Influence of recombinant bovine interleukin-1β and interleukin-2 in pigs vaccinated and challenged with Streptococcus suis

An experiment was conducted to determine the adjuvanticity of recombinant bovine IL-1β (rBoIL-1β) and recombinant bovine IL-2 (rBoIL-2) administered in conjunction with a single Streptococcus suis vaccination in pigs. Sixty 4-week-old pigs were allotted to eight groups: nonvaccinated controls; vaccinated controls; rBoIL-β at 0.1, 1, and 10 μg kg−1; rBoIL-2 at 2.5, 25, and 250 μg kg−1. All pigs (except nonvaccinated controls) were vaccinated on Day 0 with a commercial Streptococcus suis vaccine (serotypes 1 and 2). At vaccination, pigs were injected intramuscularly with their respective cytokine treatments. Pigs received additional cytokine injections on 2 consecutive days. On Day 21, all pigs were challenged intravenously with 3.2×109 colony forming units of a log phase culture of S. suis (serotype 2). The highest dose of rBoIL-1β exceeded the maximum tolerable dose for the cytokine; however, this dose of rBoIL-1β protected pigs from the S. suis challenge. Pigs administered rBoIL-1β at 10 μg kg−1 had higher antibody responses to S. suis, less severe clinical signs of the disease after challenge, better growth performance during the infection, and less severe gross pathological lesions caused by the bacteria. No pigs in this treatment group died from the bacterial challenge. These data suggest that rBoIL-1β (10 μg kg−1), administered intramuscularly for 3 consecutive days at vaccination, is more effective than a single S. suis vaccination alone in protecting pigs against a S. suis challenge.