Haptoglobin Responses Towards Vaccination with Three Different Antigens in Pigs

Haptoglobin (Hp), an acute phase protein, is elevated in animals exposed to immunological burdens. In order to be able to use Hp concentrations in blood as an indicator for animal health in general, the potential changes induced by common vaccinations need to be characterised and eventually be considered. We therefore recorded Hp serum concentrations in pigs before and after vaccinations against the porcine respiratory and reproductive syndrome (PRRS), against Aujeszky's disease (AD) and mycoplasma hyopneumonia (Myc).

PRRS vaccination was done in 25 piglets one day after weaning at 4 weeks of age and blood samples for Hp analyses were collected on day 0 and 28 from all animals and on days 7, 14 and 21 from 4 animals. PRRS titres were determined in day 0 and day 28 samples. In addition, 10 sows being pregnant for 6 weeks were monitored after a PRRS booster injection. Blood samples were taken on day 0, 1, 2, 3, 4, 7, 10, 14, 21 and 28. Hp concentrations and PRRS titres were determined in all samples. Vaccinations against AD and Myc were done in F2-offsprings of an experimental population based on the reciprocal cross of Berlin Miniature Pig and Duroc. 150 piglets being 7 weeks old were immunised against Myc; at 14 weeks of age these animals were then immunised against AD. Blood samples were taken on day 0 before and day 7 after the vaccinations. The same antigens were used in another trial in which the experimental design was identical except that control groups were included: for Myc, 28 pigs were immunised and 19 pigs served as controls. AD vaccination was done in 23 pigs with 17 control pigs.

Hp concentration in piglets was increased after immunisation against PRRS on day 7 and 14. Compared to the initial baseline concentrations, 10-fold and 8-fold higher values were observed, respectively. 11 out of the 25 piglets were PRRS titre positive before vaccination, but there was no difference between basal Hp concentrations in these animals compared to the PRRS negative ones. Hp response between day 0 and day 7 was not related to the extent of titre increases between day 0 and day 28. In sows, Hp concentrations were increased until day 4 after vaccination. The maximal Hp concentrations were 1.5-fold higher than prevaccination levels. After day 7 baseline values were reached again. PRRS titres in sows were increased on days 21 and 28. Following vaccination against Myc or AD, Hp concentrations in pigs were consistently increased.

Vaccination against viral and bacterial antigens uniformly led to an increase of Hp concentrations. The extent of the elevations observed showed no perceptible relation to the antigen used. In conclusion, increased haptoglobin serum concentrations have to be expected when animals are vaccinated. Efforts towards characterisations of animal health by means of haptoglobin measurements therefore will have to consider anamnesis to be able to differentiate between increases of haptoglobin induced by either vaccination or by immunological burdens.