins, the modification of viral glycoprotein maturation and the control of NF-kappa B activation. These molecules represent an interesting model for the development of novel antiviral drugs that can affect different targets during the virus life cycle.

Assessment of antiviral activity, efficacy, and toxicity of prostaglandin A2 in a rabbit model of herpetic keratitis

Prostaglandin A2 (PGA2) inhibited the replication of herpes simplex virus type 1 in rabbit and human cornea stromal cells at concentrations of 1 to 5 microM while causing significant toxicity at 55 to 150 microM. Despite favorable therapeutic indices in cultured cells, PGA2 was not effective as a therapeutic agent in the treatment of herpetic keratitis in a rabbit model. The sequelae of disease appeared more severe in animals receiving PGA2 than in untreated or placebo-treated controls. The recovery of virus from tissues of latently infected rabbits was not affected by therapy. PGA2 therapy alone induced breakdown of the blood-aqueous barrier, indicating that pharmacologically active concentrations of drug were achieved in the eye. Thus, PGA2 had antiviral activity, but its proinflammatory effects appeared to be more detrimental than beneficial in the treatment of herpetic keratitis.

Inhibition of HIV-1 replication by cyclopentenone prostaglandins in acutely infected human cells. Evidence for a transcriptional block

Cyclopentenone prostaglandins (PGs) inhibit virus replication in several DNA and RNA virus models, in vitro and in vivo. In the present report we demonstrate that the cyclopentenone prostaglandins PGA(1) and PGJ(2) at nontoxic concentrations can dramatically suppress HIV-1 replication during acute infection in CEM-SS cells. PGs did not affect HIV-1 adsorption, penetration, reverse transcriptase activity nor viral DNA accumulation in HIV-1 infected cells. A dramatic reduction in HIV-1 mRNA levels was detected up to 48-72 h after infection (p.i.) in PG-treated cells, and HIV-1 protein synthesis was greatly reduced by a single PG-treatment up to 96 h p.i. Repeated PGA(1)-treatments were effective in protecting CEM-SS cells by the cytopathic effect of the virus, and in dramatically reducing HIV-1 RNA levels up to 7 d after infection. The antiviral effect was not mediated by alterations in the expression of alpha-, beta-, or gamma-interferon,TNFalpha, TNFbeta, IL6, and IL10 in HIV-infected CEM-SS cells. The fact that prostaglandins are used clinically in the treatment of several diseases, suggests a potential use of cyclopentenone PGs in the treatment of HIV-infection.

Effect of combined alpha IFN and prostaglandin A1 treatment on vesicular stomatitis virus replication and heat shock protein synthesis in epithelial cells

The antiviral activity of prostaglandin A (PGA) and interferons (IFNs) has been widely described. In the present report, we investigated the effect of combined alpha IFN and PGA1 treatment on vesicular stomatitis virus (VSV) replication and on heat shock protein (HSP) induction in monkey epithelia cells. In uninfected cells, PGA1 caused a dose-dependent induction of HSP70, HSP90 and HSP110, while alpha IFN did not affect HSP synthesis. Alpha-IFN suppressed VSV replication dose-dependently, even when cells were treated after virus infection. VSV protein synthesis was not affected by alpha IFN, indicating a block at the level of virus assembly or maturation. PGA1 caused a dose-dependent inhibition of VSV replication, and suppressed VSV protein synthesis at concentrations which induced the synthesis of high levels of HSP70. The combined treatment with low doses of alpha IFN or PGA1, which only moderately inhibited VSV replication when administered separately, was found to suppress VSV production by more than 95%, and resulted in a 3-fold increase of HSP70 synthesis as compared to PGA1 alone. These results demonstrate a co-operative effect of PGA1 and alpha IFN against VSV infection and suggest that alpha IFN can potentiate the cellular response to HSP induction in virus-infected cells.

Inhibition of poliovirus replication by prostaglandins A and J in human cells

Cyclopentenone prostaglandins (PGs) inhibit the replication of a wide variety of enveloped DNA and RNA viruses. The antiviral activity is associated with alterations in the synthesis, maturation, and intracellular translocation of viral proteins. In the present report, we describe the effects of cyclopentenone PGs PGA1 and delta 12-PGJ2 on poliovirus (PV) replication in HeLa cells. Both PGs were found to inhibit PV replication dose dependently. Virus yield was significantly reduced at nontoxic concentrations, which did not suppress RNA or protein synthesis in uninfected or PV-infected cells. Both the pattern of PV proteins synthesized and the kinetics of viral protein synthesis and degradation appeared to be similar in PGA1-treated cells and control cells. Antiviral PGs have been shown to selectively inhibit virus protein synthesis during the replication of several viruses, including vesicular stomatitis virus (VSV), and this effect has been recently associated with the induction of a 70-kDa heat shock protein (HSP70). PGA1 and delta 12-PGJ2 were found to induce HSP70 synthesis in uninfected or VSV-infected HeLa cells. PV infection was found to inhibit PG-induced HSP70 synthesis in these cells, suggesting that the lack of ability of cyclopentenone PGs to block PV protein synthesis could be related to an impaired heat shock response in PV-infected cells. The finding that PV protein synthesis was not inhibited by PGs suggests that cyclopentenone PGs could interfere with a late event in the virus replication cycle, such as protein assembly and maturation of PV virions.

Antiviral effect of cyclopentenone prostaglandins on vesicular stomatitis virus replication

Prostaglandins are potentially useful antiviral agents, however their mechanism of action is unclear. Recent evidence suggests that RNA transcription of vesicular stomatitis virus (VSV) is inhibited by prostaglandins (Bader and Ankel, J. Gen. Virol. 71, 2823-2832, 1990). Prostaglandins are known to have multiple effects on cells which may or may not be related to their antiviral action. We examined the effects of prostaglandins on cells and on VSV RNA polymerase in vitro to seek the mechanism of antiviral action. Actinomycin D inhibited cellular RNA synthesis but failed to block the antiviral activity of prostaglandins on VSV. Thus induction of host cell RNA transcription is not involved in the antiviral action. Neither modulation of the cellular glutathione level by prostaglandins nor formation of prostaglandin-glutathione conjugates was required for the antiviral action. The relative inhibition of VSV RNA polymerase in vitro by prostaglandins with different structures correlated to inhibition of VSV replication in infected cells. This result indicates that the same step in VSV replication is inhibited by prostaglandins both in the in vitro RNA polymerase assay and in the infected cell.

Heat shock proteins and virus replication: hsp70s as mediators of the antiviral effects of prostaglandins

Acute infection of mammalian cells with several types of RNA and DNA viruses often results in induction of heat-shock gene expression. The presence of hsp70 in intact virions, as well as the transient association of HSP with viral proteins and assembly intermediates during virus replication, has also been reported in several experimental models. Moreover, a possible role of heat shock proteins in the beneficial effect of fever and local hyperthermia during acute virus infection has been hypothesized. However, the role of HSP in virus replication remains to be defined. At the beginning of the 1980s, the use of virus models to investigate the molecular events that follow the exposure of mammalian cells to prostaglandins led to the serendipitous discovery that specific arachidonic acid derivatives are potent inhibitors of virus replication. This finding was rapidly followed by the observation that treatment of virus-infected cells with the antiviral prostaglandin A1 (PGA1) resulted in the accumulation of a 70 KDa cellular protein, which was identified as hsp70. It is now well established that cyclopentenone prostaglandins, which exert potent antiviral activity in several DNA and RNA virus models, induce hsp70 synthesis through cycloheximide-sensitive activation of heat shock transcription factor. This chapter discusses the role of heat shock proteins in the control of virus replication and summarizes the results of our recent work, which indicate that hsp70 is actively involved in the antiviral activity of prostaglandins.

Selective inhibition of virus protein synthesis by prostaglandin A1: a translational block associated with HSP70 synthesis

Cyclopentenone prostaglandins are potent inhibitors of virus replication. The antiviral activity has been associated with the induction of 70-kDa heat shock protein (HSP70) synthesis. In this report, we describe that in African green monkey kidney cells infected with Sendai virus (SV) and treated with prostaglandin A1 (PGA1), SV protein synthesis was selectively blocked as long as HSP70 was being synthesized by the host cell. The block appeared to be at the translational level, as indicated by the following (i) PGA1 had no effect on SV primary transcription, and a dramatic decrease in the abundance of SV mRNA occurred only at later stages of infection; and (ii) treatment with PGA1 started at 6 h postinfection, at which time SV mRNA had already accumulated in infected cells, did not suppress the levels of NP mRNA, but it reduced the amount of ribosome-bound NP mRNA and caused a dramatic decrease in the level of genomic RNA. The PGA1-induced block of SV protein synthesis appeared to be cell mediated, since it was prevented by actinomycin D, while PGA1 had no effect on SV mRNA translation in vitro. The possibility that HSP70 could be a mediator of the antiviral effect is suggested by the fact that treatment with other classical inducers of HSP70, including sodium arsenite, cadmium, and heat shock at 42 degrees C for 5 h, also selectively prevented SV protein synthesis as long as heat shock protein synthesis occurred. Moreover, SV protein synthesis was not inhibited by PGA1 in murine Friend erythroleukemic cells, which lack the ability to induce HSP70 expression in response to PGA1.

Inhibition of Sindbis virus replication by cyclopentenone prostaglandins: a cell-mediated event associated with heat-shock protein synthesis

Cyclopentenone prostaglandins (PGs) have been shown to inhibit the replication of several DNA and RNA viruses. Here we report on the effect of prostaglandin A1 (PGA1) on the multiplication of a positive strand RNA virus, Sindbis virus, in Vero cells under one-step multiplication conditions. PGA1 was found to inhibit Sindbis virus production dose-dependently, and virus yield was reduced by more than 90% at the concentration of 8 micrograms/ml, which was non-toxic to the cells and did not inhibit DNA, RNA or protein synthesis in Vero cells. The cyclopentenone prostaglandin delta 12-PGJ2 was also shown to be a potent inhibitor of Sindbis virus replication. Virus-induced reduction of [3H]uridine uptake by cells was partially prevented by PGA1 treatment, which also caused a 1 h delay in the peak of virus RNA synthesis. SDS-PAGE analysis of [35S]methionine-labeled proteins showed that PGA1 moderately inhibited the synthesis of the viral structural proteins E1, E2 and C, and induced the synthesis of a 72 kDa M(r) protein, identified as a heat-shock protein related to the HSP70 group, in both virus-infected and uninfected cells. Actinomycin D treatment completely prevented PGA1-antiviral activity, indicating that a cellular product is responsible for this action. PGA1-induced HSP70 is a good candidate for this role.

Inhibition of vesicular stomatitis virus replication by delta 12-prostaglandin J2 is regulated at two separate levels and is associated with induction of stress protein synthesis

delta 12-Prostaglandin J2 (delta 12-PGJ2), a naturally occurring dehydration product of prostaglandin D2, is shown to suppress the replication of vesicular stomatitis virus (VSV) in two different epithelial monkey cell lines. A significant delay in the virus-induced cytopathic effect and a dramatic inhibition of virus production can be obtained at doses which do not inhibit protein synthesis in uninfected cells, and induce the synthesis of heat shock proteins (HSPs) in both uninfected and VSV-infected cells. delta 12-PGJ2 is shown to block VSV replication at two separate levels in the early and late phase of the virus replication cycle. Treatment started soon after VSV infection greatly suppresses viral (but not cellular) protein synthesis and prevents the virus-induced shut-off of host cell protein synthesis. This effect is accompanied by the induction of HSP synthesis. delta 12-PGJ2-treatment in a late phase of the virus replication cycle, when all virus proteins have been synthesized, still causes a dramatic block of infectious virus production. This block is accompanied by a decrease in [3H]glucosamine incorporation into the virus glycoprotein G, at concentrations which do not alter glucosamine uptake by the cells, suggesting that a defect in virus protein glycosylation could be responsible for the antiviral activity. Finally, delta 12-PGJ2 causes a decrease of glucosamine incorporation into at least two host cell polypeptides, while the majority of cellular proteins are unaffected and glycosylation of a 47 kDa cellular protein is strongly induced. These selective alterations of protein glycosylation suggest that delta 12-PGJ2 affects a specific group of glycosylated proteins. The finding that cyclopentenone prostaglandins act on different events during the virus cycle explains the effectiveness of these compounds in controlling the replication of different types of viruses and presents an attractive new approach to antiviral chemotherapy.

Glutathione inhibits replication and expression of viral proteins in cultured cells infected with Sendai virus

Addition of reduced glutathione inhibited the production of Sendai virus in African green monkey kidney (AGMK) cells. This result could be accounted for by a direct action of GSH on viral replication. The inhibitory action was associated to an increase of the GSH intracellular level, while the host cell metabolism was unaffected. The antiviral effect was related to decrease and inactivation of the hemagglutinin-neuraminidase (HN) virus glycoprotein.

Formation of a prostaglandin A2-glutathione conjugate in L1210 mouse leukemia cells

Prostaglandins containing a cyclopentenone moiety are potent antiviral and antigrowth compounds. Some evidence indicates that these prostaglandins are conjugated to glutathione by cells. However, the metabolism of one group, the prostaglandins of the A type, is unclear due to conflicting reports. We studied the uptake and metabolism of prostaglandin A2 (PGA2) in mouse L1210 leukemia and L929 fibroblast cell lines in which this prostaglandin has antiviral and antigrowth effects. Both cell types took up the PGA2 and then metabolized it to a more polar compound. Inside L1210 cells, PGA2 was initially conjugated to glutathione and then reduced at the 9-keto position to form 9-OH-PGA2-GSH. The 9-OH-PGA2-GSH was then secreted from the cells and apparently degraded to form the CysGly and Cys derivatives. Intracellular glutathione was decreased markedly by the addition of the PGA2 in L1210 and L929 cells. This result confirms that conjugation of PGA2 to glutathione occurs in both cell types. Formation of the 9-OH-PGA2-GSH and other glutathione-related conjugates was prevented when glutathione was depleted by growth in buthionine sulfoximine. The glutathione-depleted cells were insensitive to the cytotoxicity of the PGA2, suggesting that one of the glutathione-related conjugates may be involved in the cytotoxicity of PGA2. These results end the controversy over the metabolism of PGA2 and suggest mechanisms for its antiviral and antigrowth actions.

Antiviral activity of the prostanoid clavulone II against vesicular stomatitis virus

Prostaglandins of the A series exhibit the most pronounced antiviral activity in cells infected with RNA or DNA viruses as compared to other prostaglandins. Clavulone is a prostaglandin A analog found in the soft coral Clavularia viridis. Using vesicular stomatitis virus in mouse L929 fibroblasts as a model system, 50% inhibition of viral yield was seen at a concentration of 1-1.5 microM, whereas 50% cytotoxicity required 50-70 times higher inhibitor concentrations. For a further elucidation of the antiviral mechanism a temperature-sensitive mutant, tsG 41, was used, which is replication-negative at the restrictive temperature. Results obtained with this mutant suggest that inhibition of VSV replication occurs at the level of transcription.

Experimental encephalomyocarditis virus infection in Mongolian gerbils (Meriones unguiculatus)

Two strains of Mongolian gerbils (Meriones unguiculatus), Tumble Brook (TUM) and Japan Medical Science (JMS), were intraperitoneally inoculated with the D variant of encephalomyocarditis virus (EMC-D) and killed 3 days later. Mortality was significantly higher in females than in males. Evidence of viral replication was detected in the heart of both strains and in the pancreas of the TUM strain. Histopathological alterations were found in the heart and pancreas. Heart lesions involved foci of necrosis with inflammatory cell infiltration and calcification in both strains. Pancreatic lesions were restricted to the exocrine glands; islets of Langerhans were rarely and secondarily involved in the extensive destruction of exocrine glands. Severe acinar cell necrosis with marked inflammatory edema was conspicuous in TUM, whereas only slight acinar cell involvement was detected in JMS gerbils. Immunoperoxidase staining showed viral antigens in intracytoplasmic vacuoles in damaged acinar cells.

Interferon treatment inhibits onset of herpes simplex virus immediate-early transcription

Pretreatment of primary cultures of splenic mouse macrophages with murine IFN-alpha/beta leads to a stable inhibition of herpes simplex virus type 1. Analysis of viral DNA, RNA, and protein synthesis identifies expression of "immediate-early" genes as a major target of IFN-mediated inhibition. Determination of viral DNA in the nuclei early after infection, i.e., before onset of DNA replication, suggests that virus uptake, transport to the nucleus, and DNA stability are not decreased in IFN-pretreated macrophages. Nuclear runoff transcription analysis shows a significant reduction of immediate-early transcription rates following IFN treatment. End-specific probes for the ICP4 gene locate the inhibition to the onset of transcription. Northern blot analysis reveals a decrease in ICP4 transcripts in accordance with the observed inhibition of transcription. The observed inhibition of early gene transcription may be a consequence of decreased immediate-early gene expression.

Antiviral activity of a synthetic analog of prostaglandin A in mice infected with influenza A virus

We have previously shown that prostaglandins of the A series potently inhibit virus replication in several virus-host systems in vitro. In the present report we have studied the effect of a long-acting synthetic analog of PGA, 16,16-dimethyl-PGA2(Di-M-PGA2), on virus infection in vivo, using as a model Balb/c mice infected with influenza A (PR8) virus. Depending upon the dose of viral inoculum, PR8 virus caused the death of 50 to 100% of the animals in a period of 8-20 days. Di-M-PGA2-treatment significantly increased mouse survival by an average of 40%, independently of the dose of inoculum and the age of the animals. The fact that Di-M-PGA2-treatment decreased virus titers in the lungs and did not alter the host immune response, suggested that PGA's therapeutic action was due to suppression of virus replication. Finally, two anti-inflammatory compounds, which inhibit prostaglandin synthesis, aspirin and indomethacin, were shown not to significantly alter mouse survival in this system.

Mechanism of inhibition of herpes simplex virus replication by delta 7-prostaglandin A1 and delta 12-prostaglandin J2

We studied the effect of prostaglandins (PGs) A1, delta 7-A1, A2, D2, E1, E2, F2 alpha, J2 and delta 12-J2 on the replication of herpes simplex virus type 2 (HSV-2). Of nine PGs we tested, delta 7-PGA1 was found to have the most potent inhibitory effect; 50% inhibitory dose (ID50) was 0.35 microgram/ml in the plaque reduction assays and HSV-2 induced protein synthesis was strongly suppressed at 0.5 microgram/ml whereas at this dose, the protein synthesis of uninfected cells was not inhibited. Dot blot hybridization analysis revealed that delta 7-PGA1 and delta 12-PGJ2 inhibited the primary transcription of HSV-2. Thus we suggest that those PGs are primarily active at the level of mRNA synthesis.