Peripheral immune response in resistant and susceptible Creole kids experimentally infected with Haemonchus contortus

The objective of this study was to characterize the peripheral immune response during haemonchosis in goats by comparing genetically resistant and susceptible animals. We analyzed the changes of circulating lymphocyte populations after experimental infection with Hoemonchus contortus in nematode resistant and susceptible Creole kids. Kinetics of faecal egg count (FEC), packed cell volume (PCV), eosinophilia, as well as body weight (BW), were weekly monitored. The average breeding values on egg excretion at 7 months of age were distant of 1.16 genetic standard deviation. Flow cytometry was used to follow changes in peripheral blood mononuclear cell (PBMC) populations at days 0, 3 and 35 days post-infection (d.p.i.). Data of FEC, PCV, eosinophilia and BW were analyzed by non-orthogonal contrast of SAS, while evolution of lymphocytes populations and relative proportion of T lymphocyte (LT) sub-populations were compared across time by using REML and GLIM-MIX respectively (SAS, 2000). No significant differences in eosinophil count and PCV values were observed between resistant and susceptible animals during the course of the experiment. Nonetheless, from 28 to 35 d.p.i.. FEC in resistant animals were significantly lower than in susceptible. Thus, at the end of the infection, susceptible animals showed a FEC 11 times higher than resistant (P=0.031). However, no evolution across time and no difference between resistant and susceptible kids were evidenced in circulating activated sub-populations of LTCD8+ and LTCD4+. The levels of B lymphocyte (LB) were lower in susceptible animals across time (P<0.01). In contrast, the levels of circulating LTCD4+ and LTCD8+ were higher in susceptible animals after 35 days of infection (P<0.01) suggesting a mucosal localization of activated cells in resistant animals. The analysis of the local immune response in the abomasal mucosa Could help to verify this hypothesis. (C) 2009 Elsevier B.V. All rights reserved.