Background: L2-based Human Papillomavirus (HPV) prophylactic vaccines, containing
epitopes from HPV minor capsid proteins, are under investigation as second-generation HPV vaccines.
No such vaccine has passed clinical trials yet, mainly due to the low immunogenicity of peptide vaccines;
so efforts are being continued. A candidate vaccine composed of two HPV16 L2 epitopes, flagellin
and a Toll-Like Receptor (TLR) 4 agonist (RS09) as adjuvants, and two universal T-helper
epitopes was designed in silico in our previous researches.
Methods: The designed vaccine construct was expressed in E. coli BL21 (DE3) and purified through
metal affinity chromatography. Following mice vaccination, blood samples underwent ELISA and
flow cytometry analyses for the detection of IgG and seven Th1 and Th2 cytokines.
Results: Following immunization, Th1 (IFN-γ, IL-2) and Th2 (IL-4, IL-5, IL-10) type cytokines, as
well as IgG, were induced significantly compared with the PBS group. Significant increases in IFN-γ,
IL-2, and IL-5 levels were observed in the vaccinated group versus Freund’s adjuvant group.
Conclusion: The obtained cytokine induction profile implied both cellular and humoral responses,
with a more Th-1 favored trend. However, an analysis of specific antibodies against L2 is required to
confirm humoral responses. No significant elevation in inflammatory cytokines, (IL-6 and TNF-α),
suggested a lack of unwanted inflammatory side effects despite using a combination of two TLR agonists.
The designed construct might be capable of inducing adaptive and innate immunity; nevertheless,
comprehensive immune tests were not conducted at this stage and will be a matter of future work.