Biology subjects

Simmons, S. R.

Publications and source records attributed to Simmons, S. R..

6 recordsLinked to original sources

bioRxiv2026

CD73 controls neutrophil responsiveness to type I interferon impairing antibacterial responses during influenza A virus/ Streptococcus pneumoniae co-infection

Streptococcus pneumoniae (pneumococcus) are asymptomatic colonizers of the nasopharynx but can progress to pulmonary and systemic pathogens upon influenza A virus (IAV) infection. Polymorphonuclear cells (PMNs) are required to control bacterial numbers, but we previously found that IAV infection impairs their ability to kill S. pneumoniae. Here, using a model that allows transition of pneumococci from colonizers to disease-causing pathogens upon IAV co-infection, we examined the signaling pathways impairing PMN responses. When we investigated the effect of type I interferons (IFN) produced upon IAV infection on PMN antibacterial activity, we found that PMNs treated with IFN were unable to kill S. pneumoniae ex vivo, and that in vivo blocking of IFN receptor 1 (IFNAR1) in IAV infected mice rescued PMN antibacterial function. In exploring what controls PMN responsiveness to IFN, we examined CD73, an ectonucleotidase that is known to regulate PMN function in primary pneumococcal pneumonia. To test if there is an intersection between CD73 and IFN signaling, we examined receptor levels and IFN production in wildtype versus CD73KO mice and found no difference in IFNAR expression on PMNs or IFN[a] and IFN levels in the lungs and circulation. However, CD73KO PMNs expressed significantly lower levels of the interferon stimulated protein IFIT1. When we looked at ex vivo PMN responsiveness to IFNs, CD73KO PMNs were less responsive to IFN-mediated inhibition of antimicrobial activity. In exploring mechanisms, we found that CD73 expressing PMNs had elevated production of reactive oxygen species in response to IAV challenge, that paradoxically impaired their ability to kill S. pneumoniae. Importantly, despite similar pathogen loads in the respiratory tract, co-infected CD73KO mice cleared bacteremia and survived significantly better than wildtype controls. These findings suggest that CD73 impairs host defense against IAV/S. pneumoniae co-infection in part by sensitizing PMNs to type I IFN-mediated inhibition of antibacterial function. Author SummaryDespite available therapeutics and vaccines, secondary bacterial pneumonia following influenza A virus (IAV) infection remains a major cause of disease. A common cause of secondary bacterial pneumonia are Streptococcus pneumoniae (pneumococcus), bacteria that resides asymptomatically in the nasopharynx, but upon viral infection can transition to cause severe disease in susceptible hosts. In this study we examined how host responses change during single versus polymicrobial infections. We focused on neutrophils, which are innate immune cells that are required for effective clearance of S. pneumoniae, and proper control of IAV. We found that the immune response to IAV, mediated by type I interferons (IFN), impair the ability of neutrophils to kill bacteria. We identified an enzyme called CD73 to be required for the ability of neutrophils to respond to IFN. In exploring mechanisms, we found that IFN and CD73 result in dysregulated reactive oxygen species production by neutrophils. Importantly, this impairs the ability of the host to clear bacteria that spread from the lungs to the blood upon viral co-infection and results in overall worse host outcome. This study describes a novel interaction between CD73 and type I interferons and provides a new therapeutic target to treat secondary pneumococcal pneumonia.

immunology↗

bioRxiv2025

Basal activation of ERK1/2 blunts the antimicrobial activity of neutrophils from aged hosts against antibody opsonized Streptococcus pneumoniae

The decline in neutrophil antimicrobial function renders vaccinated aged hosts less protected against Streptococcus pneumoniae infection. In vaccinated hosts, activation of neutrophils via phagocytic receptors, like complement and Fc{gamma} receptors, mediates bacterial uptake and killing. However, the mechanisms behind changes in signaling downstream of these receptors with age is not known. Mitogen-activated protein kinases (MAPK) are signaling cascades activated in response to cell surface receptors. Using bone marrow neutrophils isolated from young and aged mice, and MAPK phosphorylation array, we found differences in MAPK activation in an opsonin dependent manner (complement vs antibody). Neutrophils from aged mice failed to increase MAPK phosphorylation upon infection with pneumococci opsonized with heat-inactivated (HI) sera from hosts immunized with the pneumococcal conjugate vaccine (PCV), indicating an age-related defect in Fc{gamma}R signaling. Neutrophils from aged mice had higher basal levels of MAPK phosphorylation when compared to young controls, including a 15-fold increase in ERK1/2 phosphorylation. Inhibition of ERK1/2 signaling blunted pneumococcal killing by PMNs from young mice, but improved killing by neutrophils from aged mice, only when the bacteria were opsonized with HI immune but not naive sera. In young human participants, in vitro inhibition of ERK1/2 in neutrophils resulted in decreased pneumococcal killing, but only following PCV vaccination, suggesting that the effects of ERK1/2 inhibition are clinically relevant in vaccinated hosts. This study identifies age-related changes in ERK1/2 activation and demonstrates that balanced activation of this pathway is crucial for neutrophil antimicrobial activity against antibody opsonized bacteria following vaccination in both mice and humans. Summary sentenceImbalanced ERK1/2 activation impairs neutrophil activity in aged hosts. LEGENDS O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=134 SRC="FIGDIR/small/656427v1_ufig1.gif" ALT="Figure 1"> View larger version (21K): org.highwire.dtl.DTLVardef@179c31forg.highwire.dtl.DTLVardef@f95d4borg.highwire.dtl.DTLVardef@15c1dcborg.highwire.dtl.DTLVardef@a8076e_HPS_FORMAT_FIGEXP M_FIG C_FIG Graphical AbstractGraphic Abstract Created in BioRender. Bou Ghanem, E. (2025) https://BioRender.com/jjoodsu.

immunology↗

bioRxiv2025

Adenosine 2B receptor signaling impairs vaccine-mediated protection against pneumococcal infection in young hosts by blunting neutrophil killing of antibody opsonized bacteria

Background/ObjectiveNeutrophils are essential for vaccine-mediated protection against pneumococcal infection and impairment in their antibacterial function contributes to reduced vaccine efficacy during aging. However, the signaling pathways controlling neutrophil responses in vaccinated hosts are not fully understood. The extracellular adenosine pathway is a known regulator of neutrophils in naive hosts. The aim of this study was to test the role of this pathway in neutrophil function and protection against infection upon vaccination across host age. MethodsTo test the role of adenosine in the antimicrobial activity of neutrophils against antibody-opsonized pneumococci, we used bone marrow derived neutrophils isolated from wild type or specific adenosine receptors knock-out mice. To measure the effect of adenosine receptor signaling in vivo, we treated vaccinated mice with agonists or antagonists specific to the different adenosine receptors prior to pulmonary challenge with pneumococci and assessed bacterial burden and clinical score post infection. ResultsWe found that signaling via the adenosine 2B (A2BR) but not A2A or A1 receptor diminished intracellular pneumococcal killing following antibody-mediated uptake in young hosts. In vivo, agonism of A2BR significantly worsened pneumococcal infection outcome in young, vaccinated mice. In contrast, A2BR signaling had no effect on intracellular bacterial killing by neutrophils from aged mice. Further, in vivo A2BR inhibition had no effect on pneumococcal disease progression in aged, vaccinated mice. ConclusionsA2BR signaling reduced pneumococcal vaccine-mediated protection by impairing neutrophil antimicrobial activity against antibody-opsonized bacteria in young hosts. However, inhibiting this pathway was not sufficient to boost responses in aged hosts.

immunology↗

bioRxiv2024

Activating A1 adenosine receptor signaling boosts early pulmonary neutrophil recruitment in aged mice in response to Streptococcus pneumoniae infection

BackgroundStreptococcus pneumoniae (pneumococcus) is a leading cause of pneumonia in older adults. Successful control of pneumococci requires robust pulmonary neutrophil influx early in infection. However, aging is associated with aberrant neutrophil recruitment and the mechanisms behind that are not understood. Here we explored how neutrophil recruitment following pneumococcal infection changes with age and the host pathways regulating this. ResultsFollowing pneumococcal infection there was a significant delay in early neutrophil recruitment to the lungs of aged mice. Neutrophils from aged mice showed defects in trans-endothelial migration in vitro compared to young controls. To understand the pathways involved, we examined immune modulatory extracellular adenosine (EAD) signaling, that is activated upon cellular damage. Signaling through the lower affinity A2A and A2B adenosine receptors had no effect on neutrophil recruitment to infected lungs. In contrast, inhibition of the high affinity A1 receptor in young mice blunted neutrophil recruitment to the lungs following infection. A1 receptor inhibition decreased expression of CXCR2 on circulating neutrophils, which is required for transendothelial migration. Indeed, A1 receptor signaling on neutrophils was required for their ability to migrate across endothelial cells in response to infection. Aging was not associated with defects in EAD production or receptor expression on neutrophils. However, agonism of A1 receptor in aged mice rescued the early defect in neutrophil migration to the lungs and improved control of bacterial burden. ConclusionsThis study suggests age-driven defects in EAD damage signaling can be targeted to rescue the delay in pulmonary neutrophil migration in response to bacterial pneumonia.

immunology↗

bioRxiv2021

Liposomal encapsulation of polysaccharides (LEPS) as an effective vaccine strategy to protect aged hosts against S. pneumoniae infection

Despite the availability of licensed vaccines, pneumococcal disease caused by the bacteria Streptococcus pneumoniae (pneumococcus), remains a serious infectious disease threat globally. Disease manifestations include pneumonia, bacteremia, and meningitis, resulting in over a million deaths annually. Pneumococcal disease disproportionally impacts elderly individuals [≥]65 years old. Interventions are complicated through a combination of complex disease progression and 100 different bacterial capsular polysaccharide serotypes. This has made it challenging to develop a broad vaccine against S. pneumoniae, with current options utilizing capsular polysaccharides as the primary antigenic content. However, current vaccines are substantially less effective in protecting the elderly. We previously developed a Liposomal Encapsulation of Polysaccharides (LEPS) vaccine platform, designed around limitations of current pneumococcal vaccines, that allowed the non-covalent coupling of polysaccharide and protein antigen content and protected young hosts against pneumococcal infection in murine models. In this study, we modified the formulation to make it more economical and tested the novel LEPS vaccine in aged hosts. We found that in young mice (2-3 months), LEPS elicited comparable responses to the pneumococcal conjugate vaccine Prevnar-13. Further, LEPS immunization of old mice (20-22 months) induced comparable antibody levels and improved antibody function compared to Prevnar-13. Importantly, LEPS protected old mice against both invasive and lung localized pneumococcal infections. In summary, LEPS is an alternative and effective vaccine strategy that protects aged hosts against different manifestations of pneumococcal disease.

microbiology↗

bioRxiv2020

Extracellular adenosine signaling reverses the age-driven decline in the ability of neutrophils to kill S. pneumoniae

The elderly are susceptible to serious infections by Streptococcus pneumoniae (pneumococcus), which calls for a better understanding of the pathways driving the decline in host defense in aging. We previously found that extracellular adenosine (EAD) shaped polymorphonuclear cell (PMN) responses, which are crucial for controlling infection. EAD is produced by CD39 and CD73, and signals via A1, A2A, A2B and A3 receptors. The objective of this study was to explore the age-driven changes in the EAD pathway and its impact on PMN function. We found in comparison to young mice, PMNs from old mice expressed significantly less CD73, but similar levels of CD39 and adenosine receptors. PMNs from old mice failed to efficiently kill pneumococci ex vivo; however, supplementation with adenosine rescued this defect. Importantly, transfer of PMNs expressing CD73 from young mice reversed the susceptibility of old mice to pneumococcal infection. To identify which adenosine receptor(s) is involved, we used specific agonists and inhibitors. We found that A1 receptor signaling was crucial for PMN function as inhibition or genetic ablation of A1 impaired the ability of PMNs from young mice to kill pneumococci. Importantly, activation of A1 receptors rescued the age-associated defect in PMN function. In exploring mechanisms, we found that PMNs from old mice failed to efficiently kill engulfed pneumococci and that A1 receptor controlled intracellular killing. In summary, targeting the EAD pathway reverses the age-driven decline in PMN antimicrobial function, which has serious implications in combating infections.

immunology↗