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Expression of chicken interleukin-2 by a highly virulent strain of Newcastle disease virus leads to decreased systemic viral load but does not significantly affect mortality in chickens.

Susta L, Diel DG, Courtney S, Cardenas-Garcia S, Sundick RS, Miller PJ, Brown CC, Afonso CL - Virol. J. (2015)

Bottom Line: Compared to rZJ1-GFP strain, rZJ1-IL2 caused milder lesions and displayed decreased viral load in blood, spleen and mucosal secretions of infected birds.Further, expression of IL-2 did not significantly affect the ICPI scores, compared to rZJ1-GFP strain.Increased expression of chicken IL-2 during virulent NDV replication in naïve chickens decreased viral titers in blood, spleens, oral and cloacal secretions on day 4-5 post infection.

View Article: PubMed Central - PubMed

Affiliation: USDA ARS, Southeast Poultry Research Laboratory, 934 College Station Rd, Athens, GA, 30605, USA. lsusta@uoguelph.ca.

ABSTRACT

Background: In mammals, interleukin 2 (IL-2) has been shown to decrease replication or attenuate pathogenicity of numerous viral pathogens (herpes simplex virus, vaccinia virus, human respiratory syncytial virus, human immunodeficiency virus) by activating natural killer cells (NK), cytotoxic T lymphocytes and expanding subsets of memory cells. In chickens, IL-2 has been shown to activate T cells, and as such it might have the potential to affect replication and pathogenesis of Newcastle disease virus (NDV).

Methods: To assess the effect of IL-2 during NDV infection in chickens, we produced a recombinant virulent NDV strain expressing chicken IL-2 (rZJ1-IL2). The effects of IL-2 expression were investigated in vivo using the intracerebral pathogenicity index (ICPI) in day-old chicks and pathogenesis experiments in 4-week-old chickens. In these studies, rZJ1-IL2 was compared to a control virus expressing the green fluorescent protein (rZJ1-GFP). Assessed parameters included survival curves, detailed histological and immunohistochemical grading of lesions in multiple organs, and virus isolation in blood, spleen and mucosal secretions of infected birds.

Results: At the site of infection (eyelid), expression of IL-2 was demonstrated in areas of rZJ-IL2 replication, confirming IL-2 production in vivo. Compared to rZJ1-GFP strain, rZJ1-IL2 caused milder lesions and displayed decreased viral load in blood, spleen and mucosal secretions of infected birds. In the rZJ1-IL2-infected group, virus level in the blood peaked at day 4 post-infection (pi) (10(3.46) EID50 /0.1 ml) and drastically decreased at day 5 pi (10(0.9) EID50/0.1 ml), while in the rZJ1-GFP-infected group virus levels in the blood reached 10(5.35) EID50/0.1 ml at day 5. However, rZJ1-IL2-infected groups presented survival curves similar to control birds infected with rZJ1-GFP, with comparable clinical signs and 100 % mortality. Further, expression of IL-2 did not significantly affect the ICPI scores, compared to rZJ1-GFP strain.

Conclusions: Increased expression of chicken IL-2 during virulent NDV replication in naïve chickens decreased viral titers in blood, spleens, oral and cloacal secretions on day 4-5 post infection. This is consistent with the previously described role of IL-2 in enhancing the clearance of viruses in mammals, such as human respiratory syncytial virus.

No MeSH data available.


Related in: MedlinePlus

Photomicrographs illustrating immunohistochemistry (IHC) for NDV NP (first column of panels) and IL-2 (second column of panels) on sections of eyelids. Tissues were harvested from 4-week-old White Leghorn chickens infected with rZJ1-IL2 (a-d) and rZJ1-GFP (e, f) at day 5 pi. Alkaline phosphatase method and hematoxylin counterstain. At low magnification, in the eyelids of rZJ1-IL2-infected birds, the same areas that are immunolabeled for NDV NP are also positive for chicken IL-2 (dotted circles). At higher magnification, scattered cells in consecutive sections are immunolabeled for both NDV NP and IL-2 (arrows). No signal for IL-2 is observed in sections of eyelids from rZJ1-GFP-infected animals (f)
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Fig6: Photomicrographs illustrating immunohistochemistry (IHC) for NDV NP (first column of panels) and IL-2 (second column of panels) on sections of eyelids. Tissues were harvested from 4-week-old White Leghorn chickens infected with rZJ1-IL2 (a-d) and rZJ1-GFP (e, f) at day 5 pi. Alkaline phosphatase method and hematoxylin counterstain. At low magnification, in the eyelids of rZJ1-IL2-infected birds, the same areas that are immunolabeled for NDV NP are also positive for chicken IL-2 (dotted circles). At higher magnification, scattered cells in consecutive sections are immunolabeled for both NDV NP and IL-2 (arrows). No signal for IL-2 is observed in sections of eyelids from rZJ1-GFP-infected animals (f)

Mentions: Sections of eyelid, which showed highest level of NDV replication by IHC, were chosen to assess IL-2 production by using IHC against chicken IL-2. Eyelids from rZJ1-IL2- and rZJ1-GFP-infected birds at day 4 and 5 pi were assayed for IHC for both NDV NP (Fig. 6, panels a, c, e) and chicken IL-2 (Fig. 6, panels b, d, f). Results showed that the all the eyelids of rZJ1-IL2-infected birds showed positive staining for IL-2 and NDV NP, while the eyelids of rZJ1-GFP-infected were negative for IL-2 and positive for NDV NP. In consecutive sections, NDV NP and IL-2 expression could be observed in the same areas, and occasionally in the same cells (in Fig. 6, compare panels a with b and c with d). These results show that IL-2 is expressed in the context of rZJ1-IL2 virus replication in vivo.Fig. 6


Expression of chicken interleukin-2 by a highly virulent strain of Newcastle disease virus leads to decreased systemic viral load but does not significantly affect mortality in chickens.

Susta L, Diel DG, Courtney S, Cardenas-Garcia S, Sundick RS, Miller PJ, Brown CC, Afonso CL - Virol. J. (2015)

Photomicrographs illustrating immunohistochemistry (IHC) for NDV NP (first column of panels) and IL-2 (second column of panels) on sections of eyelids. Tissues were harvested from 4-week-old White Leghorn chickens infected with rZJ1-IL2 (a-d) and rZJ1-GFP (e, f) at day 5 pi. Alkaline phosphatase method and hematoxylin counterstain. At low magnification, in the eyelids of rZJ1-IL2-infected birds, the same areas that are immunolabeled for NDV NP are also positive for chicken IL-2 (dotted circles). At higher magnification, scattered cells in consecutive sections are immunolabeled for both NDV NP and IL-2 (arrows). No signal for IL-2 is observed in sections of eyelids from rZJ1-GFP-infected animals (f)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4528788&req=5

Fig6: Photomicrographs illustrating immunohistochemistry (IHC) for NDV NP (first column of panels) and IL-2 (second column of panels) on sections of eyelids. Tissues were harvested from 4-week-old White Leghorn chickens infected with rZJ1-IL2 (a-d) and rZJ1-GFP (e, f) at day 5 pi. Alkaline phosphatase method and hematoxylin counterstain. At low magnification, in the eyelids of rZJ1-IL2-infected birds, the same areas that are immunolabeled for NDV NP are also positive for chicken IL-2 (dotted circles). At higher magnification, scattered cells in consecutive sections are immunolabeled for both NDV NP and IL-2 (arrows). No signal for IL-2 is observed in sections of eyelids from rZJ1-GFP-infected animals (f)
Mentions: Sections of eyelid, which showed highest level of NDV replication by IHC, were chosen to assess IL-2 production by using IHC against chicken IL-2. Eyelids from rZJ1-IL2- and rZJ1-GFP-infected birds at day 4 and 5 pi were assayed for IHC for both NDV NP (Fig. 6, panels a, c, e) and chicken IL-2 (Fig. 6, panels b, d, f). Results showed that the all the eyelids of rZJ1-IL2-infected birds showed positive staining for IL-2 and NDV NP, while the eyelids of rZJ1-GFP-infected were negative for IL-2 and positive for NDV NP. In consecutive sections, NDV NP and IL-2 expression could be observed in the same areas, and occasionally in the same cells (in Fig. 6, compare panels a with b and c with d). These results show that IL-2 is expressed in the context of rZJ1-IL2 virus replication in vivo.Fig. 6

Bottom Line: Compared to rZJ1-GFP strain, rZJ1-IL2 caused milder lesions and displayed decreased viral load in blood, spleen and mucosal secretions of infected birds.Further, expression of IL-2 did not significantly affect the ICPI scores, compared to rZJ1-GFP strain.Increased expression of chicken IL-2 during virulent NDV replication in naïve chickens decreased viral titers in blood, spleens, oral and cloacal secretions on day 4-5 post infection.

View Article: PubMed Central - PubMed

Affiliation: USDA ARS, Southeast Poultry Research Laboratory, 934 College Station Rd, Athens, GA, 30605, USA. lsusta@uoguelph.ca.

ABSTRACT

Background: In mammals, interleukin 2 (IL-2) has been shown to decrease replication or attenuate pathogenicity of numerous viral pathogens (herpes simplex virus, vaccinia virus, human respiratory syncytial virus, human immunodeficiency virus) by activating natural killer cells (NK), cytotoxic T lymphocytes and expanding subsets of memory cells. In chickens, IL-2 has been shown to activate T cells, and as such it might have the potential to affect replication and pathogenesis of Newcastle disease virus (NDV).

Methods: To assess the effect of IL-2 during NDV infection in chickens, we produced a recombinant virulent NDV strain expressing chicken IL-2 (rZJ1-IL2). The effects of IL-2 expression were investigated in vivo using the intracerebral pathogenicity index (ICPI) in day-old chicks and pathogenesis experiments in 4-week-old chickens. In these studies, rZJ1-IL2 was compared to a control virus expressing the green fluorescent protein (rZJ1-GFP). Assessed parameters included survival curves, detailed histological and immunohistochemical grading of lesions in multiple organs, and virus isolation in blood, spleen and mucosal secretions of infected birds.

Results: At the site of infection (eyelid), expression of IL-2 was demonstrated in areas of rZJ-IL2 replication, confirming IL-2 production in vivo. Compared to rZJ1-GFP strain, rZJ1-IL2 caused milder lesions and displayed decreased viral load in blood, spleen and mucosal secretions of infected birds. In the rZJ1-IL2-infected group, virus level in the blood peaked at day 4 post-infection (pi) (10(3.46) EID50 /0.1 ml) and drastically decreased at day 5 pi (10(0.9) EID50/0.1 ml), while in the rZJ1-GFP-infected group virus levels in the blood reached 10(5.35) EID50/0.1 ml at day 5. However, rZJ1-IL2-infected groups presented survival curves similar to control birds infected with rZJ1-GFP, with comparable clinical signs and 100 % mortality. Further, expression of IL-2 did not significantly affect the ICPI scores, compared to rZJ1-GFP strain.

Conclusions: Increased expression of chicken IL-2 during virulent NDV replication in naïve chickens decreased viral titers in blood, spleens, oral and cloacal secretions on day 4-5 post infection. This is consistent with the previously described role of IL-2 in enhancing the clearance of viruses in mammals, such as human respiratory syncytial virus.

No MeSH data available.


Related in: MedlinePlus