Prospecting potential links between PRRSV infection susceptibility of alveolar macrophages and other respiratory infectious agents present in conventionally reared pigs.

Porcine Reproductive and Respiratory Syndrome virus (PRRSV) is one of the main component of the porcine respiratory disease complex (PRDC), which strongly impact the pig production. Although PRRSV is often considered as a primary infection that eases subsequent respiratory coinfections, the possibility that other PRDC components may facilitate PRRSV infection has been largely overlooked. The main cellular targets of PRRSV are respiratory macrophages among them alveolar macrophages (AM) and pulmonary intravascular macrophages (PIM). AM, contrarily to PIM, are directly exposed to the external respiratory environment, among them co-infectious agents. In order to explore the possibility of a co-infections impact on the capacity of respiratory macrophages to replicate PRRSV, we proceed to in vitro infection of AM and PIM sampled from animals presenting different sanitary status, and tested the presence in the respiratory tract of these animals of the most common porcine respiratory pathogens (PCV2, Actinobacillus pleuropneumoniae, Mycoplasma hyopneumoniae, Mycoplasma hyorhinis, Mycoplasma floculare, Pasteurella multocida, Bordetella bronchiseptica, Streptoccocus suis). In this exploratory study with a limited number of animals, no statistic differences were observed between AM and PIM susceptibility to in vitro PRRSV infection, nor between AM coming from animals presenting very contrasting respiratory coinfection loads.