Search

Plasma medicine is a rapidly expanding field that utilizes nonequilibrium plasma discharges at atmospheric conditions or in liquids for clinical applications. There is a significant interest in the production of plasma in the liquid phase for wastewater treatment, agricultural applications, and medical purposes. However, little investigation has been done about the effects of dielectric coatings on submerged electrodes, which is of significant interest to limit electrical current flow in the liquid. This article investigates the effect of different dielectric coatings, including aluminum oxide, parylene C, and bi-layer combinations, on plasma discharge characteristics in phosphate-buffered saline ( $\mathbf {\sigma = 18}$ mS/cm) from nanosecond high-voltage pulses. Observed results for aluminum oxide are consistent with past works, including micron-sized clusters of holes generated in the layer due to dielectric breakdown. A bi-layer combination of parylene C on top of aluminum oxide resulted in a longer lifetime for electrodes, possibly due to the melting/solidification behavior of the polymer, which may have a “healing” effect. The use of a thick parylene C layer resulted in a different, “creeping,” discharge regime, which is hypothesized to be similar to triple-gap discharge observed in space plasma physics and high-voltage insulators, in which the electric field is enhanced at the boundary of a conductor, dielectric, and a vacuum/fluid, resulting in discharge at this junction point. Temporally-resolved and high-spatial-resolution imaging are required for verification.

Coronavirus disease 2019 (Covid-19) has caused over 5.5 million deaths worldwide, and viral mutants continue to ravage communities with limited access to injectable vaccines or high rates of vaccine hesitancy. Inhalable vaccines have the potential to address these distribution and compliance issues as they are less likely to require cold storage, avoid the use of needles, and can elicit localized immune responses with only a single dose. Alveolar macrophages represent attractive targets for inhalable vaccines as they are abundant within the lung mucosa (up to 95% of all immune cells) and are important mediators of mucosal immunity, and evidence suggests that they may be key cellular players in early Covid-19 pathogenesis. Here, we report inhalable coronavirus mimetic particles (CoMiP) designed to rapidly bind to, and be internalized by, alveolar macrophages to deliver nucleic acid-encoded viral antigens. Inspired by the SARS-CoV-2 virion structure, CoMiP carriers package nucleic acid cargo within an endosomolytic peptide envelope that is wrapped in a macrophage-targeting glycosaminoglycan coating. Through this design, CoMiP mimic several important features of the SARS-CoV-2 virion, particularly surface topography and macromolecular chemistry. As a result, CoMiP effect pleiotropic transfection of macrophages and lung epithelial cells in vitro with multiple antigen-encoding plasmids. In vivo immunization yields increased mucosal IgA levels within the respiratory tract of CoMiP vaccinated mice.

Francisella tularensis (Ft) is a Gram-negative, facultative intracellular coccobacillus that is the etiological agent of tularemia. Interestingly, the disease tularemia has variable clinical presentations that are dependent upon the route of infection with Ft. Two of the most likely routes of Ft infection include intranasal and intradermal, which result in pneumonic and ulceroglandular tularemia, respectively. While there are several differences between these two forms of tularemia, the most notable disparity is between mortality rates: the mortality rate following pneumonic tularemia is over ten times that of the ulceroglandular disease. Understanding the differences between intradermal and intranasal Ft infections is important not only for clinical diagnoses and treatment but also for the development of a safe and effective vaccine. However, the immune correlates of protection against Ft, especially within the context of infection by disparate routes, are not yet fully understood. Recent advances in different animal models have revealed new insights in the complex interplay of innate and adaptive immune responses, indicating dissimilar patterns in both responses following infection with Ft via different routes. Further investigation of these differences will be crucial to predicting disease outcomes and inducing protective immunity via vaccination or natural infection.

Emergence and spread of antibiotic resistance calls for development of non-chemical treatment options for bacterial infections. Plasma medicine applies low-temperature plasma (LTP) physics to address biomedical problems such as wound healing and tumor suppression. LTP has also been used for surface disinfection. However, there is still much to be learned regarding the effectiveness of LTP on bacteria in suspension in liquids, and especially on porous surfaces. We investigated the efficacy of LTP treatments against bacteria using an atmospheric-pressure plasma jet and show that LTP treatments have the ability to inhibit both gram-positive (S. aureus) and gram-negative (E. coli) bacteria on solid and porous surfaces. Additionally, both direct LTP treatment and plasma-activated media were effective against the bacteria suspended in liquid culture. Our data indicate that reactive oxygen species are the key mediators of the bactericidal effects of LTP and hydrogen peroxide is necessary but not sufficient for antibacterial effects. In addition, our data suggests that bacteria exposed to LTP do not develop resistance to further treatment with LTP. These findings suggest that this novel atmospheric-pressure plasma jet could be used as a potential alternative to antibiotic treatments in vivo.

OBJECTIVES: Selenium (Se), which exerts its effects via selenoproteins, is an essential micronutrient that has been shown to be required for optimal functioning of the immune system. Although numerous studies have examined the effects of selenoproteins on various aspects of the immune response, few studies have investigated the effects of Se on antigen presentation. Moreover, these studies have provided conflicting results indicating the need for further research regarding the effect of Se on Antigen Presenting Cells (APCs). Our goal is to identify the role of selenoproteins in antigen presentation in professional APCs. METHODS: Mice deficient in selenoproteins in a cell specific manner were generated by knocking out the trspgene, which encodes for an essential tRNA for selenocysteine synthesis, utilizing the cre/lox system. The resulting mice are referred to asTrsp(DC)and Trsp(B)representing selenoprotein deficiency specifically in dendritic cells (DCs) and B cells, respectively. Additional studies were done utilizing a diet model of Se deficiency to isolate Se-deficient DCs and B cells. Rate of endocytosis by specific receptors and expression of various surface molecule characteristics of APCs were determined by flow cytometry. Degradation of antigens by APCs in the presence or absence of selenoproteins was measured by western blot. RESULTS: In B cells, selenoprotein deficiency results in a decrease in the number of B220 + Splenocytes, B Cell Receptor (BCR) endocytosis, calcium flux following antigen stimulation, and BCR degradation following internalization. Similarly, selenoprotein deficiency in DCs results in decreased DEC-205 (a collectin-like receptor for multiple antigens) endocytosis; and a reduction in the expression of MHCII, CD80, and CD86. These results suggest a role for selenoproteins during the processing and presentation of peptides to T cells. CONCLUSIONS: Loss of selenoproteins results in the decreased functionality of both B cells and DCs, which suggests that Se and selenoproteins may be involved in the regulation of antigen presentation. Further studies are needed to elucidate the underlying mechanism by which selenoproteins regulate antigen presentation. Such studies are likely to reveal novel targets for enhancing the immune response to vaccines and other specific antigens. FUNDING SOURCES: NIH/NIAID to GK; NIH/GM to SS; NIH/NIDDK to KSP.