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Most vaccines for protection against Mycoplasma bovis disease are made of bacterins, and they offer varying degrees of protection. Our focus is on the development of a subunit-based protective vaccine, and to that end, we have identified 10 novel vaccine candidates. After formulation of these candidates with TriAdj, an experimental tri-component novel vaccine adjuvant developed at VIDO-InterVac, we measured humoral and cell-mediated immune responses in vaccinated animals. In addition, we compared the immune responses after formulation with TriAdj with the responses measured in animals vaccinated with a mix of a commercial adjuvant (Emulsigen™) and 2 of the components of the TriAdj, namely polyinosinic:polycytidylic acid (poly I:C) and the cationic innate defense regulator (IDR) peptide 1002 (VQRWLIVWRIRK). In this latter trial, we detected significant IgG1 humoral immune responses to 8 out of 10 M. bovis proteins, and IgG2 responses to 7 out of 10 proteins. Thus, we concluded that the commercial adjuvant formulated with poly I:C and the IDR peptide 1002 is the best formulation for the experimental vaccine.

Mycoplasma bovis is a pathogen globally affecting cattle and bison herds, causing pneumonia, arthritis, mastitis, abortions, and other symptoms, leading to huge economic losses. Many studies have been done regarding the antimicrobial susceptibility of M. bovis isolated from cattle, but no such study is available for isolates recovered from bison. For the first time, in vitro susceptibilities of 40 M. bovis clinical isolates collected from bison herds in Canada are reported here. Minimal inhibitory concentration (MIC) values were determined using Sensititre® plates. The most effective MIC50 and MIC90 were for spectinomycin (1 and >64 μg/mL), tiamulin (1 and >32 μg/mL), and tulathromycin (16 and 64 μg/mL), whereas tetracyclines, fluoroquinolones, and florfenicol failed to inhibit growth of M. bovis bison isolates. Isolates were nonsusceptible to tetracyclines (100%), fluoroquinolones (97.5%), and tilmicosin (100%), whereas the highest susceptibility of bison clinical isolates was seen with spectinomycin (95%) and tulathromycin (67.5%). Two lung isolates (Mb283 and 348) were found resistant to both spectinomycin and tulathromycin. These results show a marked difference in antimicrobial susceptibility of bison isolates as compared with previously reported and laboratory reference cattle isolates, emphasizing the necessity of testing antimicrobial susceptibility of M. bovis bison isolates and to generate better therapeutic regime for improved recovery chances for infected bison herds across North America.