The inflammatory cytokine effect of Pam3CSK4 TLR2 agonist alone or in combination with Leishmania infantum antigen on ex-vivo whole blood from sick and resistant dogs

Background: a wide spectrum of clinical manifestations and immune responses exist in canine l. infantum infection. ibizan hounds are more resistant to disease than other dog breeds. recognition of pathogen-associated molecule patterns by toll like receptors (tlrs) rapidly triggers a variety of anti-microbial immune responses through the induction of pro-inflammatory cytokines such as tnf-α and il-6 which may play an important role in controlling leishmania infection. the main objective of this study was to investigate and compare the effect of a tlr2 agonist (tlr2a) alone or in combination with l. infantum antigen (lsa) on ex vivo whole blood cytokine production from healthy seronegative ifn-γ non-producer dogs from an area of low in canine leishmaniosis endemicity (n = 11); sick seropositive dogs with low production of ifn-γ (n = 17) and healthy seronegative or low positive ibizan hounds with a predominant ifn-γ production (n = 21) from a highly endemic area. whole blood was stimulated with medium alone (ø),lsa,concanavalin a,tlr2 (pam3csk4) receptor agonist (ø + tlr2a) and tlr2a and lsa (lsa + tlr2a) for 48 h. supernatants were harvested for measurement of canine tnf-α and il-6 cytokines by elisa. results: a significant increase of tnf-α was found in the supernatants of stimulated blood from all groups (ø + tlr2a and lsa + tlr2a) when compared with medium alone. a similar pattern was observed for il-6. interestingly,a significant increase of tnf-α production was only observed when stimulation with lsa + tlr2a was compared with tlr2a alone in ibizan hounds. a significant increase of tnf-α production was observed with stimulation of lsa + tlr2a when compared with lsa in all groups. significantly higher concentrations of tnf-α and il-6 were detected in ibizan hounds,especially for the ø + tlr2a and lsa + tlr2a treatments compared with other groups. conclusions: this study demonstrated that tlr2a alone enhances the production of the inflammatory cytokines tnf-α and il-6 in sick,resistant and healthy non-infected dogs. in addition,a combination of lsa+tlr2a promoted a synergistic pro-inflammatory effect with tnf-α in ibizan hounds but not in seropositive sick dogs and seronegative healthy dogs. these findings might suggest the importance of pam3csk4 as a possible immunomodulator for canl. © 2017 the author(s).