RESUMO
Natural planned exposure (NPE) remains one of the most common methods in swine herds to boost lactogenic immunity against rotaviruses. However, the efficacy of NPE protocols in generating lactogenic immunity has not been investigated before. A longitudinal study was conducted to investigate the dynamics of genotype-specific antibody responses to different doses (3, 2 and 1) of Rotavirus A (RVA) NPE (genotypes G4, G5, P[7] and P[23]) in gilts and the transfer of lactogenic immunity to their piglets. Group 1 gilts received three doses of NPE at 5, 4 and 3 weeks pre-farrow (WPF), group 2 received two doses at 5 and 3 WPF, group 3 received one dose at 5 WPF, and group 4 received no NPE (control group). VP7 (G4 and G5) and truncated VP4* (P[7] and P[23]) antigens of RVA were expressed in mammalian and bacterial expression systems, respectively, and used to optimize indirect ELISAs to determine antibody levels against RVA in gilts and piglets. In day-0 colostrum samples, group 1 had significantly higher IgG titers compared to the control group for all four antigens, and either significantly or numerically higher IgG titers than groups 2 and 3. Group 1 also had significantly higher colostrum IgA levels than the control group for all antigens (except G4), and either significantly or numerically higher IgA levels compared to groups 2 and 3. In piglet serum, group 1 piglets had higher IgG titers for all four antigens at day 0 than the other groups. Importantly, RVA NPE stimulated antibodies in all groups regardless of the treatment doses and prevented G4, G5, P[7] and P[23] RVA fecal shedding prior to weaning in piglets in the absence of viral challenge. The G11 and P[34] RVA genotypes detected from pre-weaning piglets differed at multiple amino acid positions with parent NPE strains. In conclusion, the results of this study suggest that the group 1 NPE regimen (three doses of NPE) resulted in the highest anti-RVA antibody (IgG and IgA) levels in the colostrum/milk, and the highest IgG levels in piglet serum.
RESUMO
The objective of this study was to investigate intestinal function and morphology associated with peri-weaning failure to thrive syndrome (PFTS) in swine. Jejunum and distal ileum from control and pigs exhibiting PFTS was harvested at weaning, 4 and 11 days post-weaning (PW) for intestinal barrier function studies and histological analyses (n=6 pigs per group). Marked disturbances in intestinal barrier function was observed in PFTS pigs, compared with controls, indicated by lower (p<0.05) TER and increased (p<0.01) permeability to FITC dextran (4 kDa). Intestines from weaned pigs, subjected to a 4-day fast, exhibited minor disturbances in intestinal barrier function. Villus atrophy and crypt hyperplasia were observed in the PFTS intestine compared with control and fasted pigs. These data demonstrate that PFTS is associated with profound disturbances in intestinal epithelial barrier function and alterations in mucosal and epithelial morphology in which anorexia is not the sole factor.
