Evaluation of a Newly Developed Live Attenuated Vaccine Candidate Against Lawsonia intracellularis.

Background/

Objectives

Lawsonia intracellularis (L. intracellularis) is an important intestinal pathogen that causes porcine proliferative enteropathy (PPE) in swine production worldwide. Currently, only a few commercially available vaccines are available for PPE prevention.

Methods

In this study, an attenuated L. intracellularis variant of JS-G90 was obtained through subculturing of L. intracellularis JS isolates in McCoy cells for 90 generations, and its immune response was evaluated in pigs.

Results

The results demonstrated that pigs who underwent intragastric administration of JS-G90 had lower fecal bacterial shedding and no histopathological lesions, indicating that it was safe in pigs. Therefore, JS-G90 was selected to develop the attenuated PPE vaccine. The immune response of JS-G90 in pigs was further evaluated based on fecal bacterial shedding, histopathological lesions, and humoral and cell-mediated immune responses following challenge with pathogenic L. intracellularis. The results revealed that JS-G90 significantly decreased the copies of L. intracellularis in rectal swabs containing feces and ileum infection (p < 0.001), reduced histopathological lesions in the ileum, and elicited non-specific humoral (IgG and sIgA) and cell-mediated immune responses (p < 0.001) compared with the challenge control and mock groups.

Conclusions

In conclusion, the attenuated vaccine JS-G90 is safe and induced humoral and cell-mediated immune responses in pigs against pathogenic L. intracellularis infection. It may serve as an effective strategy for preventing and controlling PPE.