Introduction

Paratuberculosis, caused by Mycobacterium avium ssp. paratuberculosis (MAP), constitutes a global threat to ruminant health. Eradication of paratuberculosis could be aided with a vaccine. The use of current whole bacterin vaccines is limited due to lack of efficacy and interference with tuberculosis eradication strategies. In the current study we evaluated recombinant MAP heat shock protein 70kD (Hsp70) as a subunit vaccine candidate.

Materials and Methods

In total 40 female calves were randomly assigned to one of 4 experimental groups (n=10 each) which were orally infected (groups G3 and G4), or left uninfected (groups G1 and G2). Calves of G2 and G4 were vaccinated with 100 ug of Hsp70 in DDA adjuvant at day 0 and 365 of the experiment. Blood samples were taken every 2 weeks, and used for isolation of lymphocytes, and serological analysis. Antigen specific activation of lymphocytes was evaluated in flowcytometry and IFN-γ Elispot. Fecal samples were taken for culture of MAP 7 times during the first 2 years of the experiment, in which the calves were raised and fed conventionally.

Results

The animals in G1 and G2 remained culture negative throughout the experiment. From the calves in G3, infection with MAP only, in total 8 out of 10 animals were tested positive for MAP at least once. In G4 calves, which were both infected and immunized, 4 out of 10 animals tested positive once at day 126 of the experiment. In the 2 years since, only 1 G4 animal of the 9 remaining animals tested positive for MAP while the other calves remained culture negative.

Conclusions

Seen the strongly reduced shedding in G4 as compared to G3 we conclude that use of MAP Hsp70 as a subunit vaccine can aid in the eradication of bovine paratuberculosis.