RBF Protein with MA103 Adjuvant Elicited Protective Immunity against Human Respiratory Syncytial Virus in BALB/c Mice.

The development of a vaccine against human respiratory syncytial virus (HRSV) has been hampered by enhanced respiratory disease due to the Th2-biased immune response. In the present study, MA103 and aluminum phosphate (Adju-Phos) adjuvants were used to verify the immunogenicity of the recombinant fusion (RBF) protein (F protein expressed by Escherichia coli). Both adjuvants significantly increased the neutralizing antibody titer and number of interferon gamma (IFN-γ)-secreting CD4+ T cells in mice. Based on the immunoglobulin G1 (IgG1)/IgG2a and IFN-γ/interleukin 4-secreting CD4+ T cell ratio, however, MA103 significantly enhanced the Th1-biased immune response. The pathological damage to the lung in the RBF/MA103 group was less than what was seen in the RBF/Adju-Phos group. Additionally, the number of HRSV copies in the lungs of the RBF/MA103 group decreased by approximately 3 × log₁₀. These results suggested that MA103 provides better protection against HRSV in mice.