Serum IgG immunoglobulin levels correlate with clearance of Mycoplasma bovis in naturally infected North American bison (Bison bison)

Authors: Kaplan, Bryan; MALMBERG, JENNIFER - UNIVERSITY OF WYOMING; SONDGEROTH, KERRY - UNIVERSITY OF WYOMING; Dassanayake, Rohana; Sacco, Randy; Casas, Eduardo; BUTTKE, DANIELLE - U.S. NATIONAL PARK SERVICE

Submitted to: Journal of Wildlife Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Mycoplasma bovis (M. bovis) is a bacterial pathogen of cattle and bison capable of causing severe respiratory disease. In bison, M. bovis is responsible for large outbreaks of fatal disease with mortality exceeding 25%. Despite the significant, negative impacts of M. bovis on bison ranching and conservation efforts, little information is available regarding the natural course and immune response to infection. To better characterize the kinetics of bacterial shedding and serum antibody responses, a cohort of bison that were naturally infected with M. bovis was created. Over a 12-month period, the cohort was sampled every 2-3 months for a total of 5 samplings. Nearly half of the 41 bison in the cohort tested positive by PCR for M. bovis. A majority of bison were seropositive for M. bovis specific antibody. A group of M. bovis infected bison were determined to have high levels of M. bovis specific IgG that correlated with a decline in PCR positive nasal swabs. These data suggest that antibody is important for the recovery of bison from M. bovis infection.

Technical Abstract: Mycoplasma bovis is an important pathogen of North American bison (Bison bison) associated with high morbidity and mortality epizootics of respiratory and reproductive disease. Despite the significant negative impact on bison health, little is known about the kinetics of disease and the host immune response to infection. To address these questions, a cohort of bison was created and serially sampled 5 times, once every 2-3 months, over a 12-month period. At each sampling period shallow and deep nasal swab samples were collected and tested by PCR for the presence of M. bovis. Serum samples were also collected and assessed for M. bovis specific antibodies using both a commercial and an in-house ELISA. Overall, out of 41 bison, 19 (46.3%) had positive PCR tests while 31 (75.6%) were seropositive. Over the course of the study, the frequency of PCR positive nasal swabs and the ELISA scores decreased, though serum samples remained positive for at least 6 months following final, positive PCR test. Bison were grouped according to results from the in-house ELISA into high responder (n = 7), low responder (n = 5), and seronegative (n = 7) groups. M. bovis specific IgG antibody levels were significantly elevated in the high responder group compared to the low responder and seronegative groups. The differences were statistically significant for 3 of the 5 sampling periods. A trend toward increased IgG2 levels was observed in the high responder group. High total IgG responses correlated with a decline in positive PCR tests from nasal swabs. These data provide evidence that a strong humoral response is beneficial and involved in the clearance of M. bovis from bison.