Immunogenicity of HPV and HBV vaccines: adjuvanticity of synthetic analogs of monophosphoryl lipid A combined with aluminum hydroxide.

Monophosphoryl lipid A (MPL), a purified and detoxified product of lipopolysaccharide (LPS) of Salmonella minnesota R595, has been used as an adjuvant in different vaccines. In this study, the efficacy of human papillomaviruses (HPV) and hepatitis B virus (HBV) vaccines formulated with aluminum hydroxide combined with two different synthetic MPLs, 3D-(6-acyl)-PHAD or 3D-PHAD, or aluminum hydroxide combined with the mixtures of such MPLs, has been assessed. The immunogenicity in female BALB/c mice was verified by two intramuscular injections of differently formulated HPV and HBV vaccines and the total immunoglobulin G (IgG) antibody response was considered to compare the employed adjuvants. As verified experimentally, a mixture of 3D-(6-acyl)-PHAD and 3D-PHAD was able to induce significantly higher antibody titer than that of either 3D-(6-acyl)-PHAD or 3D-PHAD, when used individually. Interestingly, based on the responses achieved in terms of the total antibody levels, such mixture of synthetic MPLs was found to be even more effective than the bacterially derived MPL. Accordingly, the obtained results indicated that, if designed appropriately, synthetic MPL molecules could provide improved adjuvanticity with high level of consistency.