Immunogenicity of an electron beam inactivated Rhodococcus equi vaccine in neonatal foals.
Authors: Bordin Angela I, Pillai Suresh D, Brake Courtney, Bagley Kaytee B, Bourquin Jessica R, Coleman Michelle, Oliveira Fabiano N, Mwangi Waithaka, McMurray David N, Love Charles C, Felippe Maria Julia B, Cohen Noah D
Journal: PloS one
Summary
Rhodococcus equi remains a significant respiratory pathogen in foals, yet no licensed vaccine currently offers reliable protection against infection. Researchers tested whether electron beam irradiation could produce a safe, immunogenic vaccine by identifying a radiation dose that eliminated R. equi replication whilst preserving outer cell wall architecture, then administered this inactivated preparation orally to neonatal foals. The vaccine successfully stimulated both cell-mediated immunity (measured through interferon-γ production by peripheral blood mononuclear cells when challenged with virulent R. equi) and mucosal immunity (generating nasopharyngeal IgA antibodies), demonstrating efficacy despite passive transfer of maternal antibodies—a response pattern previously associated with protection following live organism exposure. No adverse effects occurred in vaccinated foals, suggesting that this orally-delivered, inactivated approach may offer a safer alternative to current protocols. For practitioners managing young stock, these findings provide evidence that an electron beam-inactivated vaccine could potentially fill a critical gap in R. equi prevention strategies, though further efficacy trials would be required before clinical implementation.
Read the full abstract on PubMed
Practical Takeaways
- •An effective R. equi vaccine candidate has been developed using electron beam inactivation, offering a safer alternative to live vaccines for neonatal foals
- •Oral administration of the inactivated vaccine successfully triggers both mucosal and cell-mediated immunity even when maternal antibodies are present
- •This vaccine approach could reduce the significant mortality and morbidity from R. equi pneumonia in foal operations once clinical trials and licensing are completed
Key Findings
- •Electron beam irradiation successfully inactivated R. equi while preserving outer cell wall integrity
- •Enteral administration of eBeam-inactivated R. equi stimulated interferon-γ production by peripheral blood mononuclear cells in response to virulent R. equi
- •eBeam-inactivated vaccine generated naso-pharyngeal R. equi-specific IgA in newborn foals despite maternal antibodies
- •Immune response pattern was comparable to live organism administration with no adverse effects observed