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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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Ascorbic acid inhibits the in vitro plasma virucidal activity present in 5th instar larval Heliothis virescens HzSNPV. Following a 1 hr incubation with HzSNPV plasma was assayed for virucidal activity (letters indicate significant differences between treatments; n = 4, mean ± SEM).
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i1536-2442-6-13-1-f502: Ascorbic acid inhibits the in vitro plasma virucidal activity present in 5th instar larval Heliothis virescens HzSNPV. Following a 1 hr incubation with HzSNPV plasma was assayed for virucidal activity (letters indicate significant differences between treatments; n = 4, mean ± SEM).

Mentions: Plasma collected from early 5th instar H. virescens larvae reared on basal diet, and from larvae reared on diets supplemented with from 4.8 to 14.4 mg/ml ascorbic acid, did not exhibit significant inhibition of virucidal activity (n = 4, p < 0.001, Dunn’s method multiple comparison test; Fig. 5A). However, plasma collected from larvae reared on diets with from 24.0 to 48.0 mg/ml ascorbic acid contained no residual virucidal activity (Fig. 5A). Because high dietary levels of ascorbic acid may result in higher plasma concentrations of ascorbic acid it is probable that HvPO activity was reduced in these larvae. We did not measure plasma ascorbic acid concentrations following dietary supplementation. However, in support of the hypothesis, aliquots of the diluted plasma collected from larvae reared on the 24.0 and 48.0 mg/ml ascorbic acid diets failed to melanize. Aliquots of plasma collected from basal diet fed larvae, and 4.8 to 14.4 mg/ml ascorbic acid fed larvae did visibly melanize. Visible melanization of plasma aliquots correlated very strongly with plasma virucidal activity. Addition of increasing concentrations of ascorbic acid directly to plasma from larvae reared on basal diet exhibited a similar pattern of inhibition of virucidal activity (Fig. 5B). In vitro, virucidal activity was completely inhibited at concentrations of 10 and 50 mg/ml (n = 4, p < 0.002, Student-Newman-Keuls multiple comparison test; Fig. 5B).


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

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

Ascorbic acid inhibits the in vitro plasma virucidal activity present in 5th instar larval Heliothis virescens HzSNPV. Following a 1 hr incubation with HzSNPV plasma was assayed for virucidal activity (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-f502: Ascorbic acid inhibits the in vitro plasma virucidal activity present in 5th instar larval Heliothis virescens HzSNPV. Following a 1 hr incubation with HzSNPV plasma was assayed for virucidal activity (letters indicate significant differences between treatments; n = 4, mean ± SEM).
Mentions: Plasma collected from early 5th instar H. virescens larvae reared on basal diet, and from larvae reared on diets supplemented with from 4.8 to 14.4 mg/ml ascorbic acid, did not exhibit significant inhibition of virucidal activity (n = 4, p < 0.001, Dunn’s method multiple comparison test; Fig. 5A). However, plasma collected from larvae reared on diets with from 24.0 to 48.0 mg/ml ascorbic acid contained no residual virucidal activity (Fig. 5A). Because high dietary levels of ascorbic acid may result in higher plasma concentrations of ascorbic acid it is probable that HvPO activity was reduced in these larvae. We did not measure plasma ascorbic acid concentrations following dietary supplementation. However, in support of the hypothesis, aliquots of the diluted plasma collected from larvae reared on the 24.0 and 48.0 mg/ml ascorbic acid diets failed to melanize. Aliquots of plasma collected from basal diet fed larvae, and 4.8 to 14.4 mg/ml ascorbic acid fed larvae did visibly melanize. Visible melanization of plasma aliquots correlated very strongly with plasma virucidal activity. Addition of increasing concentrations of ascorbic acid directly to plasma from larvae reared on basal diet exhibited a similar pattern of inhibition of virucidal activity (Fig. 5B). In vitro, virucidal activity was completely inhibited at concentrations of 10 and 50 mg/ml (n = 4, p < 0.002, Student-Newman-Keuls multiple comparison test; Fig. 5B).

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