The mannose receptor is a key player in the non-bactericidal innate interaction between B. pertussis and macrophages.

VALDEZ HUGO; BALBOA, L; GORGOJO JUAN; REA LUNA; ALVAREZ HAYES J; CARRICA M; SASIAIN, MC; RODRIGUEZ, ME

San Luis

Congreso; LXXI REUNIÓN CIENTÍFICA ANUAL DE LA SOCIEDAD ARGENTINA DE INMUNOLOGÍA (SAI); 2023

Sociedad Argentina de Inmunologia

The mannose receptor is a key player in the non-bactericidal innate interaction between B. pertussis and macrophages.Valdez, HA1; Balboa, L2; Gorgojo, JP1; Rea Luna, E1; Alvarez Hayes, J1; Carrica, M1 Sasiain, MC2; and Rodriguez, ME1. CINDEFI (UNLP CONICET La Plata), Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina. 2IMEX-CONICET, Academia Nacional de Medicina, Buenos Aires, Argentina.Our previous work revealed that macrophage (MØ) polarization into alternatively activated cells (M2) enhances B. pertussis (Bp) intracellular survival. CR3 has been historically acknowledged as the main target of Bp on these immune cells. Moreover, previous studies suggested that the non-bactericidal macrophage phagocytosis of Bp critically depends on the bacteria- MØ interaction through CR3. In this study, we aimed at evaluating the relative contribution of the mannose receptor (CD206, MR), highly expressed in M2, in the non-bactericidal Bp interaction with macrophages. To this end, primary human monocytes were differentiated into M2 phenotype in the presence of M-CSF+IL-4. We used blocking antibodies against MR and CR3 to selectively study the bacterial interaction of each receptor. M2 macrophages were incubated or not with 10 µg/ml anti-MR or 10 µg/ml anti-CR3 antibody prior to the addition of Bp at an MOI of 100. After 30 min at 37°C, bacterial binding and phagocytosis were quantified by confocal microscopy with double staining to discriminate intracellular and surface attached bacteria. Bacterial trafficking and intracellular survival were evaluated by confocal microscopy and Polymyxin B protection assays, respectively. The use of blocking antibodies against MR resulted in a significant drop in Bp attachment to and phagocytosis by macrophages. We observed a 66 % (p < 0.05) decrease of bacterial attachment and a 90% (p < 0.05) decrease of bacterial phagocytosis. Surprisingly, in the presence anti-CR3 blocking antibody only the number of bacteria attached per macrophage was affected but not bacterial phagocytosis. We observed a 70 % (p < 0.05) decrease of bacterial attachment to macrophage surfaces but no changes in the percentage of phagocytosed bacteria. These findings challenge the previous assumption that the non-bactericidal interaction between Bp and macrophages relied predominantly on CR3, proposing instead receptor cooperation and highlighting that while CR3 serves as a docking molecule for Bp, it is the PAMP receptor, MR, that plays a pivotal role in facilitating Bp phagocytosis and subsequent survival within macrophages.