Macrophages largely contribute to heterologous anti-Propionibacterium acnes antibody-mediated protection from Actinobacillus pleuropneumoniae infection in mice

• Published in: Microbiology and immunology Vol. 59; no. 3; p. 166
• Main Authors: Ma, Qiuyue, Sun, Changjiang, Yang, Feng, Wang, Lei, Qin, Wanhai, Xia, Xiaojing, Feng, Xin, Du, Chongtao, Gu, Jingmin, Han, Wenyu, Lei, Liancheng
• Format: Journal Article
• Language: English
• Published: Australia 01.03.2015
• Subjects: Actinobacillus Infections - immunology; Actinobacillus Infections - microbiology; Actinobacillus Infections - pathology; Actinobacillus Infections - veterinary; Actinobacillus pleuropneumoniae - immunology; Actinobacillus pleuropneumoniae - physiology; Animals; Antibodies, Bacterial - immunology; Cross Protection; Disease Models, Animal; Female; Gram-Positive Bacterial Infections - immunology; Gram-Positive Bacterial Infections - microbiology; Gram-Positive Bacterial Infections - pathology; Gram-Positive Bacterial Infections - veterinary; Immunization, Passive; Macrophages - immunology; Mice; Mice, Inbred BALB C; Phagocytosis; Propionibacterium acnes - immunology; Propionibacterium acnes - physiology; Swine; Swine Diseases - immunology; Swine Diseases - microbiology; Swine Diseases - pathology; passive immunization; anti-Propionibacterium acnes antibody
• ISSN: 1348-0421
• DOI: 10.1111/1348-0421.12240

Actinobacillus pleuropneumoniae is the causative agent of acute and chronic pleuropneumonia. Propionibacterium acnes is a facultative anaerobic gram-positive corynebacterium. We have previously found that anti-P. acnes antibodies can prevent A. pleuropneumoniae infections in mice. To investigate the role of macrophages in this process, affinity-purified anti-P. acnes IgG and anti-A. pleuropneumoniae IgG were used in opsonophagocytosis assays. Additionally, the efficacy of passive immunization with P. acnes serum against A. pleuropneumoniae was tested in macrophage-depleted mice. It was found that anti-P. acnes IgG had an effect similar to that of anti-A. pleuropneumoniae IgG (P > 0.05), which significantly promotes phagocytosis of A. pleuropneumoniae by macrophages (P < 0.01). It was also demonstrated that, after passive immunization with anti-P. acnes serum, macrophage-replete mice had the highest survival rate (90%), whereas the survival rate of macrophage-depleted mice was only 40% (P < 0.05). However, macrophage-depleted mice that had been passively immunized with naïve serum had the lowest survival rate (20%), this rate being lower than that of macrophage-replete mice that had been passively immunized with naïve serum. Overall, anti-P. acnes antibodies did not prevent A. pleuropneumoniae infection under conditions of macrophage depletion (P > 0.05). Furthermore, in mice that had been passively immunized with anti-P. acnes serum, macrophage depletion resulted in a greater A. pleuropneumoniae burden and more severe pathological features of pneumonia in lung tissues than occurred in macrophage-replete mice. It was concluded that macrophages are essential for the process by which anti-P. acnes antibody prevents A. pleuropneumoniae infection in mice.