[Construction and characterization of Salmonella Pathogenicity Island 2 (SPI-2) deletion mutant of Salmonella Pullorum S06004].

To research the pathogenicity of Salmonella Pathogenicity Island 2 (SPI-2) deletion mutant of Salmonella Pullorum and preliminary explore the feasibility of developing safe attenuated Salmonella Pullorum candidate vaccine strain. The SPI-2 (-40 kb) deletion mutant of Salmonella Pullorum S06004 was constructed using the λ-red recombinant system. Then the biological characteristics such as growth rate, biochemical properties, genetic stability and virulence were evaluated between the deletion mutant strain S06004ΔSPI2 and its parent strain S06004. S06004ΔSPI2 was successfully constructed. The growth rate and biochemical properties of S06004ΔSPI2 were consistent with those of its parent strain S06004. The mutant was stable with the deletion of SPI-2. Chicken lethal test showed that the LD50 of S06004ΔSPI2 was 252 times higher than the parent strain S06004. The virulence of S06004ΔSPI2 was obviously attenuated. This study provided basic data for further study of the functions of SPI-2, and implied its potential to develop attenuated Salmonella vaccine.

Yin J ，Wu Y ，Lin Z ，Wang X ，Hu Y ，Li Q ，Geng S ，Jiao X ... -  《-》

Evaluation of the Salmonella enterica Serovar Pullorum Pathogenicity Island 2 Mutant as a Candidate Live Attenuated Oral Vaccine.

Salmonella enterica serovar Pullorum (S. Pullorum) is a highly adapted pathogen that causes pullorum disease (PD), an important systemic disease of poultry that causes severe economic losses in developing countries. In the interests of developing a safe and immunogenic oral vaccine, the efficacy of a Salmonella pathogenicity island 2 (SPI2)-deleted mutant of S. Pullorum (S06004ΔSPI2) was evaluated in chickens. S06004ΔSPI2 was severely less virulent than the parental wild-type strain S06004 as determined by the 50% lethal dose (LD50) for 3-day-old chickens when injected intramuscularly. Two-day-old chickens immunized with a single oral dose of S06004ΔSPI2 showed no differences in body weight or clinical symptoms compared with those in the negative-control group. S06004ΔSPI2 bacteria were not isolated from livers or spleens of immunized chickens after a short period of time, and specific humoral and cellular immune responses were significantly induced. Immunized chickens were challenged with S. Pullorum strain S06004 and Salmonella enterica serovar Gallinarum (S. Gallinarum) strain SG9 at 10 days postimmunization (dpi), and efficient protection against the challenges was observed. None of the immunized chickens died, the clinical symptoms were slight and temporary following challenge in immunized chickens compared with those in the control group, and these chickens recovered by 3 to 5 dpi. Overall, these results demonstrate that S06004ΔSPI2 can be used as a live attenuated oral vaccine.

Yin J ，Cheng Z ，Wang X ，Xu L ，Li Q ，Geng S ，Jiao X ... -  《-》

Construction and characterization of a cigR deletion mutant of Salmonella enterica serovar Pullorum.

Yin J ，Xia J ，Tao M ，Xu L ，Li Q ，Geng S ，Jiao X ... -  《-》

Salmonella enterica serovar Pullorum requires the Salmonella pathogenicity island 2 type III secretion system for virulence and carriage in the chicken.

Functional mutations were made in the type III secretion systems encoded by Salmonella pathogenicity island 1 (SPI 1) and Salmonella pathogenicity island 2 (SPI 2) of Salmonella enterica serovar Pullorum, the cause of pullorum disease in poultry. Their role in cell invasion in vitro, and in virulence in vivo was determined. The SPI 1 mutant showed decreased invasiveness for chicken cells but was capable of causing disease in orally infected 1-day-old chicks, although it showed some reduction in virulence. The SPI 2 mutant showed no reduction in invasiveness, but was fully attenuated for virulence in 1-day-old chicks, and was not detected following oral infection in 1-week-old chickens. Following intravenous infection, the SPI 2 mutant was also attenuated and cleared more rapidly than the parent strain. This indicates that S. Pullorum requires SPI 2 for virulence and persistence but SPI 1 appears to contribute to, but is not essential for, the virulence of S. Pullorum.

Wigley P ，Jones MA ，Barrow PA 《AVIAN PATHOLOGY》

Immunogenicity and protective efficacy of Salmonella enterica serovar Pullorum pathogenicity island 2 mutant as a live attenuated vaccine candidate.

Yin J ，Cheng Z ，Xu L ，Li Q ，Geng S ，Pan Z ，Jiao X ... -  《BMC Veterinary Research》