Background: Bursal Pentapeptide (BPP)-(III-V) are peptides isolated from the Bursa of
Method: The peptides' adjuvant activities were evaluated in mice immunized with the H9N2 avian
Results: The results showed that BPP-IV did not promote humoral or cellular immune responses.
BPP-III had no effect on antibody production, but increased populations of CD3+ and CD8+ T cells,
CTL levels and proliferation activities of splenic T-lymphocytes. BPP-V increased the level of antibodies
(HI, IgG and its subtype IgG1) and the cytokine IL-4, as well as the ratio of CD3+ T cells and
its subsets CD4+ and CD8+ T cells, BPP-V also increased CTL level and promoted the proliferation
activity of T- and B-lymphocyte. Furthermore, in animal challenge experiment, BPP-III and BPP-V
reduced viral RNA copies and viral titers, and reduced inflammatory cell infiltration.
Conclusion: In summary, BPP-IV did not have an effect on specific immune responses, therefore it
could not reduce pathological damage in mice lungs; BPP-III provided resistance to the antigen
through the cell-mediated immune response; BPP-V enhanced both humoral and cellular immune
responses, therefore provided protections against the H9N2 Avian Influenza Virus (AIV). Altogether,
BPP-III and BPP-V could be adjuvant candidates for the H9N2 avian influenza vaccine.