Avaliação da Viabilidade de Lawsonia intracellularis em Lâmina Própria Intestinal, Placas de Peyer e Linfonodos Mesentéricos de Suínos: Implicações na Patogênese

Abstract

Lawsonia intracellularis (L. intracellularis) is the etiological agent of porcine proliferative enteropathy, characterized by the colonization of intestinal epithelial cells, particularly in the crypts of the ileum. Although there have been some advances in understanding its pathogenesis over the past decade, the dissemination and secondary sites of colonization remain incompletely understood. This study investigated the viability of L. intracellularis in the lamina propria and mesenteric lymph nodes of infected pigs. Using immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH), labeling was observed in intestinal epithelial cells and in the lamina propria in all animals from the infected group. These animals had been experimentally challenged with L. intracellularis in a previous study, presented anatomopathological lesions compatible with the infection, and their paraffin blocks were used for the present analysis. The intensity of labeling varied among individuals. FISH revealed the presence of L. intracellularis predominantly in the intestinal epithelium, along with cytoplasmic labeling in interstitial cells, suggesting the release of host cells or a possible transition in the stage of infection. In the mesenteric lymph nodes, IHC detected bacterial antigens, but FISH did not reveal viable microorganisms. The absence of labeling in lymphoid tissues suggests that the bacterium does not directly colonize these sites. The study also addressed the attempted use of combined IHC and FISH techniques for phenotypic double labeling. However, this approach could not be standardized, as the available antibodies did not yield satisfactory labeling, even after multiple optimization attempts. This study contributes to the understanding of L. intracellularis dissemination and proposes new approaches for future investigations, such as the use of specific probes to identify host cells.