In vivo phagocytosis of MRSA by neonatal and adult mice.

<p>Neonate and adult mice were infected with 2x10⁷ CFU’s of TAMRA-MRSA or unlabeled MRSA. The lungs were removed 30 min pi and intracellular expression of TAMRA was measured by flow cytometry. The level of background fluorescence measured using unlabeled MRSA was 6.7%. NSA = neonatal / MRSA infection, ASA = adult / MRSA infection.</p

Neonatal mice mounted limited Th1 and Th17 response to MRSA infection.

<p>Neonate and adult mice were infected with 1.24 x10⁷ CFU’s of MRSA or vehicle. Lung single cells were isolated at 6 dpi and Th profile was measured by flow cytometry. (A) Th1/Th2 cell percentage of CD4+ T cells. (B) Representative flow plots of Th1/Th2 percentage of CD4+ T cells. (C) Th1/Th17 cell subsets. (D) Representative flow plots of Th1/Th17 subsets. NSA = neonatal / MRSA infection, NS = Neonatal / sham infection, ASA = adult / MRSA infection, AS = Adult sham infection.</p

Immune cell recruitment into the lungs of neonatal and adult mice infected with MRSA.

<p>Neonatal (5 d) and adult mice (6 wks) were infected with 1x10⁷ CFU’s of MRSA and BAL performed at 1 and 3 dpi. The cells recovered from the BALF were counted by differential staining. NSA = neonatal / MRSA infection, ASA = adult / MRSA infection.</p

Survival and bacterial clearance of neonatal mice to MRSA.

<p>(A) C57Bl/6 neonate (5 d) and adult mice (6 wks) were intranasally infected with increasing doses of USA300 (6 mice/group) and survival was determined over a 6 d period. (B) C57Bl/6 pups (5 d) and adult mice (6 wks) were intranasally infected with 1x10⁷ CFU’s of MRSA and the level of bacteria in the lung was measured on 1, 2 3 and 6 dpi. NSA = neonatal / MRSA infection, ASA = adult / MRSA infection.</p

A Neonatal Murine Model of MRSA Pneumonia

<div><p>Pneumonia due to methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) is a significant cause of morbidity and mortality in infants particularly following lower respiratory tract viral infections such as Respiratory Syncytial Virus (RSV). However, the mechanisms by which co-infection of infants by MRSA and RSV cause increased lung pathology are unknown. Because the infant immune system is qualitatively and quantitatively different from adults we developed a model of infant MRSA pneumonia which will allow us to investigate the effects of RSV co-infection on disease severity. We infected neonatal and adult mice with increasing doses of MRSA and demonstrate that neonatal mice have delayed kinetics in clearing the bacteria in comparison to adult mice. There were differences in recruitment of immune cells into the lung following infection. Adult mice exhibited an increase in neutrophil recruitment that coincided with reduced bacterial titers followed by an increase in macrophages. Neonatal mice, however, exhibited an early increase in neutrophils that did not persist despite continued presence of the bacteria. Unlike the adult mice, neonatal mice failed to exhibit an increase in macrophages. Neonates exhibited a decrease in phagocytosis of MRSA suggesting that the decrease in clearance was partially due to deficient phagocytosis of the bacteria. Both neonates and adults responded with an increase in pro-inflammatory cytokines following infection. However, in contrast to the adult mice, neonates did not express constitutive levels of the anti-microbial peptide Reg3γ in the lung. Infection of neonates did not stimulate expression of the co-stimulatory molecule CD86 by dendritic cells and neonates exhibited a diminished T cell response compared to adult mice. Overall, we have developed a neonatal model of MRSA pneumonia that displays a similar delay in bacterial clearance as is observed in the neonatal intensive care unit and will be useful for performing co-infection studies.</p></div

Interfacial Ring-Opening Polymerization of Amino-Acid-Derived <i>N</i>‑Thiocarboxyanhydrides Toward Well-Defined Polypeptides

Interfacial ring-opening polymerizations (iROP) of α-amino-acid derived <i>N</i>-thiocarboxyanhydrides (NTAs) in hexanes or heptane suspension using soluble primary amine initiators have been demonstrated to produce polypeptides with controlled molecular weight and low-to-moderate molecular weight distribution under mild conditions. The NTA monomers were shown to have significantly enhanced moisture and thermal stability relative to <i>N</i>-carboxyanhydrides (NCAs), resulting in long shelf life and allowing the polymerization to occur quantitatively in open air

Proinflammatory cytokine and anti-microbial peptide expression in neonatal and adult mice.

<p>Neonate and adult mice were infected with 1x10⁷ CFU’s of MRSA and cytokine gene expression measured at 6 and 24 hr pi (A-F). Expression of mRNA for cytokines and anti-microbial peptides was determined by qRT-PCR on RNA isolated from individual lung lobes (n = 5–6 mice per group) and relative expression is fold induction over WT unexposed mice of the same age. The level of IL6 (G)and IFNγ (H) in the lung homogenates was measured by ELISA. The data represent mean ± SEM of duplicate samples and significance was determined using one-way ANOVA with Tukey post-hoc test. NSA = neonatal / MRSA infection, NS = Neonatal / sham infection, ASA = adult / MRSA infection, AS = Adult sham infection.</p

Interfacial Ring-Opening Polymerization of Amino-Acid-Derived <i>N</i>‑Thiocarboxyanhydrides Toward Well-Defined Polypeptides

Interfacial ring-opening polymerizations (iROP) of α-amino-acid derived <i>N</i>-thiocarboxyanhydrides (NTAs) in hexanes or heptane suspension using soluble primary amine initiators have been demonstrated to produce polypeptides with controlled molecular weight and low-to-moderate molecular weight distribution under mild conditions. The NTA monomers were shown to have significantly enhanced moisture and thermal stability relative to <i>N</i>-carboxyanhydrides (NCAs), resulting in long shelf life and allowing the polymerization to occur quantitatively in open air

Interfacial Ring-Opening Polymerization of Amino-Acid-Derived <i>N</i>‑Thiocarboxyanhydrides Toward Well-Defined Polypeptides

Interfacial ring-opening polymerizations (iROP) of α-amino-acid derived <i>N</i>-thiocarboxyanhydrides (NTAs) in hexanes or heptane suspension using soluble primary amine initiators have been demonstrated to produce polypeptides with controlled molecular weight and low-to-moderate molecular weight distribution under mild conditions. The NTA monomers were shown to have significantly enhanced moisture and thermal stability relative to <i>N</i>-carboxyanhydrides (NCAs), resulting in long shelf life and allowing the polymerization to occur quantitatively in open air

Interfacial Ring-Opening Polymerization of Amino-Acid-Derived <i>N</i>‑Thiocarboxyanhydrides Toward Well-Defined Polypeptides

Interfacial ring-opening polymerizations (iROP) of α-amino-acid derived <i>N</i>-thiocarboxyanhydrides (NTAs) in hexanes or heptane suspension using soluble primary amine initiators have been demonstrated to produce polypeptides with controlled molecular weight and low-to-moderate molecular weight distribution under mild conditions. The NTA monomers were shown to have significantly enhanced moisture and thermal stability relative to <i>N</i>-carboxyanhydrides (NCAs), resulting in long shelf life and allowing the polymerization to occur quantitatively in open air