Humoral and cellular immune response to Histophilus somni recombinant heat shock protein 60 kDa in farm animals

The aim of this study was to evaluate the effects of immunising farm animals with the Histophilus somni recombinant heat shock protein 60kDa (H. somni rHsp60) in field conditions. Fifty piglets, 10 calves and 30 hens were immunised twice, and the same number of each species was used as the control. The humoral immune response was evaluated using ELISA in piglets (IgG, IgA and IgM) and calves (IgG1, IgG2 and IgM) sera and in hen egg yolks (IgY). Cell-mediated immune responses were evaluated using the skin test. Concentrations of serum haptoglobin in calves and piglets and plasma fibrinogen in calves, daily weight gain in piglets, as well as the inner body temperature and clinical signs in calves were measured to evaluate the clinical effects of vaccination. In animals immunised twice with H. somni rHsp60, a statistically significant increase in IgY antibodies in egg yolk as well as serum IgG1 and IgG2 antibodies in calves (P < 0.05) was found. In piglets, the antibody reaction against H. somni rHsp60 was higher in the experimental than in the control group, but the difference was significant only for the IgG class (P < 0.05). A moderate cell-mediated immune response to H. somni rHsp60 measured using the skin test was observed in piglets after 24 h (P < 0.05), but not in calves and hens. The daily weight gain was significantly higher in the experimental than in the control piglets (P < 0.05). The fibrinogen and haptoglobin levels in calves, as well as the inner body temperature, indicated a reduced risk of pathology in the experimental group of calves. The preliminary results confirmed the immunogenicity of H. somni rHsp60. A beneficial effect on piglet weight gain was observed. The obtained results warrant further studies of the protective effects of H. somni rHsp60 as an ingredient of subunit vaccines in farm animals.