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Alveolar macrophages support interferon gamma-mediated viral clearance in RSV-infected neonatal mice.

Eichinger KM, Egaña L, Orend JG, Resetar E, Anderson KB, Patel R, Empey KM - Respir. Res. (2015)

Bottom Line: The presence of AMs were independently associated with improved RSV clearance, whereas AM depletion but not IFNγ exposure, significantly impaired weight gain in RSV-infected neonates.Early reductions in viral burden are likely to have profound short- and long-term immune effects in the vulnerable post-natally developing lung environment.Studies are ongoing to elucidate the pathologic effects associated with early versus delayed RSV clearance in developing neonatal airways.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacy and Therapeutics, Center for Clinical Pharmaceutical Sciences, University of Pittsburgh School of Pharmacy, Pittsburgh, PA, USA.

ABSTRACT

Background: Poor interferon gamma (IFNγ) production during respiratory syncytial virus (RSV) is associated with prolonged viral clearance and increased disease severity in neonatal mice and humans. We previously showed that intra-nasal delivery of IFNγ significantly enhances RSV clearance from neonatal lungs prior to observed T-lymphocyte recruitment or activation, suggesting an innate immune mechanism of viral clearance. We further showed that alveolar macrophages dominate the RSV-infected neonatal airways relative to adults, consistent with human neonatal autopsy data. Therefore, the goal of this work was to determine the role of neonatal alveolar macrophages in IFNγ-mediated RSV clearance.

Methods: Clodronate liposomes, flow cytometry, viral plaque assays, and histology were used to examine the role of alveolar macrophages (AMs) and the effects of intra-nasal IFNγ in RSV infected neonatal Balb/c mice. The functional outcomes of AM depletion were determined quantitatively by viral titers using plaque assay. Illness was assessed by measuring reduced weight gain.

Results: AM activation during RSV infection was age-dependent and correlated tightly with IFNγ exposure. Higher doses of IFNγ more efficiently stimulated AM activation and expedited RSV clearance without significantly affecting weight gain. The presence of AMs were independently associated with improved RSV clearance, whereas AM depletion but not IFNγ exposure, significantly impaired weight gain in RSV-infected neonates.

Conclusion: We show here for the first time, that IFNγ is critical for neonatal RSV clearance and that it depends, in part, on alveolar macrophages (AMs) for efficient viral clearing effects. Early reductions in viral burden are likely to have profound short- and long-term immune effects in the vulnerable post-natally developing lung environment. Studies are ongoing to elucidate the pathologic effects associated with early versus delayed RSV clearance in developing neonatal airways.

No MeSH data available.


Related in: MedlinePlus

Age-dependent IFNγ pharmacokinetics result in differential AM activation. AUCs were determined for uninfected pup and adult BALB/c mice following a single i.n. dose of IFNγ (16 ng/g) through intense sampling from LD over 48 h (a). Biologically, this translated to significantly greater activation of AMs (b) in adults beginning at 8 h and continuing through 48 and 24 h, respectively. Data represent ≥ 3 mice per group and 2 separate experiments. * Indicates significant differences based on a 2-way ANOVA with a Bonferroni post-test, between groups at the indicated time points; p < 0.5
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Fig3: Age-dependent IFNγ pharmacokinetics result in differential AM activation. AUCs were determined for uninfected pup and adult BALB/c mice following a single i.n. dose of IFNγ (16 ng/g) through intense sampling from LD over 48 h (a). Biologically, this translated to significantly greater activation of AMs (b) in adults beginning at 8 h and continuing through 48 and 24 h, respectively. Data represent ≥ 3 mice per group and 2 separate experiments. * Indicates significant differences based on a 2-way ANOVA with a Bonferroni post-test, between groups at the indicated time points; p < 0.5

Mentions: Based on the age-dependent associations between IFNγ exposure with AM activation and viral clearance, we next sought to determine the effect of age on the IFNγ area under the concentration-time (AUC) curve. Following a single 16 ng/g dose of i.n. IFNγ, AUCs averaged 3.6 times greater in adults versus neonatal mice (Fig. 3a). This was associated with significant increases in the expression of MHC class II on adult compared to neonatal CD11c + CD11b- cells through 48 h (Fig. 3b). To optimize neonatal IFNγ AUCs, a non-compartmental pharmacokinetic approach, as described in our methods, estimated a new 60 ng/g dose of i.n. IFNγ would be required to achieve adult-level AUCs (280 ng*hr/ml) in the neonatal mice. Thus, we predicted that 60 ng/g of i.n. IFNγ would generate faster and greater expression of MHC class II on CD11c + CD11b- cells, with corresponding enhancement of RSV clearance.Fig. 3


Alveolar macrophages support interferon gamma-mediated viral clearance in RSV-infected neonatal mice.

Eichinger KM, Egaña L, Orend JG, Resetar E, Anderson KB, Patel R, Empey KM - Respir. Res. (2015)

Age-dependent IFNγ pharmacokinetics result in differential AM activation. AUCs were determined for uninfected pup and adult BALB/c mice following a single i.n. dose of IFNγ (16 ng/g) through intense sampling from LD over 48 h (a). Biologically, this translated to significantly greater activation of AMs (b) in adults beginning at 8 h and continuing through 48 and 24 h, respectively. Data represent ≥ 3 mice per group and 2 separate experiments. * Indicates significant differences based on a 2-way ANOVA with a Bonferroni post-test, between groups at the indicated time points; p < 0.5
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4594958&req=5

Fig3: Age-dependent IFNγ pharmacokinetics result in differential AM activation. AUCs were determined for uninfected pup and adult BALB/c mice following a single i.n. dose of IFNγ (16 ng/g) through intense sampling from LD over 48 h (a). Biologically, this translated to significantly greater activation of AMs (b) in adults beginning at 8 h and continuing through 48 and 24 h, respectively. Data represent ≥ 3 mice per group and 2 separate experiments. * Indicates significant differences based on a 2-way ANOVA with a Bonferroni post-test, between groups at the indicated time points; p < 0.5
Mentions: Based on the age-dependent associations between IFNγ exposure with AM activation and viral clearance, we next sought to determine the effect of age on the IFNγ area under the concentration-time (AUC) curve. Following a single 16 ng/g dose of i.n. IFNγ, AUCs averaged 3.6 times greater in adults versus neonatal mice (Fig. 3a). This was associated with significant increases in the expression of MHC class II on adult compared to neonatal CD11c + CD11b- cells through 48 h (Fig. 3b). To optimize neonatal IFNγ AUCs, a non-compartmental pharmacokinetic approach, as described in our methods, estimated a new 60 ng/g dose of i.n. IFNγ would be required to achieve adult-level AUCs (280 ng*hr/ml) in the neonatal mice. Thus, we predicted that 60 ng/g of i.n. IFNγ would generate faster and greater expression of MHC class II on CD11c + CD11b- cells, with corresponding enhancement of RSV clearance.Fig. 3

Bottom Line: The presence of AMs were independently associated with improved RSV clearance, whereas AM depletion but not IFNγ exposure, significantly impaired weight gain in RSV-infected neonates.Early reductions in viral burden are likely to have profound short- and long-term immune effects in the vulnerable post-natally developing lung environment.Studies are ongoing to elucidate the pathologic effects associated with early versus delayed RSV clearance in developing neonatal airways.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacy and Therapeutics, Center for Clinical Pharmaceutical Sciences, University of Pittsburgh School of Pharmacy, Pittsburgh, PA, USA.

ABSTRACT

Background: Poor interferon gamma (IFNγ) production during respiratory syncytial virus (RSV) is associated with prolonged viral clearance and increased disease severity in neonatal mice and humans. We previously showed that intra-nasal delivery of IFNγ significantly enhances RSV clearance from neonatal lungs prior to observed T-lymphocyte recruitment or activation, suggesting an innate immune mechanism of viral clearance. We further showed that alveolar macrophages dominate the RSV-infected neonatal airways relative to adults, consistent with human neonatal autopsy data. Therefore, the goal of this work was to determine the role of neonatal alveolar macrophages in IFNγ-mediated RSV clearance.

Methods: Clodronate liposomes, flow cytometry, viral plaque assays, and histology were used to examine the role of alveolar macrophages (AMs) and the effects of intra-nasal IFNγ in RSV infected neonatal Balb/c mice. The functional outcomes of AM depletion were determined quantitatively by viral titers using plaque assay. Illness was assessed by measuring reduced weight gain.

Results: AM activation during RSV infection was age-dependent and correlated tightly with IFNγ exposure. Higher doses of IFNγ more efficiently stimulated AM activation and expedited RSV clearance without significantly affecting weight gain. The presence of AMs were independently associated with improved RSV clearance, whereas AM depletion but not IFNγ exposure, significantly impaired weight gain in RSV-infected neonates.

Conclusion: We show here for the first time, that IFNγ is critical for neonatal RSV clearance and that it depends, in part, on alveolar macrophages (AMs) for efficient viral clearing effects. Early reductions in viral burden are likely to have profound short- and long-term immune effects in the vulnerable post-natally developing lung environment. Studies are ongoing to elucidate the pathologic effects associated with early versus delayed RSV clearance in developing neonatal airways.

No MeSH data available.


Related in: MedlinePlus