While current events have shone the spotlight on vaccines, pork producers have long known their value when it comes to reducing treatment expense and lost productivity. As scientists work to increase disease resilience in pigs through genomics, a project aimed at predicting vaccine success is a key piece of the puzzle.
“This vaccine project came about because vaccine response is variable among pigs, just as it is with people,” said Dr. Peris Munyaka, a Postdoctoral Fellow in the Faculty of Agriculture, Life & Environmental Sciences at the University of Alberta. “You expect that when you vaccinate animals, they are protected, but some pigs still fall ill, while others recover or are fully protected and show no symptoms.”
The objective of the study was to identify biomarkers that could be predictive of a successful vaccine response. In that regard, scientists focused on blood transcriptomes and gut microbiota.
Gut reactions
“We looked at the composition of the gut microbiota before vaccination and how that related to the way pigs responded to a specific vaccine,” said Dr. Munyaka. “The vaccine we chose for this purpose was the one against Mycoplasma hyopneumoniae [a type of bacteria that causes enzootic pneumonia, a chronic respiratory disease in pigs]. We needed a vaccine against an organism that was absent in the facility at the time, to avoid the chance that pigs might have already been exposed to it, so that whatever response we saw was strictly due to exposure to the vaccine, not prior exposure to the organism.”
Researchers actually conducted two studies, with one taking place in Canada and the other in France. Both studies used the same vaccine and pigs around the same age. In both cases, they took blood and fecal samples before and after vaccination, focusing on a couple of key questions: Did we trigger an immune response? If so, what level of immunity did we attain?
“We observed that pigs had different levels of immunity. Because we wanted to focus on the extreme responders (‘High’ vs. ‘Low’ responders), we identified and selected the animals with the highest and lowest levels of specific antibodies.”
Group dynamics
They then looked more closely at the two groups to determine why one responded more effectively to the vaccine, comparing blood transcriptome and gut microbiota profiles prior to vaccination. For the blood transcriptome, the only striking difference was that two days post-vaccination, increased activation of immune cells was observed in the high responder group. This could be useful in telling producers which pigs will respond well to vaccination.
“When we looked at the gut microbiota, we saw that some bacteria showed a high correlation with greater levels of antibodies.”
Overall, both the French and Canadian studies emphasized the importance of the microbiota early in life and its critical role in vaccine response.
“The two studies pointed to the importance of further research around sequencing and the role of these bacteria. What function do they serve? How can we isolate the bacteria, sequence it and characterize it to see which strains are having this positive effect that might promote the production of antibodies?”
The answers to these questions may help producers implement disease control strategies, promoting colonization of the gut microbiome with certain helpful microbes through diet or the use of probiotics.
More questions remain, but clearly, improving the effectiveness of vaccines could have a profound impact on industry.
