IN VITRO ANTIVIRAL ACTIVITY OF POLY-Γ-GLUTAMATE AGAINST NEWCASTLE DISEASE VIRUS INFECTION ON MURINE MACROPHAGE CELLS

Abstract

The High-molecular-weight Poly-γ-glutamate (HM-γ-PGA) is a promising natural and edible polymer with diverse biological functions. Among the applications of HM-γ-PGA, its capacity to promote immune-stimulating effect via Toll-like receptor-4 (TLR4) signaling solidifies its significance as a potential natural antiviral agent. In the pre-treatment assay, HM-γ-PGA can protect murine macrophage cells (RAW 264.7) against Newcastle Disease (ND) infection. Such protection can be explained by the induction of antiviral state of HM-γ-PGA in RAW 264.7 cells via TLR4-mediated IRF-3, IFN-B, and IFN-related gene induction as shown in time-dependent changes in mRNA expression confirmed by polymerase chain reaction (PCR). Moreover, since mRNA expression does not necessarily correlate with the secreted protein levels, pro-inflammatory cytokine secretion was also measured by murine Enzyme-Linked Immunosorbent Assay (ELISA). Therefore, our findings suggest that HM-γ–PGA can be a potential antiviral substance that can inhibit NDV infection through its stimulation of antiviral state on RAW 264.7 cells. These results have been consistent with the previous studies showing that this natural polymer can protect RAW 264.7 and mice against influenza infection. However, it should be noted that although murine macrophage cells are susceptible to NDV, they are not the natural host cells of the virus, thus further in vitro and in vivo studies using chicken and chicken-derived cells are needed to fully assess the efficacy and applicability of HM-γ–PGA in the poultry industry.