Previous work with small-animal laboratory models of tuberculosis has shown that vaccination strategies based on heterologous prime-boost protocols using Mycobacterium bovis bacillus Calmette-Guérin ...(BCG) to prime and modified vaccinia virus Ankara strain (MVA85A) or recombinant attenuated adenoviruses (Ad85A) expressing the mycobacterial antigen Ag85A to boost may increase the protective efficacy of BCG. Here we report the first efficacy data on using these vaccines in cattle, a natural target species of tuberculous infection. Protection was determined by measuring development of disease as an end point after M. bovis challenge. Either Ad85A or MVA85A boosting resulted in protection superior to that given by BCG alone: boosting BCG with MVA85A or Ad85A induced significant reduction in pathology in four/eight parameters assessed, while BCG vaccination alone did so in only one parameter studied. Protection was particularly evident in the lungs of vaccinated animals (median lung scores for naïve and BCG-, BCG/MVA85A-, and BCG/Ad85A-vaccinated animals were 10.5, 5, 2.5, and 0, respectively). The bacterial loads in lymph node tissues were also reduced after viral boosting of BCG-vaccinated calves compared to those in BCG-only-vaccinated animals. Analysis of vaccine-induced immunity identified memory responses measured by cultured enzyme-linked immunospot assay as well as in vitro interleukin-17 production as predictors of vaccination success, as both responses, measured before challenge, correlated positively with the degree of protection. Therefore, this study provides evidence of improved protection against tuberculosis by viral booster vaccination in a natural target species and has prioritized potential correlates of vaccine efficacy for further evaluation. These findings also have implications for human tuberculosis vaccine development.
Experiments in the late 19th century sought to define the host specificity of the causative agents of tuberculosis in mammals. Mycobacterium tuberculosis, the human tubercle bacillus, was ...independently shown by Smith, Koch, and von Behring to be avirulent in cattle. This finding was erroneously used by Koch to argue the converse, namely that Mycobacterium bovis, the agent of bovine tuberculosis, was avirulent for man, a view that was subsequently discredited. However, reports in the literature of M. tuberculosis isolation from cattle with tuberculoid lesions suggests that the virulence of M. tuberculosis for cattle needs to be readdressed. We used an experimental bovine infection model to test the virulence of well-characterized strains of M. tuberculosis and M. bovis in cattle, choosing the genome-sequenced strains M. tuberculosis H37Rv and M. bovis 2122/97. Cattle were infected with approximately 106 CFU of M. tuberculosis H37Rv or M. bovis 2122/97, and sacrificed 17 weeks post-infection. IFN-γ and tuberculin skin tests indicated that both M. bovis 2122 and M. tuberculosis H37Rv were equally infective and triggered strong cell-mediated immune responses, albeit with some indication of differential antigen-specific responses. Postmortem examination revealed that while M. bovis 2122/97–infected animals all showed clear pathology indicative of bovine tuberculosis, the M. tuberculosis–infected animals showed no pathology. Culturing of infected tissues revealed that M. tuberculosis was able to persist in the majority of animals, albeit at relatively low bacillary loads. In revisiting the early work on host preference across the M. tuberculosis complex, we have shown M. tuberculosis H37Rv is avirulent for cattle, and propose that the immune status of the animal, or genotype of the infecting bacillus, may have significant bearing on the virulence of a strain for cattle. This work will serve as a baseline for future studies into the genetic basis of host preference, and in particular the molecular basis of virulence in M. bovis.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The aim of this work was to determine the minimum infective dose of Mycobacterium bovis necessary to stimulate specific immune responses and generate pathology in cattle. Four groups of calves (20 ...animals) were infected by the intratracheal route with 1,000, 100, 10, or 1 CFU of M. bovis. Specific immune responses (gamma interferon IFN-gamma and interleukin-4 IL-4 responses) to mycobacterial antigens were monitored throughout the study, and the responses to the tuberculin skin test were assessed at two times. Rigorous post mortem examinations were performed to determine the presence of pathology, and samples were taken for microbiological and histopathological confirmation of M. bovis infection. One-half of the animals infected with 1 CFU of M. bovis developed pulmonary pathology typical of bovine tuberculosis. No differences in the severity of pathology were observed for the different M. bovis doses. All animals that developed pathology were skin test positive and produced specific IFN-gamma and IL-4 responses. No differences in the sizes of the skin test reactions, the times taken to achieve a positive IFN-gamma result, or the levels of the IFN-gamma and IL-4 responses were observed for the different M. bovis doses, suggesting that diagnostic assays (tuberculin skin test and IFN-gamma test) can detect cattle soon after M. bovis infection regardless of the dose. This information should be useful in modeling the dynamics of bovine tuberculosis in cattle and in assessing the risk of transmission.
Background. We evaluated the immunological responses of African green monkeys immunized with multiple F and G protein—based vaccines and assessed protection against the Memphis 37 strain of ...respiratory syncytial virus (RSV). Methods. Monkeys were immunized with F and G proteins adjuvanted with immunostimulatory (CpG) oligodeoxyribonucleotides admixed with either Alhydrogel or ISCOMATRIX adjuvant. Delivery of F and G proteins via replication incompetent recombinant vesicular stomatitis viruses (VSVs) and human adenoviruses was also evaluated. Mucosally or parenterally administered recombinant adenoviruses were used in prime-boost regimens with adjuvanted proteins or recombinant DNA. Results. Animals primed by intranasal delivery of recombinant adenoviruses, and boosted by intramuscular injection of adjuvanted F and G proteins, developed neutralizing antibodies and F/G protein—specific T cells and were protected from RSV infection. Intramuscular injections of Alhydrogel (plus CpG) adjuvanted F and G proteins reduced peak viral loads in the lungs of challenged monkeys. Granulocyte numbers were not significantly elevated, relative to controls, in postchallenge bronchoalveolar lavage samples from vaccinated animals. Conclusions. This study has validated the use of RSV (Memphis 37) in an African green monkey model of intranasal infection and identified nonreplicating vaccines capable of eliciting protection in this higher species challenge model.
1 Veterinary Laboratories Agency (Weybridge), New Haw, Addlestone, Surrey KT15 3NB, UK.
2 Bacterial Microarray Group, Department of Cellular and Molecular Medicine, St George's Hospital Medical ...School, Cranmer Terrace, London SW17 0RE, UK
Correspondence Stephen V. Gordon stephen.gordon{at}ucd.ie
Genome sequencing of Mycobacterium tuberculosis complex members has accelerated the search for new disease-control tools. Antigen mining is one area that has benefited enormously from access to genome data. As part of an ongoing antigen mining programme, we screened genes that were previously identified by transcriptome analysis as upregulated in response to an in vitro acid shock for their in vivo expression profile and antigenicity. We show that the genes encoding two methyltransferases, Mb1438c/Rv1403c and Mb1440c/Rv1404c , were highly upregulated in a mouse model of infection, and were antigenic in M. bovis -infected cattle. As the genes encoding these antigens were highly upregulated in vivo , we sought to define their genetic regulation. A mutant was constructed that was deleted for their putative regulator, Mb1439/Rv1404 ; loss of the regulator led to increased expression of the flanking methyltransferases and a defined set of distal genes. This work has therefore generated both applied and fundamental outputs, with the description of novel mycobacterial antigens that can now be moved into field trials, but also with the description of a regulatory network that is responsive to both in vivo and in vitro stimuli.
Abbreviations: IFN- , gamma-interferon; PPD, purified protein derivative (tuberculin); qRT-PCR, quantitative real-time polymerase chain reaction
Present address: Emergent Biosolutions, 540–545 Eskdale Road, Winnersh Triangle, Wokingham, Berkshire RG41 5TU, UK.
Present address: School of Agriculture, Food Science and Veterinary Medicine, College of Life Sciences, University College Dublin, Belfield, Dublin 4, Republic of Ireland.
The ArrayExpress (and BµG@Sbase) accession number for the microarray data in this paper is A-BUGS-59.
Two supplementary tables of primers are available with the online version of this paper.
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