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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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Age-differential gene expression of IL-1ββ in tissue, plasma, BALF after RSV infection.Young and aged BALB/c mice (n = 4/group) were intranasally infected with a dose of 106 pfu/mouse of A2 or 105 pfu/mouse of rA2-L19F or 2-20 and total lung RNA was collected on time points indicated. (A) RNA transcripts of IL-1β were analyzed with qRT-PCR and represented as a relative ratio of target gene expression to endogenous mouse HPRT and examined with rA2-L19F, 2-20, or A2 at various timepoints. (B) Lung tissue collected and homogenized for plaque assay was used for protein analysis using standard ELISA. Levels of IL-1β from rA2-L19F and 2-20 infected young and aged mice were obtained in pg/mg of starting wet-lung tissue. Levels of IL-1β were unchanged in A2 RSV infections and are not shown. (C) Levels of IL-1β in serum and BALF were analyzed using standard ELISA. Serum and BALF were obtained from individual mice and not pooled (n>4 per group). Horizontal line indicates the limit of detection using the ELISA method. Data are represented as means ±SEM. Experiments were performed in triplicate.
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pone-0088764-g006: Age-differential gene expression of IL-1ββ in tissue, plasma, BALF after RSV infection.Young and aged BALB/c mice (n = 4/group) were intranasally infected with a dose of 106 pfu/mouse of A2 or 105 pfu/mouse of rA2-L19F or 2-20 and total lung RNA was collected on time points indicated. (A) RNA transcripts of IL-1β were analyzed with qRT-PCR and represented as a relative ratio of target gene expression to endogenous mouse HPRT and examined with rA2-L19F, 2-20, or A2 at various timepoints. (B) Lung tissue collected and homogenized for plaque assay was used for protein analysis using standard ELISA. Levels of IL-1β from rA2-L19F and 2-20 infected young and aged mice were obtained in pg/mg of starting wet-lung tissue. Levels of IL-1β were unchanged in A2 RSV infections and are not shown. (C) Levels of IL-1β in serum and BALF were analyzed using standard ELISA. Serum and BALF were obtained from individual mice and not pooled (n>4 per group). Horizontal line indicates the limit of detection using the ELISA method. Data are represented as means ±SEM. Experiments were performed in triplicate.

Mentions: We were interested in comparing antiviral gene induction observed with moderate dose of A2 with more virulent RSV strains that induce more severe pathology and mucin production in BALB/c mice [26]; therefore qRT-PCR was performed on individual aliquots of total lung RNA from mice infected with either moderate dose of non-mucogenic A2 (106 pfu/mouse) or low dose (105 pfu/mouse) of mucogenic RSV strains rA2-L19F or 2–20 (Fig. 6A). Gene expression of mouse IL-1β was normalized to endogenous mouse HPRT mRNA levels. IL-1β mRNA levels are significantly elevated in aged mice as compared to young in the absence of infections. Upon RSV rA2-L19F-infections, IL-1β is diminished in aged mice compared to young on days 1 and 5 dpi; by 8 dpi, levels are comparable between age groups. Conversely, IL-1β mRNA levels were similar between young and aged on 1 dpi with RSV strains 2–20 and A2, but by 8 dpi with either strain, gene expression of IL-1β in aged mice of exceeds that of young. Of interest, IL-1β mRNA expression from aged mice infected with RSV 2–20 and A2 dropped at 4 dpi or 5 dpi; these occurred inversely proportional to maximum peaks of RSV N transcripts.


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)

Age-differential gene expression of IL-1ββ in tissue, plasma, BALF after RSV infection.Young and aged BALB/c mice (n = 4/group) were intranasally infected with a dose of 106 pfu/mouse of A2 or 105 pfu/mouse of rA2-L19F or 2-20 and total lung RNA was collected on time points indicated. (A) RNA transcripts of IL-1β were analyzed with qRT-PCR and represented as a relative ratio of target gene expression to endogenous mouse HPRT and examined with rA2-L19F, 2-20, or A2 at various timepoints. (B) Lung tissue collected and homogenized for plaque assay was used for protein analysis using standard ELISA. Levels of IL-1β from rA2-L19F and 2-20 infected young and aged mice were obtained in pg/mg of starting wet-lung tissue. Levels of IL-1β were unchanged in A2 RSV infections and are not shown. (C) Levels of IL-1β in serum and BALF were analyzed using standard ELISA. Serum and BALF were obtained from individual mice and not pooled (n>4 per group). Horizontal line indicates the limit of detection using the ELISA method. Data are represented as means ±SEM. Experiments were performed in triplicate.
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Related In: Results  -  Collection

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pone-0088764-g006: Age-differential gene expression of IL-1ββ in tissue, plasma, BALF after RSV infection.Young and aged BALB/c mice (n = 4/group) were intranasally infected with a dose of 106 pfu/mouse of A2 or 105 pfu/mouse of rA2-L19F or 2-20 and total lung RNA was collected on time points indicated. (A) RNA transcripts of IL-1β were analyzed with qRT-PCR and represented as a relative ratio of target gene expression to endogenous mouse HPRT and examined with rA2-L19F, 2-20, or A2 at various timepoints. (B) Lung tissue collected and homogenized for plaque assay was used for protein analysis using standard ELISA. Levels of IL-1β from rA2-L19F and 2-20 infected young and aged mice were obtained in pg/mg of starting wet-lung tissue. Levels of IL-1β were unchanged in A2 RSV infections and are not shown. (C) Levels of IL-1β in serum and BALF were analyzed using standard ELISA. Serum and BALF were obtained from individual mice and not pooled (n>4 per group). Horizontal line indicates the limit of detection using the ELISA method. Data are represented as means ±SEM. Experiments were performed in triplicate.
Mentions: We were interested in comparing antiviral gene induction observed with moderate dose of A2 with more virulent RSV strains that induce more severe pathology and mucin production in BALB/c mice [26]; therefore qRT-PCR was performed on individual aliquots of total lung RNA from mice infected with either moderate dose of non-mucogenic A2 (106 pfu/mouse) or low dose (105 pfu/mouse) of mucogenic RSV strains rA2-L19F or 2–20 (Fig. 6A). Gene expression of mouse IL-1β was normalized to endogenous mouse HPRT mRNA levels. IL-1β mRNA levels are significantly elevated in aged mice as compared to young in the absence of infections. Upon RSV rA2-L19F-infections, IL-1β is diminished in aged mice compared to young on days 1 and 5 dpi; by 8 dpi, levels are comparable between age groups. Conversely, IL-1β mRNA levels were similar between young and aged on 1 dpi with RSV strains 2–20 and A2, but by 8 dpi with either strain, gene expression of IL-1β in aged mice of exceeds that of young. Of interest, IL-1β mRNA expression from aged mice infected with RSV 2–20 and A2 dropped at 4 dpi or 5 dpi; these occurred inversely proportional to maximum peaks of RSV N transcripts.

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