# Ultraviolet C inactivation of Coxiella burnetii for production of a structurally preserved whole cell vaccine antigen

## TL;DR

Researchers used ultraviolet light to inactivate Coxiella burnetii bacteria, creating a preserved whole cell antigen that could be used for vaccines or diagnostics.

## Contribution

The study introduces UVC inactivation as a novel method to preserve structural and antigenic properties of Coxiella burnetii for vaccine development.

## Key findings

- UVC inactivation at specific intensities effectively killed Coxiella burnetii without immediate structural damage.
- Rabbit immunization with UVC-treated bacteria induced a strong antibody response.
- UVC-treated bacteria showed delayed morphological changes after 24-48 hours, indicating potential for antigenic preservation.

## Abstract

Q fever, a worldwide-occurring zoonotic disease, can cause economic losses for public and veterinary health systems. Vaccines are not yet available worldwide and currently under development. In this regard, it is important to produce a whole cell antigen, with preserved structural and antigenic properties and free of chemical modifications. Thus, inactivation of Coxiella burnetii with ultraviolet light C (UVC) was evaluated. C. burnetii Nine Mile phase I (NMI) and phase II (NMII) were exposed to decreasing intensities in a time-dependent manner and viability was tested by rescue cultivation in axenic medium or cell culture. Effects on the cell structure were visualized by transmission electron microscopy and antigenicity of UVC-treated NMI was studied by immunization of rabbits. NMI and NMII were inactivated at UVC intensities of 250 µW/cm2 for 5 min or 100 µW/cm2 for 20 min. Reactivation by DNA repair was considered to be unlikely. No morphological changes were observed directly after UVC inactivation by transmission electron microscopy, but severe swelling and membrane degradation of bacteria with increasing severity occurred after 24 and 48 h. Immunization of rabbits resulted in a pronounced antibody response. UVC inactivation of C. burnetii resulted in a structural preserved, safe whole cell antigen and might be useful as antigen for diagnostic purposes or as vaccine candidate.