Immunological adjuvant effect of the peptide fraction from the larvae of Musca domestica

BACKGROUND: The larvae of Musca domestica (Diptera: Muscidae) have been used traditionally for malnutritional stagnation, decubital necrosis, osteomyelitis, ecthyma and lip scald and also to treat coma and gastric cancer in the traditional Chinese medicine. Its immunomodulatory effects in naïve mice in relation to the traditional uses were also reported. However, the immunological adjuvant potentials of this insect have not yet been studied. METHODS: The peptide fraction from the larvae of Musca domestica L. (MDPF) was evaluated for its adjuvant potentials on the immune responses to ovalbumin (OVA) and avian influenza vaccine (rL–H5) by determining antigen-specific antibody titers, splenocyte proliferation, activity of natural killer (NK) cell, the secretion of cytokines from splenocytes in the immunized mice. RESULTS: MDPF significantly enhanced not only the concanavalin A (Con A)-, lipopolysaccharide (LPS)- and antigen-stimulated splenocyte proliferation, but serum antigen-specific IgG, IgG1, IgG2a, and IgG2b antibody titers in the mice immunized with OVA and rL–H5. MDPF also remarkably promoted the killing activities of NK cells in splenocytes from the mice immunized with rL–H5. Furthermore, MDPF significantly promoted the production of Th1 (IL-2 and IFN-γ) and Th2 (IL-10) cytokines from splenocytes in the immunized mice. CONCLUSIONS: The results indicated that MDPF had a potential to increase both cellular and humoral immune responses and elicit a balanced Th1/Th2 response, and that MDPF may be a safe and efficacious vaccine adjuvant candidate. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12906-015-0951-6) contains supplementary material, which is available to authorized users.