Mycoplasma hyopneumoniae is the primary agent of enzootic pneumonia in pigs. M. hyopneumoniae elimination programs have been used for many decades and the improved production and economic performance of the growing pig makes elimination very attractive. This is especially true when M. hyopneumonia elimination can be accomplished at the same time as a breeding herd is closed to new introductions as part of a PRRS elimination project. The goal in an elimination program is to improve sow and piglet immunity at the same time as the infection pressure of the targeted organism is minimized. A significant part of a M. hyopneumoniae elimination program is the sow vaccination strategy. In a research setting sows and piglets are usually tested for the level of humoral antibodies in order to assess the response to vaccination. Although it has been suggested that cell mediated immunity (CMI) may play a role in protection against M. hyopneumoniae, its transfer from sows to their offspring has not received much investigation.
These Belgian researchers wanted to study maternally-derived CMI in piglets from vaccinated and non-vaccinated sows. They also wanted to study the potential influence of cross-fostering piglets before colostrum ingestion on the transfer of CMI from dam to piglets. Six M. hyopneumoniae vaccinated sows from an endemically infected herd and 47 of their piglets, of which 24 piglets were cross-fostered, were included, as well as three non-vaccinated control sows from an M. hyopneumoniae-free herd and 24 of their piglets. This was not a large study but the types of tests used in the investigation were quite advanced. Vaccinated sows received a commercial bacterin intramuscularly at 6 and 3 weeks prior to farrowing. The TNF-α, IFN-γ and IL-17A production by different T-cell subsets in blood of sows, colostrum and blood of piglets was assessed using a recall assay.
The researchers found the following:
- Cytokine producing T-cells were increased in the blood of sows when they were vaccinated with M. hyopneumoniae vaccine.
- M. hyopneumoniae-specific T-cells were detected in blood of 2-day-old piglets born from these vaccinated sows.
- The Maternally Derived Immune (MDI) cells isolated from piglets were able to proliferate in number when challenged with M. hyopneumoniae organism in vitro.
- No M. hyopneumoniae-specific cytokine producing T-cells were found in blood of piglets from control sows that were from a M. hyopneumoniae negative herd.
- No difference was found in M. hyopneumoniae-specific CMI between cross-fostered and non-cross-fostered piglets.
- Even when some of the vaccinated sows did not appear to respond to the M. hyopneumonia vaccination based on an blood antibody response they did show evidence of a cell mediated response
Take Home Message:
- This research demonstrated for the first time that M. hyopneumoniae-specific T-cell ( white blood cells) are transferred from the sow to the offspring via colostrum. The piglet is better protected when receiving antibodies that are set to fight M. hyopneumoniae as well a functional white blood cells that are ready to orchestrate a cell mediated response.
- These researchers suggest that additional studies are required to investigate the role of these transferred cells on immune responses in piglets and their potential protective effect against M. hyopneumoniae challenge.
- These findings reinforce the notion that attention to detail of colostral management should be an essential part of a M. hyopneumonia elimination protocol.
Ref: Evelien Biebaut , Lisa Beuckelaere , Filip Boyen , Freddy Haesebrouck , Charles-Oliver Gomez-Duran , Bert Devriendt , Dominiek Maes Transfer of Mycoplasma hyopneumoniae-specific cell mediated immunity to neonatal piglets Vet Res . 2021 Jun 30;52(1):96. doi: 10.1186/s13567-021-00968-0.