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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 hematoxylin and eosin staining (HE, first and third rows of panels) and immunohistochemistry (IHC, second and fourth rows of panels) on sections of eyelid (panels a-d) and spleen (e-f) at day 5 pi. Tissues were harvested from 4-week-old White Leghorn chickens infected with rZJ1-IL2 (first column of panels), and rZJ1-GFP (second column of panels). Alkaline phosphatase method and hematoxylin counterstain. In the eyelid, histopathological changes consist of severe edema (asterisks), which markedly expands the submucosa, accumulation of pleomorphic cellular infiltrate (macrophages, heterophils, lymphocytes), exudation of fibrin, and multifocal areas of coagulative necrosis. This severe conjunctivitis is similar in intensity in both rZJ1-Il2 (panel a) and rZJ1-GFP (panel b) groups. Presence of lesion in the eyelid is associated with positive immunohistochemical labeling, which is intense and diffuse in rZJ1-GFP-infected birds (panel d), while in rZJ1-IL2-infected birds is less intense and multifocal (panel c). In the spleen, rZJ1-IL2-infected birds display mild to moderate lymphoid depletion and accumulation of prominent macrophage in the ellipsoid areas, which appear confluent (dashed lines, panel e). These changes are associated with minimal NDV immunohistochemical labeling, which is not present at day 5 pi (panel g). Birds infected with rZJ1-GFP show severe lesions in the spleen, consisting of lymphoid depletion, prominent macrophages, exudation of fibrin and accumulation of necrotic debris (arrows, panel f). These lesions are associated with intense and diffuse immunohistochemical labeling for NDV (panel h)
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Fig5: Photomicrographs illustrating hematoxylin and eosin staining (HE, first and third rows of panels) and immunohistochemistry (IHC, second and fourth rows of panels) on sections of eyelid (panels a-d) and spleen (e-f) at day 5 pi. Tissues were harvested from 4-week-old White Leghorn chickens infected with rZJ1-IL2 (first column of panels), and rZJ1-GFP (second column of panels). Alkaline phosphatase method and hematoxylin counterstain. In the eyelid, histopathological changes consist of severe edema (asterisks), which markedly expands the submucosa, accumulation of pleomorphic cellular infiltrate (macrophages, heterophils, lymphocytes), exudation of fibrin, and multifocal areas of coagulative necrosis. This severe conjunctivitis is similar in intensity in both rZJ1-Il2 (panel a) and rZJ1-GFP (panel b) groups. Presence of lesion in the eyelid is associated with positive immunohistochemical labeling, which is intense and diffuse in rZJ1-GFP-infected birds (panel d), while in rZJ1-IL2-infected birds is less intense and multifocal (panel c). In the spleen, rZJ1-IL2-infected birds display mild to moderate lymphoid depletion and accumulation of prominent macrophage in the ellipsoid areas, which appear confluent (dashed lines, panel e). These changes are associated with minimal NDV immunohistochemical labeling, which is not present at day 5 pi (panel g). Birds infected with rZJ1-GFP show severe lesions in the spleen, consisting of lymphoid depletion, prominent macrophages, exudation of fibrin and accumulation of necrotic debris (arrows, panel f). These lesions are associated with intense and diffuse immunohistochemical labeling for NDV (panel h)

Mentions: Severity of histopathological lesions in selected organs is summarized in Table 2. Overall, lesions between the two groups had similar severity at day 2 and 3 pi, while significant differences became evident at day 4 and 5 pi, when lesions were markedly milder in rZJ1-IL2- compared to rZJ1-GFP-infected birds (Table 2). In both groups at days 2 and 3 pi, there was prominent conjunctivitis, with abundant infiltration of inflammatory cells and extensive edema that progressed at days 4 and 5 pi displaying fibrin exudation and necrosis (Fig. 5, panel a, b). At day 2 and 3 pi, in both rZJ1-IL2- and rZJ1-GFP-infected birds, the spleen showed prominent macrophages compared to mock-infected birds, resulting in overall increased size of the Schweigger-Seidel sheaths (splenic ellipsoids), which appeared almost confluent.Table 2


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 hematoxylin and eosin staining (HE, first and third rows of panels) and immunohistochemistry (IHC, second and fourth rows of panels) on sections of eyelid (panels a-d) and spleen (e-f) at day 5 pi. Tissues were harvested from 4-week-old White Leghorn chickens infected with rZJ1-IL2 (first column of panels), and rZJ1-GFP (second column of panels). Alkaline phosphatase method and hematoxylin counterstain. In the eyelid, histopathological changes consist of severe edema (asterisks), which markedly expands the submucosa, accumulation of pleomorphic cellular infiltrate (macrophages, heterophils, lymphocytes), exudation of fibrin, and multifocal areas of coagulative necrosis. This severe conjunctivitis is similar in intensity in both rZJ1-Il2 (panel a) and rZJ1-GFP (panel b) groups. Presence of lesion in the eyelid is associated with positive immunohistochemical labeling, which is intense and diffuse in rZJ1-GFP-infected birds (panel d), while in rZJ1-IL2-infected birds is less intense and multifocal (panel c). In the spleen, rZJ1-IL2-infected birds display mild to moderate lymphoid depletion and accumulation of prominent macrophage in the ellipsoid areas, which appear confluent (dashed lines, panel e). These changes are associated with minimal NDV immunohistochemical labeling, which is not present at day 5 pi (panel g). Birds infected with rZJ1-GFP show severe lesions in the spleen, consisting of lymphoid depletion, prominent macrophages, exudation of fibrin and accumulation of necrotic debris (arrows, panel f). These lesions are associated with intense and diffuse immunohistochemical labeling for NDV (panel h)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4528788&req=5

Fig5: Photomicrographs illustrating hematoxylin and eosin staining (HE, first and third rows of panels) and immunohistochemistry (IHC, second and fourth rows of panels) on sections of eyelid (panels a-d) and spleen (e-f) at day 5 pi. Tissues were harvested from 4-week-old White Leghorn chickens infected with rZJ1-IL2 (first column of panels), and rZJ1-GFP (second column of panels). Alkaline phosphatase method and hematoxylin counterstain. In the eyelid, histopathological changes consist of severe edema (asterisks), which markedly expands the submucosa, accumulation of pleomorphic cellular infiltrate (macrophages, heterophils, lymphocytes), exudation of fibrin, and multifocal areas of coagulative necrosis. This severe conjunctivitis is similar in intensity in both rZJ1-Il2 (panel a) and rZJ1-GFP (panel b) groups. Presence of lesion in the eyelid is associated with positive immunohistochemical labeling, which is intense and diffuse in rZJ1-GFP-infected birds (panel d), while in rZJ1-IL2-infected birds is less intense and multifocal (panel c). In the spleen, rZJ1-IL2-infected birds display mild to moderate lymphoid depletion and accumulation of prominent macrophage in the ellipsoid areas, which appear confluent (dashed lines, panel e). These changes are associated with minimal NDV immunohistochemical labeling, which is not present at day 5 pi (panel g). Birds infected with rZJ1-GFP show severe lesions in the spleen, consisting of lymphoid depletion, prominent macrophages, exudation of fibrin and accumulation of necrotic debris (arrows, panel f). These lesions are associated with intense and diffuse immunohistochemical labeling for NDV (panel h)
Mentions: Severity of histopathological lesions in selected organs is summarized in Table 2. Overall, lesions between the two groups had similar severity at day 2 and 3 pi, while significant differences became evident at day 4 and 5 pi, when lesions were markedly milder in rZJ1-IL2- compared to rZJ1-GFP-infected birds (Table 2). In both groups at days 2 and 3 pi, there was prominent conjunctivitis, with abundant infiltration of inflammatory cells and extensive edema that progressed at days 4 and 5 pi displaying fibrin exudation and necrosis (Fig. 5, panel a, b). At day 2 and 3 pi, in both rZJ1-IL2- and rZJ1-GFP-infected birds, the spleen showed prominent macrophages compared to mock-infected birds, resulting in overall increased size of the Schweigger-Seidel sheaths (splenic ellipsoids), which appeared almost confluent.Table 2

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