Transfer of Mycoplasma hyopneumoniae-specific cell mediated immunity to neonatal piglets

Abstract

Mycoplasma hyopneumoniae is the primary agent of enzootic pneumonia in pigs. Although cell mediated immunity (CMI) may play a role in protection against M. hyopneumoniae, its transfer from sows to their offspring is poorly characterized. Therefore, maternally-derived CMI was studied in piglets from vaccinated and non-vaccinated sows. The potential influence of cross-fostering before colostrum ingestion on the transfer of CMI from dam to piglets was also investigated. 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. 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. In blood of sows cytokine producing T-cells were increased upon M. hyopneumoniae vaccination. Similarly, M. hyopneumoniae-specific T-cells were detected in blood of 2-day-old piglets born from these vaccinated sows. In contrast, no M. hyopneumoniae-specific cytokine producing T-cells were found in blood of piglets from control sows. No difference was found in M. hyopneumoniae-specific CMI between cross-fostered and non-cross-fostered piglets. In conclusion, different M. hyopneumoniae-specific T-cell subsets are transferred from the sow to the offspring. Further studies are required to investigate the role of these transferred cells on immune responses in piglets and their potential protective effect against M. hyopneumoniae infections.

Keywords: Mycoplasma hyopneumoniae; cell mediated immunity; cross-fostering; maternal immunity.

Figure 1

Design of the study. Farm A: endemically infected with M. hyopneumoniae; Farm B: free of M. hyopneumoniae. On farm A, six sows and 47 piglets were included (23 non-cross-fostered and 24 cross-fostered before colostrum ingestion), while on farm B three sows and 24 non-cross-fostered piglets were included. w = weeks, d = days.

Figure 2

Mycoplasma hyopneumoniae-specific IgG and IgA levels in sows and piglets. Farm A: endemically infected with M. hyopneumoniae; Farm B: free of M. hyopneumoniae. A, B: individual levels in serum of sows; C, D: individual levels in colostrum of sows; E, F: average levels in serum of 2-day-old piglets (4 piglets per sow on farm A; 8 piglets per sow on farm B). On farm A, sows (n = 6) were vaccinated against M. hyopneumoniae at 6 and 3 weeks before farrowing and blood samples were taken before the first vaccination (pre vacc.) and at the time of farrowing (post vacc.). On farm B, blood of the sows (n = 3) was sampled at the time of farrowing. Color coding of the piglets corresponds to the color of their mother of which they ingested colostrum. Red line: cut-off optical density value for positive samples.

Figure 3

Frequencies (%) of CD3⁺ T-cells in sows and piglets. Farm A: endemically infected M. hyopneumoniae; Farm B: free of M. hyopneumoniae. A Blood of sows; B colostrum; C, D blood of 2-day-old piglets (4 piglets per sow on farm A; 8 piglets per sow on farm B). On farm A, sows (n = 6) were vaccinated against M. hyopneumoniae at 6 and 3 weeks before farrowing and blood samples were taken before the first vaccination (pre vacc.) and at the time of farrowing (post vacc.), on farm B blood was sampled of the sows (n = 3) at the time of farrowing. *, P < 0.05 between pre- and post-vaccination on farm A; **, P < 0.05 between farm A and B.

Figure 4

CirculatingMycoplasma hyopneumoniae-specific cytokine producing T-cell subsets and IFN-γ production in blood of sows. A–D Circulating Mycoplasma hyopneumoniae-specific cytokine producing T-cell subsets in blood of sows; E average IFN-γ production by the different T-cell subsets. PBMCs were stimulated with M. hyopneumoniae J strain bacterin and T-cell phenotype and cytokine production were assessed by flow cytometry. Farm A: endemically infected with M. hyopneumoniae; Farm B: free of M. hyopneumoniae. On farm A, sows (n = 6) were vaccinated against M. hyopneumoniae at 6 and 3 weeks before farrowing, blood samples were taken before the first vaccination (pre vacc.) and at the time of farrowing (post vacc.), on farm B blood was sampled of the sows (n = 3) at the time of farrowing. *, P < 0.05 between pre- and post-vaccination on farm A; **, P < 0.05 between farm A and B.

Figure 5

Circulating Mycoplasma hyopneumoniae-specific cytokine producing T-cell subsets and IFN-γ production in blood of neonatal piglets. A–C Circulating Mycoplasma hyopneumoniae-specific cytokine producing T-cell subsets in neonatal piglets; D IFN-γ production by CD3⁻ cells; E IFN-γ production in different T-cell subsets. PBMCs were stimulated with M. hyopneumoniae J strain bacterin and T-cell phenotype and cytokine production were assessed by flow cytometry. Farm A: n = 23 piglets, endemically infected with M. hyopneumoniae; Farm B: n = 24 piglets, free of M. hyopneumoniae. On farm A, sows were vaccinated against M. hyopneumoniae at 6 and 3 weeks before farrowing, while sows on farm B were not vaccinated. *, P < 0.05 between farm A and B.

Figure 6

Effect of cross-fostering on maternally-derived immunity in piglets. A, B Mycoplasma hyopneumoniae-specific IgG and IgA levels; C–E percentage of Mycoplasma hyopneumoniae-specific cytokine producing T-cells; F Mycoplasma hyopneumoniae-specific proliferation of CD3⁺ T-cells in blood of 2-day-old non-cross-fostered (n = 23) and cross-fostered (n = 24) piglets on an endemically infected M. hyopneumoniae farm. Red line: cut-off optical density value for positive samples.