Pro-inflammatory cytokine and acute phase protein responses to low-dose lipopolysaccharide (LPS) challenge in pigs

The objective of this study was to establish the pro-inflammatory cytokine and acute phase protein responses to low-dose lipopolysaccharide (LPS) challenge in pigs and to determine whether these immune parameters could also be measured in saliva. Possible gender differences in the acute phase reaction were also assessed. At 6 weeks of age, 24 male and 24 female pigs were injected intraperitoneally with a single dose of 0 or 5 μg/kg live weight (LW) of LPS fromEscherichia coli(treatment). Matched saliva and blood samples were taken at 0, 2, 4, 8, 12 or 24 h after treatment administration. Samples were analysed for concentrations of the pro-inflammatory cytokines tumor necrosis factor-alpha (TNF-α) and interleukin-1beta (IL-1β), the acute phase proteins C-reactive protein (CRP), serum amyloid A (SAA), haptoglobin (Hp), and cortisol. Low-dose LPS administration increased plasma levels of TNF-α (P<0·001), CRP (P<0·05) and SAA (P<0·05) but did not affect plasma concentrations of IL-1β or Hp (P>0·1). Treatment by time interactions showed that plasma levels of TNF-α and CRP in LPS-treated pigs peaked at 2 h (P<0·001) and 12 h (P<0·01), respectively. Low-dose LPS injection tended to increase plasma concentrations of cortisol (P=0·056) and the response to LPS differed between genders (P<0·05), with females showing higher cortisol responsiveness to the challenge (P<0·01). Males showed higher levels of both cytokines regardless of the treatment (P<0·05), probably due to the inhibition of cytokine synthesis by cortisol. Concentrations of both pro-inflammatory cytokines were consistently detectable in saliva and were present in higher concentrations than in plasma (P<0·001). Hence, plasma TNF-α, CRP and SAA are useful indicators of sub-acute inflammation/infection in pigs as simulated by a low-dose LPS challenge and gender differences exist in the pro-inflammatory cytokine response after a low dose of LPS.

Age-related changes in pro-inflammatory cytokines, acute phase proteins and cortisol concentrations in neonatal piglets

Age-related changes have been described in the resting levels of cortisol and acute phase proteins in the neonatal pig. This study evaluated the plasma concentrations of the pro-inflammatory cytokines tumour necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), the acute phase proteins C-reactive protein (CRP), serum amyloid A (SAA) and haptoglobin (Hp), as well as cortisol during the first week of postnatal life in piglets. The influence of invasive managerial practices such as teeth clipping, ear notching and tail docking on possible age-related changes in the production of these inflammatory mediators was also assessed. A total of 96 piglets were selected from 24 litters at birth, and were randomly assigned to one of four sampling times over the first week of life and one of two treatments. Blood samples were taken at 1, 3, 5 or 7 days of age. Piglets were ear notched, teeth clipped and tail docked (NCD), or were left untreated (CON). Significant effects of age were found in plasma concentrations of TNF-alpha, SAA, Hp and cortisol (p < 0.001). Concentrations of TNF-alpha and Hp increased with age, and peak concentrations were found on day 5. SAA and cortisol levels were highest on day 1, decreasing gradually with age. NCD piglets tended to have higher levels of plasma Hp than CON animals (p = 0.066). However, no differences between NCD and CON piglets were found in any other parameter measured. Furthermore, age effects were not affected by these husbandry practices. These results indicate that age-related changes exist in several inflammatory mediators, and suggest that these managerial practices do not result in systemic inflammation in early postnatal life of piglets.