The acute-phase protein response in parasite infection. Nippostrongylus brasiliensis and Trichinella spiralis in the rat.

During acute inflammation, the mammalian liver responds with increased production and secretion of a series of plasma glycoproteins, collectively termed the acute-phase proteins, resulting from the release at the site of inflammation of polypeptide cytokines, including IL-1 and IL-6, which interact with receptors on hepatocytes and alter gene expression. This attribute of the systemic acute-phase response was studied throughout the course of infection with two nematode parasites in rats. Significant increases in serum haptoglobin, alpha 1-acid glycoprotein and alpha 1-cysteine protease inhibitor were detected coincident with episodes of skin, lung and intestinal pathology during Nippostrongylus brasiliensis, but were not seen during Trichinella spiralis, infection of the rat despite similar intestinal pathology. These changes were seen at both the protein and mRNA levels in the liver. Infection with T. spiralis was not anti-inflammatory, as macrophages from various sites could be induced in vitro to release inflammatory cytokines, and in vivo induction of inflammation by turpentine injection was similar in control and infected animals. However, macrophage populations recovered from animals infected with T. spiralis were not activated. Moreover, intestinal infection alone with intestinal stages of N. brasiliensis also failed to elicit the systemic acute-phase protein response, requiring an explanation involving skin and lung for the acute-phase response during gut inflammation in a primary infection with N. brasiliensis. Taken together, these data suggest that during the intestinal phase of nematode infection, with pathological changes to the gut, the systemic acute-phase response is not elicited through compromise or lack of stimulation of inflammatory cells in the intestine. The systemic parameters of the acute-phase response may not be a component of gastrointestinal pathology.