Differences in the peripheral immune response between lambs and adult ewes experimentally infected with Mycobacterium avium subspecies paratuberculosis

Abstract

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Pathological Findings in Young and Adult Sheep Following Experimental Infection With 2 Different Doses of Mycobacterium avium Subspecies paratuberculosis

“…According to the results of this study, the experimental inoculation with Map was able to infect both the ewes and lambs, but detectable lesions and immune response 13 were observed only in those animals challenged with a high dose of the mycobacteria. Adult HD-infected sheep developed lesions consistent with Map infection, with clear differences in the pathological features when compared with the HD-infected lambs.…”

“…Besides, the peripheral immune response, evaluated by the specific interferon (IFN)-g production, was similar to that from the control group. 13 These results indicate that the establishment of an infection and the formation of granulomatous lesions is directly dependent on the infectious dose. This hypothesis has already been suggested by other authors, who established a correlation between the amount of the dose received and the severity of the infection induced, in ovine, 5,30,31 bovine, 39 or red deer.…”

“…All of them were randomly selected from a flock without clinical cases of paratuberculosis in the past 5 years and in which no vaccination against paratuberculosis was practiced before. 13 After a period of adaptation once in the experimental facilities of the University of León, the animals were housed in separate barns to prevent direct contact between the groups. Both adult and young ovine were randomly divided into 3 groups: one infected with the high dose of Map inoculum (HD group; n ¼ 13 ewes and 8 lambs), the second one with the low dose (LD group; n ¼ 10 ewes and 8 lambs), and a third group of uninfected control animals, challenged with saline solution (n ¼ 7 ewes and 8 lambs).…”

“…Two grams of tissues or feces was processed for culture onto tubes containing Löwenstein Jensen and Middlebrook 7H11 solid medium, supplemented with mycobactin J and previously decontaminated with hexadecylpyridinium chloride (Merck, Darmstadt, Germany), as described by Aduriz et al 1 The procedure is explained in detail in a previous publication. 13 …”

“…13 Both the humoral and specific cell-mediated immune responses appeared earlier and more intensely in the adult sheep than in the lambs, probably due to previous contact with Map or other mycobacteria, whereas the Map-challenged lambs showed a more immature immune response, unable to control the progression of the infection. 13 The main objective of the present work is to study and characterize the pathological response of Map infection in the same experiment, by comparing the differences observed in the pathological evolution of these experimentally infected lambs and ewes and evaluating the severity of the lesions with a detailed count of the granulomas formed. The effect of the challenge inoculum dose in the establishment and developmental stage of the lesions in these animals is also assessed.…”