Haemophilus parasuis is the etiological agent of Glässer’s disease, which is characterized
by fibrinous polyserositis, polyarthritis and meningitis in pigs. This study was focused
on the characterization of the acute-phase response after immunization and infection of
colostrum-deprived pigs with H. parasuis serovar 5, by measuring serum concentrations of
three positive acute-phase proteins (APPs) (pig major acute-phase protein pig, MAP; haptoglobin,
HPG; C-reactive protein, CRP) and one negative APP (apolipoprotein A-I, ApoA-I).
Six experimental groups were established: a non-immunized but infected control group
(CTL); two groups immunized with either a recombinant transferrin-binding protein (Tbp)
A or TbpB fragment from H. parasuis Nagasaki strain (rTbpA and rTbpB, respectively); two
groups immunized with native outer membrane proteins with affinity to porcine transferrin
(NPAPT), one of them inoculated intramuscularly (NPAPTim) and the other intratracheally
(NPAPTit), and the last group receiving a commercially available bacterin (PG). The greatest
concentrations of the three positive APPs and the lowest concentration of the negative APP
were detected in CTL group, as well as in those animals belonging to rTbpA or rTbpB groups
that died in response to challenge. Significant differences (P < 0.005) were found in these
groups when comparing challenge with the following days after it. However, no significant
differences were seen for the remaining vaccinated groups (NPAPTim, NPAPTit and PG),
which were effectively protected against Glässer’s disease. Therefore, APPs could be used
as useful biomarkers for both evaluating disease progression and determining vaccination
effectiveness
