Evaluation of immune effect to recombinant potential protective antigens of Mycoplasma ovipneumoniae in mice.

Mycoplasma ovipneumoniae is a primary causative agent of pneumonia in ruminants, causing chronic non-progressive pneumonia in domestic sheep and goats, but leading to higher morbidity and mortality in bighorn sheep and wild small ruminants. This disease has become a widespread epidemic, resulting in significant losses to the sheep industry. In this study, we evaluated the immunogenicity and initial protective effects of four antigenic proteins of M. ovipneumoniae, namely Eno, EF-Tu, Ulad, and T4SS. These proteins were used to immunize BALB/c mice either individually or in a combination (rProteins group). The mice were intranasally infected with 10 CCU/mL M. ovipneumoniae strain NJ01 twice, on days 28 and 30 after immunization. Among the four recombinant proteins, rEno demonstrated the most promising results in terms of inducing specific humoral and cellular immune responses. It also resulted in the lowest lung lesion scores and the lowest M. ovipneumoniae loads in the lungs and bronchoalveolar lavage fluid (BALF). Compared to the other three proteins, rEno provided superior protection. Furthermore, the rEno vaccine significantly reduced the inflammatory response in the lungs of mice, as evidenced by the evaluation of pro-inflammatory cytokines. The expression of IL-1β and NF-κB was significantly reduced, while the expression of IL-4 was significantly increased. In conclusion, the rEno vaccine elicited a favorable immunological response and conferred protection against M. ovipneumoniae. This finding presents a novel approach to controlling the global spread of this pathogen.