Augmentation of Secreted and Intracellular Gamma Interferon following Johnin Purified Protein Derivative Sensitization of Cows Naturally Infected with<i>Mycobacterium Avium</i>Subsp.<i>Paratuberculosis</i>

The objective of this study was to observe early markers of cell-mediated immunity in naïve calves infected with Mycobacterium avium subsp. paratuberculosis and how expression of these markers evolved over the 12-month period of infection. Groups for experimental infection included control (noninfected), oral (infected orally with M. avium subsp. paratuberculosis strain K-10), oral/DXM (pretreatment with dexamethasone before oral inoculation), intraperitoneal (i.p.) inoculation, and oral/M (oral inoculation with mucosal scrapings from a cow with clinical disease) groups. One of the earliest markers to emerge was antigen-specific gamma interferon (IFN-␥). Only i.p. inoculated calves had detectable antigen-specific IFN-␥ responses at 7 days, with responses of the other infection groups becoming detectable at 90 and 120 days. All infection groups maintained robust IFN-␥ responses for the remainder of the study. At 1 month, calves in the oral and oral/M groups had higher antigen-stimulated interleukin-10 (IL-10) levels than calves in the other treatment groups, but IL-10 secretion declined by 12 months for all calves. T-cell activation markers such as CD25, CD26, CD45RO, and CD5 were significantly upregulated in infected calves compared to noninfected controls. Oral inoculation of calves resulted in significantly increased antigen-specific lymphocyte proliferation at 9 and 12 months, as well as inducible nitric oxide synthase (iNOS) secretion at 6 and 12 months. These results demonstrate that infection of naïve calves with M. avium subsp. paratuberculosis invoked early immunologic responses characterized by robust antigen-specific IFN-␥ responses and induction of CD25 and CD45RO expression on T-cell subsets. These were followed by antigen-specific lymphocyte proliferation, iNOS secretion, and expression of CD26 and CD5 bright markers in the latter part of the 12-month study.Deciphering host immune responses upon exposure to Mycobacterium avium subsp. paratuberculosis, differentiating the responses due to exposure from true infection, and then further characterizing responses at different stages of infection have been daunting and complex tasks that remain elusive. Early measures of host immune responses to infection with mycobacteria, including M. avium subsp. paratuberculosis, have been dominated by a strong bias toward Th1-mediated gamma interferon (IFN-␥) production. Higher levels of antigen-specific IFN-␥ secreted by peripheral blood mononuclear cells (PBMCs) have been reported for animals in the early stages of M. avium subsp. paratuberculosis infection, whether it be natural or experimental infection (11,18,22,24). Since IFN-␥ is a key effector cytokine involved in the activation of T cells and macrophages, maturation of dendritic cells, upregulation of major histocompatibility complex (MHC) class I and II molecules, and production of reactive oxygen and nitrogen species by macrophages, it is purported to be not only an immune response variable but also a correlate of immune protection (7,16). However, it is u...

Section: Discussionsupporting

confidence: 48%

Early Immune Markers Associated withMycobacterium aviumsubsp.paratuberculosisInfection in a Neonatal Calf Model

Stabel

Robbe‐Austerman

2011

“…CD8 ϩ and CD8 ϩ ␥␦T cells also contributed to IFN-␥ production on PPDj stimulation and were the main IFN-␥ producers in unstimulated samples. IFN-␥ production from CD8 ϩ cells has previously been seen in both unstimulated samples (38) and antigen-stimulated samples from M. avium subsp. paratuberculosis-infected or vaccinated ruminants (3,16,38), while studies with contradictory results regarding the ability of ruminant ␥␦T cells to produce IFN-␥ in response to mycobacterial antigens exist (3,16,32).…”

Section: Discussionmentioning

confidence: 99%

Neutralization of Interleukin-10 from CD14⁺Monocytes Enhances Gamma Interferon Production in Peripheral Blood Mononuclear Cells fromMycobacterium aviumsubsp.paratuberculosis-Infected Goats

Lybeck

Storset

Olsen

2009

The gamma interferon assay is used to identify Mycobacterium avium subsp. paratuberculosis-infected animals. It has been suggested that regulatory mechanisms could influence the sensitivity of the test when it is performed with cells from cattle and that the neutralization of interleukin-10 (IL-10) in vitro would increase the gamma interferon responses. To investigate the regulatory mechanisms affecting the gamma interferon assay with cells from goats, blood was collected from M. avium subsp. paratuberculosis-infected, M. avium subsp. paratuberculosis-exposed, and noninfected goats. Neutralization of IL-10 by a monoclonal antibody resulted in increased levels of gamma interferon production in M. avium subsp. paratuberculosis purified protein derivative (PPDj)-stimulated samples from both infected and exposed goats. However, the levels of gamma interferon release were also increased in unstimulated cells and in PPDj-stimulated cells from some noninfected animals following neutralization. Depletion of putative regulatory CD25 high T cells had no clear effect on the number of gamma-interferon-producing cells. The IL-10-producing cells were identified to be mainly CD14 ؉ major histocompatibility complex class II-positive monocytes in both PPDj-stimulated and control cultures and not regulatory T cells. However, possible regulatory CD4 ؉ CD25 ؉ T cells produced IL-10 in response to concanavalin A stimulation. The numbers of CD4 ؉ , CD8 ؉ , and CD8 ؉ ␥␦T-cell receptor-positive cells producing gamma interferon increased following IL-10 neutralization. These results provide insight into the source and the role of IL-10 in gamma interferon assays with cells from goats and suggest that IL-10 from monocytes can regulate both innate and adaptive gamma interferon production from several cell types. Although IL-10 neutralization increased the sensitivity of the gamma interferon assay, the specificity of the test could be compromised.

“…CD4 CD25 ϩ T cells are highly induced in both experimentally and naturally infected animals, as well as animals vaccinated for paratuberculosis, and represent a highly activated T cell subpopulation (9,22,25,27,33). Coexpression of CD25 and the transcription factor FoxP3 on CD4 ϩ cells defines T regulatory cells, a subpopulation that is critical in controlling inflammatory responses in the host (5).…”

Section: Paratuberculosismentioning

confidence: 99%

Mediation of Host Immune Responses after Immunization of Neonatal Calves with a Heat-Killed Mycobacterium avium subsp. paratuberculosis Vaccine

Stabel

Waters

Bannantine

et al. 2011

A major drawback of current whole-cell vaccines for Mycobacterium avium subsp. paratuberculosis is the interference with diagnostic tests for bovine tuberculosis (TB) and paratuberculosis. The current study was designed to explore the effects of immunization with a heat-killed whole-cell vaccine (Mycopar) on diagnostic test performance and to characterize host immune responses to vaccination over a 12-month period. Neonatal dairy calves were assigned to treatment groups consisting of (i) controls, not vaccinated (n ‫؍‬ 5), and (