Immune response to Rhodococcus equi ATCC 33701-secreted proteins in mice and identification of immunogenic recombinant proteins by dot-blotting.

This research study focused on the identification of proteins secreted by the bacterium Rhodococcus equi that might stimulate an immune response, which could then be used in the development of a vaccine. The results demonstrated that certain proteins – when combined with a specific adjuvant – were quite immunogenic in a mouse model, leading to strong immune responses that could potentially lay groundwork for future vaccine development.

Explanation of the Research

• This research was conducted with the goal of better understanding the immune response in horses to Rhodococcus equi, a bacterium that can cause severe pneumonia in foals.
• The study focussed on the proteins secreted by a specific strain of this bacterium, R. equi ATCC 33701.
• The researchers isolated these secreted proteins and combined them with an adjuvant, Montanide® ISA70, to increase the body’s immune response.
• They then tested this combination on mice.

Key Findings of the Study

• Among the key findings was that a crude extract of the bacterium’s secreted proteins, when combined with the ISA70 adjuvant, was found to be highly immunogenic in mice.
• This indicates that the tested combination stimulated a strong immune response.
• The highest immune response was seen on day 42 post the first subcutaneous immunization with an immune response titer of 99,000.
• This response was shown to be dependent on two key factors – the amount of proteins injected and the presence of the adjuvant.
• The research team then used a technique called “dot-blotting” to further identify which specific proteins from the bacterial secretome reacted strongly with the sera taken from the immunized mice.
• Eight proteins were identified in this manner, four of which were only found to be immunogenic when they had been paired with the adjuvant.

Implications of the Research

• The research could be vital in leading to the development of new vaccines to prevent pneumonia caused by Rhodococcus equi in foals.
• Further, the protein-adjuvant combinations identified in this study could be used to develop a serologic diagnosis of R. equi infections.
• However, further research is needed to ascertain whether these combinations also prompt a similarly enhanced immune response in horses, the target species for a potential vaccine.