Monthly Archives: January 2013

The lack of available vaccines against African swine fever virus (ASFV) means that the evaluation of new immunization strategies is required. Here we show that fusion of the extracellular domain of the ASFV Hemagglutinin (sHA) to p54 and p30, two immunodominant structural viral antigens, exponentially improved both the humoral and the cellular responses induced in pigs after DNA immunization. However, immunization with the resulting plasmid (pCMV-sHAPQ) did not confer protection against lethal challenge with the virulent E75 ASFV-strain. Due to the fact that CD8(+) T-cell responses are emerging as key components for ASFV protection, we designed a new plasmid construct, pCMV-UbsHAPQ, encoding the three viral determinants above mentioned (sHA, p54 and p30) fused to ubiquitin, aiming to improve Class I antigen presentation and to enhance the CTL responses induced. As expected, immunization with pCMV-UbsHAPQ induced specific T-cell responses in the absence of antibodies and, more important, protected a proportion of immunized-pigs from lethal challenge with ASFV. In contrast with control pigs, survivor animals showed a peak of CD8(+) T-cells at day 3 post-infection, coinciding with the absence of viremia at this time point. Finally, an in silico prediction of CTL peptides has allowed the identification of two SLA I-restricted 9-mer peptides within the hemagglutinin of the virus, capable of in vitro stimulating the specific secretion of IFNγ when using PBMCs from survivor pigs. Our results confirm the relevance of T-cell responses in protection against ASF and open new expectations for the future development of more efficient recombinant vaccines against this disease.

Our objective was to compare effects of a conventional dry (CD, 152.4-cm-wide, 5-space, Staco Inc., Schaefferstown, PA) and a wet-dry (WD, double-sided, each side = 38.1-cm-space, Crystal Springs, GroMaster Inc., Omaha, NE) feeder using various feeder adjustment openings on the growth performance and carcass characteristics of growing-finishing pigs (Sus scrofa). In Exp. 1, 1,296 pigs (BW 19 kg) were used in a 27-d study to evaluate 3 feeder openings nested within each feeder design. From d 0 to 27, pigs fed with a WD feeder had similar ADG, but lower (P < 0.02) ADFI and greater G:F than pigs fed with a CD feeder. Increased adjustment opening increased (linear, P < 0.01) ADG and ADFI by pigs fed with a WD feeder, and increased (linear, P < 0.01) ADFI by pigs fed with a CD feeder. In Exp. 2, 1,248 pigs (BW 33 kg) were used to evaluate 3 feeder openings nested within each feeder design in a 93-d study. Pigs fed with a WD feeder had greater (P < 0.05) ADG, ADFI, final BW, HCW, and backfat, but decreased fat-free lean index (FFLI) than those fed with a CD feeder. Increased opening of the WD feeder resulted in greater (linear, P < 0.05) ADG, ADFI, HCW, and backfat, but lower FFLI. No differences among CD feeder openings were observed, and G:F did not differ among all feeder treatments. In Exp. 3, 1,287 pigs (BW 38 kg) were used in a 92-d factorial experiment with 4 feeder treatments and 2 diet types (low and high byproduct diets). Feeder treatments were CD at approximately a 2.4-cm opening, WD at a 3.2-cm opening, WD changed to a 2.5-cm opening on d 56, and WD changed to a 2.5-cm opening on d 28 and a 1.9-cm opening on d 56. Pigs fed with a WD feeder had greater (P < 0.01) ADG, ADFI, HCW, and backfat, but decreased FFLI than pigs fed with a CD feeder. Decreasing the WD feeder opening during the study decreased (P < 0.05) ADG. Pigs with the WD feeder opening decreased to 1.9 cm had reduced (P < 0.05) ADFI and backfat, but increased FFLI compared with pigs with a WD feeder opening of 3.2 cm. Feed efficiency did not differ among treatments. In conclusion, ADG, ADFI, HCW, and backfat were increased with the WD feeder evaluated in this experiment, but the growth of pigs fed with a WD feeder was more sensitive to differences in feeder adjustment than that of pigs fed with a CD feeder.