Cytopathic “activity

The 7-azabenzisoselenazol-3(27/)-ones (169) (Fig. 12), substituted at the 2-position with phenyl or alkyl groups, and the methiodides (170) were found in the antiviral assay to be strong inhibitors of cytopathic activity of herpes simplex type 1 virus (HSV-1) and encephalomyocarditis virus (EMCV), more potent than ebselen. The minimal inhibitory concentration (MIC) values were in the range 0.4-6.0 pg mL 1, substantially lower than those when toxicity was observed. The vesicular stomatis virus (VSV) remained resistant toward tested compounds, except moderately active methiodide (171) [51, 271],... 

It was reported licochalcone A inhibits the cytopathic activity of human immunodeficiency virus (HIV) by Okuda s group [22], A cell line named OKM-1, sensitive to the cytopathic activity of HIV, was established from the peripheral blood of a patient with adult T-cell leukemia. Giant cells due to the cytopathic activity, were formed within a day on co-culture with HIV-infected Molt-4 cell (OKM-1 OKM-4 = 3 1). Licochalcone A inhibited the giant cell formation at concentration 20 ig/ml without observable cytotoxicity. Besides, licochalcone A has a radical scavenging effect, inhibition of leukotriene synthesis in human polymorphonuclear neutrophils and xanthine oxidase. 

Okuda et al. have reported that some licorice flavonoids, isolico-flavonol (171), glycycoumarin (172), licochalcones A and B (213 and 214), glycyrrhisoflavone (250) and licopyranocoumarin (256), inhibit the cytopathic activity of HIV (427). Shibata et al. have reported that licochalcone A (213) shows anti-tumor promoting activity in a two-stage mouse skin carcinogenesis experiment (428). Inhibitory activity of... 

CarbocycHc 2/3 -didehydro-2/3 -dideoxyguanosine [118353-05-2] (carbovk, CBV, 66), C H 2N502, synthesized in 1988 (177), is a promising candidate for the chemotherapy of AIDS. CBV inhibits HIV repHcation and HIV-induced cytopathic effects in a variety of human T-lymphoblastoid ceU lines at concentrations approximately two hundred- to four hundredfold below its cytotoxic concentrations (177). CBV is as effective as AZT and DDC in reducing the expression of vkal antigen in HIV-infected CEM ceUs (177). The antivkal potency and selectivity of carbovk is comparable to the anti-HIV-1 potency and selectivity of 2/3 -dideoxyadenosine (178). The exact mode of antivkal action of carbovk has not yet been elucidated, but may be the modulating effect of intraceUular nucleotides on 5 -nucleotidase activity (179). 

Inoculation of cell cultures with virus-containing material produces characteristic changes in the cells. The replication of many types of viruses produces the cytopathic effect (CPE) in which cells degenerate. This effect is seen as the shrinkage or sometimes ballooning of cells and the disruption of the monolayer by death and detachment of the cells (Fig. 3.6). The replicating virus can then be identified by inoculating a series of cell cultures with mixtures of the virus and different known viral antisera. If the virus is the same as one of the types used to prepare the various antisera, then its activity will be neutralized by that particular antiserum and CPE will not be apparent in that tube. Alternatively viral antisera labelled with a fluorescent dye can be used to identify the virus in the cell culture. 

Studies have demonstrated that one such method is to examine the effects of disinfectants on endogenous RNA-dependent DNA polymerase (i.e. reverse transcriptase) activity. In essence, HIV is an RNA virus after it enters a cell the RNA is converted to DNA under the influence of reverse transcriptase. The virus induces a cytopathic effect on T lymphocytes, and in the assay reverse transcriptase activity is determined after exposure to different concentrations of various disinfectants. However, it has been suggested that monitoring residual viral reverse transcriptase activity is not a satisfactory alternative to tests whereby infectious HIV can be detected in systems employing fresh human peripheral blood mononuclear cells. 

Fig. 8.5 Demonstration of IFNa2b functionality by the ability of IF-Na2b to protect HeLa cells against the cytopathic effect of encephalomyocarditis virus (EMC). Chloroplast derived IFNa2bwas as active as commercially produced Intron A.

A few nitrogen-substituted allenes themselves are known as biologically active compounds [154], For example, the 9-(4 -hydroxy-1, 2 -butadienyl)adenine (268a) was found to inhibit in vitro replication and cytopathic effects of human immunodeficiency viruses HIV-1 and HIV-2 [155], More recently, an increase in the anti-HIV activity in cell cultures using the adenallene phosphotriester derivative 268b was reported (Scheme 8.72) [156]. 

Vandenbroeck et al.7 used an ELISA to determine the recovery of immu-noreactive porcine interferon-gamma (IFN-y) from E. coli inclusion bodies. The ELISA used a polyclonal coating antibody with detection by a MAb. The inclusion bodies were solubilized in diluted 6 M guanidine/HCl and IFN subsequently refolded by its removal. The antiviral activity of the interferon was measured with a bioassay using the cytopathic effect (CPE) of vesicular stomatitis virus (VSV) on bovine kidney cells. The results of this study showed that the immu-noreactivity measured by ELISA matched the biological activity measured by bioassay. 

Classical bacterial exotoxins, such as diphtheria toxin, cholera toxin, clostridial neurotoxins, and the anthrax toxins are enzymes that modify their substrates within the cytosol of mammalian cells. To reach the cytosol, these toxins must first bind to different cell-surface receptors and become subsequently internalized by the cells. To this end, many bacterial exotoxins contain two functionally different domains. The binding (B-) domain binds to a cellular receptor and mediates uptake of the enzymatically active (A-) domain into the cytosol, where the A-domain modifies its specific substrate (see Figure 1). Thus, three important properties characterize the mode of action for any AB-type toxin selectivity, specificity, and potency. Because of their selectivity toward certain cell types and their specificity for cellular substrate molecules, most of the individual exotoxins are associated with a distinct disease. Because of their enzymatic nature, placement of very few A-domain molecules in the cytosol will normally cause a cytopathic effect. Therefore, bacterial AB-type exotoxins which include the potent neurotoxins from Clostridium tetani and C. botulinum are the most toxic substances known today. However, the individual AB-type toxins can greatly vary in terms of subunit composition and enzyme activity (see Table 2). 

In 2000, Boyd et al. reported for the first time an anti-HIV active carbazole alkaloid, siamenol (89) (see Scheme 2.17). This prenylated carbazole alkaloid inhibited HIV-1 induced cytopathic inhibitor activity in an XTT-tetrazolium assay with EC50 2.6 pg/mL (85,449). Recently, Kongkathip et al. reported anti-HIV-1 activity for O-methylmukonal (glycosinine) (38) (see Scheme 2.9), 7-methoxy-O-methylmu-konal (2,7-dimethoxy-3-formylcarbazole) (48) (see Scheme 2.10), and clausine K (clausazoline-J) (51). These studies showed strong anti-HIV-1 activity for... 

Certain scrapie-like diseases of sheep in Iceland and some chronic encephalopathies in man (including kuru, the laughing disease of New Guinea) are the result of slow virus infections with long incubation periods. 1-Methylisatin 3-thiosemicar-bazone has been found to reduce the reverse transcriptase activity and cytopathic effect of the RNA slow viruses producing the sheep diseases and hence may provide a chemotherapeutic method for their control118. ... 

The antiviral activity of 431-438 has been investigated to study their cytotoxicity and capability to inhibit HIV-1-induced cytopathicity in MT-4 cells. AZT and nevirapine have been used as the references. A majority of these compounds were found to be noncytotoxic for MT-4 cells at doses higher than 300 pM. Maximum activity was obtained with the compounds of series 431 and other related chloro derivatives 432, some of which displayed highest potency with ECso= 1.0 and 0.5 pM, respectively. Compounds belonging to other series were found to be considerably less potent and selective or totally inactive <1996BMC837>. 

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