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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

Inhaled IFNγ contributes to RSV clearance. Pup BALB/c or IFNγRKO mice were infected with RSV L19. Pups were treated with 16 ng/g of IFNγ or equal volumes of PBS on 1 and 3 dpi. Left lungs were harvested to quantify RSV using H&E plaque assays. * indicates p < 0.05 using a Kruskal-Wallis non-parametric analysis with Dunn’s multiple comparison test. Data represent the means and individual replicates for ≥ 3 mice per group and 2 separate experiments
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Fig1: Inhaled IFNγ contributes to RSV clearance. Pup BALB/c or IFNγRKO mice were infected with RSV L19. Pups were treated with 16 ng/g of IFNγ or equal volumes of PBS on 1 and 3 dpi. Left lungs were harvested to quantify RSV using H&E plaque assays. * indicates p < 0.05 using a Kruskal-Wallis non-parametric analysis with Dunn’s multiple comparison test. Data represent the means and individual replicates for ≥ 3 mice per group and 2 separate experiments

Mentions: We first sought to determine whether an absence of IFNγ signaling would alter viral clearance. To test this, viral clearance capacity was determined in IFNγR knock-out (IFNγRKO) mice compared to wild-type (WT) pups, both on a BALB/c background, with or without intranasal (i.n.) delivery of IFNγ as described in the methods (Fig. 1). Viral quantification by viral plaque assay at 4 dpi demonstrates that IFNγ does not kill RSV directly, but requires interaction with the IFNγR to elicit its anti-viral effects. No difference in viral titers between KO and WT pups confirms negligible production of endogenous IFNγ in early RSV infection, while reduced RSV titers in IFNγ-treated, WT controls suggests that intact IFNγ receptors are required for efficient RSV clearance.Fig. 1


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)

Inhaled IFNγ contributes to RSV clearance. Pup BALB/c or IFNγRKO mice were infected with RSV L19. Pups were treated with 16 ng/g of IFNγ or equal volumes of PBS on 1 and 3 dpi. Left lungs were harvested to quantify RSV using H&E plaque assays. * indicates p < 0.05 using a Kruskal-Wallis non-parametric analysis with Dunn’s multiple comparison test. Data represent the means and individual replicates for ≥ 3 mice per group and 2 separate experiments
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig1: Inhaled IFNγ contributes to RSV clearance. Pup BALB/c or IFNγRKO mice were infected with RSV L19. Pups were treated with 16 ng/g of IFNγ or equal volumes of PBS on 1 and 3 dpi. Left lungs were harvested to quantify RSV using H&E plaque assays. * indicates p < 0.05 using a Kruskal-Wallis non-parametric analysis with Dunn’s multiple comparison test. Data represent the means and individual replicates for ≥ 3 mice per group and 2 separate experiments
Mentions: We first sought to determine whether an absence of IFNγ signaling would alter viral clearance. To test this, viral clearance capacity was determined in IFNγR knock-out (IFNγRKO) mice compared to wild-type (WT) pups, both on a BALB/c background, with or without intranasal (i.n.) delivery of IFNγ as described in the methods (Fig. 1). Viral quantification by viral plaque assay at 4 dpi demonstrates that IFNγ does not kill RSV directly, but requires interaction with the IFNγR to elicit its anti-viral effects. No difference in viral titers between KO and WT pups confirms negligible production of endogenous IFNγ in early RSV infection, while reduced RSV titers in IFNγ-treated, WT controls suggests that intact IFNγ receptors are required for efficient RSV clearance.Fig. 1

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