Pathogens Inactivated by Low-Energy-Electron Irradiation Maintain Antigenic Properties and Induce Protective Immune Responses

Abstract

Inactivated vaccines are commonly produced by incubating pathogens with chemicals such as formaldehyde or β-propiolactone. This is a time-consuming process, the inactivation efficiency displays high variability and extensive downstream procedures are often required. Moreover, application of chemicals alters the antigenic components of the viruses or bacteria, resulting in reduced antibody specificity and therefore stimulation of a less effective immune response. An alternative method for inactivation of pathogens is ionizing radiation. It acts very fast and predominantly damages nucleic acids, conserving most of the antigenic structures. However, currently used irradiation technologies (mostly gamma-rays and high energy electrons) require large and complex shielding constructions to protect the environment from radioactivity or X-rays generated during the process. This excludes them from direct integration into biological production facilities. Here, low-energy electron irradiation (LEEI) is presented as an alternative inactivation method for pathogens in liquid solutions. LEEI can be used in normal laboratories, including good manufacturing practice (GMP)- or high biosafety level (BSL)-environments, as only minor shielding is necessary. We show that LEEI efficiently inactivates different viruses (influenza A (H3N8), porcine reproductive and respiratory syndrome virus (PRRSV), equine herpesvirus 1 (EHV-1)) and bacteria (Escherichia coli) and maintains their antigenicity. Moreover, LEEI-inactivated influenza A viruses elicit protective immune responses in animals, as analyzed by virus neutralization assays and viral load determination upon challenge. These results have implications for novel ways of developing and manufacturing inactivated vaccines with improved efficacy.

Automated application of low energy electron irradiation enables inactivation of pathogen- and cell-containing liquids in biomedical research and production facilities

“…Calibration was carried out in a petri dish system using a foil of oriented polypropylene (OPP) to generate a thin liquid layer (approx. 85 μm) of TTC irradiated with a very low dose gradient of 13% 23 . For the irradiation with the slit diaphragm, a dose reduction of 99% was measured.…”

Low-Energy Electron Irradiation Efficiently Inactivates the Gram-Negative Pathogen Rodentibacter pneumotropicus—A New Method for the Generation of Bacterial Vaccines with Increased Efficacy

“…We have previously shown that LEEI can successfully be used to inactivate a number of pathogens, such as influenza (H3N8), Equid herpesvirus 1, porcine reproductive and respiratory syndrome virus (PRRSV) or respiratory syncytial virus (RSV) [13,17]. Here we report that a bacterin including the LEEI-inactivated Gram-negative pathogen R. pneumotropicus elicited a prominent humoral immune response and protection against infection of the lower respiratory tract in mice, the natural host.…”

“…This makes LEEI applicable in normal laboratory settings. We have shown previously that LEEI can be used to generate efficient vaccines against viruses and parasites [13,17,18]. To evaluate the potential of LEEI for the development of bacterins with increased protective efficacy, we chose a challenge experiment with R. pneumotropicus in its natural host, the mouse.…”

Radiation resistance of novel SARS-CoV-2: A Monte Carlo investigation on characterization and determination of gamma-ray attenuation properties

“…Additionally, the effect on the proteins can be reduced with the use of electron, but electron irradiation is less penetrating than gamma rays [15]. In contrast to high energy electron (>1 MeV), the low energy electron irradiation (LEEI, <500 keV), does not generate x ray radiation and thus, does not require complex shielding [18]. LEEI works efficiently in inactivation of different viruses such as (influenza A (H3N8) and porcine reproductive and respiratory syndrome virus (PRRSV) [18].…”

“…In contrast to high energy electron (>1 MeV), the low energy electron irradiation (LEEI, <500 keV), does not generate x ray radiation and thus, does not require complex shielding [18]. LEEI works efficiently in inactivation of different viruses such as (influenza A (H3N8) and porcine reproductive and respiratory syndrome virus (PRRSV) [18]. On the other hand, ultraviolet radiation demonstrated an efficient role in inactivation of the enveloped MHV coronavirus [19], the enteric human adenovirus (HAdV) reported to be the most UVresistant virus [20].…”