An Adenoviral Vector Based Vaccine for Rhodococcus equi

Abstract

Rhodococcus equi is a respiratory pathogen which primarily infects foals and is endemic on farms around the world with 50% mortality and 80% morbidity in affected foals. Unless detected early and treated appropriately the disease can be fatal. Currently, there is no vaccine available to prevent this disease. For decades researchers have endeavoured to develop an effective vaccine to no avail. In this study a novel human adenoviral vector vaccine for R. equi was developed and tested in the mouse model. This vaccine generated a strong antibody and cytokine response and clearance of R. equi was demonstrated following challenge. These results show that this vaccine could potentially be developed further for use as a vaccine to prevent R. equi disease in foals.

Protective immune responses against Rhodococcus equi : an innate immunity-focused review

“…239 However, IM LVRE induced higher R. equi bacterial clearance after aerosolized challenge than other groups, and was also associated with higher INF-γ, IL-2, and IL-10 production by lung cells post-challenge. 239 The researchers speculated that the lack of antibody response in the IM LVRE vaccine control group was due to the rapid clearance of R. equi by the innate immune system before humoral immunity could be generated. 239 However, that does not explain the increased bacterial clearance post-challenge observed in the IM LVRE group.…”

“…93 In a vaccine experiment testing an adenoviral vector containing vapA, intramuscular (IM) injection of LVRE was used as a positive control for immunization. 239 Interestingly, the adenoviral vaccine induced VapAspecific antibody response, but the IM LVRE did not. 239 However, IM LVRE induced higher R. equi bacterial clearance after aerosolized challenge than other groups, and was also associated with higher INF-γ, IL-2, and IL-10 production by lung cells post-challenge.…”

“…239 Interestingly, the adenoviral vaccine induced VapAspecific antibody response, but the IM LVRE did not. 239 However, IM LVRE induced higher R. equi bacterial clearance after aerosolized challenge than other groups, and was also associated with higher INF-γ, IL-2, and IL-10 production by lung cells post-challenge. 239 The researchers speculated that the lack of antibody response in the IM LVRE vaccine control group was due to the rapid clearance of R. equi by the innate immune system before humoral immunity could be generated.…”

Rhodococcus equifoal pneumonia: Update on epidemiology, immunity, treatment and prevention

“…A variety of technological platforms have been explored, including inactivated, sub-unit, DNA, auxotrophic, viral-vectored and genetically-modified live vaccines. 74,75,[78][79][80]84,[142][143][144][145][146][147][148][149][150][151][152][153][154][155] Recently, the immunogenicity and efficacy of a vaccine based on a synthetic peptide of the R. equi pilus (Rpl) was evaluated as a candidate vaccine. 155 The pilus vaccine significantly increased titres in the serum and colostrum of mares and in the serum and BAL fluid of foals that suckled vaccinated mares (relative to unvaccinated mares and their foals); however, there were no significant differences after intrabronchial infection between foals of vaccinated dams and foals of unvaccinated dams in physical examination scores, thoracic ultrasound lesion scores, the proportion of lung lesions, R. equi recovered from lungs, or concentrations of white blood cells or fibrinogen.…”

“…To date, an effective vaccine against R. equi for foals has been elusive. A variety of technological platforms have been explored, including inactivated, sub‐unit, DNA, auxotrophic, viral‐vectored and genetically‐modified live vaccines 74,75,78–80,84,142–155 . Recently, the immunogenicity and efficacy of a vaccine based on a synthetic peptide of the R. equi pilus (Rpl) was evaluated as a candidate vaccine 155 .…”