Immunogenicity ofMycobacterium tuberculosisAntigens inMycobacterium bovisBCG-Vaccinated andM. bovis-Infected Cattle

Abstract

The development of novel vaccine strategies supplementing Mycobacterium bovis BCG (BCG) constitutes an urgent research challenge. To identify potential subunit vaccine candidates, we have tested a series of eight recently identified Mycobacterium tuberculosis antigens in M. bovis-infected and BCG-vaccinated cattle. These antigens were characterized on the basis of their ability to induce in vitro gamma interferon responses in infected or BCG-vaccinated calves. We were able to establish a hierarchy of these antigens based on how frequently they were recognized in both groups of animals. In particular, we were able to prioritize frequently recognized proteins like Rv0287, Rv1174, and Rv1196 for future evaluation as subunit vaccines to be used in BCG-protein heterologous prime-boost vaccination scenarios. In addition, the antigen most dominantly recognized in M. bovis-infected cattle in this study, Rv3616c, was significantly less frequently recognized by BCG vaccinees and could be a target to improve BCG, for example, by increasing its secretion, in a recombinant BCG vaccine.

Specific Recognition of Mycobacterial Protein and Peptide Antigens by γδ T Cell Subsets following Infection with VirulentMycobacterium bovis

“…The specific protein and nonprotein Ags used in this study were .98% pure and were tested for endotoxin levels using the ToxinSensor Chromogenic LAL Endotoxin Assay Kit (GenScript). Levels of endotoxin were ,3 endotoxin U/mg, a concentration similar to that found in mycobacterial Ags used in other studies (47).…”

Multivalent TB vaccines targeting the esx gene family generate potent and broad cell-mediated immune responses superior to BCG

“…14 These proteins are attractive targets because they are potent T cell antigens that encode several immunodominant molecules, which are strongly recognized by the immune systems in both animals and humans. 12,13,15 These are small, secreted antigenic proteins that have been demonstrated to likely be required for the growth and pathogenicity of Mtb. 12 A few of the esx members are deleted in BCG, which has been associated with its attenuation and therefore, its low efficacy, 12 which also suggests they may represent important immune targets to alter pathogenicity.…”

The Transcriptional Regulator Rv0485 Modulates the Expression of a pe and ppe Gene Pair and Is Required for Mycobacterium tuberculosis Virulence

“…High-density transposon mutagenesis screening suggests that neither of these genes is essential for in vitro growth or in vivo survival (55,56). However, it has been demonstrated that the proteins encoded by these genes are expressed and recognized in M. tuberculosis-infected and M. bovis-infected hosts, suggesting that they do play a role during infection (22,40). Of particular note, PPE18 (also known as Mtb39A and Rv1196) was identified by serological expression screening (22) and is undergoing evaluation as part of the promising polyprotein vaccine candidate Mtb72f (http://clinicaltrials.gov/ct2 /show/NCT00600782) (58,64).…”

“…1A). Although not predicted to be essential (55,56), a number of reports indicate that PE13 and PPE18 are expressed and recognized during infection (22,40). Furthermore, PPE18 constitutes part of the polyprotein vaccine candidate, Mtb72f (58).…”