Abstract
Background and Purpose: In the development of vaccines, it is important
to increase the antigen of the vaccine. We have confirmed the potential
of Morus alba L., a Toll-like receptor 4 (TLR4) activator, as an
adjuvant as a method for increasing the antigenicity of the vaccine.
Experimental Approach: TLR4 is highly expressed on immune cells,
therefore, the present study was undertaken to investigate the
underlying immunological processes of Morus alba L. as an oral adjuvant
in a mouse model. Mice were immunized with two types of antigen
(ovalbumin (OVA) or inactivated influenza vaccine) combined with Morus
alba L. Key Results: In the OVA antigen model, the co-administration of
Morus alba L. significantly promoted phagocytosis in murine peritoneal
macrophages. The maturation and function of dendritic cells were
significantly up-regulated the expression of MHC-II, CD86, and CD80
compared to OVA alone. The titers of OVA-specific IgG, IgG subtype
responses, and IgA were increased, the proliferation of T and B-cells
was markedly enhanced, and the production of IL-12, IFN-, and IL-4 was
better than OVA alone. In the inactivated influenza H1N1(PR8) vaccine
model, the co-administration of Morus alba L. with vaccine significantly
increased the IgM, IgG, and IgG subtype responses. The immunization of
mice with Morus alba L. adjuvant reduced mortality in mice after a
lethal challenge with influenza virus. Conclusion and Implications:
Morus alba L. is a novel mucosal adjuvant for vaccination that provided
safe and effective adjuvant effects and successfully induced both serum
and mucosal antibody responses and cell-mediated responses.