Antibody responses in reindeer (Rangifer tarandus) infected with Mycobacterium bovis

Post-Translational Protein Deimination Signatures in Plasma and Plasma EVs of Reindeer (Rangifer tarandus)

Simple Summary

Reindeer are an important wild and domesticated species of the Arctic, Northern Europe, Siberia and North America. As reindeer have developed various strategies to adapt to extreme environments, this makes them an interesting species for studies into diversity of immune and metabolic functions in the animal kingdom. Importantly, while reindeer carry natural infections caused by viruses (including coronaviruses), bacteria and parasites, they can also act as carriers for transmitting such diseases to other animals and humans, so called zoonosis. Reindeer are also affected by chronic wasting disease, a neuronal disease caused by prions, similar to scrapie in sheep, mad cows disease in cattle and Creutzfeldt-Jakob disease in humans. The current study assessed a specific protein modification called deimination/citrullination, which can change how proteins function and allow them to take on different roles in health and disease processes. Profiling of deiminated proteins in reindeer showed that many important pathways for immune defenses, prion diseases and metabolism are enriched in deiminated proteins, both in plasma, as well as in plasma extracellular vesicles. This study provides a platform for the development of novel biomarkers to assess wild life health status and factors relating to zoonotic disease.

Abstract

The reindeer (caribou) Rangifer tarandus is a Cervidae in the order Artiodactyla. Reindeer are sedentary and migratory populations with circumpolar distribution in the Arctic, Northern Europe, Siberia and North America. Reindeer are an important wild and domesticated species, and have developed various adaptive strategies to extreme environments. Importantly, deer have also been identified to be putative zoonotic carriers, including for parasites, prions and coronavirus. Therefore, novel insights into immune-related markers are of considerable interest. Peptidylarginine deiminases (PADs) are a phylogenetically conserved enzyme family which causes post-translational protein deimination by converting arginine into citrulline in target proteins. This affects protein function in health and disease. Extracellular vesicles (EVs) participate in cellular communication, in physiological and pathological processes, via transfer of cargo material, and their release is partly regulated by PADs. This study assessed deiminated protein and EV profile signatures in plasma from sixteen healthy wild female reindeer, collected in Iceland during screening for parasites and chronic wasting disease. Reindeer plasma EV profiles showed a poly-dispersed distribution from 30 to 400 nm and were positive for phylogenetically conserved EV-specific markers. Deiminated proteins were isolated from whole plasma and plasma EVs, identified by proteomic analysis and protein interaction networks assessed by KEGG and GO analysis. This revealed a large number of deimination-enriched pathways for immunity and metabolism, with some differences between whole plasma and EVs. While shared KEGG pathways for whole plasma and plasma EVs included complement and coagulation pathways, KEGG pathways specific for EVs were for protein digestion and absorption, platelet activation, amoebiasis, the AGE–RAGE signaling pathway in diabetic complications, ECM receptor interaction, the relaxin signaling pathway and the estrogen signaling pathway. KEGG pathways specific for whole plasma were pertussis, ferroptosis, SLE, thyroid hormone synthesis, phagosome, Staphylococcus aureus infection, vitamin digestion and absorption, and prion disease. Further differences were also found between molecular function and biological processes GO pathways when comparing functional STRING networks for deiminated proteins in EVs, compared with deiminated proteins in whole plasma. This study highlights deiminated proteins and EVs as candidate biomarkers for reindeer health and may provide information on regulation of immune pathways in physiological and pathological processes, including neurodegenerative (prion) disease and zoonosis.

Diagnosis of tuberculosis in wildlife: a systematic review

Animal tuberculosis (TB) is a multi-host disease caused by members of the Mycobacterium tuberculosis complex (MTC). Due to its impact on economy, sanitary standards of milk and meat industry, public health and conservation, TB control is an actively ongoing research subject. Several wildlife species are involved in the maintenance and transmission of TB, so that new approaches to wildlife TB diagnosis have gained relevance in recent years. Diagnosis is a paramount step for screening, epidemiological investigation, as well as for ensuring the success of control strategies such as vaccination trials. This is the first review that systematically addresses data available for the diagnosis of TB in wildlife following the Preferred Reporting Items of Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The article also gives an overview of the factors related to host, environment, sampling, and diagnostic techniques which can affect test performance. After three screenings, 124 articles were considered for systematic review. Literature indicates that post-mortem examination and culture are useful methods for disease surveillance, but immunological diagnostic tests based on cellular and humoral immune response detection are gaining importance in wildlife TB diagnosis. Among them, serological tests are especially useful in wildlife because they are relatively inexpensive and easy to perform, facilitate large-scale surveillance and can be used both ante- and post-mortem. Currently available studies assessed test performance mostly in cervids, European badgers, wild suids and wild bovids. Research to improve diagnostic tests for wildlife TB diagnosis is still needed in order to reach accurate, rapid and cost-effective diagnostic techniques adequate to a broad range of target species and consistent over space and time to allow proper disease monitoring.

OUTBREAK OF MYCOBACTERIUM TUBERCULOSIS IN A HERD OF CAPTIVE ASIAN ELEPHANTS ( ELEPHAS MAXIMUS): ANTEMORTEM DIAGNOSIS, TREATMENT, AND LESSONS LEARNED

Tuberculosis (TB) was diagnosed in four Asian elephants ( Elephas maximus) in a zoo in the United States. The first case was detected by isolation of Mycobacterium tuberculosis during routine trunk wash (TW) culture testing of a herd of eight elephants. Retrospective antibody analyses revealed seroconversion 1 yr before diagnosis. Serological testing of the whole elephant herd identified two additional suspect bulls with detectable antibody, but which remained culture-negative and had no clinical signs of disease. In the following months, M. tuberculosis, identical to the isolate from the index case, was isolated from TW samples of these two elephants. A fourth elephant seroconverted nearly 4 yr after the first TB case was detected, and M. tuberculosis was isolated from a TW sample collected 1 mo later. All four infected elephants received anti-TB therapy. Two treated elephants were eventually euthanized for reasons unrelated to M. tuberculosis and found to be culture-negative on necropsy, although one of them had PCR-positive lung lesions. One infected animal had to be euthanized due to development of a drug-resistant strain of M. tuberculosis; this animal did not undergo postmortem examination due to risk of staff exposure. The fourth animal is currently on treatment. Serial serological and culture results of the other four herd mates have remained negative.

Immunological responses of European badgers (Meles Meles) to infection with Mycobacterium bovis

Mycobacterium bovis is the main cause of bovine tuberculosis and its eradication is proving difficult in many countries because of wildlife reservoirs, including European badgers (Meles meles) in the UK Ireland. Following the development of badger specific immunological reagents, many studies have shown that some aspects of the cellular and serological immune responses of badgers to virulent M. bovis and the attenuated M. bovis BCG (Bacille of Calmette and Guérin) strain are similar to those seen in other animal hosts infected with M. bovis. However, badgers also appear to have developed specific immunological responses to M. bovis infection which may be associated with mild inflammatory responses. Badgers may therefore represent an interesting natural host for M. bovis that can provide a more thorough understanding of efficient immunological responses to tuberculosis.

Point of Care Tuberculosis Sero-Diagnosis Kit for Wild Animals: Combination of Proteins for Improving the Diagnostic Sensitivity and Specificity

Tuberculosis is a significant problem globally for domestic animals as well as captive and free ranging wild life. Rapid point of care (POC) serology kits are well suited for the diagnosis of TB in wild animals. However, wild animals are invariably exposed to environmental non-pathogenic mycobacterium species with the development of cross reacting antibodies. In the present study, POC TB diagnosis kit was developed using a combination of pathogenic Mycobacteria specific recombinant antigens and purified protein derivatives of pathogenic and non-pathogenic Mycobacteria. To benchmark the TB antibody detection kit, particularly in respect to specificity which could not be determined in wildlife due to the lack of samples from confirmed uninfected animals, we first tested well-characterized sera from 100 M. bovis infected and 100 uninfected cattle. Then we investigated the kit's performance using sera samples from wildlife, namely Sloth Bears (n = 74), Elephants (n = 9), Cervidae (n = 14), Felidae (n = 21), Cape buffalo (n = 2), Wild bear (n = 1) and Wild dog (n = 1).In cattle, a sensitivity of 81% and a specificity of 90% were obtained. The diagnostic sensitivity of the kit was 94% when the kit was tested using known TB positive sloth bear sera samples. 47.4% of the in-contact sloth bears turned seropositive using the rapid POC TB diagnostic kit. Seropositivity in other wild animals was 25% when the sera samples were tested using the kit. A point of care TB sero-diagnostic kit with the combination of proteins was developed and the kit was validated using the sera samples of wild animals.

Rapid detection of serum antibody by dual-path platform VetTB assay in white-tailed deer infected with Mycobacterium bovis

Bovine tuberculosis (TB) in cervids remains a significant problem affecting farmed herds and wild populations. Traditional skin testing has serious limitations in certain species, whereas emerging serological assays showed promising diagnostic performance. The recently developed immunochromatographic dual-path platform (DPP) VetTB assay has two antigen bands, T1 (MPB83 protein) and T2 (CFP10/ESAT-6 fusion protein), for antibody detection. We evaluated the diagnostic accuracy of this test by using serum samples collected from groups of white-tailed deer experimentally inoculated with Mycobacterium bovis, M. avium subsp. paratuberculosis, or M. bovis BCG Pasteur. In addition, we used serum samples from farmed white-tailed deer in herds with no history of TB, as well as from free-ranging white-tailed deer culled during field surveillance studies performed in Michigan known to have bovine TB in the wild deer population. The DPP VetTB assay detected antibody responses in 58.1% of experimentally infected animals within 8 to 16 weeks postinoculation and in 71.9% of naturally infected deer, resulting in an estimated test sensitivity of 65.1% and a specificity of 97.8%. The higher seroreactivity found in deer with naturally acquired M. bovis infection was associated with an increased frequency of antibody responses to the ESAT-6 and CFP10 proteins, resulting in a greater contribution of these antigens, in addition to MPB83, to the detection of seropositive animals, compared with experimental M. bovis infection. Deer experimentally inoculated with either M. avium subsp. paratuberculosis or M. bovis BCG Pasteur did not produce cross-reactive antibodies that could be detected by the DPP VetTB assay. The present findings demonstrate the relatively high diagnostic accuracy of the DPP VetTB test for white-tailed deer, especially in the detection of naturally infected animals.

Facts and dilemmas in diagnosis of tuberculosis in wildlife

Mycobacterium bovis, causing bovine tuberculosis (BTB), has been recognized as a global threat at the wildlife-livestock-human interface, a clear "One Health" issue. Several wildlife species have been identified as maintenance hosts. Spillover of infection from these species to livestock or other wildlife species may have economic and conservation implications and infection of humans causes public health concerns, especially in developing countries. Most BTB management strategies rely on BTB testing, which can be performed for a range of purposes, from disease surveillance to diagnosing individual infected animals. New diagnostic assays are being developed for selected wildlife species. This review investigates the most frequent objectives and associated requirements for testing wildlife for tuberculosis at the level of individual animals as well as small and large populations. By aligning those with the available (immunological) ante mortem diagnostic assays, the practical challenges and limitations wildlife managers and researchers are currently faced with are highlighted.

Pinniped tuberculosis in Malayan tapirs (Tapirus indicus) and its transmission to other terrestrial mammals

In the last 7 yr, three different species of terrestrial mammals were diagnosed with Mycobacterium pinnipedii either within one collection or through the introduction of an infected animal from another zoo. The affected species included the Malayan tapir (Tapirus indicus), Bactrian camel (Camelus bactrianus bactrianus), and crested porcupine (Hystrix cristata). In the first zoo, all of these were living in exhibits adjacent to a group of South American sea lions (Otariaflavescens) and were cared for by the same keeper. One infected tapir was transferred to a different zoo and transmitted M. pinnipedii infection to three other Malayan tapirs. The tapirs were tested with various diagnostic methods, including comparative intradermal tuberculin test, PCR and culture of sputum samples, Rapid Test (RT), and multiantigen print immunoassay (MAPIA). The M. pinnipedii infection was confirmed at postmortem examination in all animals. RT and MAPIA showed the diagnostic potential for rapid antemortem detection of this important zoonotic disease.

Evaluation of Serodiagnostic Assays for Mycobacterium bovis Infection in Elk, White-Tailed Deer, and Reindeer in the United States

In 2011, the United States Department of Agriculture conducted a project in which elk (Cervus elaphus spp.), white-tailed deer (WTD) (Odocoileus virginianus), and reindeer (Rangifer tarandus) were evaluated by the single cervical tuberculin test (SCT), comparative cervical tuberculin test (CCT), and serologic tests. The rapid antibody detection tests evaluated were the CervidTB Stat-Pak (Stat-Pak), and the Dual Path Platform VetTB (DPP). Blood was collected from presumably uninfected animals prior to tuberculin injection for the SCT. A total of 1,783 animals were enrolled in the project. Of these, 1,752 (98.3%) were classified as presumably uninfected, based on originating from a captive cervid herd with no history of exposure to TB. Stat-Pak specificity estimates were 92.4% in reindeer, 96.7% in WTD, and 98.3% in elk and were not significantly different from SCT specificity estimates. Using the DPP in series on Stat-Pak antibody-positive samples improved specificity in the three species. Thirty one animals were classified as confirmed infected, based on necropsy and laboratory results, and 27/31 were antibody positive on Stat-Pak for an estimated sensitivity of 87.1%. The study findings indicate that rapid serologic tests used in series are comparable to the SCT and CCT and may have a greater ability to detect TB-infected cervids.

Bovine tuberculosis in a nebraska herd of farmed elk and fallow deer: a failure of the tuberculin skin test and opportunities for serodiagnosis

In 2009, Mycobacterium bovis infection was detected in a herd of 60 elk (Cervus elaphus) and 50 fallow deer (Dama dama) in Nebraska, USA. Upon depopulation of the herd, the prevalence of bovine tuberculosis (TB) was estimated at ∼71-75%, based upon histopathology and culture results. Particularly with elk, gross lesions were often severe and extensive. One year ago, the majority of the elk had been tested for TB by single cervical test (SCT), and all were negative. After initial detection of a tuberculous elk in this herd, 42 of the 59 elk were tested by SCT. Of the 42 SCT-tested elk, 28 were TB-infected with only 3/28 reacting upon SCT. After SCT, serum samples were collected from the infected elk and fallow deer from this herd at necropsy and tested by three antibody detection methods including multiantigen print immunoassay, cervidTB STAT-PAK, and dual path platform VetTB (DPP). Serologic test sensitivity ranged from 79 to 97% depending on the test format and host species. Together, these findings demonstrate the opportunities for use of serodiagnosis in the rapid detection of TB in elk and fallow deer.

Ante-mortem testing wild fallow deer for bovine tuberculosis

This study aimed to maximize the sensitivity of bovine tuberculosis detection in living wild fallow deer (Dama dama) under field conditions. We evaluated the rapid test (RT; CervidTB STAT-PAK Assay, Chembio Diagnostic Systems, Inc., USA) in comparison with the comparative cervical skin test (CCT). A total of 134 fallow deer were captured between January and March 2008. At time 0, 0.1 ml of avian purified protein derivative (avian PPD; Cooper-Zeltia, Spain), 0.1 ml bovine PPD (Cooper-Zeltia, Spain), 0.1 ml negative control PBS and 0.1 ml of a positive control (the mitogen phytohaemagglutinin, PHA; containing 250 mg PHA, diluted in PBS) were injected intradermally at four shaved sites in the neck. The skin fold thickness at each injection site was measured at time 0 and 72 h (3 repeats each time). Animals with a skin test response of 2mm or more at the bovine PPD injection site and animals with any visible reactivity in the RT were necropsied and tissues submitted for culture and for histopathology. A total of 36 fallow deer were considered reactors to bovine PPD or to the RT (apparent prevalence 27%). Regarding both bovine PPD reactivity and the skin fold increase at the PHA injection site, we found significant effects of age and sex by age interaction. Adult males had the largest responses. Mycobacterium bovis was isolated from lymphoid tissues of 21 fallow deer. Skin test sensitivity, as compared to M. bovis culture confirmed deer, was 80.1% (17/21). But, the CCT alone would have missed 4 of 21 culture confirmed animals. RT sensitivity, based on culture confirmed deer, was also 80.1% (17/21). Similarly, the RT alone would have missed another 4 of 21 culture confirmed deer. However, combining the CCT and the RT allowed for detecting all 21 culture positive fallow deer. We conclude that the combined application of the RT and the skin testing can maximize the sensitivity of bTB detection in living fallow deer, thus facilitating control programs for wildlife disease surveillance.

Application of Elephant TB STAT-PAK assay and MAPIA (multi-antigen print immunoassay) for detection of tuberculosis and monitoring of treatment in black rhinoceros (Diceros bicornis)

Many wildlife species including rhinos are susceptible to infection with Mycobacterium tuberculosis or M. bovis. Antemortem diagnostic testing in large exotic hoof stock species has been limited by challenges associated with test administration, sample collection, and interpretation. Hence, a simple, rapid, blood-based test is needed. Two confirmed M. tuberculosis-infected black rhinoceros and one exposed suspect were evaluated for antibody responses using a lateral-flow rapid test (ElephantTB STAT-PAK) and multi-antigen print immunoassay (MAPIA). All three animals were seropositive by both tests. MAPIA detected antibodies to ESAT-6, CFP10, and MPB83 antigens. When the rhinos were treated with antitubercular therapeutics, their antibody responses gradually declined. One rhinoceros died approximately 9 mo after initiation of treatment and showed an increase in antibody titer shortly before death. The other two rhinoceros, which were treated for 1 and 2 yr, respectively, had no clinical signs or positive culture for M. tuberculosis at the time of necropsy performed 2 or 6 yr later for unrelated reasons. The antibody levels in these rhinos continued to be significantly decreased. The findings suggest that the ElephantTB STAT-PAK and MAPIA may be useful tools to detect M. tuberculosis infection and monitor treatment in black rhinoceros.

Single-antigen serological testing for bovine tuberculosis

Antibody responses are useful indicators of Mycobacterium bovis infection of cattle. Tests for such responses often use multiple M. bovis antigens as detection probes. This is recommended because responses to single antigens may be too variable for consistent diagnosis. However, the use of multiple antigens increases costs and the risk of false-positive results. As an alternative, the SeraLyte-Mbv system detects responses to a single M. bovis antigen, MPB83, by using a chemiluminescent testing platform with a high degree of analytical sensitivity. Testing with the SeraLyte-Mbv system was conducted in a blinded fashion with sera from experimentally infected and control cattle. To assess the species specificity of the single-antigen test, the sample included sera from animals infected with M. bovis (n = 27), M. kansasii (n = 4), M. avium subsp. paratuberculosis (n = 11), M. avium subsp. avium (n = 12), and uninfected animals (n = 15). Upon unblinding of the results, the sensitivity of the SeraLyte-Mbv system relative to the results for animals with known M. bovis infection was 89%. Consistent with the conservation of MPB83 sequences within the genus Mycobacterium, all 4 M. kansasii-infected animals tested positive with the SeraLyte-Mbv system and all 23 M. avium-infected animals tested negative. Blinded analysis of 30 serum samples collected from nine animals at various time points postinfection indicated 100% sensitivity after > or = 3 months postinfection. All 15 uninfected samples in the blinded sample set tested negative with the SeraLyte-Mbv system. Unblinded analysis of sera from an additional 895 animals in 10 accredited bovine tuberculosis-free states revealed 98% specificity overall. The results support the feasibility of single-antigen testing for bovine tuberculosis with the SeraLyte-Mbv system.

Accuracy of three diagnostic tests for determining Mycobacterium bovis infection status in live-sampled wild meerkats (Suricata suricatta)

Accurate diagnosis of Mycobacterium bovis infection (bovine tuberculosis [bTB]) in live animals is notoriously problematic. The aim of the present study was to evaluate the diagnostic potential of 2 new serologic tests (multiantigen print immunoassay [MAPIA] and lateral flow immunoassay rapid test [RT]) in comparison with mycobacterial culture of tracheal washes for determining M. bovis infection status in a free-ranging population of wild meerkats (Suricata suricatta). During a longitudinal study lasting 2.5 years, 240 individually identifiable meerkats were each sampled up to 8 times under anesthesia every 3 months. Diagnostic accuracy was determined through Bayesian and maximum likelihood estimations of sensitivity, specificity, and likelihood ratios for each diagnostic test when used independently and in parallel to classify the disease status of individual meerkats in the absence of a gold standard. Culture of tracheal washes was highly specific (0.99; 95% confidence interval [CI] = 0.77, 1.00) but of low sensitivity (0.36; 95% CI = 0.24, 0.50) for diagnosing M. bovis-infected individuals. The longitudinal nature of the study with repeated sampling of the same individual animals served simultaneously to improve chances of detecting infection and increase confidence in a negative result in individual animals repeatedly testing negative. Although MAPIA and RT were individually of limited diagnostic use, interpreting the results of these 2 tests in parallel produced estimates of sensitivity (0.83; 95% CI = 0.67, 0.93) and specificity (0.73; 95% CI = 0.62, 0.82) high enough to usefully inform decision making when determining exposure to bTB in wild meerkats and potentially other species in which bTB poses a diagnostic challenge.

Highly accurate antibody assays for early and rapid detection of tuberculosis in African and Asian elephants

Tuberculosis (TB) in elephants is a reemerging zoonotic disease caused primarily by Mycobacterium tuberculosis. Current methods for screening and diagnosis rely on trunk wash culture, which has serious limitations due to low test sensitivity, slow turnaround time, and variable sample quality. Innovative and more efficient diagnostic tools are urgently needed. We describe three novel serologic techniques, the ElephantTB Stat-Pak kit, multiantigen print immunoassay, and dual-path platform VetTB test, for rapid antibody detection in elephants. The study was performed with serum samples from 236 captive African and Asian elephants from 53 different locations in the United States and Europe. The elephants were divided into three groups based on disease status and history of exposure: (i) 26 animals with culture-confirmed TB due to M. tuberculosis or Mycobacterium bovis, (ii) 63 exposed elephants from known-infected herds that had never produced a culture-positive result from trunk wash samples, and (iii) 147 elephants without clinical symptoms suggestive of TB, with consistently negative trunk wash culture results, and with no history of potential exposure to TB in the past 5 years. Elephants with culture-confirmed TB and a proportion of exposed but trunk wash culture-negative elephants produced robust antibody responses to multiple antigens of M. tuberculosis, with seroconversions detectable years before TB-positive cultures were obtained from trunk wash specimens. ESAT-6 and CFP10 proteins were immunodominant antigens recognized by elephant antibodies during disease. The serologic assays demonstrated 100% sensitivity and 95 to 100% specificity. Rapid and accurate antibody tests to identify infected elephants will likely allow earlier and more efficient treatment, thus limiting transmission of infection to other susceptible animals and to humans.

Safety and immunogenicity of the Mycobacterium tuberculosis DeltalysA DeltapanCD vaccine in domestic cats infected with feline immunodeficiency virus

Feline immunodeficiency virus (FIV)-positive and FIV-negative cats (n=4/group) received 2 x 10(6) CFU Mycobacterium tuberculosis DeltalysA DeltapanCD intramuscularly. Vaccination elicited antibody responses, albeit at lower levels in FIV-positive cats than in FIV-negative cats. Delayed-type hypersensitivity responses were minimal in both groups. No adverse reactions were found.

Humoral immune responses of white-tailed deer (Odocoileus virginianus) to Mycobacterium bovis BCG vaccination and experimental challenge with M. bovis

Monitoring of the kinetics of production of serum antibodies to multiple mycobacterial antigens can be useful as a diagnostic tool for the detection of Mycobacterium bovis infection as well as for the characterization of disease progression and the efficacy of intervention strategies in several species. The humoral immune responses to multiple M. bovis antigens by white-tailed deer vaccinated with BCG orally via a lipid-formulated bait (n=5), orally in liquid form (n=5), and subcutaneously (n=6) were evaluated over time after vaccination and after experimental challenge with virulent M. bovis and were compared to the responses by unvaccinated deer (n=6). Antibody responses were evaluated by using a rapid test (RT), a multiantigen print immunoassay (MAPIA), a lipoarabinomannan enzyme-linked immunosorbent assay (LAM-ELISA), and immunoblotting to whole-cell sonicate and recombinant antigen MPB83. MAPIA and RT detected minimal to no antibody responses over those at the baseline to multiple M. bovis antigens in vaccinated white-tailed deer after challenge. This was in contrast to the presence of more readily detectable antibody responses in nonvaccinated deer with more advanced disease. The LAM-ELISA results indicated an overall decrease in the level of production of detectable antibodies against lipoarabinomannan-enriched mycobacterial antigen in vaccinated animals compared to that in nonvaccinated animals after challenge. Immunoblot data were inconsistent but did suggest the occurrence of unique antibody responses by certain vaccinated groups to Ag85 and HSP70. These findings support further research toward the improvement and potential use of antibody-based assays, such as MAPIA, RT, and LAM-ELISA, as tools for the antemortem assessment of disease progression in white-tailed deer in both experimental and field vaccine trials.

Antibody responses of cervids (Cervus elaphus) following experimental Mycobacterium bovis infection and the implications for immunodiagnosis

Captive and free-ranging wildlife animals are implicated in the maintenance and transmission of bovine tuberculosis and therefore pose a significant obstacle to eradication of the disease from domestic livestock. The current antemortem diagnostic method, the intradermal tuberculin skin test, is impractical for routine use with many wild animals. Antibody-based assays are particularly attractive because the animals are handled only once and immediate processing of the sample is not required. This report characterizes the antibody responses of red deer-elk hybrids (Cervus elaphus) against Mycobacterium bovis and subsequently evaluates the diagnostic performance of select antigens in a rapid-test format. Sequential serum samples were collected from 10 animals experimentally infected with M. bovis and 5 noninfected animals over a 7-month period postinfection (p.i.). Samples were evaluated by enzyme-linked immunosorbent assays, immunoblot analyses, and multiantigen print immunoassays for seroreactivity to mycobacterial antigens. Although all infected animals produced antibodies to M. bovis protein antigens, there was significant animal-to-animal variation in the kinetics and magnitudes of responses and the antigens recognized. The most frequently recognized antigens included MPB83, ESAT-6, CFP10, and MPB70. Responses to some antigens, such as MPB83, were consistently detected as early as 4 weeks after inoculation, whereas other antigens were detected only much later (>140 days p.i.). Antibody responses were boosted by injection of tuberculin for intradermal tuberculin skin testing. Comparison of single-antigen (fluorescence polarization assay) with multiantigen (CervidTB STAT-PAK) rapid tests demonstrated that a highly sensitive and specific serodiagnostic test for tuberculosis in cervids will require multiple and carefully selected seroreactive antigens covering a broad spectrum of antibody specificities.

Animal-side serologic assay for rapid detection of Mycobacterium bovis infection in multiple species of free-ranging wildlife

Numerous species of mammals are susceptible to Mycobacterium bovis, the causative agent of bovine tuberculosis (TB). Several wildlife hosts have emerged as reservoirs of M. bovis infection for domestic livestock in different countries. In the present study, blood samples were collected from Eurasian badgers (n=1532), white-tailed deer (n=463), brushtail possums (n=129), and wild boar (n=177) for evaluation of antibody responses to M. bovis infection by a lateral-flow rapid test (RT) and multiantigen print immunoassay (MAPIA). Magnitude of the antibody responses and antigen recognition patterns varied among the animals as determined by MAPIA; however, MPB83 was the most commonly recognized antigen for each host studied. Other seroreactive antigens included ESAT-6, CFP10, and MPB70. The agreement of the RT with culture results varied from 74% for possums to 81% for badgers to 90% for wild boar to 97% for white-tailed deer. Small numbers of wild boar and deer exposed to M. avium infection or paratuberculosis, respectively, did not cross-react in the RT, supporting the high specificity of the assay. In deer, whole blood samples reacted similarly to corresponding serum specimens (97% concordance), demonstrating the potential for field application. As previously demonstrated for badgers and deer, antibody responses to M. bovis infection in wild boar were positively associated with advanced disease. Together, these findings suggest that a rapid TB assay such as the RT may provide a useful screening tool for certain wildlife species that may be implicated in the maintenance and transmission of M. bovis infection to domestic livestock.

Development and use of a partial Mycobacterium avium subspecies paratuberculosis protein array

As an initial step toward systematically characterizing all antigenic proteins produced by a significant veterinary pathogen, 43 recombinant Mycobacterium avium subspecies paratuberculosis (M. paratuberculosis) expression clones were constructed, cataloged, and stored. NC filters were spotted with purified proteins from each clone along with a whole cell lysate of M. paratuberculosis. Spots on the resulting dot array consisted of hypothetical proteins (13), metabolic proteins (3), cell envelope proteins (7), known antigens (4), and unique proteins with no similarity in public sequence databases (16). Dot blot arrays were used to profile antibody responses in a rabbit and mouse exposed to M. paratuberculosis as well as in cattle showing clinical signs of Johne's disease. The M. paratuberculosis heat shock protein DnaK, encoded by ORF MAP3840 and a membrane protein (MAP2121c), were identified as the most strongly immunoreactive in both the mouse and rabbit hosts, respectively. MAP3155c, which encodes a hypothetical protein, was most strongly immunoreactive in sera from Johne's disease cattle. This study has enabled direct comparisons of antibody reactivity for an entire panel of over 40 proteins and has laid the foundation for future high throughput production and arraying of M. paratuberculosis surface proteins for immune profiling experiments in cattle.

Tuberculosis in elephants: antibody responses to defined antigens of Mycobacterium tuberculosis, potential for early diagnosis, and monitoring of treatment

Tuberculosis (TB) in elephants is a re-emerging zoonotic disease caused primarily by Mycobacterium tuberculosis. Current diagnosis relies on trunk wash culture, the only officially recognized test, which has serious limitations. Innovative and efficient diagnostic methods are urgently needed. Rapid identification of infected animals is a crucial prerequisite for more effective control of TB, as early diagnosis allows timely initiation of chemotherapy. Serology has diagnostic potential, although key antigens have not been identified and optimal immunoassay formats are not established. To characterize the humoral responses in elephant TB, we tested 143 serum samples collected from 15 elephants over time. These included 48 samples from five culture-confirmed TB cases, of which four were in Asian elephants infected with M. tuberculosis and one was in an African elephant with Mycobacterium bovis. Multiantigen print immunoassay (MAPIA) employing a panel of 12 defined antigens was used to identify serologic correlates of active disease. ESAT-6 was the immunodominant antigen recognized in elephant TB. Serum immunoglobulin G antibodies to ESAT-6 and other proteins were detected up to 3.5 years prior to culture of M. tuberculosis from trunk washes. Antibody levels to certain antigens gradually decreased in response to antitubercular therapy, suggesting the possibility of treatment monitoring. In addition to MAPIA, serum samples were evaluated with a recently developed rapid test (RT) based on lateral flow technology (ElephantTB STAT-PAK). Similarly to MAPIA, infected elephants were identified using the RT up to 4 years prior to positive culture. These findings demonstrate the potential for TB surveillance and treatment monitoring using the RT and MAPIA, respectively.