Biology subjects

Lefort, C. T.

Publications and source records attributed to Lefort, C. T..

5 recordsLinked to original sources

bioRxiv2025

Neutrophil progenitor cell therapy rescues host defense against Staphylococcus aureus in murine chronic granulomatous disease

Despite advances in engineered adaptive immune cell therapies, current options for innate immune cell therapies are sparse. In this work, we demonstrate the utility of a neutrophil progenitor-based cell therapy. Murine conditionally-immortalized neutrophil progenitors (NPs) overcome the hurdles of alternative cell therapies by engrafting in the unconditioned host and substantially contributing to the host neutrophil population. Here we demonstrate the therapeutic value of NPs using a murine model of the primary immunodeficiency chronic granulomatous disease (CGD). Those with CGD are highly susceptible to infection with Staphylococcus aureus because of genetic mutations that impair neutrophil antimicrobial function. We find that the prophylactic treatment of CGD mice with transfused NPs rescue them from an otherwise lethal S. aureus pulmonary infection. In investigating the mechanisms behind the improved clearance of S. aureus and survival of CGD mice, our data suggests that the antimicrobial function of host CGD neutrophils is rescued by the presence of donor-derived wild-type neutrophils. We also observe that survival is improved to >50% in the CGD model when mice receive NPs post-infection. This work highlights the application of NPs to improving outcomes to acute bacterial infection in CGD, demonstrating the translational potential of conditionally-immortalized myeloid progenitors as a cellular therapy.

immunology↗

bioRxiv2022

Identification and Mechanistic Basis of non-ACE2 Blocking Neutralizing Antibodies from COVID-19 Patients with Deep RNA Sequencing and Molecular Dynamics Simulations

Variants of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) continue to cause disease and impair the effectiveness of treatments. The therapeutic potential of convergent neutralizing antibodies (NAbs) from fully recovered patients has been explored in several early stages of novel drugs. Here, we identified initially elicited NAbs (Ig Heavy, Ig lambda, Ig kappa) in response to COVID-19 infection in patients admitted to the intensive care unit at a single center with deep RNA sequencing (>100 million reads) of peripheral blood as a diagnostic tool for predicting the severity of the disease and as a means to pinpoint specific compensatory NAb treatments. Clinical data were prospectively collected at multiple time points during ICU admission, and amino acid sequences for the NAb CDR3 segments were identified. Patients who survived severe COVID-19 had significantly more of a Class 3 antibody (C135) to SARS-CoV-2 compared to non-survivors (16,315 reads vs 1,412 reads, p=0.02). In addition to highlighting the utility of RNA sequencing in revealing unique NAb profiles in COVID-19 patients with different outcomes, we provided a physical basis for our findings via atomistic modeling combined with molecular dynamics simulations. We established the interactions of the Class 3 NAb C135 with the SARS-CoV-2 spike protein, proposing a mechanistic basis for inhibition via multiple conformations that can effectively prevent ACE2 from binding to the spike protein, despite C135 not directly blocking the ACE2 binding motif. Overall, we demonstrate that deep RNA sequencing combined with structural modeling offers the new potential to identify and understand novel therapeutic(s) NAbs in individuals lacking certain immune responses due to their poor endogenous production. Our results suggest a possible window of opportunity for administration of such NAbs when their full sequence becomes available. A method involving rapid deep RNA sequencing of patients infected with SARS-CoV-2 or its variants at the earliest infection time could help to develop personalized treatments using the identified specific NAbs.

immunology↗

bioRxiv2022

Vinculin plays a role in neutrophil stiffening and transit through model capillary segments

Neutrophils are rapidly mobilized from the circulation to sites of inflammation. The mechanisms of neutrophil trafficking in the lung are distinct from those in the periphery, in part because the pulmonary capillaries are the primary site of neutrophil emigration rather than postcapillary venules. Since the diameter of a neutrophil is greater than the width of most pulmonary capillary segments, they must deform to transit through this capillary network, even at homeostasis. Resistance to deformation is primarily due to cortical actin that is rapidly assembled when a neutrophil is exposed to a priming or activation stimulus, resulting in neutrophil stiffening and subsequent sequestration within the pulmonary capillary network. In the current study, we use a microfluidic assay to characterize neutrophil transit through model capillary-like channels. Using techniques from single-particle tracking, we analyzed the cumulative distribution of neutrophil transit times and resolve population-based effects. We found that vinculin, an actin-binding adaptor protein, plays an essential role in neutrophil stiffening in response to formyl-Met-Leu-Phe (fMLP). Vinculin-deficient neutrophils lack the development of a population with slow transit through narrow channels that was observed in both wild-type murine bone marrow neutrophils and HoxB8-conditional progenitor-derived neutrophils. Atomic force microscopy studies provide further evidence that vinculin is required for neutrophil stiffening. Consistent with these findings, we observed that neutrophil sequestration in the lungs of mice is attenuated in the absence of vinculin. Together, our studies indicate that vinculin mediates actin-dependent neutrophil stiffening that leads to their sequestration in capillaries.

cell biology↗

bioRxiv2021

Engraftment, fate, and function of HoxB8-conditional neutrophil progenitors in the unconditioned murine host

The development and use of murine myeloid progenitor cell lines that are conditionally immortalized through expression of HoxB8 has provided a valuable tool for studies of neutrophil biology. Recent work has extended the utility of HoxB8-conditional progenitors to the in vivo setting via their transplantation into irradiated mice. Here, we describe the isolation of HoxB8-conditional progenitor cell lines that are unique in their ability to engraft in the naive host in the absence of conditioning of the hematopoietic niche. Our results indicate that HoxB8-conditional progenitors engraft in a {beta}1 integrin-dependent manner and transiently generate donor-derived mature neutrophils. Furthermore, we show that neutrophils derived in vivo from transplanted HoxB8-conditional progenitors are mobilized to the periphery and recruited to sites of inflammation in a manner that depends on the C-X-C chemokine receptor 2 and {beta}2 integrins, the same mechanisms that have been described for recruitment of endogenous primary neutrophils. Together, our studies advance the understanding of HoxB8-conditional neutrophil progenitors and describe an innovative tool that, by virtue of its ability to engraft in the naive host, will facilitate mechanistic in vivo experimentation on neutrophils.

immunology↗

bioRxiv2019

Context-dependent role of vinculin in neutrophil adhesion, motility and trafficking

Neutrophils are innate immune effector cells that traffic from the peripheral blood to extravascular sites of inflammation. {beta}2 integrins are involved during multiple phases of neutrophil recruitment, including the transition from rolling to arrest, firm attachment and motility within the vasculature. Following neutrophil arrest, adhesion stabilization occurs as the neutrophil interacts with the endothelial surface and crawls into a favorable position for extravasation. The cytoskeletal protein vinculin has been implicated in other cell types as a regulator of adhesion strength by promoting focal adhesion maturation and as a sensor of the mechanical properties of the microenvironment. Neutrophils express vinculin but do not form mature focal adhesions. Here, we characterize the role of vinculin in {beta}2 integrin-dependent neutrophil adhesion, motility, mechanosensing, and recruitment. We observe that knockout of vinculin attenuates, but does not completely abrogate, neutrophil adhesion, spreading, and crawling under static conditions. In the presence of forces from fluid flow, vinculin was not required for neutrophil adhesion or migration. Vinculin deficiency only mildly attenuated neutrophil traction stresses and spreading on stiff, but not soft, polyacrylamide gels indicating a minor role for vinculin in the mechanosensing of the neutrophil as compared to slower moving mesenchymal cells that form mature focal adhesions. Consistent with these findings, we observe in vivo neutrophil recruitment into the inflamed peritoneum of mice remains intact in the absence of vinculin. Together, these data suggest that while vinculin regulates some aspects of neutrophil adhesion and spreading, it may be dispensable for neutrophil recruitment and motility in vivo.

immunology↗