Single and repeat-dose toxicity and local tolerance assessment of newly developed oil emulsion adjuvant formulations for veterinary purposes

Abstract

Adjuvants are components of vaccines that boost the intensity, duration, and breadth of the immune response. Insight into the mechanisms responsible for the immunotoxicity of both local and systemic adverse reactions following the use of adjuvants has been gained through research over the past twenty years. In the present study, single and repeated-dose toxicity and local tolerance of newly developed Water-in-Oil (W/O) and Water-in-Oil-in-Water (W/O/W) Emulsion adjuvants (Coralvac RZ 528, Coralvac RZ 506, Coralvac AT 318, Coralvac AT 318 SIS and Coralvac 252) by Coral Biotechnology Industry and Trade Incorporated Company were demonstrated after intramuscular injection in mice. In both toxicity studies, no adverse reactions such as death, general appearance, behavior, or weight loss were observed in the mice in the experimental groups. The results indicate that clinical chemistry parameters demonstrated normal function of the major organs and no irreversible damage to the mice in all adjuvant groups compared to the control group. In histopathologic investigation of single dose toxicity study, inflammation, edema, and large amounts of lipid droplets were observed on the 7th day in all experimental groups. On the 14th day, when the control group and the experimental groups were compared, it was seen that inflammation and edema had decreased considerably. Similarly, repeated dose toxicity study showed mild inflammation and edema in the control group, while quite widespread and severe inflammation, edema, and diffuse lipid droplets of varying sizes were observed in all adjuvant groups compared to the control group. These observations would be useful for the future development of oil-based adjuvants and their use in veterinary inactive vaccines.

Keywords:

• Adjuvants
• veterinary vaccines
• emulsions
• single dose toxicity
• repeated dose toxicity
• local tolerance

Data availability statement

The datasets generated during and/or analyzed during the current study are available from the corresponding author on request.

Additional information

Funding

This research was supported by Ege University Research Foundation (FDK-2023-30779).