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

## TL;DR

A new live attenuated vaccine against Lawsonia intracellularis was developed and shown to be safe and effective in pigs, reducing infection and triggering immune responses.

## Contribution

Development and evaluation of a novel live attenuated vaccine candidate, JS-G90, for porcine proliferative enteropathy.

## Key findings

- JS-G90 reduced fecal bacterial shedding and caused no histopathological lesions in pigs.
- JS-G90 significantly decreased L. intracellularis copies in rectal swabs and ileum infection.
- The vaccine elicited non-specific humoral and cell-mediated immune responses in pigs.

## Abstract

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.