Concurrent infection modulates host immunity resulting in impaired control of infection in pigs.

is one of the most widespread helminth infections, leading to chronic morbidity in humans and considerable economic losses in pig farming. In addition, pigs are an important reservoir for the zoonotic salmonellosis where pigs can serve as asymptomatic carriers. Here, we investigated the impact of an ongoing infection on the immune response to in pigs. We observed higher bacterial burdens in experimentally coinfected pigs compared to pigs infected with alone. The impaired control of in the coinfected pigs was associated with repressed interferon gamma responses in the small intestine and with the alternative activation of gut macrophages evident in elevated CD206 expression. single and coinfection were associated with a rise of CD4CD8αFoxP3 Treg in the lymph nodes draining the small intestine and liver. In addition, macrophages from coinfected pigs showed enhanced susceptibility to infection and the induced monocytosis and tumor necrosis factor alpha production by myeloid cells was repressed in pigs coinfected with . Hence, our data indicate that acute infection modulates different immune effector functions with important consequences for the control of tissue-invasive coinfecting pathogens.IMPORTANCEIn experimentally infected pigs, we show that an ongoing infection with the parasitic worm modulates host immunity, and coinfected pigs have higher burdens compared to pigs infected with alone. Both infections are widespread in pig production and the prevalence of is high in endemic regions of human Ascariasis, indicating that this is a clinically meaningful coinfection. We observed the type 2/regulatory immune response to be induced during an infection correlates with increased susceptibility of pigs to the concurrent bacterial infection.