Microbial Physiology and Genomics

Biography

Biography: Elgabry

Abstract

All strains of Corynebacterium pseudotuberculosis have two virulence factors ,the first is an  exotoxin virulence factor  called phospholipase D that increasing vascular permeability and enhances dissemination of the bacteria by damaging endothelial cells .The second virulence factor is an external lipid coat that  protect the bacteria  from hydrolytic enzymes in host phagocytes where the bacteria replicate and release when rupture . The ongoing process of bacterial replication, followed by attraction and inducing an inflammatory response , increasing the vascular permeability and lymph flow ,forms the characteristic abscesses associated with CL .The objective of the present study was directed to perform a comparative study for the protective efficacy of cell mediated immune response by lymphocyte proliferation assay (LPA) for different vaccine formulation to evoke protection against caseous lymphadenitis in sheep . The protective efficacy of four formulated vaccines against Corynebacterium pseudotuberculosis biotype 1 was tested on 15 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. The animals were divided into 5 groups each of 3 animals. each one group was immunized with combined vaccine , the first vaccine composed of Toxoid PLD vaccine  ,second vaccine composed of with Toxoid ‎PLD with Bacterine (formaline ‎killed bacteria‎) vaccine ,third vaccine  composed of  toxoid PLD plus Covaccine 8 ,fourth  vaccine composed of toxoid PLD plus polyvalent clostridial vaccine locally produced and control groups of unvaccinated animals. All groups were challenged by 4 ×10⁶ CFU forming unit per ml of live virulent strain of Corynebacterium pseudotuberculosis isolated from local sheep infected with caseous lymphadenitis. Unvaccinated animals showed manifestations of caseous lymphadenitis (CLA) that Cleary observed in naturally diseased animals. The proliferation response of lymphocytes to PLD antigen were measured at 4 weeks after challenge by lymphocyte proliferation assay (LPA)using ELISA Brdu (colorimetric) kit. The results of this work revealed that PLD toxoid could evoke cell mediated immunity measured by lymphocyte proliferation assay showing the highest stimulation index (9.12%).On the other hand combined PLD toxoid and clostridial toxoid vaccine either locally prepared clostridial vaccine (polyvalent clostridial vaccine ) or imported one  (Covaccine 8)could provide protection against C. pseudotuberculosis challenge but  less than that provided by vaccination with PLD alone as lymphocyte proliferation activity decreased from SI 9.12 in vaccinated sheep with single PLD toxoid vaccine to SI 5.73 in case of combined vaccine. The present study indicated that the toxoid PLD alone vaccine is most efficient vaccine was provided in animals against CLA.