Abstract
Simple SummaryThe potential of the bovine intelectin 2 as a biomarker of Mycobacterium avium subsp. paratuberculosis infection was investigated using quantitative immunohistochemical analysis of ileocecal valve samples of animals with increasing degrees of lesion severity (focal, multifocal and diffuse histological lesions) and control animals without detected lesions. Significant differences were observed in the mean number of intelectin 2 immunolabelled cells between the three histopathological types and the control. Specifically, the mean number of intelectin 2 labelled cells was indicative of disease progression as the focal group had the highest number of intelectin 2 secreting cells followed by the multifocal, diffuse and control groups indicating that intelectin 2 is a good biomarker for the different stages of Mycobacterium avium subsp. paratuberculosis infection. Quantification of bovine intelectin 2 secreting cells could constitute a good post-mortem tool, complementary to histopathology, to improve detection of Mycobacterium avium subsp. Paratuberculosis infections, especially latent forms of infection.Paratuberculosis (PTB), a chronic granulomatous enteritis caused by Mycobacterium avium subsp. paratuberculosis (MAP), is responsible for important economic losses in the dairy industry. Our previous RNA-sequencing (RNA-Seq) analysis showed that bovine intelectin 2 (ITLN2) precursor gene was overexpressed in ileocecal valve (ICV) samples of animals with focal (log2 fold-change = 10.6) and diffuse (log2 fold-change = 6.8) PTB-associated lesions compared to animals without lesions. This study analyzes the potential use of ITLN2, a protein that has been described as fundamental in the innate immune response to infections, as a biomarker of MAP infection. The presence of ITLN2 was investigated by quantitative immunohistochemical analysis of ICV samples of 20 Holstein Friesian cows showing focal (n = 5), multifocal (n = 5), diffuse (n = 5) and no histological lesions (n = 5). Significant differences were observed in the mean number of ITLN2 immunostained goblet and Paneth cells between the three histopathological types and the control. The number of immunolabelled cells was higher in the focal histopathological type (116.9 ± 113.9) followed by the multifocal (108.7 ± 140.5), diffuse (76.5 ± 97.8) and control types (41.0 ± 81.3). These results validate ITLN2 as a post-mortem biomarker of disease progression.
Highlights
Bovine paratuberculosis (PTB) or Johne’s disease, is a chronic granulomatous enteritis of ruminants responsible for important economic losses in dairy herds worldwide due to reduced milk production, premature culling and reduced slaughter value [1,2]
PTB is caused by Mycobacterium avium subsp. paratuberculosis (MAP), a mycobacteria with zoonotic potential since it has been postulated as a possible trigger factor in several autoimmune diseases in humans such as Crohn’s disease [3,4], rheumatoid arthritis [5,6], multiple sclerosis [7,8] or type I diabetes [9]
In spite of the small sample size used in this study (n = 5 for each histopathological type) significant differences in the geometric mean number of intelectin 2 (ITLN2) immunolabelled cells were found between the different histopathological types and the control group with no lesions detected beyond the standard p < 0.05 indicating that ITLN2 is a good biomarker for the different stages of MAP infection
Summary
Bovine paratuberculosis (PTB) or Johne’s disease, is a chronic granulomatous enteritis of ruminants responsible for important economic losses in dairy herds worldwide due to reduced milk production, premature culling and reduced slaughter value [1,2]. PTB control programs are currently based on testing and culling test-positive cows combined with good management practices including appropriate hygienic-sanitary strategies [11,12,13] These control programs are strongly conditioned by the low sensitivities and specificities for the detection of latent forms of infection because bacteria are excreted in low numbers and animals have low titers of specific antibodies [14,15,16,17,18]. Emerging -omic technologies have been used for the identification of host biomarkers [19,20,21,22,23,24,25,26,27,28,29,30] that could help to understand the factors that determine disease progression from the latent to the patent form of infection and could be used in biomarkerbased diagnostic methods for PTB Most of these biomarkers have not yet been applied and validated for PTB diagnosis in naturally infected cattle
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