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Respiratory syncytial virus (RSV) infection in elderly mice results in altered antiviral gene expression and enhanced pathology.

Wong TM, Boyapalle S, Sampayo V, Nguyen HD, Bedi R, Kamath SG, Moore ML, Mohapatra S, Mohapatra SS - PLoS ONE (2014)

Bottom Line: The expression of five antiviral genes, including pro-inflammatory cytokines IL-1β and osteopontin (OPN), was altered by both age and infection, while age was associated with the expression of 15 antiviral genes.Both kinetics and magnitude of antiviral gene expression were diminished as a result of older age.In conclusion, this study demonstrates inherent differences in response to RSV infection in young vs. aged mice, accompanied by delayed antiviral gene induction and cytokine signaling.

View Article: PubMed Central - PubMed

Affiliation: Department of Internal Medicine, James A. Haley Veterans Affairs Hospital, Tampa, Florida, United States of America ; Division of Translational Medicine and Nanomedicine Research Center, Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America.

ABSTRACT
Elderly persons are more susceptible to RSV-induced pneumonia than young people, but the molecular mechanism underlying this susceptibility is not well understood. In this study, we used an aged mouse model of RSV-induced pneumonia to examine how aging alters the lung pathology, modulates antiviral gene expressions, and the production of inflammatory cytokines in response to RSV infection. Young (2-3 months) and aged (19-21 months) mice were intranasally infected with mucogenic or non-mucogenic RSV strains, lung histology was examined, and gene expression was analyzed. Upon infection with mucogenic strains of RSV, leukocyte infiltration in the airways was elevated and prolonged in aged mice compared to young mice. Minitab factorial analysis identified several antiviral genes that are influenced by age, infection, and a combination of both factors. The expression of five antiviral genes, including pro-inflammatory cytokines IL-1β and osteopontin (OPN), was altered by both age and infection, while age was associated with the expression of 15 antiviral genes. Both kinetics and magnitude of antiviral gene expression were diminished as a result of older age. In addition to delays in cytokine signaling and pattern recognition receptor induction, we found TLR7/8 signaling to be impaired in alveolar macrophages in aged mice. In vivo, induction of IL-1β and OPN were delayed but prolonged in aged mice upon RSV infection compared to young. In conclusion, this study demonstrates inherent differences in response to RSV infection in young vs. aged mice, accompanied by delayed antiviral gene induction and cytokine signaling.

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Aged mice have enhanced pathology upon infection with mucogenic RSV.(A) Young and aged mice were infected with a dose of 105 pfu/mouse of either RSV 2–20 or rA2-L19F or 106 pfu/mouse of A2 for comparison. Lungs were collected on days indicated and sectioned at 5 µm, air dried, then stained with PAS and counterstained with hematoxylin and eosin. Representative images of either aged or young mice are shown in two main columns, with rows indicating mock-infection or infection with either rA2-L19F, 2–20 or A2; scale bars indicate 200 µm (first column, 40X) or 40 µm (second column, 200X), respectively. At 40X magnification, hematoxylin stained nuclei were quantified with ImageJ analysis. Five bronchioles were quantified per field of view and at least 8 images were collected from a single mouse (n = 4/group). (B) Individual dots in the box plot represent a mean infiltration density count (# cells/mm2) from each mouse within a mock-infected or group infected with RSV. Significance was obtained through ANOVA and Fisher's exact post hoc test, p<0.05. Histological analysis was repeated in two separate experiments.
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pone-0088764-g001: Aged mice have enhanced pathology upon infection with mucogenic RSV.(A) Young and aged mice were infected with a dose of 105 pfu/mouse of either RSV 2–20 or rA2-L19F or 106 pfu/mouse of A2 for comparison. Lungs were collected on days indicated and sectioned at 5 µm, air dried, then stained with PAS and counterstained with hematoxylin and eosin. Representative images of either aged or young mice are shown in two main columns, with rows indicating mock-infection or infection with either rA2-L19F, 2–20 or A2; scale bars indicate 200 µm (first column, 40X) or 40 µm (second column, 200X), respectively. At 40X magnification, hematoxylin stained nuclei were quantified with ImageJ analysis. Five bronchioles were quantified per field of view and at least 8 images were collected from a single mouse (n = 4/group). (B) Individual dots in the box plot represent a mean infiltration density count (# cells/mm2) from each mouse within a mock-infected or group infected with RSV. Significance was obtained through ANOVA and Fisher's exact post hoc test, p<0.05. Histological analysis was repeated in two separate experiments.

Mentions: We infected young and aged BALB/c mice with the mucogenic RSV strains rA2-L19F and 2-20 and laboratory strain A2 to observe how aging affects mucogenesis and cell infiltration. Upon intranasal infection, cell infiltration was found to be greatest among aged mice between 4-5 dpi with rA2-L19F or 2-20, however pathology was less apparent in A2 infection (Fig. 1A). The pathology was still visible on day 8 in aged mice while infiltration was diminished in young mice. To compare the cellular clearance at late stages of infections, hematoxylin stained nuclei were quantified with ImageJ analysis and represented as infiltration density box plots at 8 dpi (Fig. 1B). Infection with RSV rA2-L19F and 2-20 resulted significant cell infiltration on 8dpi in aged mice, while young mice infected with 2-20, but not rA2-L19F, had significant cellular densities. Upon histological analysis of lungs obtained from rA2-L19F and 2-20 infected mice at 4 and 8 dpi, both young and aged mice have dense cell infiltration at 4 dpi (data not shown). Although not statistically significant, 2-20 infections in aged mice had a trend of delayed cellular clearance at 8 dpi as compared to young. In contrast, A2 did not induce substantial mucin production which was examined using PAS-stained lungs and color deconvolution analysis (data not shown). Although not statistically significant, we observed a trend of reduced mucin staining in the lungs of infected aged mice as compared to young and this was supported further with gene expression of MUC5AC (data not shown).


Respiratory syncytial virus (RSV) infection in elderly mice results in altered antiviral gene expression and enhanced pathology.

Wong TM, Boyapalle S, Sampayo V, Nguyen HD, Bedi R, Kamath SG, Moore ML, Mohapatra S, Mohapatra SS - PLoS ONE (2014)

Aged mice have enhanced pathology upon infection with mucogenic RSV.(A) Young and aged mice were infected with a dose of 105 pfu/mouse of either RSV 2–20 or rA2-L19F or 106 pfu/mouse of A2 for comparison. Lungs were collected on days indicated and sectioned at 5 µm, air dried, then stained with PAS and counterstained with hematoxylin and eosin. Representative images of either aged or young mice are shown in two main columns, with rows indicating mock-infection or infection with either rA2-L19F, 2–20 or A2; scale bars indicate 200 µm (first column, 40X) or 40 µm (second column, 200X), respectively. At 40X magnification, hematoxylin stained nuclei were quantified with ImageJ analysis. Five bronchioles were quantified per field of view and at least 8 images were collected from a single mouse (n = 4/group). (B) Individual dots in the box plot represent a mean infiltration density count (# cells/mm2) from each mouse within a mock-infected or group infected with RSV. Significance was obtained through ANOVA and Fisher's exact post hoc test, p<0.05. Histological analysis was repeated in two separate experiments.
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Related In: Results  -  Collection

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pone-0088764-g001: Aged mice have enhanced pathology upon infection with mucogenic RSV.(A) Young and aged mice were infected with a dose of 105 pfu/mouse of either RSV 2–20 or rA2-L19F or 106 pfu/mouse of A2 for comparison. Lungs were collected on days indicated and sectioned at 5 µm, air dried, then stained with PAS and counterstained with hematoxylin and eosin. Representative images of either aged or young mice are shown in two main columns, with rows indicating mock-infection or infection with either rA2-L19F, 2–20 or A2; scale bars indicate 200 µm (first column, 40X) or 40 µm (second column, 200X), respectively. At 40X magnification, hematoxylin stained nuclei were quantified with ImageJ analysis. Five bronchioles were quantified per field of view and at least 8 images were collected from a single mouse (n = 4/group). (B) Individual dots in the box plot represent a mean infiltration density count (# cells/mm2) from each mouse within a mock-infected or group infected with RSV. Significance was obtained through ANOVA and Fisher's exact post hoc test, p<0.05. Histological analysis was repeated in two separate experiments.
Mentions: We infected young and aged BALB/c mice with the mucogenic RSV strains rA2-L19F and 2-20 and laboratory strain A2 to observe how aging affects mucogenesis and cell infiltration. Upon intranasal infection, cell infiltration was found to be greatest among aged mice between 4-5 dpi with rA2-L19F or 2-20, however pathology was less apparent in A2 infection (Fig. 1A). The pathology was still visible on day 8 in aged mice while infiltration was diminished in young mice. To compare the cellular clearance at late stages of infections, hematoxylin stained nuclei were quantified with ImageJ analysis and represented as infiltration density box plots at 8 dpi (Fig. 1B). Infection with RSV rA2-L19F and 2-20 resulted significant cell infiltration on 8dpi in aged mice, while young mice infected with 2-20, but not rA2-L19F, had significant cellular densities. Upon histological analysis of lungs obtained from rA2-L19F and 2-20 infected mice at 4 and 8 dpi, both young and aged mice have dense cell infiltration at 4 dpi (data not shown). Although not statistically significant, 2-20 infections in aged mice had a trend of delayed cellular clearance at 8 dpi as compared to young. In contrast, A2 did not induce substantial mucin production which was examined using PAS-stained lungs and color deconvolution analysis (data not shown). Although not statistically significant, we observed a trend of reduced mucin staining in the lungs of infected aged mice as compared to young and this was supported further with gene expression of MUC5AC (data not shown).

Bottom Line: The expression of five antiviral genes, including pro-inflammatory cytokines IL-1β and osteopontin (OPN), was altered by both age and infection, while age was associated with the expression of 15 antiviral genes.Both kinetics and magnitude of antiviral gene expression were diminished as a result of older age.In conclusion, this study demonstrates inherent differences in response to RSV infection in young vs. aged mice, accompanied by delayed antiviral gene induction and cytokine signaling.

View Article: PubMed Central - PubMed

Affiliation: Department of Internal Medicine, James A. Haley Veterans Affairs Hospital, Tampa, Florida, United States of America ; Division of Translational Medicine and Nanomedicine Research Center, Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America.

ABSTRACT
Elderly persons are more susceptible to RSV-induced pneumonia than young people, but the molecular mechanism underlying this susceptibility is not well understood. In this study, we used an aged mouse model of RSV-induced pneumonia to examine how aging alters the lung pathology, modulates antiviral gene expressions, and the production of inflammatory cytokines in response to RSV infection. Young (2-3 months) and aged (19-21 months) mice were intranasally infected with mucogenic or non-mucogenic RSV strains, lung histology was examined, and gene expression was analyzed. Upon infection with mucogenic strains of RSV, leukocyte infiltration in the airways was elevated and prolonged in aged mice compared to young mice. Minitab factorial analysis identified several antiviral genes that are influenced by age, infection, and a combination of both factors. The expression of five antiviral genes, including pro-inflammatory cytokines IL-1β and osteopontin (OPN), was altered by both age and infection, while age was associated with the expression of 15 antiviral genes. Both kinetics and magnitude of antiviral gene expression were diminished as a result of older age. In addition to delays in cytokine signaling and pattern recognition receptor induction, we found TLR7/8 signaling to be impaired in alveolar macrophages in aged mice. In vivo, induction of IL-1β and OPN were delayed but prolonged in aged mice upon RSV infection compared to young. In conclusion, this study demonstrates inherent differences in response to RSV infection in young vs. aged mice, accompanied by delayed antiviral gene induction and cytokine signaling.

Show MeSH
Related in: MedlinePlus