Studies on virulence factors and pathogenecity of Haemophilus parasuis have long been hindered by a lack of a consistent system for genetic manipulation. In this study, competence was induced by transferring H. parasuis from rich medium to starvation medium media-IV (M-IV) and iscR gene deficient mutants of H. parasuis were generated efficiently. Transformation frequency varied from 4.1 × 10(−5) to 1.1 × 10(−8) when using circular plasmid, and increased to about 2- to 31-fold when transformed using linearized plasmid. Allele replacement occurred efficiently in 6 strains, which are transformable using both circular and linearized pTRU, but not in another 2 strains which could only be transformed using linearized plasmid. The iscR mutants were stable for at least 20 passages in vitro. Haemophilus parasuis strains vary extensively in natural transformation efficiency and the method established here allows for transformation of a larger spectrum of strains with an easily accessed plasmid. This provides important tools for genetic manipulation of H. parasuis.

Haptoglobin (HP), an acute-phase protein, is detected in serum of cows with hepatic lipidosis (fatty liver). To assess the relevance of Hp in fatty liver, induction of Hp was examined, using conditions similar to those involving development of fatty liver in cows. Induction of Hp was achieved by a combination of dexamethasone administration (0.1 mg/kg of body weight) and 2 days' starvation. Haptoglobin appearance in serum was not associated with the increase of alpha 1-acid glycoprotein (a marker for inflammation). This treatment increased serum nonesterified fatty acids concentration and decreased serum triglycerides concentration. Protein kinase C activity was decreased in the cytosolic fractions of liver and mononuclear cells. Reduction of protein kinase C-catalyzed endogenous protein phosphorylation also was observed, particularly in the cytosolic fractions of the tissue and cells. Detection of Hp in serum of cows with fatty liver appears to be explained by the fact that Hp is induced by dexamethasone administration and starvation, which are similar to the condition responsible for fatty liver development. The change of protein kinase C-catalyzed phosphorylation was suggested to be involved in the induction of Hp in cows.