Phenotypic modulation of porcine CD14+ monocytes, natural killer/natural killer T cells and CD8αβ+ T cell subsets by an antibody-derived killer peptide (KP)

- KP strongly modulates monocytes by inducing CD172α+CD14+high cells potentially sustaining immune activation/inflammation
- KP stimulates an intense increase of CD3+CD16+ NKT cells and CD16+ cells expressing CD25 as activation marker
- KP promotes a significant increase of activated CD8β+CD25+ cytotoxic T lymphocytes (CTL)
- KP modulates CD4+ and CD8α+ cells by inducing Th lymphocytes to acquire the CD4+CD8α+ memory phenotype and upregulate CD8α
- KP potentially induces classical CTL (CD4-CD8α+high) to acquire CD4 expression.

An engineered killer peptide (KP) based on a recombinant anti-idiotypic antibody representing the functional image of a yeast killer toxin (KT) was demonstrated to mediate antimicrobial effects against fungi and viruses. KP binds to murine dendritic cells and macrophages and up-regulate co-receptor expression, thus sustaining CD4+ lymphocyte activation. No immunological data are available in domestic animals thus KP-induced immunomodulation was evaluated in porcine monocyte and lymphocyte subsets. PBMC from healthy adult pigs were stimulated with KP or a scramble peptide (SP), or kept unstimulated for 24, 48 and 72 h, and subsequently analyzed by flow cytometry.In monocytes, KP induced a strong dose-dependent shift from a major fraction of CD172α+CD14+low cells to a predominant fraction of CD172α+CD14+high cells, known to sustain leukocyte activation/differentiation and inflammatory responses. The CD16+ cell percentages, specifically the CD3+CD16+ natural killer T (NKT) cell fraction and CD16 expression showed an intense and stable dose-dependent increase while the CD3−CD16+ NK cell fraction decreased. CD4+ and CD8+ T cells increased and CD8α and CD8β expression were up-regulated. CD8β+ cytotoxic T cells and CD16+ cells comparably increased. A marked stimulation of activated CD16+CD25+ and CD8β+CD25+ cells was observed at 24 h.The increase of CD8α+ cells and CD8α expression were due to increased CD4+CD8α+ (memory T helper) cells, also showing a CD8α+high phenotype. Concomitantly, the CD4+CD8α- T helper lymphocyte fraction significantly decreased.Overall, KP induced a wide modulation of innate immune and T cells that can exert regulatory and cytotoxic functions, which are fundamental for an efficient Th1 response.