Co-administration of toll-like receptor (TLR)-3 and 4 ligands augments immune response to Newcastle disease virus (NDV) vaccine in chicken. 
Toll-like receptors (TLRs) are pattern recognition receptors (PRRs) that mediate first line of host defence to pathogens.  TLR agonists are potent immunostimulatory agents that help to prime a robust adaptive immune response.  In the present study, adjuvant potential of Poly I:C and lipopolysaccharide (LPS) were evaluated with live Newcastle disease virus (NDV) vaccine.  Cornish chickens were immunized with live Newcastle disease virus (NDV) vaccine (R2B-mesogenic strain) adjuvanted either with Poly I:C (TLR3 agonist) or LPS-TLR4 agonist and both.  Humoral Immune response to ND vaccine was evaluated through haemagglutination inhibition (HI) test and ELISA, while the cellular immune response (CMI) was quantified by lymphocyte transformation test (LTT).  IL-1β cytokine mRNA levels in spleen tissue were also quantified by real time PCR.  The results suggest that TLR3 and TLR4 agonists are an efficient immune-stimulators separately, as LPS co-administered group has shown significantly higher serum titre on second week post-immunization and Poly I:C group on third week post-immunization both by HI and ELISA (P < 0.01), however, the combined administration of both LPS and Poly I:C did not give any complementary effect on serum titre.  There were no significant differences in stimulation indices (SI) and IL-1β cytokine levels between groups at different intervals post-immunization.  Hence, TLR agonists LPS followed by Poly I:C could be used as adjuvant to enhance the immune response to NDV vaccine in chicken.