Glycoprotein analysis of porcine bronchoalveolar lavage fluid reveals potential biomarkers corresponding to resistance to Actinobacillus pleuropneumoniae infection

Biomarkers facilitating both pathogen-independent diagnosis of respiratory health and breeding selection of pigs with increased resistance to respiratory tract infections would be of considerable interest to the pig industry. Following this concept we performed a comparative glycoproteome analysis of bronchoalveolar lavage fluid (BALF) from healthy pigs and pigs 4 days (acute) and 20 days (chronic) after an experimental infection with Actinobacillus pleuropneumoniae. In order to identify possible differences in BALF glycoprotein patterns we investigated pigs of three different breeding lines (German Landrace, Pietrain, Hampshire). In total, 12 glycosylated proteins (alpha-1-acid glycoprotein, fetuin A, properdin, haptoglobin precursor, haptoglobin, hemoglobin, hyaluronidase, inter-alpha-trypsin inhibitor family heavy chain-related protein, alpha-1-antichymotrypsin 3, pulmonary surfactant-associated protein D (SP-D), transferrin, and alpha-1B-glycoprotein) were identified as being differentially expressed depending on the health status of the animal. Fetuin A levels were consistently low in chronically infected pigs thereby being a potential marker for chronic infection. Hyaluronidase levels were consistently high in all pigs after experimental infection independent on isolation of the pathogen thereby being a potential marker for previous pathogen contact and latent infection. High levels of fetuin A as well as low levels of haptoglobin and pulmonary SP-D correlated with the absence of lung lesions in pigs of the Hampshire breeding line, implying a potential application as selection markers for breeding programmes.