Potential use of local and systemic humoral immune response parameters to forecast Mycoplasma hyopneumoniae associated lung lesions

Abstract

Immunopathological events are key for the development of enzootic pneumonia (EP), which is macroscopically observed as cranioventral pulmonary consolidation (CVPC). This study aimed to investigate the putative association between the humoral immune response against Mycoplasma hyopneumoniae (M. hyopneumoniae) and prevalence and extension of CVPC in 1) experimentally infected pigs, 2) slaughtered pigs and 3) sequentially necropsied pigs in a longitudinal study. CVPC was scored by means of the European Pharmacopoeia recommended methodology. Specific IgG, IgG1 and IgG2 antibodies were assessed in serum. In addition, mucosal IgG and IgA antibodies were analyzed in broncho-alveolar lavage fluid (BALF) from experimentally challenged pigs. The systemic humoral immune response in experimentally infected pigs was delayed in onset whereas humoral respiratory mucosal immune response appeared more rapidly but declined earlier. Although low, BALF IgG antibodies showed the highest correlation with CVPC scores (r = 0.49, p<0.05). In slaughter-aged pigs, both percentage of lungs with CVPC and mean lung lesion score were significantly higher inM. hyopneumoniae seropositive farms compared to the seronegative ones (p<0.001). Similarly, seropositive sequentially necropsied pigs showed more severe CVPC than seronegative ones. Overall, mean serological values might help to forecast prevalence and severity of EP-like lung lesions using a population based approach. Remarkably, the specific systemic humoral immune response was found to be predominated by the IgG2 subclass, suggesting a dominant Th1- mediated immune response toM. hyopneumoniae.

This work was supported by a collaborative agreement for independent research from Boehringer Ingelheim and a grant from Secretaria del Departament d'Economia i Creixement de la Generalitat de Catalunya (Industrial Doctorate: DI2013-0039). Boehringer Ingelheim provided support in the form of salaries for authors BGM and TC. The specific roles of BGM and TC are articulated in the ªauthor contributionsº section.