Characterization, identification, and purification of the bacterial receptor expressed by turkey peripheral blood monocytes for serogroup A:3 of Pasteurella multocida

Abstract

Capsular hyaluronic acid (HA) mediates adhesion of serogroup A strains of P. multocida to elicited turkey air sac macrophages (TASM). In contrast, freshly isolated turkey peripheral blood monocytes (TPBM) do not bind serogroup A strains. Following culture of TPBM for 6 days in chamber slides, adhesion of the bacteria to TPBM increased gradually. Incubation in chamber slides coated with Entactin-CoUagen IV-Laminin attachment (ECL) matrix or exposure to phorbol myristate acetate (PMA) fiirther enhanced the adhesion of P. multocida to TPBM. Addition of HA to TPBM culture, but not Arg-Gly-Asp peptide, inhibited bacterial adherence similarly to that previously reported for TASM Exposure of TPBM to MAb directed against HA-binding cell surfece proteoglycan (CD44) decreased binding of P. multocida. Collectively, these findings indicate that P. multocida adhesion to TPBM is mediated by capsular HA and can be up-regulated by culture on ECL matrix or PMA exposure. Additionally, the findings suggest that the capsular mucopolysaccharide of serogroup A strains of P. multocida recognizes an 69 isoform of CD44 expressed on cultured TPBM. INTRODUCTION Pasteurella multocida causes fowl cholera, a widely distributed disease occurring in most poultry-producing countries of the world. Annual worldwide losses to the poultry industry were estimated at 200 million US dollars in 1986 (11). Serogroup A strains of P. multocida are the major cause of fowl cholera in turkeys. Survival of P. multocida outside the host and resistance to phagocytosis in non-immunized birds are associated with the presence of a capsule. With serogroup A strains of P. multocida, the capsule contains HA, an anionic polysaccharide composed of repetitive disaccharidic units of A'-acet>l-D-glucuronic acid and A^'-acetyl-D- glucosamine. Invasion by P. multocida is believed to occur through the lymphoid tissues of the respiratory tract, and the bacterial capsule is suspected to play a major role in this event. Previous studies from our laboratory demonstrated that serogroup A strains of P. multocida adhere to TASM but are not internalized. Although we showed that bacterial adhesion to TASM occurs through specific recognition of capsular hyaluronate by a cell surface glycoprotein (10), the host cell receptor was not identified. CD44, an 85-kDa transmembrane glycoprotein found on a variety of cell types, is one of several receptors capable of binding HA. Because CD44 is an HA receptor also associated with lung macrophages (3, 5), we suspected that it might be involved in adhesion of serogroup A strains of P. multocida to TASM. However, with avian species, the number of resident macrophages in the lungs and air sacs is low and recovery by lavage is poor (12). Consequently, our initial attempts to isolate CD44 from TASM foiled due to the inability to acquire suflBcient numbers of cells. This failure prompted a study to