Corynebacterium pseudotuberculosiscp09 mutant and cp40 recombinant protein partially protect mice against caseous lymphadenitis

Abstract

BackgroundCaseous lymphadenitis (CLA) is an infectious disease that affects small ruminants and is caused by Corynebacterium pseudotuberculosis. This disease is responsible for high economic losses due to condemnation and trim of infected carcasses, decreased leather and wool yield, loss of sales of breeding stock and deaths from internal involvement. Treatment is costly and ineffective; the most cost-effective strategy is timely immunisation. Various vaccine strategies have been tested, and recombinant vaccines are a promising alternative. Thus, in this study, different vaccine formulations using a recombinant protein (rCP40) and the CP09 live recombinant strain were evaluated. Five groups of 10 mice each were immunised with saline (G1), rCP40 (G2), CP09 (G3), a combination of CP09 and rCP40 (G4) and a heterologous prime-boost strategy (G5). Mice received two immunisations within 15 days. On day 30 after primary immunisation, all groups were challenged with a C. pseudotuberculosis virulent strain. Mice were monitored and mortality was recorded for 30 days after challenge.ResultsThe G2, G4 and G5 groups showed high levels of IgG1 and IgG2a; G2 presented significant IgG2a production after virulent challenge in the absence of IgG1 and IgG3 induction. Thirty days after challenge, the mice survival rates were 20 (G1), 90 (G2), 50 (G3), 70 (G4) and 60% (G5).ConclusionsrCP40 is a promising target in the development of vaccines against caseous lymphadenitis.

Evaluation of the aroA mutant of Corynebacterium pseudotuberculosis in cellular and murine models

“…One problem associated with experimental live vaccines of C. pseudotuberculosis is the occurrence of lesions at the vaccination site 9,16 . To demonstrate the in vivo mutant attenuation, the degree of the lesion at the vaccination site was evaluated.…”

“…The control group was injected with PBS. The challenge was performed on day 21 post-vaccination using the ATCC 43924 C. pseudotuberculosis strain at a concentration of 1 x 10 4 /0.1 ml in PBS, by intraperitoneal route 9 . The animals were monitored daily, and on day 28, they were euthanized and underwent necropsy for bacteriological studies in the liver and spleen.…”

“…This study was performed because of the need for a live vaccine to prevent caseous lymphadenitis. To date, the mutant strains that have been evaluated as possible C. pseudotuberculosis immunogens have failed to confer adequate protection to susceptible animals 9,21,22 . Here, the aroA mutant of C. pseudotuberculosis was chosen based on the good results that were obtained by applying the aroA mutant of Salmonella enterica, subsp.…”

“…The cellular immune response is known to be important for the resolution (or control) of diseases caused by intracellular bacteria, such as C. pseudotuberculosis, but its aroA mutant bacteria failed to elicit an adequate TH1 response. This was reflected by the aroA mutant's poor ability to adhere to and invade the murine cells, thereby reducing the bacterial antigen presentation by the main histocompatibility complex type I because these antigens were not found in adequate levels in the intracellular compartments 9 .…”

“…Additionally, these mutations altered the regulation of the murA gene, which is involved in peptidoglycan synthesis, thereby causing several defects in the bacterial cell wall and the outer bacterial membrane and facilitating phagocytosis of the mutant 6,8 . In a study of the cp09 mutant of C. pseudotuberculosis, BALB/c mice were immunized and showed 50 % survival after being challenged, intraperitoneally (i. p.), with a virulent strain at a dose of 1 x 10 4 colony-forming units (CFU) 9 .…”