Multi-epitope recombinant chimera and inactivated Escherichia coli expressing chimeric gene of Corynebacterium pseudotuberculosis as vaccines for caseous lymphadenitis

The complete genome sequence of the FRC41 strain of Corynebacterium pseudotuberculosis allowing the identification of genes that code for proteins considered to be potential virulence factors (NanH, PknG, SodC and SpaC). In this study, a multi-epitope chimeric protein vaccine derived from these virulence factors was tested for efficacy in mice. Chimeric protein was expressed in Escherichia coli in purified and unpurified forms and used in immunization trial and challenge. Mice were immunized with a sterile 0.9 % saline solution (G1), recombinant chimera emulsified in Montanide ISA 61 (v/v) (G2), recombinant chimera emulsified in 15 % of adjuvant aluminum hydroxide (Al(OH)₃) (G3), inactivated Escherichia coli/chimera combined with Montanide (G4) and inactivated Escherichia coli/chimera combined with Al(OH)₃ (G5). Animals received two doses of vaccines with 21-days interval, and were challenge with Corinebacterium pseudotuberculosis MIC-6 strain. The total IgG, IgG1, and IgG2a production levels increased significantly in the experimental groups (G2-G5) from day 21. The IgG2a/IgG1 ratio suggests a Th1/Th2 immune response in all groups. The significant survival of 60 % was observed only in G5. The IFN-γ mRNA expression were up-regulated (p < 0.05) in G3, G4 and G5, the G4 and G5 also showed a significant increase in the IL-4 levels. On the other hand, only G3 presented significant higher levels of TNF-α in relation to control (G1). IL-12 expression was down-regulated (p < 0.05) in all experimental groups (G2-G5). Overall, the results obtained by G5 elicited a strong humoral and cellular immune response, highlighting its potential as a promising CLA vaccine candidate.