The humoral immune response is essential for successful vaccine protection against paratuberculosis in sheep

Superior protection against paratuberculosis by a heterologous prime-boost immunization in a murine model

Vaccination is the best strategy to control Paratuberculosis (PTB), which is a significant disease in cattle and sheep. Previously we showed the humoral and cellular immune response induced by a novel vaccine candidate against PTB based on the Argentinian Mycobacterium avium subspecies paratuberculosis (Map) 6611 strain. To improve 6611 immunogenicity and efficacy, we evaluated this vaccine candidate in mice with two different adjuvants and a heterologous boost with a recombinant modified vaccinia Ankara virus (MVA) expressing the antigen 85A (MVA85A). We observed that boosting with MVA85A did not improve total IgG or specific isotypes in serum induced by one or two doses of 6611 formulated with incomplete Freund's adjuvant (IFA). However, when 6611 was formulated with ISA201 adjuvant, MVA85A boost enhanced the production of IFNγ, Th1/Th17 cytokines (IL-2, TNF, IL-17A) and IL-6, IL-4 and IL-10. Also, this group showed the highest levels of IgG2b and IgG3 isotypes, both important for better protection against Map infection in the murine model. Finally, the heterologous scheme elicited the highest levels of protection after Map challenge (lowest CFU count and liver lesion score). In conclusion, our results encourage further evaluation of 6611 strain + ISA201 prime and MVA85A boost in bovines.

Investigating the Taenia solium Fatty Acid Binding Protein Superfamily for Their Immunological Outlook and Prospect for Therapeutic Targets

Taenia solium, like other helminthic parasites, lacks key components of cellular machinery required for endogenous lipid biosynthesis. This deficiency compels the parasite to obtain all of its lipid requirements from its host. The passage of lipids across the cell membrane is tightly regulated. To facilitate effective lipid transport, the cestode parasite utilizes certain lipid binding proteins called FABPs. These FABPs bind with the lipid ligands and allow the transport of lipids across the membranes and into the cytosol. Here, by integrating a computational with homology protein prediction tools, we had identified five FABPs in the T. solium proteome. We confirmed their presence by RNA expression analysis of respective genes from the parasite's cysticerci transcript. During the molecular modeling and MD simulation studies, two of them, TsM_000544100 and TsM_001185100, were most stable. Furthermore, they had a robust interaction with the IgG1 molecule, as evidenced by MD simulation. In addition, by employing in silico screening, we had identified potential ligand interacting residues that are present on the probable druggable site. In combination with in vitro cysticidal assays, enalaprilat dihydrate showed efficacy against cysticerci, which suggests that FABPs play a significant role in the cysticercus life cycle. Together, we provided a detailed distribution of all FABPs expressed by T. solium cysticerci and the critical role of TsM_001185100 in cysticercus viability.

Selection of vaccine-candidate peptides from Mycobacterium avium subsp. paratuberculosis by in silico prediction, in vitro T-cell line proliferation, and in vivo immunogenicity

Mycobacterium avium subspecies paratuberculosis (MAP) is a global concern in modern livestock production worldwide. The available vaccines against paratuberculosis do not offer optimal protection and interfere with the diagnosis of bovine tuberculosis. The aim of this study was to identify immunogenic MAP-specific peptides that do not interfere with the diagnosis of bovine tuberculosis. Initially, 119 peptides were selected by either (1) identifying unique MAP peptides that were predicted to bind to bovine major histocompatibility complex class II (MHC-predicted peptides) or (2) selecting hydrophobic peptides unique to MAP within proteins previously shown to be immunogenic (hydrophobic peptides). Subsequent testing of peptide-specific CD4+ T-cell lines from MAP-infected, adult goats vaccinated with peptides in cationic liposome adjuvant pointed to 23 peptides as being most immunogenic. These peptides were included in a second vaccine trial where three groups of eight healthy goat kids were vaccinated with 14 MHC-predicted peptides, nine hydrophobic peptides, or no peptides in o/w emulsion adjuvant. The majority of the MHC-predicted (93%) and hydrophobic peptides (67%) induced interferon-gamma (IFN-γ) responses in at least one animal. Similarly, 86% of the MHC-predicted and 89% of the hydrophobic peptides induced antibody responses in at least one goat. The immunization of eight healthy heifers with all 119 peptides formulated in emulsion adjuvant identified more peptides as immunogenic, as peptide specific IFN-γ and antibody responses in at least one heifer was found toward 84% and 24% of the peptides, respectively. No peptide-induced reactivity was found with commercial ELISAs for detecting antibodies against Mycobacterium bovis or MAP or when performing tuberculin skin testing for bovine tuberculosis. The vaccinated animals experienced adverse reactions at the injection site; thus, it is recommend that future studies make improvements to the vaccine formulation. In conclusion, immunogenic MAP-specific peptides that appeared promising for use in a vaccine against paratuberculosis without interfering with surveillance and trade tests for bovine tuberculosis were identified by in silico analysis and ex vivo generation of CD4+ T-cell lines and validated by the immunization of goats and cattle. Future studies should test different peptide combinations in challenge trials to determine their protective effect and identify the most MHC-promiscuous vaccine candidates.

Adjuvants influence the immune cell populations present at the injection site granuloma induced by whole-cell inactivated paratuberculosis vaccines in sheep

Vaccination is the most effective tool for paratuberculosis control. Currently, available vaccines prevent the progression of clinical disease in most animals but do not fully protect them against infection and induce the formation of an injection site granuloma. The precise mechanisms that operate in response to vaccination and granuloma development, as well as the effect that adjuvants could trigger, have not been fully investigated. Therefore, this study aimed to investigate the injection site granulomas induced by two inactivated paratuberculosis vaccines, which differ in the adjuvant employed. Two groups of 45-day-old lambs were immunized with two commercially available vaccines-one (n = 4) with Gudair® and the other (n = 4) with Silirum®. A third group (n = 4) was not vaccinated and served as control. The peripheral humoral response was assessed throughout the study by a commercial anti-Mycobacterium avium subspecies paratuberculosis (Map) antibody indirect ELISA, and the cellular immune response was assessed similarly by the IFN-γ release and comparative intradermal tests. The injection site granulomas were measured during the experiment and sampled at 75 days post-vaccination (dpv) when the animals were euthanized. The tissue damage, antigen and adjuvant distribution, and the presence and amount of immune cells were then determined and assessed by immunohistochemical methods. Antibodies against Map antigens; a general macrophage marker (Iba1), M1 (iNOS), and M2 (CD204) macrophages; T (CD3), B (CD20), and γδ T lymphocytes, proteins MHC-II and NRAMP1, and cytokines IL-4, IL-10, TNF, and IFN-γ were employed. Silirum® elicited a stronger peripheral cellular immune response than Gudair®, while the latter induced larger granulomas and more tissue damage at the site of injection. Additionally, adjuvant and Map antigen distribution throughout the granulomatous inflammatory infiltrate, as well as the NRAMP1 cell expression, which is linked to antigen phagocytosis, were highly irregular. In Silirum® induced granulomas, a higher number of MHC-II and TNF-expressing cells and a lower number of M2 macrophages suggested an improved antigen presentation, which could be due to the better antigen distribution and reduced tissue damage induced by this vaccine.

A candidate subunit vaccine induces protective immunity against Mycobacterium avium subspecies paratuberculosis in mice

Mycobacterium avium subspecies paratuberculosis (MAP) causes paratuberculosis (PTB), which is a granulomatous enteritis in ruminants that threatens the dairy industry's healthy development and public health safety worldwide. Because the commercial inactivated vaccines are not completely protective and interfere with bovine tuberculosis diagnostics, we tested four fusion proteins, namely 66NC, 66CN, 90NC, and 90CN, which were constructed with MAP3527, Ag85B, and Hsp70 of MAP in different tandem combinations. Notably, 66NC, which encodes a 66 kDa fusion protein that combines in linear order MAP3527_N40-232, Ag85B_41-330, and MAP3527_C231-361, induced a powerful and specific IFN-γ response. Immunization of C57BL/6 mice with the 66NC fusion protein formulated in Montanide ISA 61 VG adjuvant generated robust Th1, Th2, and Th17 type immune responses and strong antibody responses. The 66NC vaccine protected C57BL/6 mice against virulent MAP K-10 infection. This resulted in a reduction of bacterial load and improvement of pathological damage in the liver and intestine, in addition to a reduction of body weight loss; significantly better protection than the reported 74 F vaccine was also induced. Furthermore, vaccine efficacy correlated with the levels of IFN-γ-, TNF-α-, and IL-17A-secreting antigen-specific CD4⁺ and CD8⁺ T lymphocytes as well as with serum IFN-γ and TNF-α levels after vaccination. These results demonstrate that recombinant protein 66NC is an efficient candidate for further development into a protective vaccine in terms of inducing specific protection against MAP.

Effects of Silirum®-Based Vaccination Programs on Map Fecal Shedding and Serological Response in Seven French Dairy Herds

(1) Background: paratuberculosis is an important disease in ruminants, causing worldwide economic losses to the livestock industry. Although vaccination is known not to prevent transmission of the causative agent Mycobacterium avium subsp. paratuberculosis (Map), it is considered an effective tool for paratuberculosis in infected herds. The objectives of this controlled field study were to evaluate the effects of the whole-cell heat-killed Silirum^® vaccine on Map fecal shedding and serological status in dairy herds infected with paratuberculosis. (2) Methods: The serological status (ELISA) and fecal shedding (qPCR) of 358 vaccinated cows were assessed over 3 years in 7 infected dairy herds in the Meuse department, France. Within each herd, cows from the last non-vaccinated birth cohort (n = 265) were used as controls. The probability and level of Map fecal shedding and the serological status were modeled using multivariable mixed general linear regression models. (3) Results: Overall, 34.7% of cows tested positive at least once on fecal qPCR, with significant differences between herds, but high shedding levels were observed in only 5.5% of cows. Compared to non-vaccinated seronegative cows, a statistically significant reduction in the probability of Map shedding was found only in cows vaccinated before 4 to 5 months of age that tested negative for Map antibodies throughout the study period (odds ratio = 0.5, 95% confidence interval: 0.3-0.9, p = 0.008), but no significant effect of vaccination on the amount of Map shedding could be evidenced. Finally, the younger the cows were when vaccinated, the less they tested positive on the serum ELISA. (4) Conclusions: a beneficial effect of vaccination on Map fecal shedding may exist in cows vaccinated before 4 to 5 months of age. The variability of the serum ELISA response in vaccinated cows remains to be investigated.

Mycobacterium avium subsp. paratuberculosis antigens induce cellular immune responses in cattle without causing reactivity to tuberculin in the tuberculosis skin test

Mycobacterium avium subspecies paratuberculosis (MAP) causes chronic progressive granulomatous enteritis leading to diarrhea, weight-loss, and eventual death in ruminants. Commercially available vaccine provides only partial protection against MAP infection and can interfere with the use of current diagnostic tests for bovine tuberculosis in cattle. Here, we characterized immune responses in calves to vaccines containing four truncated MAP antigens as a fusion (Ag85A^202-347-SOD^1-72-Ag85B^173-330-74F^{1-148+669-786}), either displayed on protein particles, or expressed as a soluble recombinant MAP (rMAP) fusion protein as well as to commercially available Silirum^® vaccine. The rMAP fusion protein elicited the strongest antigen-specific antibody responses to both PPDA and recombinant antigen and strong and long-lasting T-cell immune responses to these antigens, as indicated by increased production of IFN-γ and IL-17A in antigen-stimulated whole blood cultures. The MAP fusion protein particle vaccine induced minimal antibody responses and weak IFN-γ responses but stimulated IL-17A responses to recombinant antigen. The immune response profile of Silirum^® vaccine was characterized by weak antibodies and strong IFN-γ and IL-17A responses to PPDA. Transcription analysis on antigen-stimulated leukocytes from cattle vaccinated with rMAP fusion protein showed differential expression of several immune response genes and genes involved in costimulatory signaling, TLR4, TLR2, PTX3, PTGS2, PD-L1, IL1B, IL2, IL6, IL12B, IL17A, IL22, IFNG, CD40, and CD86. Moreover, the expression of several genes of immune pathways correlated with cellular immune responses in the rMAP fusion protein vaccinated group. These genes have key roles in pathways of mycobacterial immunity, including autophagy, manipulation of macrophage-mediated killing, Th17- and regulatory T cells- (Treg) mediated responses. Calves vaccinated with either the rMAP fusion protein or MAP fusion protein particle vaccine did not induce reactivity to PPDA and PPDB in a comparative cervical skin test, whereas Silirum^® induced reactivity to these tuberculins in most of the vaccinated animals. Overall, our results suggest that a combination of recombinant MAP antigens in the form of a soluble fusion protein vaccine are capable of inducing strong antigen-specific humoral and a balanced Th1/Th17-cell immune response. These findings, together with the absence of reactivity to tuberculin, suggest this subunit vaccine could provide protective immunity against intracellular MAP infection in cattle without compromising the use of current bovine tuberculosis surveillance test.

B cell phenotypes and maturation states in cows naturally infected with Mycobacterium avium subsp. Paratuberculosis

Little is known about the role that B cells play in immune responses to infection with the intracellular pathogen, Mycobacterium avium subsp. paratuberculosis (MAP). Traditionally, the role of B cells has been constrained to their function as antibody-producing cells, however, antibodies are not thought to play a protective role in mycobacterial infections. The present study was designed to characterize B cell subpopulations as well as activation/maturation states in cattle with paratuberculosis. Peripheral blood mononuclear cells (PBMCs) were isolated from noninfected control cows (n = 8); as well cattle naturally infected with MAP in the subclinical (n = 8) and clinical (n = 7) stage of infection and stimulated with MAP antigen for 6 days. MAP infection resulted in greater numbers of total B cells for clinical cows compared to control noninfected cows. The major subpopulation in freshly isolated PBMCs in clinical cows was B-1a B cells, but this shifted to a composite of both B-1a and B-2 B cells upon stimulation of PBMCs with either MAP antigen or pokeweed mitogen, with higher numbers of B-2 B cells. Early B cells were observed to predominate the population of B cells in PBMCs, with lesser populations of germinal B cells, memory B cells and plasma cells. These subpopulations were elevated in clinical cows upon stimulation of PBMCs with MAP antigen, except for plasma cells which were lower compared to control noninfected cows. Increased numbers of B cells in clinical cows aligned with higher expression of B cell markers such as MAPK1/3, BTG1, Bcl2, CD79A and SWAP70, depending upon in vitro stimulation with either mitogen or antigen. This would indicate that the B cells were capable of activation but were anti-apoptotic in nature. The shift to B-2 B cells in the periphery of clinical cows seems to be indicative of an expansion of memory B cells, rather than plasma cells. This may be a last attempt by the host to control the rampant inflammatory state associated with advanced clinical disease.

Presence of antibodies against Mycobacterium avium subspecies paratuberculosis in Brazilian high-producing dairy herds

This study aimed to determine the presence of antibodies against Mycobacterium avium subspecies paratuberculosis (MAP) in high-producing dairy cows, the presence of the pathogen in the feces, and the risk factors associated with the disease. Blood and fecal samples were collected from 708 dairy cows over 2 years from 54 herds located in five municipalities of Paraná, Brazil. The serum samples were evaluated for the presence of antibodies against MAP using enzyme-linked immunosorbent assay (ELISA). Fecal samples from 100 cows (69 seropositive and 31 seronegative) were assessed using real-time PCR (qPCR) for IS900 of MAP. The herd prevalence of antibodies against MAP was 61.1% (33/54; 95% CI 46.88-74.08), ranging from 12.5 to 80% across the municipalities, and the prevalence in the animals was 9.8% (69/708; 95% CI 7.77-12.15); it ranged from 0 to 87.5% per herd. Only one of the 69 (1.45%) fecal samples from the seropositive cows was positive for the qPCR. The factors associated with the occurrence of paratuberculosis in herds were the use of compost barn system and the type of bed, whereas only the type of bed was associated with the infection of cows. The only risk factor (OR = 2.45; 95% CI 1.03-5.85) associated with the occurrence of paratuberculosis was the introduction of animals purchased from other dairy farms. The prevalence of active infection was low; however, our results demonstrate the presence of MAP in high-producing dairy herds in Paraná state, Brazil.

Immunoinformatics analysis of candidate proteins for controlling bovine paratuberculosis

BACKGROUND

Paratuberculosis is debilitating chronic enteritis usually characterized by diarrhea, decreased milk production, and progressive cachexia. Mycobacterium avium subspecies paratuberculosis (MAP) causes significant economic losses by affecting dairy herds globally. Development of protective vaccines is considered as one of the most effective controlling measures for MAP infections. In the current study, hydrophilic parts of MAP2191 and FAP-P proteins as two vaccine candidates were analyzed using immunoinformatics approaches.

METHODS

After selecting the most hydrophilic parts of MAP2191 and FAP-P, helper and cytotoxic T-cell epitopes of ht-MAP2191 and ht-FAP-P were identified. The immunogenic, toxicity and physicochemical properties were assessed. Secondary structures of these proteins were predicted, and their tertiary structures were modeled, refined, and validated. Linear and conformational epitopes of corresponding B-cells were recognized. Then ht-MAP2191 and ht-FAP-P epitopes were employed for molecular docking simulations.

RESULTS

The results indicated that ht-MAP2191 and ht-FAP-P were immunogenic, non-allergenic, and non-toxic and possess potent T-cell and B-cell epitopes. Eventually, these protein constructs were docked favorably against TLR4.

CONCLUSION

According to the findings, ht-MAP2191 and ht-FAP-P could be effective protein-based vaccine candidates for paratuberculosis. It should be noted that to examine their efficacy, further in vitro and in vivo experiments are underway.

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.

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.

Antibodies from healthy or paratuberculosis infected cows have different effects on Mycobacterium avium subspecies paratuberculosis invasion in a calf ileal loop model

In this work, we used a calf ileal loop model to evaluate whether the preincubation of Mycobacterium avium subspecies paratuberculosis (MAP) with antibodies from healthy, MAP-positive or Lipoarabinomannan (LAM) immunized cows could affect the results of infection after 3.5 h. Bacterial load in tissue was assessed by Ziehl-Neelsen and by culture for each loop. MAP was detectable in all infected loops after 3.5 h.p.i.; although the presence of antibodies from MAP-positive cows significantly reduced bacterial load in loops as compared with antibodies from healthy donors (by Ziehl-Neelsen and culture, p-value < 0.003 and 0.0203, respectively). A possible direct effect of antibodies on MAP viability was shown to be not significant. Severity of histopathologic changes induced by MAP infection also varied according to the pretreatment: MAP induced less changes when inoculated in the presence of antibodies from MAP-positive cows as compared with antibodies from healthy donors. Overall, our results show that the presence of antibodies from MAP-positive cows reduced MAP invasion and consequent early histological changes in this ileal short-term loop model. These results may suggest a protective role of antibodies in the response against MAP at the portal of entry in cattle.

Evaluation of a virulent strain of Mycobacterium avium subsp. Paratuberculosis used as a heat-killed vaccine

Bovine paratuberculosis is one of the most important chronic infectious diseases in livestock. This disease is difficult to control because of its inefficient management (test and cull strategy and inadequate biosecurity). Thus, the development of an effective vaccine is essential. In this study, we evaluated a local virulent strain (6611) of Mycobacterium avium subsp. paratuberculosis as an inactivated vaccine in comparison with the Silirum vaccine in mouse model and cattle. Regarding the mice model, only the groups vaccinated with 6611 showed lower colony forming unit (CFU) counts with a lower lesion score in the liver in comparison to the control group at 6 and 12 weeks post-challenge (wpc). The immune response was predominantly humoral (IgG1), although both vaccinated groups presented a cellular response with IFNγ production as well, but the 6611 group had also significant production of IL-2, IL-6, IL-17a, TNF, and IL-10. In cattle, the 6611 vaccinated group was the only one that maintained significant antibody values at the end of the trial, with significant production of IgG2 and IFNγ. No PPDb reactor was detected in the vaccinated animals, according to the intradermal caudal fold tuberculin test. Our results indicate that the 6611 local strain protected mice from challenge with a virulent strain, by inducing a humoral and cellular immune response. In the bovine, the natural host, the evaluated vaccine also induced humoral and cellular immune responses, with higher levels of CD4 + CD25+ and CD8 + CD25+ T cells populations than the commercial vaccine. Despite the encouraging results obtained in this study, an experimental challenge trial in cattle is mandatory to evaluate the efficacy of our candidate vaccine in the main host.

Comparison of the current abattoir surveillance system for detection of paratuberculosis in Australian sheep with quantitative PCR tissue strategies using simulation modelling

Abattoir surveillance for Johne's disease monitoring in Australia has provided valuable feedback to producers about their flock's disease status since its commencement in 1999. The current surveillance system relies on the identification of gross lesions in sheep carcases at an abattoir, followed by sampling and histopathology testing. This manual inspection system has not been adapted to meet the changing disease situation, as infection prevalence levels have declined over time due to vaccination. This simulation study compares the current system with two alternative approaches utilising a validated quantitative (q)PCR method for the detection of Mycobacterium avium subsp. paratuberculosis in tissues, with random systematic sampling either alone or in conjunction with sampling of a single carcass presenting gross lesions. Consigned sheep were randomly simulated as either infected or uninfected according to defined prevalence levels of infection, with varying histopathological lesion severity and the presence or absence of gross lesions. These sheep were then allocated into multiple 'lines' (group of sheep slaughtered together) within each consignment, with each line subjected to testing with the three sampling strategies for the estimation of line and flock (consignment) sensitivity. The line sensitivity described the proportion of infected lines that tested positive, whereas the flock sensitivity was the proportion of consignments from the simulated infected flocks that had one or more lines test positive for paratuberculosis infection. The tissue qPCR strategy with gross lesion detection achieved marginally higher line sensitivity than the current abattoir surveillance strategy. The simulation of unvaccinated infected flocks with low to moderate prevalence levels demonstrated similar flock sensitivity for all three sampling models. However, the current strategy had very low line sensitivity for the simulated vaccinated infected flocks when the infection prevalence level was <2%. There were substantial differences in flock sensitivity between the two tissue qPCR approaches and the current abattoir surveillance strategy for vaccinated infected flocks, whereas, only marginal differences in flock sensitivity were evident between the two tissue qPCR models. Our results demonstrate that the current strategy is not effective at identifying infected animals at very low infection prevalence levels. The tissue qPCR approach investigated in this study is better as it removes the reliance on meat inspectors to identify gross lesions and can also assist in identifying flocks that have subclinical infected sheep not displaying gross lesions. Therefore, the sheep industry may benefit from incorporating tissue qPCR for Johne's disease surveillance, however the logistics and costs of conducting this type of testing would need to be considered prior to implementing any changes.

Oral vaccination stimulates neutrophil functionality and exerts protection in a Mycobacterium avium subsp. paratuberculosis infection model

Mycobacterium avium subsp. paratuberculosis (Map) causes paratuberculosis (PTB), a granulomatous enteritis in ruminants that exerts high economic impact on the dairy industry worldwide. Current vaccines have shown to be cost-effective against Map and in some cases confer beneficial non-specific effects against other pathogens suggesting the existence of trained immunity. Although Map infection is mainly transmitted by the fecal-oral route, oral vaccination has not been deeply studied. Therefore, the aim of this study was to compare the oral route with a set of mycobacterial and non-mycobacterial vaccines with a subcutaneously administered commercially available vaccine. Training effects on polymorphonuclear neutrophils (PMNs) and homologous and heterologous in vivo protection against Map were investigated in the rabbit infection model. Oral vaccination with inactivated or live vaccines was able to activate mucosal immunity as seen by elevation of serum IgA and the expression of IL4 in peripheral blood mononuclear cells (PBMCs). In addition, peripheral PMN phagocytosis against Map was enhanced by vaccination and extracellular trap release against Map and non-related pathogens was modified by both, vaccination and Map-challenge, indicating trained immunity. Finally, PBMCs from vaccinated animals stimulated in vitro with Map antigens showed a rapid innate activation cytokine profile. In conclusion, our data show that oral vaccination against PTB can stimulate neutrophil activity and both innate and adaptive immune responses that correlate with protection.

Early response of monocyte-derived macrophages from vaccinated and non-vaccinated goats against in vitro infection with Mycobacterium avium subsp. paratuberculosis

Paratuberculosis is a disease of ruminants caused by Mycobacterium avium subsp. paratuberculosis (Map). Vaccination is the most cost-effective control method. However, despite the fact that macrophages are the main target cells for this pathogen, the precise mechanisms behind the response of the macrophage to Map infection and how it is modified by vaccination are yet poorly understood. The aim of this study was to investigate the effect of Silirum® vaccination in the early immune response of caprine monocyte-derived macrophages (CaMØs). Peripheral blood mononuclear cells (PBMCs) were obtained from vaccinated and non-vaccinated goats, cultured in vitro until differentiation to macrophages and infected with Map. After a 24 h incubation, Map viability and DNA were assessed in culture by viable colony count and real time quantitative polymerase chain reaction (qPCR). In addition, Map phagocytosis and expression of IL-10, IL-12, IFN-γ, TNF-α, IL-17A, IL-1β, iNOS, IL-6 and MIP-1β were also evaluated through immunofluorescence labelling and reverse transcriptase qPCR (RT-qPCR), respectively. A significant reduction of Map viability was observed in both supernatants (P < 0.05) and CaMØs (P < 0.001) from the vaccinated group. Similarly, the percentage of infected CaMØs and the number of internalized Map by CaMØs (P < 0.0001) was higher in the vaccinated group. Finally, iNOS (P < 0.01) and IL-10 were significantly up-regulated in CaMØs from vaccinated goats, whereas only MIP-1β was up-regulated in non-vaccinated animals (P < 0.05). These results show that vaccination modifies the immune response of CaMØs, suggesting that the phagocytosis and microbiocidal activity of macrophages against Map is enhanced after vaccination.

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.

Biomarkers for Detecting Resilience against Mycobacterial Disease in Animals

Paratuberculosis and bovine tuberculosis are two mycobacterial diseases of ruminants which have a considerable impact on livestock health, welfare, and production. These are chronic "iceberg" diseases which take years to manifest and in which many subclinical cases remain undetected. Suggested biomarkers to detect infected or diseased animals are numerous and include cytokines, peptides, and expression of specific genes; however, these do not provide a strong correlation to disease. Despite these advances, disease detection still relies heavily on dated methods such as detection of pathogen shedding, skin tests, or serology. Here we review the evidence for suitable biomarkers and their mechanisms of action, with a focus on identifying animals that are resilient to disease. A better understanding of these factors will help establish new strategies to control the spread of these diseases.