Effect of Isolated <em>Mycobacterium bovis</em> Proteins on the Respiratory Response of Mouse Granulocytes
crossref(2023)
Abstract
Proteins are considered to be the main carriers of antigenic properties of Mycobacterium tuberculosis and Mycobacterium bovis, the causative agents of tuberculosis, the most serious infectious disease. Neutrophils, following resident macrophages, are among the first to attack the mycobacteria in defense of the organism. Neutrophils themselves are also the target of mycobacterial products; and their effect on neutrophil functions has been less studied. We have obtained about 70 protein fractions from M. bovis lysate; among them four protein fractions (10, 22, 24, and 40 kDa) had high serological activity against the serum of a rabbit immunized with M. bovis cells. We studied the effect of the serologically active proteins isolated from M. bovis on the generation of reactive oxygen species by bone marrow granulocytes of the Balb/c mouse, evaluated by luminol-dependent chemiluminescence. For comparison, two synthetic peptides (both 3 kDa) carrying immunogenic epitopes of MPB 70 protein (M. bovis) were taken. Proteins of 10, 22, and 24 kDa at concentrations of 83, 80, and 59 ng/mL, respectively, were found to activate ROS generation by mouse granulocytes. The 10- and 40-kDa antigens inhibited the receptor-mediated respiratory responses to opsonized zymosan (OZ) and N-formyl-MLF peptide (fMLF) but significantly enhanced the response to the phorbol ester PMA, which directly activates protein kinase C. Antigens with molecular weights of 22 and 24 kDa enhanced the fMLF-induced response and had no effect on the response activated by PMA. The response to OZ was suppressed in the presence of the 22 kDa protein. Synthetic peptides over a wide range of concentrations showed no activity in any case. All M. bovis proteins examined did not affect both proliferation and cell viability of the A549 and THP-1 cells; therefore, they have no cytotoxic or proliferative effects. Thus, serologically active proteins with molecular weights of 10, 22, 24, and 40 kDa isolated from M. bovis modulated the respiratory responses of mouse granulocytes induced by the formyl peptide, while proteins of 10, 22, and 40 kDa inhibited the responses induced by OZ.
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