Biology subjects

McDonald, K. A.

Publications and source records attributed to McDonald, K. A..

12 recordsLinked to original sources

bioRxiv2025

Developmental exposure to a PFAS mixture impairs the anamnestic response to influenza A virus infection in mice

Developmental exposure to per- and polyfluoroalkyl substances (PFAS) has been linked to reduced antibody responses to childhood vaccines, but the underlying mechanisms remain unclear. Antibody production relies on interactions between various immune cell types, and it is unknown which are affected by PFAS exposure during development. To investigate this in a human-health relevant system, an in vivo model was established to delineate effects of developmental exposure to a mixture of four PFAS commonly found in human serum: PFOA, PFOS, PFHxS, and PFNA. Pregnant mice consumed water containing these PFAS throughout gestation and lactation. PFAS were measured in both mothers and offspring, and an exposure that avoided overt health issues was selected. The immune response to influenza A virus (IAV) infection was assessed in male and female offspring. Results showed that developmental PFAS exposure reduced IAV-specific antibody levels in both sexes. However, it diminished T follicular helper cells and germinal center B cells--critical for antibody production--in only female offspring. These findings highlight possible sex-specific immune effects and identify potential cellular mechanisms behind reduced antibody levels. Since these immune cells are essential for antibody production in humans, this study provides valuable insights into how PFAS exposure may impact human health. SynopsisA novel mouse model of developmental exposure to a human-relevant PFAS mixture recapitulates observations in epidemiological studies and also provides new insight into potential mechanisms of the lower antibody levels observed in humans.

pharmacology and toxicology↗

bioRxiv2025

Positive joint work redistribution in running: the role of plantar flexor fatigue and the effect of advanced footwear technology

Over the course of a near-maximal effort 10 km run, positive mechanical work decreases at the ankle and increases at the knee. Although plantar flexor fatigue is believed to be responsible for the proximal shift in mechanical work generation, this has yet to be confirmed experimentally. PurposeTo 1) determine the effect of plantar flexor fatigue on lower limb positive joint work during running and 2) determine the effect of running shoes on this relationship. MethodsTrained male runners (n = 12) were analyzed over two 30 s runs at their 10 km race pace, without and with local plantar flexor fatigue induced via a calf-raise protocol to a level commensurate with that accumulated over an exhaustive run ([~]24% reduction in peak torque). Both the unfatigued and fatigued runs were performed in a traditional shoe and in advanced footwear technology on an instrumented treadmill while three-dimensional motion capture and ground reaction force data were collected. ResultsPlantar flexor fatigue led to a redistribution of joint work, with lower positive ankle work (p < 0.001), greater positive knee work (p = 0.001), and similar positive hip work (p = 0. 550) in the fatigued run as compared to the unfatigued run. The relative positive joint contributions shifted proximally with fatigue (ankle - 4%, knee +3%); however, this shift was not influenced by shoe condition (p > 0.05). ConclusionPlantar flexor fatigue contributes to the proximal redistribution of positive joint work during running. However, the adoption of a suboptimal gait strategy appears to occur regardless of whether a runner wears a traditional shoe or advanced running footwear technology.

bioengineering↗

bioRxiv2025

Expression and Characterization of SARS-CoV-2 Spike Protein in Thermothelomyces heterothallica C1

The COVID-19 pandemic demonstrated a pressing need for rapid, adaptive, and scalable manufacturing of vaccines and reagents. With the transition into an endemic disease and rising threats of other emerging pandemics, production of these biologicals requires a stable and sustainable supply chain and accessible distribution methods. In this study, we demonstrate the strength of an engineered filamentous fungal platform, Thermothelomyces heterothallica C1, for high volumetric productivity of the full-length spike glycoprotein. Spike protein produced in this system is highly thermostable and immunization of mice with spike made in C1 or mammalian platforms resulted in a similar humoral response. Additionally, it was shown that the native N-glycan profile can be redecorated with complex sialylated structures, if necessary, resulting in a more human-like glycan profile, without impacting binding characteristics as shown experimentally and in simulations. Through extensive physicochemical analysis, the C1 produced spike performs similarly to spike proteins produced in other commercially available systems. The data presented is evidence that C1 can be a strong platform for production of complex glycosylated recombinant proteins such as subunit antigen vaccines.

bioengineering↗

bioRxiv2024

Immune Checkpoint Molecules as Biomarkers of Staphylococcus aureus Bone Infection and Clinical Outcome

Staphylococcus aureus prosthetic joint infections (PJIs) are broadly considered incurable, and clinical diagnostics that guide conservative vs. aggressive surgical treatments dont exist. Multi-omics studies in a humanized NSG-SGM3 BLT mouse model demonstrate human T cells: 1) are remarkably heterogenous in gene expression and numbers, and 2) exist as a mixed population of activated, progenitor-exhausted, and terminally-exhausted Th1/Th17 cells with increased expression of immune checkpoint proteins (LAG3, TIM-3). Importantly, these proteins are upregulated in the serum and the bone marrow of S. aureus PJI patients. A multiparametric nomogram combining high serum immune checkpoint protein levels with low proinflammatory cytokine levels (IFN-{gamma}, IL-2, TNF-, IL-17) revealed that TIM-3 was highly predictive of adverse disease outcomes (AUC=0.89). Hence, T cell impairment in the form of immune checkpoint expression and exhaustion could be a functional biomarker for S. aureus PJI disease outcome, and blockade of checkpoint proteins could potentially improve outcomes following surgery.

immunology↗

bioRxiv2023

Biomechanical effects of adding an articulating toe joint to a passive foot prosthesis for incline and decline walking

Walking on sloped surfaces is challenging for many lower limb prosthesis users, in part due to the limited ankle range of motion provided by typical prosthetic ankle-foot devices. Adding a toe joint could potentially benefit users by providing an additional degree of flexibility to adapt to sloped surfaces, but this remains untested. The objective of this study was to characterize the effect of a prosthesis with an articulating toe joint on the preferences and gait biomechanics of individuals with unilateral below-knee limb loss walking on slopes. Nine active prosthesis users walked on an instrumented treadmill at a +5{degrees} incline and -5{degrees} decline while wearing an experimental foot prosthesis with two configurations: a Flexible toe joint and a Locked-out toe joint. Three participants preferred the Flexible toe joint over the Locked-out toe joint for incline and decline walking. Eight of nine participants went on to participate in a biomechanical data collection. The Flexible toe joint decreased prosthesis Push-off work by 2 J during both incline and decline walking (p=0.008). During incline walking, prosthetic limb knee flexion at toe-off was 3{degrees} greater in the Flexible configuration compared to the Locked (p=0.008). Overall, these results indicate that adding a toe joint to a passive foot prosthesis has relatively small effects on joint kinematics and kinetics during sloped walking. This study is part of a larger body of work that also assessed the impact of a prosthetic toe joint for level and uneven terrain walking and stair ascent/descent. Collectively, toe joints do not appear to substantially or consistently alter lower limb mechanics for active unilateral below-knee prosthesis users. Our findings also demonstrate that user preference for passive prosthetic technology may be both subject-specific and task-specific. Future work could investigate the inter-individual preferences and potential benefits of a prosthetic toe joint for lower-mobility individuals.

bioengineering↗

bioRxiv2022

Humans trade-off energetic cost with fatigue avoidance while walking

Metabolic cost minimization is thought to underscore the neural control of locomotion. Yet, avoiding high muscle activation, a cause of fatigue, often outperforms energy minimization in computational predictions of human gait. Discerning the relative importance of these criteria in human walking has proved elusive, in part, because they have not been empirically decoupled. Here we explicitly decouple whole-body metabolic cost and fatigue-like muscle activation costs (estimated from electromyography) by pitting them against one another using two distinct gait tasks. When experiencing these competing costs, participants (N=10) chose the task that avoided overburdening muscles (fatigue avoidance) at the expense of higher metabolic power (p<0.05). Muscle volume-normalized activation more closely models energy use and was also minimized by the participants decision (p<0.05), demonstrating that muscle activation was, at best, an inaccurate signal for metabolic energy. Energy minimization was only observed when there was no adverse effect on muscle activation costs. By decoupling whole-body metabolic and muscle activation costs, we provide among the first empirical evidence of humans embracing non-energetic optimality in favor of a clearly defined neuromuscular objective. This finding indicates that local muscle fatigue and effort may well be key factors dictating human walking behavior and its evolution.

physiology↗

bioRxiv2021

Production of novel Spike truncations in Chinese hamster ovary cells

SARS-CoV-2 Spike is a key protein that mediates viral entry into cells and elicits antibody responses. Its importance in infection, diagnostics, and vaccinations has created a large demand for purified Spike for clinical and research applications. Spike is difficult to express, prompting modifications to the protein and expression platforms to improve yields. Alternatively, Spike receptor binding domain (RBD) is commonly expressed with higher titers, though it has lower sensitivity in serological assays. Here, we improve transient Spike expression in Chinese hamster ovary (CHO) cells. We demonstrate that Spike titers increase significantly over the expression period, maximizing at 14 mg/L at day 7. In comparison, RBD titers peak at 54 mg/L at day 3. Next, we develop 8 Spike truncations (T1-T8) in pursuit of a truncation with high expression and antibody binding. The truncations T1 and T4 express at 130 mg/L and 73 mg/L, respectively, which are higher than our RBD titers. Purified proteins were evaluated for binding to antibodies raised against full-length Spike. T1 has similar sensitivity as Spike against a monoclonal antibody and even outperforms Spike for a polyclonal antibody. These results suggest T1 is a promising Spike alternative for use in various applications.

bioengineering↗

bioRxiv2021

Functionalizing silica sol-gel with entrapped plant virus-based immunosorbent nanoparticles

Advancements in understanding and engineering of virus-based nanomaterials (VBNs) for biomedical applications motivate a need to explore the interfaces between VBNs and other biomedically-relevant chemistries and materials. While several strategies have been used to investigate some of these interfaces with promising initial results, including VBN-containing slow-release implants and VBN-activated bioceramic bone scaffolds, there remains a need to establish VBN-immobilized three dimensional materials that exhibit improved stability and diffusion characteristics for biosensing and other analyte-capture applications. Silica sol-gel chemistries have been researched for biomedical applications over several decades and are well understood; various cellular organisms and biomolecules (e.g., bacteria, algae, enzymes) have been immobilized in silica sol-gels to improve viability, activity, and form factor (i.e., ease of use). Here we present the immobilization of an antibody-binding VBN in silica sol-gel by pore confinement. We have shown that the resulting system is sufficiently diffuse to allow antibodies to migrate in and out of the matrix. We also show that the immobilized VBN is capable of antibody binding and elution functionality under different buffer conditions for multiple use cycles. The promising results of the VBN and silica sol-gel interface indicate a general applicability for VBN-based bioseparations and biosensing applications.

bioengineering↗

bioRxiv2021

Affinity sedimentation and magnetic separation with plant-made immunosorbent nanoparticles for therapeutic protein purification

The virus-based immunosorbent nanoparticle is a nascent technology being developed to serve as a simple and efficacious agent in biosensing and therapeutic antibody purification. There has been particular emphasis on the use of plant virions as immunosorbent nanoparticle chassis for their diverse morphologies and accessible, high yield manufacturing via crop cultivation. To date, studies in this area have focused on proof-of-concept immunosorbent functionality in biosensing and purification contexts. Here we consolidate a previously reported pro-vector system into a single Agrobacterium tumefaciens vector to investigate and expand the utility of virus-based immunosorbent nanoparticle technology for therapeutic protein purification. We demonstrate the use of this technology for Fc-fusion protein purification, characterize key nanomaterial properties including binding capacity, stability, reusability, and particle integrity, and present an optimized processing scheme with reduced complexity and increased purity. Furthermore, we present a coupling of virus-based immunosorbent nanoparticles with magnetic particles as a strategy to overcome limitations of the immunosorbent nanoparticle sedimentation-based affinity capture methodology. We report magnetic separation results which exceed the binding capacity of current industry standards by an order of magnitude.

bioengineering↗

bioRxiv2021

Evaluating the cost of pharmaceutical purification for a long-duration space exploration medical foundry

There are medical treatment vulnerabilities in longer-duration space missions present in the current International Space Station crew health care system with risks, arising from spaceflight-accelerated pharmaceutical degradation and resupply lag times. Bioregenerative life support systems may be a way to close this risk gap by leveraging in situ resource utilization (ISRU) to perform pharmaceutical synthesis and purification. Recent literature has begun to consider biological ISRU using microbes and plants as the basis for pharmaceutical life support technologies. However, there has not yet been a rigorous analysis of the processing and quality systems required to implement biologically-produced pharmaceuticals for human medical treatment. In this work, we use the equivalent system mass (ESM) metric to evaluate pharmaceutical purification processing strategies for longer-duration space exploration missions. Monoclonal antibodies, representing a diverse therapeutic platform capable of treating multiple space-relevant disease states, were selected as the target products for this analysis. We investigate the ESM resource costs (mass, volume, power, cooling, and crew time) of an affinity-based capture step for monoclonal antibody purification as a test case within a manned Mars mission architecture. We compare six technologies (three biotic capture methods and three abiotic capture methods), optimize scheduling to minimize ESM for each technology, and perform scenario analysis to consider a range of input stream compositions and pharmaceutical demand. We also compare the base case ESM to scenarios of alternative mission configuration, equipment models, and technology reusability. Throughout the analyses, we identify key areas for development of pharmaceutical life support technology and improvement of the ESM framework for assessment of bioregenerative life support technologies.

bioengineering↗

bioRxiv2021

Analysis of variability of functionals of recombinant protein production trajectories based on limited data

We propose a method for analyzing the variability in smooth, possibly nonlinear, functionals associated with a set of product production trajectories measured under different experimental conditions. The key challenge is to make meaningful inference on these parameters across different experimental conditions when only a limited number of measurements in time are collected for each treatment, and when there are only a few, or no, replicates available. For this purpose we adopt a modeling approach by representing the production trajectories in a B-spline basis, and develop a bootstrap-based inference procedure for the parameters of interest, also accounting for multiple comparisons. The methodology is applied to study two types of quantities of interest - "time to harvest" and "maximal productivity" in the context of an experiment on the production of certain recombinant proteins under laboratory conditions. We complement the findings by extensive numerical experiments that look into the effects of different types of bootstrap procedures and associated schemes for computing p-values for tests of hypotheses.

bioengineering↗

bioRxiv2020

Development and simulation of fully glycosylated molecular models of ACE2-Fc fusion proteins and their interaction with the SARS-CoV-2 spike protein binding domain

We develop fully glycosylated computational models of ACE2-Fc fusion proteins which are promising targets for a COVID-19 therapeutic. These models are tested in their interaction with a fragment of the receptor-binding domain (RBD) of the Spike Protein S of the SARS-CoV-2 virus, via atomistic molecular dynamics simulations. We see that some ACE2 glycans interact with the S fragments, and glycans are influencing the conformation of the ACE2 receptor. Additionally, we optimize algorithms for protein glycosylation modelling in order to expedite future model development. All models and algorithms are openly available.

biophysics↗