Avian Salmonella enteritidis serovar Enteritidis with ClpP deletion is attenuated and highly immunogenic in chickens

Authors: XUHUA RAN, ZHIYUAN YANG, GUAGNXI SHAO, XIAOBO WEN, SIGUO LIU, HONGBO NI

Abstract: Salmonella enterica subsp. enterica serovars are leading causative agents of gastroenteritis in humans and numerous animal species worldwide. The ClpP from Salmonella enterica is responsible for regulation under various stress conditions. We were interested in the effect of ClpP deletion mutation on attenuation of Salmonella enterica subsp. enterica serovar Enteritidis (SE) in chickens. Therefore, SM-6/Δ ClpP , deletion of the ClpP gene from a wild-type SE-6 (SM-6) strain, was generated using the phage &lamda; Red homologous recombination. Compared with SM-6, SM-6/&DeltaClpP represented a retarded growth rate and lower concentration in LB broth with and without 5% NaCl or lower pH values, indicating that it is sensitive to conventional disinfectants. SM-6/Δ ClpP represented reduced invasion into macrophages in vitro and an approximate 400-fold attenuation based on cell invasion assay and median lethal dose (LD 50 ) in specific pathogen-free (SPF) chickens. Furthermore, SM-6/Δ ClpP showed reduced colonization in the liver and spleen and faster clearance compared with SM-6, indicating a short discharge. The survival rate of 7-day-old SPF chickens immunized with SM-6/Δ ClpP against homologous challenge and antibody kinetics indicated that SM-6/ΔClpP provided efficient protection from lethal challenge and induced robust antibody immune responses, demonstrating the potential of live, attenuated SE as a vaccine candidate.

Keywords: ClpP, Salmonella Enteritidis, chickens, vaccine, immune responses

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