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Plasma phenoloxidase of the larval tobacco budworm, Heliothis virescens, is virucidal.

Shelby KS, Popham HJ - J. Insect Sci. (2006)

Bottom Line: Preliminary results indicated that phenoloxidase is primarily responsible for this virucidal effect.Addition of the enzyme superoxide dismutase to plasma did not affect virucidal activity; however addition of catalase had an inhibitory effect.Inhibitors of nitric oxide synthase activity did not affect virucidal activity.

View Article: PubMed Central - PubMed

Affiliation: USDA, Agricultural Research Service, Biological Control of Insects Research Laboratory, Columbia, MO 65203, USA. shelbyk@missouri.edu

ABSTRACT
Heliothis virescens larval plasma contains high levels of an antiviral activity against the budded form of the Helicoverpa zea single nucleopolyhedrovirus (HzSNPV) in vitro. Preliminary results indicated that phenoloxidase is primarily responsible for this virucidal effect. However it is known that other enzymes that generate antimicrobial reactive oxygen intermediates and reactive nitrogen intermediates are present in hemolymph that could contribute to the observed virucidal activity. To elucidate the contributions of phenoloxidase and other candidate activities to plasma innate immune response against baculovirus infection specific metabolic inhibitors were used. In vitro the general inhibitors of melanization (N-acetyl cysteine, ascorbate and glutathione), and specific inhibitors of phenoloxidase (phenylthiourea and Kojic acid), completely blocked virucidal activity up to the level seen in controls. Addition of the enzyme superoxide dismutase to plasma did not affect virucidal activity; however addition of catalase had an inhibitory effect. Inhibitors of nitric oxide synthase activity did not affect virucidal activity. Our results confirm that phenoloxidase is the predominate activity in larval plasma accounting for inactivation of HzSNPV in vitro, and that phenoloxidase-dependent H(2)O(2) production may contribute to this virucidal activity.

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Enzymatic scavenging of the reactive oxygen species H2O2 from early 5th instar larvalHeliothis virescens plasma reduces virucidal activity. PBS, No plasma control; Cat, catalase (100 U/ml) control; Cat+Plasma, catalase incubated with plasma; superoxide dismutase (100 U/ml) control; superoxide dismutase +Plasma, incubation of plasma with the enzyme superoxide dismutase (100 U/ml). The enzymes were added to diluted plasma samples before the addition ofHzSNPV (letters indicate significant differences between treatments; n = 4, mean ± SEM).
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i1536-2442-6-13-1-f06: Enzymatic scavenging of the reactive oxygen species H2O2 from early 5th instar larvalHeliothis virescens plasma reduces virucidal activity. PBS, No plasma control; Cat, catalase (100 U/ml) control; Cat+Plasma, catalase incubated with plasma; superoxide dismutase (100 U/ml) control; superoxide dismutase +Plasma, incubation of plasma with the enzyme superoxide dismutase (100 U/ml). The enzymes were added to diluted plasma samples before the addition ofHzSNPV (letters indicate significant differences between treatments; n = 4, mean ± SEM).

Mentions: Addition of the enzyme catalase, which inactivates H2O2, to diluted H. virescens plasma partially inhibited the virucidal activity (n = 4, p < 0.013, Student-Newman-Keuls multiple comparison test; Fig. 6). Addition of the same amount of catalase to HzAM-1 cells had no effect on the survival of added HzSNPV. Addition of the enzyme superoxide dismutase, which inactivates superoxide, had no effect on virucidal activity. Addition of superoxide dismutase to HzAM-1 also had no effect on virus survival. This suggests that at least some of the virucidal enzymatic free radicals generated by HvPO may be H2O2.


Plasma phenoloxidase of the larval tobacco budworm, Heliothis virescens, is virucidal.

Shelby KS, Popham HJ - J. Insect Sci. (2006)

Enzymatic scavenging of the reactive oxygen species H2O2 from early 5th instar larvalHeliothis virescens plasma reduces virucidal activity. PBS, No plasma control; Cat, catalase (100 U/ml) control; Cat+Plasma, catalase incubated with plasma; superoxide dismutase (100 U/ml) control; superoxide dismutase +Plasma, incubation of plasma with the enzyme superoxide dismutase (100 U/ml). The enzymes were added to diluted plasma samples before the addition ofHzSNPV (letters indicate significant differences between treatments; n = 4, mean ± SEM).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2990302&req=5

i1536-2442-6-13-1-f06: Enzymatic scavenging of the reactive oxygen species H2O2 from early 5th instar larvalHeliothis virescens plasma reduces virucidal activity. PBS, No plasma control; Cat, catalase (100 U/ml) control; Cat+Plasma, catalase incubated with plasma; superoxide dismutase (100 U/ml) control; superoxide dismutase +Plasma, incubation of plasma with the enzyme superoxide dismutase (100 U/ml). The enzymes were added to diluted plasma samples before the addition ofHzSNPV (letters indicate significant differences between treatments; n = 4, mean ± SEM).
Mentions: Addition of the enzyme catalase, which inactivates H2O2, to diluted H. virescens plasma partially inhibited the virucidal activity (n = 4, p < 0.013, Student-Newman-Keuls multiple comparison test; Fig. 6). Addition of the same amount of catalase to HzAM-1 cells had no effect on the survival of added HzSNPV. Addition of the enzyme superoxide dismutase, which inactivates superoxide, had no effect on virucidal activity. Addition of superoxide dismutase to HzAM-1 also had no effect on virus survival. This suggests that at least some of the virucidal enzymatic free radicals generated by HvPO may be H2O2.

Bottom Line: Preliminary results indicated that phenoloxidase is primarily responsible for this virucidal effect.Addition of the enzyme superoxide dismutase to plasma did not affect virucidal activity; however addition of catalase had an inhibitory effect.Inhibitors of nitric oxide synthase activity did not affect virucidal activity.

View Article: PubMed Central - PubMed

Affiliation: USDA, Agricultural Research Service, Biological Control of Insects Research Laboratory, Columbia, MO 65203, USA. shelbyk@missouri.edu

ABSTRACT
Heliothis virescens larval plasma contains high levels of an antiviral activity against the budded form of the Helicoverpa zea single nucleopolyhedrovirus (HzSNPV) in vitro. Preliminary results indicated that phenoloxidase is primarily responsible for this virucidal effect. However it is known that other enzymes that generate antimicrobial reactive oxygen intermediates and reactive nitrogen intermediates are present in hemolymph that could contribute to the observed virucidal activity. To elucidate the contributions of phenoloxidase and other candidate activities to plasma innate immune response against baculovirus infection specific metabolic inhibitors were used. In vitro the general inhibitors of melanization (N-acetyl cysteine, ascorbate and glutathione), and specific inhibitors of phenoloxidase (phenylthiourea and Kojic acid), completely blocked virucidal activity up to the level seen in controls. Addition of the enzyme superoxide dismutase to plasma did not affect virucidal activity; however addition of catalase had an inhibitory effect. Inhibitors of nitric oxide synthase activity did not affect virucidal activity. Our results confirm that phenoloxidase is the predominate activity in larval plasma accounting for inactivation of HzSNPV in vitro, and that phenoloxidase-dependent H(2)O(2) production may contribute to this virucidal activity.

Show MeSH
Related in: MedlinePlus