Advances in understanding immunity to Rhodococcus equi infection and Vaccine Development Strategies: A Comprehensive Review

Rhodococcus equi is a Gram-positive, facultative intracellular bacterial pathogen which causes persistent purulent bronchopneumonia in foals less than six months of age. Conventional vaccine strategies, like live-attenuated and killed vaccines were ineffective in providing reliable protection against R. equi infection. On the other hand, contemporary vaccine approaches, including DNA plasmid vaccines, genetically attenuated vaccines, subunit vaccines, and e-beam inactivated bacterial vaccines, have yielded mixed results in terms of safeguarding foals from the pathogen. Recent progress in vector-based vaccines, especially when applied to the mouse model, is opening up promising pathways for the development of potentially efficacious vaccination strategies against R. equi. Hyperimmune plasma (HIP) might reduce the severity of R. equi infection in foals, but the efficacy of HIP is still a subject of debate, as it hasn't been proven to be completely efficient. This article provides an overview of current understanding of the equine immune response against R. equi infection and major research findings on the development of R. equi vaccines for the control and prevention of this economically important disease.