Effective inactivated lumpy skin disease vaccine for cattle using a field viral strain and Montanide 206

Lumpy skin disease (LSD) causes significant economic losses to cattle industries. In Mongolia, LSD outbreaks were first reported in 2021, with a few additional cases later that year. The situation has since alleviated due to effective control measures, including the use of live-attenuated vaccines. However, unlike the inactivated vaccine, live-attenuated vaccines carry risks, including genetic recombination and vaccine-associated clinical symptoms and outbreaks. Our research group previously isolated a field strain of LSDV, designated DO-21, from the first outbreak in Mongolia in 2021. Using this laboratory-adapted strain, we developed an inactivated vaccine by treating it with binary ethylenimine and formulating it with Montanide ISA 206, a water-in-oil-water adjuvant. Safety was confirmed in mice and cattle using administrations of 3- and 7-fold higher doses of the inactivated vaccine, respectively. In the challenge experiments, all rabbits and cattle were fully protected by day 14 post-booster vaccination following a severe homologous challenge with same field strain (DO-21) without any clinical signs. On the same day, all five vaccinated rabbits showed seroconversion, while all five immunised calves exhibited seroconversion and neutralising antibodies, with interferon-gamma release detected in their blood samples following viral exposure. In addition, seroconversion persisted in all three vaccinated rabbits for at least 120 days post-prime vaccination, while both seroconversion and neutralising antibodies were maintained in approximately 90% cattle for 120 days post-prime vaccination. In conclusion, inactivated vaccines are alternatives to live-attenuated vaccines, particularly in countries with sporadic cases of LSD or in non-endemic countries bordering endemic regions.