# Utilizing NF-κB Signaling in Porcine Epithelial Cells to Identify a Plant-Based Additive for the Development of a Porcine Epidemic Diarrhea Virus Vaccine

## TL;DR

Researchers used a special cell line to find plant extracts that boost immune responses, identifying chamomile as a potential ingredient for improving PEDV vaccines.

## Contribution

A novel NF-κB reporter cell line was developed to screen plant extracts for mucosal adjuvant potential in PEDV vaccines.

## Key findings

- Chamomile extract showed dose-dependent activation of NF-κB signaling in PK15-KBR cells.
- Chamomile enhanced IgG and IgA antibody levels in oral vaccination but not in intramuscular vaccination.
- The PK15-KBR cell line proved effective in identifying potential mucosal adjuvants for vaccines.

## Abstract

A porcine epithelial NF-κB reporter cell line was created to identify plant extracts that activate the NF-κB signaling pathway. Among the 224 screened extracts, 3 showed an increase in NF-κB activity and were further assessed for their potential application as additives in PEDV vaccines. Toxicity assessments, both in vitro and in vivo, were performed, resulting in the selection of chamomile as a candidate for an in vivo vaccination study. Mice received inactivated PEDV vaccinations, formulated with a commercial adjuvant and with or without the addition of chamomile, via oral and intramuscular (I.M.) routes. Vaccine efficacy was determined by measuring virus-specific IgG and IgA antibodies. Chamomile did not affect the I.M. vaccination but showed a propensity to elevate antibody titers for the oral vaccination. These results indicate that chamomile extract is worthy of more study as a potential ingredient in PEDV vaccines. This study underscores the potential of PK15-KBR cells in identifying potential mucosal adjuvants and positions chamomile extract as a valuable candidate for enhancing the creation of effective vaccines for PEDV alongside potential other viral diseases in animals.

The nuclear factor-kappa B (NF-κB) signaling pathway plays a crucial role in regulating immune responses in epithelial cells. In this study, we established a porcine epithelial NF-κB reporter cell line (PK15-KBR) as an in vitro platform to screen plant-based extracts for their potential use as vaccine adjuvants against porcine epidemic diarrhea virus (PEDV). The NF-κB inducers were further tested for toxicity assessments, either using CCK-8 assays or intramuscular injection in mice, finally followed by vaccination studies to evaluate their adjuvancy. Initial experiments confirmed that TNF-α effectively activated NF-κB signaling in PK15-KBR cells in a dose-dependent manner, validating the platform’s reliability at Z’ value of 0.68. Of the 224 testers, 3 candidates, including chamomile, mulberry and Boerhaavia diffusa, showed induction activity; however, only chamomile induced a dose-dependent response in PK15-KBR cells. As a proof of concept, chamomile, used as an adjuvant in oral vaccination, demonstrated significantly higher IgG levels at an early stage (day 14, p < 0.05) and enhanced IgA titers. These findings highlight the use of the PK15-KBR cell line in identifying mucosal adjuvants and position chamomile extract as a promising candidate for enhancing vaccine-induced immunity.