Comparison of protection against caseous lymphadenitis in sheep induced by local isolated strain of corynebacterium pseudotuberculosis by toxoid pld‎ & toxoid pld with bacterin vaccine

Background: The objective of the present study was directed to perform a comparative study for the protective efficacy of different vaccine formulation to evoke protection against caseous lymphadenitis in sheep. Materials and Methods: The protective efficacy of two formulated vaccines against Corynebacterium pseudotuberculosis biotype 1 was tested on 9 male local sheep bread (Balady) from a herd free from caseous lymphadenitis Disease. Using a virulent strain of C. pseudotuberculosis biotype 1 (nitrate negative), locally isolated from severely infected sheep with caseous lymphadenitis, all isolates were identified by standard microbiological techniques and by polymerase chain reaction targeting phospholipase D genes. Synergistic haemolysis of all isolates were assayed by modified CAMP test and reverse CAMP test. The presences of phospholipase D gene in supernatants of all isolates were performed by sodium dodecyl sulfate polyacrylamide gel electrophoresis, immunoblot technique by using hyperimmune serum raised in rabbit immunized with recombinant phospholipase D gene antigen. The animals were divided into 3 groups each of 3 animals. Group A was immunized with Toxoid PLD‎, while group B was immunized with Toxoid ‎PLD with Bacterine (formaline ‎killed bacteria‎). Group C consisted of unvaccinated animals (control). All groups were injected by 2 doses of vaccine with 4 weeks interval then challenged four weeks after second dose of vaccination by 4 ×106 CFU forming unit per ml of live local isolated bacteria. Results: Results showed. Unvaccinated animals showed manifestations of caseous lymphadenitis observed in naturally diseased animals .It was observed that antibody titer of sheep vaccinated with PLD vaccine showed the highest titer of PLD antibody and provide high level of protection against caseous lymphadenitis (91%) in compare with the other type of vaccine used (Toxoid ‎PLD+Bacterine) as it give only level of protection 75%. Conclusions: These results confirm the importance of PLD as a protective antigen and demonstrate the potential for developing caseous lymphadenitis vaccine.