Purification, Identification and Functional Analysis of a Novel Immunomodulatory Peptide from Silkworm Pupa Protein

In this study, we isolated and characterized an immunomodulatory peptide from silkworm ( Bombyx mori ) pupa protein hydrolysates. Ultrasound-pretreated hydrolysates were prepared by alcalase digestion and their pro-proliferative activity was assessed with the splenic lymphocyte proliferation assay. Peptide fractions exhibiting the highest activity were purified by Sephadex-G100 and -G15 gel filtration chromatography. The structure of the purified peptides was analyzed using Liquid Chromatography Electrospray Ionisation Tandem Mass Spectrometry (LC–ESI–MS/MS); their digestive stability and their effects of the expression on immune-related cytokines were also evaluated. We purified a novel immunomodulatory peptide with a molecular weight of about 441.06 Da. The amino acid sequence was Asp-His-Ala-Val (DHAV). The splenocyte proliferation rate was 91.1% (P < 0.05) in the presence of 100 µg/mL purified peptide. DHAV was stable in the presence of the gastrointestinal proteases pepsin and trypsin, and stimulated the expression of immune-related factors including interleukin-6 and -12, nuclear factor-κB, cyclin D1, and cyclin-dependent kinase 4. Thus, DHAV purified from silkworm pupa protein hydrolysate has immunomodulatory activity and potential therapeutic value.