# Enhanced Immunity and Infection Resistance in Mice Through Co-Expression of Porcine IL-3, IL-7, and IL-15 Fusion Molecules in Yarrowia lipolytica

## TL;DR

Mice given a fusion of three porcine immune proteins showed stronger immunity and survived bacterial infections better than controls.

## Contribution

A novel fusion molecule of porcine IL-3, IL-7, and IL-15 produced in Yarrowia lipolytica is shown to enhance immunity in mice.

## Key findings

- Mice treated with Po1h-IL-3/7/15 had significantly higher IgG and sIgA levels compared to controls.
- The fusion molecule increased survival rates to 100% after bacterial challenges, compared to 20-40% in controls.
- Immune gene expression and T cell populations were significantly altered in the treated group.

## Abstract

Animal infectious diseases have caused significant disruptions to global livestock production. This study delved into the immunomodulatory impacts of co-expression of porcine interleukin 3, 7, and 15 in Yarrowia lipolytica, designated as Po1h-IL-3/7/15. The experimental regimen encompassing mouse immunization and pathogen challenge was executed, where in vivo evaluations of antibodies, immune-related cells, and gene expressions were undertaken after oral administration of Po1h-IL-3/7/15. Remarkably, the serum IgG and intestinal sIgA concentrations in the Po1h-IL-3/7/15 group rose considerably compared to the control groups, alongside heightened levels of IL-7, IL-15, IFN-γ, IL-22, IL-23, and TNF-α. Moreover, there was a notable surge in naïve T cells and central memory T cells, accompanied by a significant decline in regulatory T cells in peripheral blood. Following the challenge with Staphylococcus aureus or Salmonella typhimurium, the expression levels of innate immunity, Jak1 and STAT1 genes in the intestines of the Po1h-IL-3/7/15 group were substantially elevated compared to the control groups. Post-challenge, the survival rate in the Po1h-IL-3/7/15 group was 100%, marking a significant increase from the 20% and 40% survival rates observed in the control groups. These findings affirm that IL-3/7/15 potently enhances innate immunity, humoral and cell-mediated immune responses, and intestinal mucosal immunity in mice, ultimately bolstering resistance to bacterial infections and exhibiting robust protective efficacy.

China’s livestock industry grapples with challenges posed by infectious diseases and the misuse of antibiotics, resulting in a heightened risk of drug-resistant pathogens. This study explored the immunomodulatory effects of co-expressing porcine interleukin 3, 7, and 15 in Yarrowia lipolytica, denoted as Po1h-IL-3/7/15. A 42-day experiment involving mouse immunization and pathogen challenge was conducted, during which in vivo assessments of antibodies, immune-related cells, and gene expression were detected following oral administration of Po1h-IL-3/7/15. Immunological alterations in mice were analyzed using flow cytometry, qRT-PCR, ELISA, and HE staining. Notably, the serum IgG and intestinal sIgA levels in the Po1h-IL-3/7/15 group were substantially elevated compared to the control groups (p < 0.01), so were the contents of IL-7, IL-15, IFN-γ, IL-22, IL-23, and TNF-α. Furthermore, there was a marked increase in naïve T cells and central memory T cells, accompanied by a significant decrease in regulatory T cells in peripheral blood. Post-challenge with Staphylococcus aureus or Salmonella typhimurium, the expression levels of BD2, IL-1β, IL-8, Jak1, RegⅢ, S100A8, STAT1, and TNF-α genes in the intestines of the Po1h-IL-3/7/15 group were markedly higher than those in the control groups (p < 0.01). Following the challenges, the survival rate of the Po1h-IL-3/7/15 group was 100%, a significant increase compared to the 20% and 40% survival rates observed in the control groups (p < 0.05). These results confirm that IL-3/7/15 significantly boosts innate immunity, humoral and cell-mediated immune responses, and intestinal mucosal immunity in mice, enhancing resistance to bacterial infections and exhibiting potent protective effects.