The Salmonella Gallinarum (SG) lon/cpxR deletion mutant JOL916 was developed as a live vaccine candidate for fowl typhoid (FT), and a SG mutant secreting an Escherichia coli heat-labile enterotoxin B subunit (LTB), designated JOL1229, was recently constructed as an adjuvant strain for oral vaccination against FT.

In a study published in BMC Veterinary Research, John Hwa Lee and colleagues at Chonbuk National University in Jeonju in the Republic of Korea evaluated the immunogenicity and protective properties of the SG mutant JOL916 and the LTB adjuvant strain JOL1229 in order to establish a prime and boost immunisation strategy for each strain.

In addition, they compared the increase in bodyweight, immunogenicity, egg production rates and bacteriological egg contamination of these strains with those of SG 9R, a widely used commercial vaccine.

Plasma IgG, intestinal secretory IgA (sIgA) and cell-mediated responses were significantly induced after a boost inoculation with a mixture of JOL916 and JOL1229, and significant reductions in the mortality of chickens challenged with a wild-type SG strain were observed in the immunised groups.

There were no significant differences in increases in bodyweight, cell-mediated immune responses, or systemic IgG responses between our vaccine mixture and the SG 9R vaccine groups. However, there was a significant elevation in intestinal sIgA in chickens immunised with the mixture at three weeks post-prime-immunisation and at three weeks post-boost-immunisation, while sIgA levels in SG 9R-immunised chickens were not significantly elevated compared to the control.

In addition, the SG strain was not detected in the eggs of chickens immunised with the mixture.

Lee and colleagues remark that their results suggest immunisation with the LTB-adjuvant strain JOL1229 can significantly increase the immune response, and provide efficient protection against FT with no side-effects on body weight, egg production or egg contamination.

Reference

^{Jeon B.W., R.M. Nandre and J.H. Lee. 2013. Oral immunization with an attenuated Salmonella Gallinarum mutant as a fowl typhoid vaccine with a live adjuvant strain secreting the B subunit of Escherichia coli heat-labile enterotoxin. BMC Veterinary Research, 9:96. doi:10.1186/1746-6148-9-96}

Further Reading

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May 2013