Sessions

The increasing antimicrobial resistance (AMR) against conventional antibacterials/antibiotics emphasises the pressing need for alternative therapeutic agents against diseases caused by bacterial infections. Host defence peptides (HDPs), also known as antimicrobial peptides (AMPs), are considered as one of such alternatives. They are recognized for their direct antimicrobial, as well as immunomodulatory effects, which offer a multifaceted strategy to combat infectious diseases. Pap12 -6, a synthetic HDP derived from its natural parent peptide papiliocin, has been regarded as a promising compound and was therefore selected as the focus of this study.

In the present experiment , the immunomodulatory effect of Pap12-6 on primary chicken hepatic co-cultures was investigated. Cultures were treated with three different concentrations of Pap12-6 (5, 25, and 50 μg/mL) alone and with 50 μg/mL of polyinosinic-polycytidylic acid (Poly I:C), which was used to mimic inflammation. The effect of Pap12-6 on cell viability was examined by measuring the extracellular lactate dehydrogenase (LDH) activity. The peptide’s immunomodulatory effect was studied by determining the concentrations of cytokines interleukin (IL)-6, IL-10, and regulated on activation, normal T-cell expressed and secreted (RANTES) with Luminex xMAP technology. Additionally, the impact on oxidative state was investigated by measuring the levels of extracellular hydrogen peroxide (H2O2) and nuclear factor erythroid 2-related factor 2 (Nrf2) using a fluorometric assay and ELISA technique, respectively.

Our results showed that neither the application of Pap12-6 alone, nor the application of the peptide under Poly I:C-evoked inflammatory conditions increased the mean LDH activity. Furthermore, when Poly I:C was applied together with the highest concentration of Pap12-6, significant reductions were observed in IL-6 and RANTES production, as well as the IL-6 to IL-10 ratio. Moreover, the 25 and 50 μg/mL concentrations of Pap12-6 were able to reduce the levels of H2O2 and Nrf2 under Poly I:C-evoked inflammation, and at a 50 μg/mL concentration, the same effect was also observed for Nrf2 in the absence of inflammation.

The abovementioned results suggest that Pap12-6 is not cytotoxic to chicken hepatic cells and has an immunomodulatory – in particular, anti-inflammatory – and antioxidant activity in chicken hepatic cell co-cultures. In conclusion, Pap12-6 can be considered as a promising candidate to serve as an alternative to conventional antibacterials/antibiotics in poultry farming, owing to its immunomodulatory activities.