Application of a cannulation model in recently weaned pigs to monitor the enteric microbiome and assess impact on vaccine efficacy
Background: There is growing evidence that the gut microbiome could impact vaccine efficacy. Pigs are commonly vaccinated at the time of weaning when they also experience other stressors including diet changes, transport, new groupings etc. It has been proposed that probiotics could improve the gut microbiome and subsequently vaccine response and efficacy. The objectives of this study were to develop a model to investigate the impact of administering antimicrobials to pigs at weaning and to assess the impact of probiotics on the microbiome and vaccine efficacy. An ileum cannulation model was used to provide access to the ileum contents which were analysed by 16S sequencing and bioinformatic analysis.   Methods: Fifteen 3-week-old pigs were weaned and transported to the Iowa State University Livestock Infectious Disease Isolation Facility, randomly divided into five treatment groups of 3 pigs each including a NEG-CONTROL group (no vaccination, no PRRSV challenge), a POS-CONTROL group (no vaccination, PRRSV challenge), a VAC-PRRSV group (vaccinated, PRRSV challenged), a VAC-PRO-PRRSV group (supplemented with probiotics, vaccinated, challenged with PRRSV) and a VAC-ANTI-PRRSV group (antibiotic administration, vaccinated, PRRSV challenged). After an acclimation period, the pigs were fitted with an ileum cannula via abdominal surgery to obtain ileum contents over time to investigate the gut microbiome. Vaccine efficacy was assessed by development of anti-PRRSV serum antibodies, comparison of PRRSV load in serum and nasal swab, and severity of macroscopic and microscopic lesions. The ileum microbiome was assessed over time.    Results: In this pilot study, 4 out of 15 pigs died or were euthanized between days 2 and 8 post-surgery, primarily due to peritonitis and abdominal adhesions. For the surviving pigs, vaccination was protective against PRRSV challenge, irrespective of other treatments. There was no discernible impact of vaccination on the diversity, structure, and taxonomic abundance among the groups. Instead, significant influences were observed in relation to time and treatment.   Conclusions: A cannulation model in weaned pigs was used to investigate the impact of antimicrobials and probiotics on ileal microbiome over time and its potential impact on PRRSV vaccine efficacy. This model will be useful for future microbiome modulation studies and its impact on immunity.