Assessment of microbiological correlates and immunostimulatory potential of electron beam inactivated metabolically active yet non culturable (MAyNC) Salmonella Typhimurium

Abstract

This study investigates the microbiological and immunological basis underlying the efficacy of electron beam-inactivated immune modulators. The underlying hypothesis is that exposure to eBeam-based ionization reactions inactivate microorganisms without modifying their antigenic properties and thereby creating immune modulators. The immunological correlates of protection induced by such eBeam based Salmonella Typhimurium (EBST) immune modulators in dendritic cell (DC) (in vitro) and mice (in vivo) models were assessed. The EBST stimulated innate pro inflammatory response (TNFα) and maturation (MHC-II, CD40, CD80 and CD86) of DC. Immuno-stimulatory potential of EBST was on par with both a commercial Salmonella vaccine, and live Salmonella cells. The EBST cells did not multiply under permissive in vitro and in vivo conditions. However, EBST cells remained metabolically active. EBST immunized mice developed Salmonella-specific CD4+ T-cells that produced the Th1 cytokine IFNγ at a level similar to that induced by the live attenuated vaccine (AroA- ST) formulation. The EBST retained stable immunogenic properties for several months at room temperature, 4°C, and -20°C as well as after lyophilization. Therefore, such eBeam-based immune modulators have potential as vaccine candidates since they offer the safety of a “killed” vaccine, while retaining the immunogenicity of an “attenuated” vaccine. The ability to store eBeam based immune modulators at room temperature without loss of potency is also noteworthy.

Investigations Into the Suitability of Bacterial Suspensions as Biological Indicators for Low-Energy Electron Irradiation

“…There are several studies dealing with the inactivation of other bacteria by accelerated electrons as source of ionizing radiation, i.e. Rodentibacter pneumotropicus (22), Salmonella enterica serovar Typhimurium (25), or Listeria monocytogenes (26). Using LEEI, a dose of 5 kGy was sufficient to inactivate E. coli DH5a from a preculture with an OD600 of 3.0 in PBS, reproducibly.…”

Fast Maturation of Splenic Dendritic Cells Upon TBI Is Associated With FLT3/FLT3L Signaling

“…Therefore, with the demonstration of increased FLT3 phosphorylation, upregulation of protein synthesis markers, and increased expression of MHC-II and lysosomal proteins LAMP1 and CD68, we believe to provide substantial evidence to state that TBI induces a quick upregulation of the splenic DC maturation process, from steady-state cells to effective APCs. Several other markers are commonly applied to the study of DC maturation, such as CD40, CD80, and CD86 (97), which are often upregulated along with MHC-II [e.g., (98)(99)(100)]. These markers were not included in the present study and further characterization of the phenotype of splenic DC cells activated upon TBI may reveal their dynamics.…”

Ionizing Radiation Technologies for Vaccine Development - A Mini Review

“…Similarly, gamma irradiation has also been shown to cause no damage to bacterial cell membranes at lethal doses (34)(35)(36). Furthermore, there is now significant evidence that in cells treated with lethal doses of ionizing radiation, there is residual metabolic activity after treatment (33,35,(37)(38)(39)(40)(41). For example, in Escherichia coli K-12 metabolic activity of E. coli was sustained for up to nine days following treatment, as demonstrated using AlamarBlue ™ as well as ATP assays (33).…”