Nicholas Hahon

Influenza virus infection in mice after exposure to coal dust and diesel engine emissions

Influenza virus infection initiated after aerosol exposure of CD-1, white Swiss mice for durations of 1, 3, and 6 months to respirable particulates maintained at 2 mg/m3 of either coal dust (CD), diesel engine emissions (DEE), a combination of both (CD/DEE), or to filtered air (control) was studied. The course of infection in mice previously exposed for 1 month to various particulates did not differ appreciably among the four animal groups with respect to mortality, virus growth in lungs, interferon levels, or hemagglutinin antibody response. In mice exposed for 3 and 6 months to different particulates, the mortality response was similar among all animal groups. However, the percentage of animals showing lung consolidation was significantly higher in the 3-month groups exposed to DEE (96.5%) and CD/DEE (97%) than in the control (61.2%); in the 6-month groups, the percentages were twice that of the control for both DEE- and CD/DEE-exposed animals. Complementing these observations of both 3- and 6-month-exposed animals was the higher virus growth levels attained in the DEE and CD/DEE animals with concomitant depressed interferon levels which were the inverse of findings noted in the control group. Hemagglutinin-antibody levels in particulate-exposed animals, especially at the 6-month interval, were fourfold less than the control. Histopathologic examination of lungs revealed no qualitative differences in the inflammatory response at any one specified time interval of exposure to influenza virus among the control and particulate-exposed animal groups. However, there were differences in severity of reaction in relation to the particulate component of the exposures. Focal macular collections of pigment-laden macrophages were seen only in DEE and CD/DEE but not in CD animals after 3- and 6-month exposures. The findings of this study indicated that the severity of influenza virus infection is more pronounced in mice exposed to diesel engine emissions than in control animals and it is not appreciably accentuated by coal dust.

Depression of viral interferon induction in cell monolayers by asbestos fibers

Abstract Studies on the induction of interferon by influenza virus revealed that this adaptive cellular response was depressed, completely or partially, in either amosite, crocidolite, anthophyllite, Canadian or Rhodesian chrysotile-treated monkey kidney (LLC-MK 2 ) cell monolayers. Asbestos fiber concentrations of 1 mg/1.0 × 10 7 cells, which minimally affected cell viability, depressed interferon production by almost 90%. Increases in the virus-cell multiplicity of infection did not significantly increase interferon yields in asbestos fiber-treated cells. Chrysotile B fibers of lengths ranging from 10 to 5 μm were more effective in reducing interferon yields than those ranging from 75 to 625 μm. Maximal depression of interferon production was dependent on prior treatment of cell monolayers with asbestos fibers before the addition of viral inducer. The processes of virus integration (attachment and penetration) into and virus multiplication in cells were unaffected by the presence of asbestos fibers, however, a slightly higher level of virus replication was noted in asbestos fiber-treated cells. When cells were primed with interferon, the presence of asbestos fibers did not interfere with the ability of the primer to enhance interferon production. Neither interferon antagonists, interference with virus-cell interactions, nor adsorption by asbestos fibers accounted for the depression of interferon yields. These findings suggest that asbestos fibers act on cell membranes in a manner, as yet undetermined, to interpose in the viral inductive process of interferon synthesis.

Interferon assessment by the immunofluorescent, immunoperoxidase, and hemadsorption cell-counting techniques

SummaryThe immunofluorescent, immunoperoxidase, and hemadsorption cell-counting techniques were quantitatively evaluated for assessing interferon activity. The three assays exhibited parallel dose-responses and were comparable in sensitivity, precision, and reproducibility.

Activity of diesel engine emission particulates on the interferon system

Abstract When mammalian (LLC-MK2) cell monolayers were pretreated with diesel engine emission particulates of respirable size, viral induction of interferon was depressed by approximately 60%. However, the presence of particulates did not impair the ability of interferon to confer antiviral cellular resistance. When either diesel emission particulates or cell monolayers were pretreated with the nonionic polymer, poly(4-vinylpyridine-N-oxide), the inhibitory activity of particulates on interferon induction was significantly diminished or abolished. Influenza virus growth in cell monolayers pretreated with diesel emission particulates attained a two- to threefold higher level than that noted in normal cell monolayers or those containing polymer-pretreated particulates. This was related to suppression of viral interferon induction by diesel emission particulates. Removal of cell membrane-bound sialic acid by neuraminidase or pretreatment of diesel emission particulates with sialic acid abolished the adverse activity of particulates on viral interferon induction. These findings suggest that the receptivity for and interaction of cell membrane-bound sialic acid with diesel emission particulates are involved in the described altered cellular behavior in response to viral induction of interferon.

Effects of lignite fly ash particulates and soluble components on the interferon system

Induction of interferon by influenza virus was depressed by approximately 50% when mammalian (LLC-MK2) cell monolayers were pretreated with lignite fly ash. The presence of fly ash, however, did not impair the ability of exogenous interferon to confer antiviral cellular resistance. Influenza virus multiplication in cell monolayers pretreated with fly ash attained a twofold higher level of growth than that noted in normal cell monolayers. This was related to suppression of viral interferon induction by fly ash. Whereas aqueous extracts of fly ash had no adverse effect on interferon induction, extractions of fly ash by either polar or nonpolar solvents, by horse serum with or without EDTA (a metal chelator), and fractionation of serum extracts yielded corresponding compounds, most likely organic and inorganic, that were antagonistic to viral interferon induction. Residual fly ash particulates after extraction by horse serum with EDTA were still capable of inhibiting viral induction of interferon. These findings indicate that several soluble components inherent to lignite fly ash and the particulate matrix per se may modify, independently or in concert, cellular defense behavior. Neither polar, nonpolar, nor horse serum extracts of lignite fly ash, however, showed mutagenic activity as determined by the Salmonella histidine reversion assay. Removal of cell-membrane-bound sialic acid (N-acetylneuraminic acid) by neuraminidase or pretreatment of lignite fly ash with sialic acid abolished the adverse activity of fly ash on viral interferon induction. This suggests that the interaction of cell-membrane-bound sialic acid residue with fly ash particulates may be involved in the altered state of cellular behavior described in response to viral induction of interferon.

In vitro biologic responses to native and surface-modified asbestos.

A comparative study was made of in vitro biologic responses to native chrysotile, amosite, and crocidolite and corresponding asbestos fibers whose surfaces were modified by metal oxides. Interferon induction by influenza virus was depressed by approximately 50% by all native asbestos whereas corresponding surface modified asbestos minimally affected this nonspecific cellular defense mechanism. The release of the cytoplasmic enzyme, lactate dehydrogenase (LDH), and lysosomal enzymes, beta-N-acetylglucosaminidase (beta-NAG) and beta-glucuronidase (beta-Gluc), by rat alveolar macrophages after exposure to either native or surface-modified asbestos (which is indicative of membrane damage) was monitored. Although both native and surface-modified asbestos induced significant leakage of LDH, generally, lesser amounts of the enzyme were released as a result of exposure to the latter than to native asbestos. Whereas all forms of native asbestos caused significant release of beta-NAG and beta-Gluc, leakage of these enzymes from macrophages exposed to surface-modified asbestos was minimal. In contrast to native asbestos which induced irritation of cell membranes, as indicated by hemolysis of sheep erythrocytes, surface-modified asbestos exhibited minimal hemolytic activity. The findings indicate that surface modification of different asbestos by metal oxides generally lessened the adverse effect of the native mineral on the aforementioned biologic entities.

Coinhibition of viral interferon induction by benzo[a]pyrene and chrysotile asbestos

Benzo[a]pyrene (B[a]P) and its noncarcinogenic analog, benzo[e]pyrene (B[e]P), each in combination with chrysotile, were studied for their inhibitory effects on interferon (IFN) induction by influenza virus in rhesus monkey kidney (LLC-MK2) cell monolayers. B[a]P alone had no adverse effect on IFN induction; however, from 60 to 70% inhibition of IFN production occurred when B[a]P was enzymatically activated by rat liver S9. Chrysotiles inhibitory effect on the IFN process was similar in magnitude to that of activated B[a]P. The combination of activated B[a]P with chrysotile resulted in coinhibition of IFN induction which significantly exceeded (P less than 0.05) the inhibitory activity of the reagents tested alone or in other combinations. B[e]P alone or with S9 neither affected IFN induction nor was it capable of further enhancing chrysotiles inhibition of IFN synthesis. These findings provide further evidence of enhanced deleterious action by the combination of asbestos and activated B[a]P on a biological defense mechanism and further support the discriminatory power and credibility of the inhibition IFN induction assay for evaluating potential carcinogens.

Inhibition of viral interferon induction in mammalian cell cultures by azo dyes and derivatives activated with rat liver S9 fraction

Four azo dyes (Benzopurpurine 4B, trypan blue, Direct Blue 15, and Congo red) and their derivatives (o-tolidine, o-dianisidine, and benzidine) were studied for their effect on induction of interferon by influenza virus in mammalian, Rhesus monkey kidney (LLC-MK2), cell monolayers. Whereas Benzopurpurine 4B, Direct Blue 15, and Congo red inhibited viral interferon induction from approximately 35 to 60%, negligible inhibition was noted with trypan blue and other derivative compounds. By comparison, when rat S9 fraction was used for enzymatic activation of azo dyes and derivatives, interferon inhibition was significantly depressed moreover (P less than 0.01 to less than 0.0001) by all chemical compounds. The concentration of rat S9 (0.5%) used for metabolic activation of dyes and congeners was critical because concentrations greater than 0.5% of S9 per se inhibited the interferon induction process. Uninduced hamster S9 and both Aroclor 1254-induced hamster and rat S9 fractions were all comparable in their ability to activate the chemical compounds tested. That potential mutagenic and carcinogenic chemicals which require metabolic activation can be discriminated on the basis of interferon induction inhibition in eukaryotic cell cultures augurs for the usefulness and credibility of this system.

Depression of viral interferon induction in cell monolayers by coal dust

Habon, N. (1974).British Journal of Industrial Medicine,31, 201-208. Depression of viral interferon induction in cell monolayers by coal dust. Studies on the induction of interferon by influenza virus revealed that this adaptive cellular response was depressed completely or partially in coal dust-treated human or simian cell monolayers. Maximal inhibition of interferon production occurred with coal particles ranging in size from < 2·0 to 19·1 μM and with coal dust concentrations ranging from 0·1 to 0·001 g per 3 × 107 cells. The longer coal dust remained in contact with cells before the addition of viral inducer, the more likely was interferon production inhibited. Interferon depression was independent of the rank and geographic source of coal dust and of the virus/cell multiplicity of infection. Enhanced interferon yields resulted in normal and coal dust-treated cells when they were pretreated or proned with interferon. Neither interferon antagonists, interference with virus-cell integration, nor adsorption by coal dust accounted for the depression of interferon yields. The data suggest that coal particles per se act on cells in a subtle manner to interpose in the inductive process of interferon synthesis.

Silicate minerals and the interferon system

Natural-occurring minerals representative of six silicate classes were examined for their influence on interferon induction by influenza virus in Rhesus monkey kidney (LLC-MK2) cell monolayers. Minerals within the classes nesosilicate, sorosilicate, cyclosilicate, and inosilicate exhibited either little or marked (50% or greater) inhibition of interferon induction. Within the inosilicate class, however, minerals of the pyroxenoid group (wollastonite, pectolite, and rhodonite) all significantly showed a two- to threefold increase in interferon production. Silicate materials in the phyllosilicate and tectosilicate classes all showed inhibitory activity for the induction process. When silicate minerals were coated with the polymer poly(4-vinylpyridine-N-oxide), the inhibitory activity of silicates on viral interferon induction was counteracted. Of nine randomly selected silicate minerals, which inhibited viral interferon induction, none adversely affected the ability of exogenous interferon to confer antiviral cellular resistance. Increased levels of influenza virus multiplication concomitant with decreased levels of interferon occurred in cell monolayers pretreated with silicates. The findings of this study demonstrate the diverse effects of minerals representative of different silicate classes on the interferon system and indicate that certain silicates in compromising the viral interferon induction process may increase susceptibility to viral infection.