Immunohistochemical expression of interferon-γ in different types of granulomatous lesions associated with bovine paratuberculosis

Effects of Paratuberculosis Vaccination at Different Ages in a Dairy Goat Herd: A 2-Year Follow-Up

Vaccination could be considered as an effective method for paratuberculosis control, although controversial, with a need for investigation in some aspects. The objective of this study was to evaluate the effect of vaccination, depending on the age of the animals, on their immune response, the reduction of paratuberculosis cases, mortality and culled animals in a commercial dairy herd. Goats from three different ages were immunized with the inactivated Gudair^® vaccine. Peripheral antibody and IFN-γ output were evaluated for 21 months post-vaccination (mpv) and intradermal skin tests (IDSTs) for tuberculosis, with avian- and bovine-purified protein derivatives (PPD), were carried out at 6 and at 18 mpv to evaluate the humoral and cellular immune peripheral responses, respectively. The number of dead or culled animals, regardless of the reason, was also monitored and the causes of death determined by pathological examination. A significant increase in the production of IFN-γ was observed in all the vaccinated groups when the blood samples were stimulated with avian PPD, from 3 mpv to 18 mpv, and with bovine PPD, between 3 and 21 mpv. Moreover, serum antibody levels increased between 3 and 21 mpv in all vaccinated groups. The highest levels were found in animals vaccinated at 5 months, and the lowest in adult individuals. No positive reactants to tuberculosis were found by intradermal skin test. No animal losses associated with clinical paratuberculosis were detected in any of the groups. The number of total culled animals was significantly lower in the vaccinated than in the unvaccinated groups, especially on 1.5-month-old vaccinated kids. These results suggest that vaccination of paratuberculosis, especially in young animals, could induce heterologous protection.

Peripheral IFN-ɣ Production after Blood Stimulation with Different Mycobacterial Antigens in Goats Vaccinated against Paratuberculosis

Vaccination can be an efficient method for the control of paratuberculosis in ruminants. However, the official tuberculosis control tests cross-interfere with the animals vaccinated against paratuberculosis. In order to test and compare new antigens that could solve this problem, the production of interferon-gamma (IFN-γ) in peripheral blood at different post-vaccination days in experimental kids and adult goats, in field conditions, using the avian and bovine purified protein derivative (PPD), the johnin, two peptide cocktails of Mycobacterium bovis (PC-EC and PC-HP) and the antigens VK 055 and VK 067 of Mycobacterium avium subspecies paratuberculosis (Map) has been analyzed in vitro. The non-specific production of IFN-γ was observed after blood stimulation with the PC-EC and PC-HP cocktail in any sample from vaccinated animals, whereas it was detected when bovine PPD was used. These results support the possible use of these new Mycobacterium bovis antigens in the in the differentiation of animals vaccinated against paratuberculosis or infected with tuberculosis by improving the specificity of bovine PPD. In contrast, the two Map antigens tested in this study did not improve the sensitivity of johnin or avian PPD in the detection of vaccinated or Map-infected goats.

Influence of Heterologous and Homologous Vaccines, and Their Components, on the Host Immune Response and Protection Against Experimental Caprine Paratuberculosis

Vaccination against paratuberculosis, a chronic disease of ruminants caused by Mycobacterium avium subsp. paratuberculosis (Map), has been considered as the most effective control method. However, protection is incomplete, and the mechanisms operating in the response of the animals to vaccination are not fully understood. Therefore, this study analyzed the immune response and the effects on protection against Map infection, elicited by paratuberculosis (Silirum®) and tuberculosis (heat-inactivated M. bovis [HIMB]) vaccines and their components in a caprine experimental model. Fifty goat kids were divided into 10 groups (n = 5) according to their vaccination (Silirum®, HIMB and nonvaccinated), immunization (inactivated bacteria or adjuvant), and/or infection. Oral challenge with Map was performed 45 days postvaccination/immunization (dpv), and animals were euthanized at 190 dpv. Peripheral immune response and proportion of lymphocyte subpopulations were assessed monthly by enzyme-linked immunosorbent assay and flow cytometry analysis, respectively. Local immune response, proportion of tissue lymphocyte subpopulations, Map detection (polymerase chain reaction), and histological examination were conducted in gut-associated lymphoid tissues. All infected groups developed paratuberculosis granulomatous lesions despite vaccination or immunization. The Silirum® and HIMB-vaccinated groups showed a considerable lesion reduction consistent with a significant peripheral cellular and humoral immune response. Besides, a lower number of granulomas were observed in groups immunized with inactivated bacteria and adjuvants in comparison to nonvaccinated and infected group. However, despite not being significant, this reduction was even higher in adjuvant immunized groups, which developed milder granulomatous lesion with no detectable peripheral immune responses associated with immunization. No changes in the peripheral and local proportion of lymphocyte subsets or local immune response were detected in relation to either vaccination/immunization or infection. Despite that paratuberculosis and tuberculosis vaccination showed a partial and cross-protection against Map infection, respectively, only histological examination could assess the progression of infection in these animals. In addition, the pattern observed in the reduction of the lesions in adjuvant immunized groups suggests the possible involvement of a nonspecific immune response that reduces the development of granulomatous lesions.

Methods in isolation and characterization of bovine monocytes and macrophages

Monocytes and macrophages belong to the mononuclear phagocyte system and play important roles in both physiological and pathological processes. The cells belonging to the monocyte/macrophage system are structurally and functionally heterogeneous. Several subsets of monocytes have been previously identified in mammalian blood, generating different subpopulations of macrophages in tissues. Although their distribution and phenotype are similar to their human counterpart, bovine monocytes and macrophages feature differences in both functions and purification procedures. The specific roles that monocytes and macrophages fulfil in several important diseases of bovine species, including among the others tuberculosis and paratuberculosis, brucellosis or the disease related to peripartum, remain still partially elusive. The purpose of this review is to discuss the current knowledge of bovine monocytes and macrophages. We will describe methods for their purification and characterization of their major functions, including chemotaxis, phagocytosis and killing, oxidative burst, apoptosis and necrosis. An overview of the flow cytometry and morphological procedures, including cytology, histology and immunohistochemistry, that are currently utilized to describe monocyte and macrophage main populations and functions is presented as well.

Local assessment of WC1+ γδ T lymphocyte subset in the different types of lesions associated with bovine paratuberculosis

The local expression of WC1⁺ γδ T lymphocytes subset has been evaluated by immunohistochemical methods at the different types of lesions present in cows naturally infected with Mycobacterium avium subsp. paratuberculosis (Map) and in non-infected control animals. Infected cattle were either in the latent/subclinical (focal lesions) or clinical (diffuse paucibacillary and multibacillary forms) stage of paratuberculosis. To assess the cell distribution, a differential cell count was carried out at the lamina propria, gut-associated lymphoid tissue and submucosa. A significant increase in the number of WC1⁺ γδ T cells was observed in all the infected animals, regardless of the type of lesion. Cows with focal lesions showed higher number of labeled cells than those with diffuse forms, where no differences were found between the two types. This increase in the number of positively immunolabelled lymphocytes in infected animals was seen in the lamina propria, with higher values in those with focal lesions. While in the lymphoid tissue no differences in the numbers were observed, in animals with focal lesions, WC1⁺ γδ T cells tended to be located at the periphery of the granulomas. These findings suggest a proinflammatory action of WC1⁺ γδ T lymphocytes in bovine paratuberculosis, which might play an important role in the containment of the Map-infection in the focal granulomas located in the lymphoid tissue, helping to prevent the progression toward diffuse forms responsible for the clinical signs.

Alternative Vaccination Routes against Paratuberculosis Modulate Local Immune Response and Interference with Tuberculosis Diagnosis in Laboratory Animal Models

Paratuberculosis (PTB) is an enteric granulomatous disease caused by Mycobacterium avium subsp. paratuberculosis (MAP) that mainly affects ruminants. Current vaccines have shown to be cost–effective control reagents, although they are restricted due to cross-interference with bovine tuberculosis (bTB). Therefore, novel vaccination strategies are needed and this study is focused on evaluating alternative vaccination routes and their effect on the local immune response. The MAP oral challenge rabbit model was used to evaluate and compare an experimental inactivated MAP vaccine through oral (VOR) and intradermal (VID) routes. The VID group presented the highest proportion of animals with no visible lesions and the lowest proportion of animals with MAP positive tissues. Immunohistochemistry analysis revealed that the VID group presented a dominantly M1 polarized response indicating an ability to control MAP infection. In general, all vaccinated groups showed lower calprotectin levels compared to the non-vaccinated challenged group suggesting less active granulomatous lesions. The VID group showed some degree of skin test reactivity, whereas the same vaccine through oral administration was completely negative. These data show that PTB vaccination has an effect on macrophage polarization and that the route influences infection outcome and can also have an impact on bTB diagnosis. Future evaluation of new immunological products against mycobacterial diseases should consider assaying different vaccination routes.